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TEXT  BOOK  OF    PHYSIOLOGY 


DALTON'S    PHYSIOLOGY. 

LATKLY    ISSUED. 

A  Trkatisk  on  Ilunian  Plivsiolo^iv.  Desi>inod  for  the  Use  of  StuckMit>;  and  Prnt'ti- 
tioiiers  of  Mfilicine.  Ry  J.  C  ballon,  M.D.,  Professor  of  Physiology  in  the  ('•.!- 
le^e  of  Physiii;ins  and  Surgt'oris  in  New  York,  eio.  Sixth  edition,  Tlioroiijclily 
Revised  and  Knlar>jed.  In  one  very  handsome  octavo  volume  of  830  pages,  witji 
SlGilliistratious:  cdoth,  $5.50;  leather,  S6.50. 

"  Prof.  Dalton  has  di.scussed  conflicting  theories  and  conclusions  regarding  physi- 
ological questions  witli  a  fairness,  a  fulness,  and  a  conciseness  which  lend  frehlmess 
and  vi;ror  to  the  entire  book.  Hut  his  discussions  have  been  so  guarded  by  a  refusal 
of  admission  to  those  sjieculative  and  theoretical  explanations,  which  at  best  exist 
in  the  minds  of  observers  themselves  as  only  probabilities,  that  none  of  his  readi;rs 
need  be  led  into  grave  errors  while  making  them  a  studv." — The  Medical  Record, 
Feb.  19,  1876. 

"  The  style  is  clear,  tlie  arrangementadmirable,  and  the  figures  excellent.  Though 
much  increased  in  bulk,  is  still  a  moderately-sized  volume.  Every  chapter  bears 
evidence  of  a  careful  revision,  and  all  the  most  important  and  trustworthy  facts  of 
recent  physiological  science  have  been  incorporated." — Canada  Medical  and  Surgical 
Journal,  ,Ian.  1876. 

"  Every  one  concedes  that  this  is  the  best  physiological  text  book  published  in 
America.'"—  Virginia  Medical  Monthly,  Jan.  1876. 

CARPENTER'S  PHYSIOLOGY. 

NEW   EDITION— LATELY   ISSUED. 

The  Principles  of  Human  Physiology.  By  William  B.  Carpenter,  M.D.,  F.R.S., 
F.G.S.,  F.L.S.,  Registrar  of  the  Univ.  of  London,  etc.  Edited  by  Henry  Power, 
MB.  Lond.,  F.R.C.S.,  Examiner  in  Natural  Sciences,  Univ.  of  Oxford.  A  New 
American,  from  the  Eighth  Revised  and  Enlarged  English  Edition.  With  notes 
and  additions,  by  Francis  G.  Smith,  M.D.,  Professor  of  the  Institutes  of  Medicine 
in  the  Univ.  of  Penna.,  etc.  In  one  very  large  and  handsome  octavo  volume  of 
1083  pp.,  with  two  plates  and  373  engravings  on  wood:  cloth,  $5.50;  leather,  $6.50. 

"The  merits  of  '  Carpenter's  Physiology'  are  so  widely  known  and  appreciated 
that  we  need  only  allude  briefly  to  the  fact  that  in  the  latest  edition  will  be  found  a 
comprehensive  embodiment  of  the  results  of  recent  physiological  investigation. 
Care  has  been  taken  to  preserve  the  practical  character  of  the  original  work.  In  fact 
the  entire  work  has  been  brought  up  to  date,  and  bears  evidence  of  the  amount  of 
labor  tliat  has  been  bestowed  upon  it  by  its  distinguished  editor,  Mr.  Henry  Power. 
The  American  editor  has  made  the  latest  additions,  in  order  fully  to  cover  the  time 
that  has  elapsed  since  the  last  English  edition." — N.  Y.  Medical  Journal,  Jan.  1877. 

'■  Under  the  able  editorship  of  Dr.  Power  it  must  still  be  regarded,  treating  it  as  a 
whole,  as  the  most  complete  exposition  of  physiological  knowledge  in  tiie  English 
language.  The  present  edition,  compared  with  the  seventh  edition,  represents  the 
advancement  of  physiology  during  the  past  five  years.  In  its  preparation  the  editor 
has  collated  most  carefully  most  of  the  recent  contributions  of  physi'  logists,  and  he 
has  got  si)ecial  and  direct  assistance  from  several.  As  a  work  of  reference  il  ought 
to  have  its  place  in  the  library  of  every  medical  man.  There  he  will  find  a  short  and 
clear  account  of  the  most  recent  investigations,  and  no  opportunity  is  missed  of 
pointing  out  any  practical  influence  the  work  may  have  on  our  theories  of  disease." 
— Edinburgh  Medical  Journal,  Jan.  1876. 


HENRY  C.  LEA'S  SON  &  CO.,  PHILADELPHIA. 


A   TEXT  BOOK 


PHYSIOLOGY. 


M.  FOSTER,  M.A.,  M.D.,  F.R.S., 

PR.ELECTOR  IX   PHYSIOLOGY  AND   FELLOAT   OF  THIXITY  COLLEGE,   CA5IBKIDGE. 


FROM  THE  THIED  AND  EEVISED  ENGLISH  EDITION, 


WITH   NOTES   AXD    ADDITIONS, 


By  EDAVARD  T.  REICHERT,  M.D., 

DEMOXSTRATOK  OF  EXPERIMENTAL  THERAPEUTICS,  UNIVERSITY  OF  PENNSYLVANIA. 


WITH  TWO  HUNDRED  AND  FIFTY-NINE  ILLUSTRATIONS, 


PHILADELPHIA: 

IIEXRY   C.   LEA'S  SOX  &   CO. 

18  80. 


F  ?/ 


Entered  according  to  Act  of  Congress,  in  the  year  1880, 

By    henry    C.    lea, 

In  the  Office  of  the  Librarian  of  Congress,  at  Washington,  D.  C. 

[all  rights  reserved.] 


'J- 

CO 


cci 


UJ 


AMERICAN  EDITOR'S  PREFACE. 


The  high  reputation  acquired,  on  both  sides  of  the  At- 
lantic, by  Dr.  Foster's  "  Text  book  of  Physiology"  as  a 
lucid  exposition  of  the  science  in  its  most  modern  aspect, 
has  seemed  to  call  for  an  edition  more  thoroughly  adapted 
to  the  wants  of  the  American  student.  The  plan  of  the 
author  has  presupposed  an  acquaintance  with  the  details  of 
physiological  anatomy,  such  as  the  student  is  accustomed  to 
look  for  in  his  treatises  on  physiology.  The  absence  of  these 
details  has  rendered  many  parts  of  the  work  yague,  if  not 
altogether  incomprehensible,  and  has  therefore  proyed  a 
serious  drawback  to  the  usefulness  of  the  book  as  an 
accompaniment  to  lectures  on  physiology  as  it  is  usually 
taught  in  our  schools,  and  this  deficiency  the  editor  has  en- 
deayored  to  supply  by  brief  notes  and  the  introduction  of  a 
large  number  of  illustrations. 

The  almost  limitless  amount  of  material  accumulated  by 
modern  research  has  rendered  difficult  the  task  of  selection 
and  compression  without  exceeding  the  reasonable  limits  of 
a  conyenient  text  book.  In  his  selections  the  editor  has 
been  guided  by  his  experience  in  the  wants  of  students,  and 
has  endeayored  only  to  present,  in  the  most  concise  form, 
such  facts  as  would  seem  to  be  indispensable  to  a  correct 
appreciation  of  the  structure  and  function  of  the  impor- 
tant organs.  In  accomplishing  this  his  additions  haye 
considerably  exceeded  his  expectations,  amounting  to  about 
one  hundred  and   forty  pages,  including  the  illustrations. 


VI  PREFACE. 

which  have  been  increased  in  nnniber  from  seventy-two  to 
two  hundred  and  fifty-nine.  A  number  of  brief  notes  on 
the  physiological  action  of  some  of  the  important  drugs 
have  also  been  added.  If  he  shall  thus  have  succeeded  in 
renderin<y  this  admirable  work  better  fitted  for  the  wants  of 

o 

the  American  student,  he  will  feel  abundantly  rewarded. 

Nothing  has  been  omitted  from  the  English  edition,  and 
all  additions  have  been  distinguished  by  insertions  in 
brackets,  [  ]. 

Philadelphia,  March,  1880. 


PREFACE  TO  THE  SECOND  EDITION, 


So  short  a  time  has  passed  since  the  appearance  of  the 
first  edition  that  it  has  not  seemed  desirable  to  make  any- 
important  changes.  My  previous  decision  not  to  introduce 
figures  of  instruments  has  been  so  generally  disapproved, 
that  I  have  waived  my  own  judgment  and  inserted  a  num- 
ber of  illustrations,  which  I  trust  will  be  found  to  assist  the 
reader.  The  areas  of  the  cerebral  convolutions,  in  spite  of 
the  difficulties  surrounding  the  true  interpretation  of  the 
phenomena  resulting  from  their  stimulation,  are  of  such 
interest,  especially  to  the  medical  profession,  that  I  have  in- 
troduced illustrative  figures,  for  which  I  have  to  thank  the 
kindness  of  Dr.  Ferrier. 

OtherAvise  my  efforts  have  been  chiefly  directed  to  re- 
moving inaccuracies  and  obscurities,  in  the  hope  of  render- 
ing the  work  more  worthy  of  the  favor  with  which  it  has 
been  received.  It  will  be  observed  that  the  largest  changes 
and  additions  occur  in  the  small  print. 

I  have  to  thank  Dr.  Pye-Smith  and  other  friends,  as  well 
as  previously  unknown  correspondents,  for  their  valuable 
suggestions;  and  I  am,  as  before,  greatly  indebted  for  the 
help  given  me  by  my  former  pupils,  Mr.  Dew  Smith,  Mr. 
Langley,  and  !Mr.  Lea. 

Trinity  College,  Cambridge, 
December,  1877. 


PREFACE  TO  THE  THIRD  EDITION. 


The  most  important  changes  in  the  present  edition  are  to 
be  fonnd  in  the  section  on  muscle  and  nerve ;  I  have  rear- 
ranged this  section  altogether,  hoping  thereby  to  render  this 
difficult  subject  more  easy  for  the  reader.  The  other  changes, 
though  immerous,  are  for  the  most  part  sliglit,  and  very 
largely  confined  to  the  small  print.  I  have  again  to  oifer 
my  best  thanks  to  my  friends  who  have  assisted  me  in  this 
as  in  the  two  former  editions. 


Trinity  College,  Cambridge, 
September,  1879. 


CONTENTS. 


PAGE 

Introductory, 13 


BOOK  I. 

BLOOD.     THE  TISSUES  OF  MOVEMENT. 
THE  VASCULAK  MECHANISM. 


CHAPTER  I. 

Blood,  23-60. 

Sec.  1.  The  Coagulation  of  Blood, 24 

Sec.  2.  The  Chemical  Composition  of  Blood, 43 

Sec.  3.  The  History  of  the  Corpuscles, 53 

Sec.  4.  The  Quantity  of  Blood,  and  its  Distribution  in  the  Body,     .  59 

CHAPTEE  II. 

The  Contractile  Tissues,  61-155. 

[The  Physiological  Anatomy  of  the  Skeletal  Muscles, .         .         .         .     G2] 

Sec.  1.  The  Phenomena  of  3Tuscle  and  Nerve, 63 

Muscular  and  nervous  irritability,  64.  The  Phenom- 
ena of  a  simple  muscular  contraction,  67.  Tetanic 
contractions,  75. 
Sec.  2.  The  Changes  in  a  Muscle  during  Muscular  Contraction,  .  81 
The  change  in  form,  81.  Electrical  Changes,  86. 
Chemical  Changes,  94.  The  changes  in  a  Xerve  dur- 
ing the  passage  of  a  Nervous  Impulse,  101. 


CONTENTS. 


Sec.  3.   TheNdtuvc  of  the  Chamjes  (Itroiu/h  which  an  Electric  Current 

ifi  able  to  Generate  a  Nervous  Impulse,  .         .         .105 

Tlie  action  of  the  Constant  Current,  105. 
Sec.  4.   The  Muscle-nerve  Preparation  as  a  Machine,        .         .         .113 
The  nature  and  mode  of  application  of  the  Stimulus  as 
affecting  the  amount  and  character  of  the  Contrac- 
tion, 114.     The  influence  of  the  Load,  118.    The  in- 
fluence of  tlie  Size  and  Form  of  the  muscle,  120. 
Sec.  5.  The  Circumstances  which  Determine  the  Degree  of  Irritability 

of  Muscles  and  Nerves, 120 

The  effects  of  severance  from  the  Central  Nervous  Sys- 
tem, 122.    The  Influence  of  Temperature,  123.    The 
Influence  of  Blood-supply,  125.      The  Influence  of 
Functional  Activity,  127. 
Sec.  6.  A  Further  Discussion  of  some  points  in  the  Physiology  of  Mus- 
cle and  Nerve,      .         .         .         .         .         .         .         .130 

The  Electrical  Phenomena  of  Muscle  and  Xerve,  130. 
The  energy  of  Muscle  and  Nerve  and  the  nature  of 
the  Chemical  Changes,  146. 

Sec.  7.    Unstriated  Muscular  Tissue, 149 

Sec.  8.  Cardiac  3Iuscles, 153 

Sec.  9.  Cilia, 154 

Sec.  10.  Migrating  Cells, 155 

CHAPTER  III. 

The  Eundamextai.  Properties  of  Nervous 
Tissues,  156-169. 

Automatic  actions,  160.    Reflex  actions,  162.    Inhibition,  166. 

CHAPTER  IV. 

The  Vascular  Mechanism,  109-297. 

I.  The  Physical  Phenomena  of  the  Circulation,      .     170 
{^The  Physiological  Ancdomy  of  the  Arteries,  Capillaries,  and  Veins,  170-175] 
Sec.  1.  Main  General  Facts  of  the  Circulation,         ....     175 
The  capillary  Circulation,  175.     The  flow  in  the  Ar- 
teries, 179.    The  flow  in  the  Veins,  189.     Hydraulic 
principles  of  the  Circulation,  190. 


CONTEXTS.  XI 

PAGE 

Sec.  2.  The  Heart, 197 

[The  Physiological  Anatomy  of  the  Heart,    .         .         .    197-203] 
The  Phenomena  of  the  Normal  Beat,  203.     The  Mech- 
anism of  the  Valves,  214.    The  sounds  of  the  Heart, 
220.     The  work  done,  223.    Variation  in  the  Heart's 
Beat,  224. 

Sec.  3.  The  Pulse, ....     226 

II.  The  Vital  Ppienomexa  of  the  Circulatiox,  .        .     238 

Sec.  4.   Changes  in  the  Beat  of  the  Heart, 240 

Nervous  Mechanism   of  the  beat,  242.     Inhibition  of 
the  beat,   245.     The   effects  on   the   circulation  of 
changes  in  the  Heart's  Beat,  256. 
vSec.  5.  Changes  in  the  Calibre  of  the  Minute  Arteries.      Vaso-motor 

Actions, 259 

Vaso-motor  Xerves,  261.  Vaso-constrictor  and  Vaso- 
dilator Nerves,  280.  The  effects  of  local  vascular 
constriction  or  dilation,  285. 

Sec.  6.   Changes  in  the  Capillary  Districts, 287 

Sec.  7.   Changes  in  the  Quantity  of  Blood, 290 

The  Mutual  Relations  and  the  Co-ordination  of  the  Vascular 
Factors, 292 

BOOK  II. 

THE  TISSUES   OF   CHEMICAL  ACTION  WITH  THEIR   EE- 
SPECTIVE  MECHANISMS.    NUTRITION. 

CHAPTER  I. 

[The  Epithelia, 299] 

The  Tissues  and  Mechanisms  of  Digestion,  303-415. 

Sec.  1.  [The  Physiological  Anatomy  of  the  Salivary  Glands,     .  303-306] 
The  Properties  of  the  Digestive  Juices. 

Saliva,  306.  [The  physiological  anatomy  of  the  mucous 
membrane  of  the  stomach,  312-314.]  Gastric  juice, 
314.  [The  physiological  anatomy  of  the  liver,  324- 
328.]  Bile,  328.  [The  physiological  anatomy  of  the 
'  pancreas,  333.]  Pancreatic  juice,  333.  [The  physio- 
logical anatomy  of  the  mucous  membrane  of  the 
small  intestine,  340-344.]     Succus  Entericus,  348. 


XII  CONTENTS. 

PACK 

Sec.  2.   The  Act  of  Secretion  in  the  rase  of  the  Digestive  Juices  and 

the  Nervous  Mechanisms  which  regulate  it,    .         .         .     345 

Sec.  3.  The  Miiscular  Mechanisms  of  Digestion,  ....  376 
Mastication,  376.  Deglutition,  377.  Peristaltic  action 
of  the  small  intestine,  379.  Movements  of  tlie  a'soph- 
agus,  383.  Movements  of  the  stomach,  385.  Move- 
ments of  the  large  intestine,  386.  Defecation,  387. 
Vomiting,  389. 

Sec.  4.   The   Changes  ichich  the   Food  undergoes  in  the  Alimentary 

Canal, 392 

Sec.  5.  Absorption  of  the  Products  of  Digestion,       ....     401 
The  course  taken  by  the  several  products  of  digestion,     408 

CHAPTER  II. 

The  Tissues  and   Mechanisms  of   Respiration,  416-500. 

[The  Physiological  Anatomy  of  the  Trachea  and  Lungs,    .         .    416-419] 

Sec.  1.   The  Mechanics  of  Pulmonary  Respiration,  .         .         .     420 

The  Rhythm  of  Respiration,  424.     The  Respiratory 

Movements,  427. 

Sec.  2.  Changes  of  the  Air  in  Respiration, 435 

Sec.  3.  The  Respiratory  Changes  in  the  Blood,         ....     438 
The   relations  of  oxygen  in  the  blood,   441.     Haemo- 
globin ;  its  properties  and  derivatives,  443.      Color 
of  venous  and  arterial  blood,  450.     The  relations  of 
the  carbonic  acid  in  the  blood,  456.  The  relations  of 
the  nitrogen  in  the  blood,  458. 
Sec.  4.  The  Respiratory  Changes  in  the  Lungs,        ....     457 
The  entrance  of  oxygen,  457.     The  exit  of  carbonic 
acid,  459. 
Sec.  5.   The  Respiratory  Changes  in  the  Tissues,      ....     462 
Sec.  6.  The  Nervous  Mechanism  of  Respiration,        ....     468 
Sec.  7.   The  Effects  of  Respiration  on  the  Circulation,       ,         .         .     479 
Sec.  8.  The  Effects  of  Changes  in  the  Air  breathed,  .         .         .     489 

The  effects  of  deficient  air.  Asphyxia.  Phenomena  of 
Asphyxia,  489.  The  circulation  in  asphyxia,  492. 
The  effects  of  an  increased  supply  of  air.  Apnoea, 
495.  The  effects  of  changes  in  the  composition  of 
the  air  breathed,  496.  The  effects  of  changes  in  the 
pressure  of  the  air  breathed,  496. 


CONTENTS.  Xlll 

PAGE 

Sec.  9.  Modified  Respiratory  Blovements,         .....     497 
Sighing,    Yawning,    Hiccough,    Sobbing,    Coughing, 
Sneezing,  and  Laughter,  498-499. 

CHAPTER  III. 

[The  Physiological  Anatomy  of  the  Skin  and  its  Appendages,     .  500-510] 
Secretion  by  the  Skin^,  510-518. 

The  Nature  and  Amount  of  Perspiration, 511 

Cutaneous  Respiration,     .         ...         .         .         .         .         .513 

The  Secretion  of  Perspiration,  . 514 

The  Xervous  Mechanism  of  Perspiration,  515. 
Absorption  by  the  Skin, 518 

CHAPTER   lY. 

\_The  Physiological  Anaicrny  of  the  Kidneys,       ....  519-522] 

Secretions  by  the  Kidneys,  523-541. 
Sec.  1.   The  Composition  of  Urine,  ......     523 

Sec.  2.  The  Secretion  of  Urine, 527 

The  relation  of  the  secretion  of  urine  to  arterial  pres- 
sure, 528.     Secretion  by  the  renal  epithelium,  532. 
Sec.  3.  Micturition, 537 

CHAPTER  V. 
The  Metabolic  Phenomena  of  the  Body,  541-624. 

Sec.  1.  Metabolic   Tissues, 542 

The  History  of  Glycogen,  542.     The  History  of  Fat. 
Adipose  Tissue,  556.     The  Mammary  Gland  [and  its 
Physiological  Anatomy],  561.     The  Spleen  [and  its 
Physiological  Anatomy],  56G. 

Sec.  2.  The  History  of  Urea  and  its  allies, 570 

Sec.  3.  The  Statistics  of  Nutrition, 579 

Comparison  of  Income  and  Outcome,  583.  Nitroge- 
nous Metabolism,  587.  The  effects  of  Fatty  or  Amy- 
loid Food,  590. 

Sec.  4.  The  Energy  of  the  Body, 594 

The  income  of  energy,  594.  The  expenditure,  595. 
The  sources  of  Muscular  Energy,  596.  The  Sources 
and  Distribution  of  Heat,  600  Regulation  by  varia- 
tions in  loss,  605.  Regulation  by  variations  in  pro- 
duction, 608. 


XIV  CONTENTS. 

PAGE 

Sec.  5.   The  Influence  of  the  Nervous  Si/stem  on  Nutrition,         .         .GIG 
Sec.  6.  Dietetics, G19 

BOOK   III. 

THE   CENTRAL   NERVOUS  SYSTEM  AND  ITS 
INSTRUMENTS. 

CHAPTER  I. 

[General  Arrangement  of  the  Nervous  System,  and  the  Physiological 

Anatomy  of  the  Nerve  Tissues,      ....  G25-633] 

Sensory  ]S'erves,  633-644. 

CHAPTER  II. 

\_The  Physiolor/ical  Anatomy  of  the  Eye, G44-G-')o] 

Sight, 655-725 

Sec.  1.  Dioptric  Mechanisms, 655 

The  Formation  of  the  Image,  G55.  Accommodation, 
657.  Movements  of  the  Pupil,  GG6.  Imperfections 
in  the  Dioptric  Apparatus,  672. 

Sec.  2.   Visual  Sensations, 676 

The  Origin  of  Visual  Impulses,  677.  Simple  Sensations, 
688.     Color  Sensations,  694. 

Sec.  3.   Visual  Perceptions,       .         .* 702 

Modified  Perceptions,  705. 

Sec.  4.  Binocular  Vision, 709 

Corresponding  or  identical  points,  709.     Movements  of 
the  eyeballs,  711.     The  Horoi)ter,  717. 
Sec.  5.   Viaual  Judgments,       .         .         .         .         .         .         .         .719 

Sec.  6.  The  Protective  Mechanisms  of  the  Eye,         ....     723 

CHAPTER  III. 

Hearing,  Smell,  and  Taste,  725-758. 

Sec.  1.  Hearing,      .......         ...     725 

\_TJie  Physiological  Anatomy  of  the  Ear,        .         .         .    725-736] 
The  Acoustic  Apparatus,  736.    Auditory  .Sensations,  740. 
Auditory  Judgments,  746. 

Sec.  2.  Smell, 747 

\^T he  Physiological  Anatomy  of  the  Nasal  FosscB,    .         .    747-749] 


CONTENTS.  XV 


Sec.  3.  Taste, 751 

[TAe  Physiological  Anaiomy  of  the  Gustatory  Mucous  Mem- 
brane,          7ol-755] 

CHAPTER  IV. 

Feelixg  axd  Touch,  758-769. 

Sec.  1.   General  Sensibility  and  Tactile  Perceptions,  ....     758 

Sec.  2.  Tactile  Sensations, 761 

Sensations  of  Pressure,  761.    Sensations  of  Temperature, 
762. 

Sec.  3.  Tactile  Perceptions  and  Judgments, 764 

Sec.  4.  The  Muscular  Sense, 766 


CHAPTER  Y. 

The  Spixal  Cord,  769-798. 

[The  Physiological  Anatomy  of  the  Spinal  Cord,         .         .         .    769-773] 

Sec.  1.  As  a  Centre  of  Reflex  Action, 773 

In  the  Frog,  733.     In  the  Mammal,  7S1.     The  time  of 
Eeflex  Actions,  783. 
Sec.  2.  As  a  Centre  or  Group  of  Centres  of  Automatic  Action,  .         .     734 
Sec.  3.  As  a  Conductor  of  Afferent  and  Efferent  Impulses,  .         .     787 

CHAPTER  YI. 
The  Bratnt,  798-873. 
[The  Physiological  Anatomy  of  the  Brain,         ....    798-810] 
Sec.  1.   On  the  Phenomena  exhibited  by  an  animal  deprived  of  its  Cere- 
bred  Hemispheres, 810 

Sec.  2.  The  Mechanisms  of  Co-ordinated  Movements,  .         .         .     816 

Forced  Movements,  826. 
Sec.  3.   The  Functions  of  the  Cerebral  Convolutions,  ....     828 
Sec.  4.   The  Functions  of  other  pai'ts  of  the  Brain,      ....     842 
Corpora  striata  and  optic  thalami,  844.     Corpora  quad- 
rigemina,  849.     Cerebellum,  853.     Crura  Cerebri  and 
Pons  Varolii,  856.     Medulla  oblongata,  857. 

Sec.  5.   The  Rapidity  of  Cerebral  Operations, 858 

Sec.  6.    The  Cranial  Nerves, 860 


XVI  CONTENTS. 

CHAPTER  yii. 

Special  Muscular  Mechanisms,  874-892. 

PAGE 

['The  riij/ffiolof/icdl  Anatoini/  of  (he  Larynx,       ....    874-877] 

Sec.  1.  The  Voice, 877 

Sec,  2.  Speech, 883 

Vowels,  883.     Consonants,  885. 
Sec.  3.  Locomotor  Mech<(nisnis, 888 

BOf)K  IV. 

THE  TISSUES  AND  MECIIAXISMS  OF  REPRO- 
UUCTIOX. 

[The  Fhi/i<iolorjic(d  Anatomy  of  the  Or(j(ms  of  Generdtion,   .         .  894-900] 

CHAPTER  I. 

Menstruation,  901-905. 

CHAPTER  II. 
Impregnation,  905-915. 

CHAPTER  III. 

The  Nutrition  of  the  E^ibryo,  915-^23. 

CHAPTER  lY. 

Parturition,  924-928. 

CHAPTER  V. 
The  Phases  of  Life,  928-941. 

CHxVPTER  VI. 
Death,  941-943. 

APPENDIX. 

On  the  Chemical  Basis  of  the  Animal  Body,  947-1008. 

INDEX,  1009. 


LIST  OF  ILLUSTRATIONS, 


PAGE 

[1.  Amoeba  Princeps,  after  Ehrenberg, 13] 

[2.  Bowl  of  Recently  Coagulated  Blood,  after  Dalton, 25] 

[3.  Bowl  of  Coagulated  Blood  after  Twelve  Hours,  after  Daltou,      .        .        .25] 

[4.  Coagulated  Fibrin,  after  Dalton, 26] 

[5.  Red  Blood-corpuscles  of  Man,  after  Gulliver, 47] 

[6.  Red  Blood-corpuscles  of  Mam.nals,  Birds,  Reptiles,  Amphibia,  and  Fish, 

after  Gulliver 48] 

[7.  Wliite  Blood-corpuscles,  after  Klein, 51] 

[8.  Embryonic  Blood-corpuscle,  after  Kirk, 55] 

[9.  Transverse  Section  of  Skeletal  Muscle,  after  Kolliker,        ....  62] 

[10.  Elementary  Structure  of  Skeletal  Muscle,  after  Todd  and  Bowman,  .        .  63] 

[11.  Lacerated  Fibre,  showing  Sarcolemraa,  after  Todd  and  Bowman,       .        .  63] 

12.  Diagram  illustrating  Apparatus  arranged  for  Experiments  with  Muscle- 

nerve  Preparations, 68 

13.  Muscle-nerve  Preparation,  with  Clamp  Electrodes  and  Electrode-holder, 

shown  on  a  larger  scale, 69 

14.  Muscle-curve  Tracing  obtained  by  the  Pendulum  Myograph,    ...  70 

15.  The  Pendulum  Myograph, 71 

16.  Curves  iliustraiiug  the  Measurement  of  the  Velocity  of  a  Nervous  Im- 

pulse,     73 

17.  Tracing  of  a  Double  Muscle-curve, 76 

18.  Tracing  for  a  Muscle  thrown  into  Tetanus  with  a  Primary  Current  of  an 

Induction  Machine, 77 

19.  Tracing  from  a  Muscle  thrown  into  Tetanus  with  an  ordinary  Magnetic 

Interrupter  of  an  Induction  Machine 78 

20.  The  Magnetic  Interruptor, 78 

[21.  Muscle-fibre,  with  termination  of  Motor  Nerve  in  an  End-plate,  after 

Cohnheim, 83] 

22.  Muscular  Fibre  undergoing  Contraction,  after  Engelmann,        ...  84 

23.  Representation  of  the  Translocation  of    the  Molecules  of  a  Muscular 

Fibre  during  Contraction  and  Relaxation, 85 

24.  Non-polarized  Electrodes, 87 

25.  Diagram  illustrating  the  Electric  Currents  of  Nerve  and  Muscle,      .        .  88 

26.  Muscle-nerve  Preparation,  showing  Application  of  Non-polarizable  Elec- 

trodes,            107 

27.  Diagram  illustrating  the  Variations  of  Irritability  during  Electrotonus, 

with  Polarizing  Currents  of  Increasing  Intensity, 109 

28.  Diagram  to  illustrate  Du  Bois-Reymoud's  Electromotive  Molecules,  Peri- 

polar Condition, 130 


XVIU  LIST    OF    ILLUSTRATIONS. 


PAGE 

29.  Diagram  to  illustrate  Du  Buis-Reyinoiid's  Molecules  in  their  Hi-polar  Con- 

dition,            131 

30.  Diaijram  to  illustrate  the  Fall-rheotoine, i'V.i 

31.  Diagram  to  illustrate  Bernstein's  Diirerential  Rheotonie,     ....  i:!5 

32.  Diaj,'ram  to  illustrate  Du  Bois-Ri-ymond's  "  Double  Variation, "  .        .        ,  l.i7 

33.  Diagran)  illustrating  Electrotouic  Currents, 142 

[34.  Three  Uustriated  Muscular    Fibre  Cells   from   Human   Arteries,   after 

Bowman 150] 

[3-5.  Muscular  Fibre  Cells  from  the  Bladder,  after  Kolliker,        ....  1-50] 
[36.  Perpendicular  Section  through  the  Scalp,  showing  Muscles  of  the  Hair- 
follicles,  after  Kolliker, l.^l] 

37.  Diagram  to  illustrate  the  Simplest  Forms  of  a  Nervous  System,        .        .  1.56 
[38.  Diagram  illustrating  the  Simplest  Form  of  Reflex  Apparatus,  .                 .  162] 
[39.  Web  of  a  Frog's  Foot,  showing  Arterioles,  Veins,  and  Intermediate  Cap- 
illaries, after  Wagner, 172] 

[40.  Structure  of  Capillaries,  after  Ebertli, 173] 

[41.  Distribution  of  Cai)illaries  in  Muscles,  after  Berres 173] 

[42.  Distril)Ution  of  Cauillaries  around  Fat-cells,  after  Berres,    ....  173] 
[43.  Distribution  of  Capillaries  on  the  Surface  of  the  Skin  of  the  Finger,  after 

Berres, 174] 

[44.  Distribution  of  Capillaries  in  the  Follicles  of  Mucous  Membrane,  after 

Berres, 174] 

[45.  Veins  with  Valves  Open,  after  Dalton, 174] 

[46.  Veins  with  Valves  Closed,  after  Dalton, 174] 

[47.  Capillaries  of  a  Web  of  a  Frog's  Foot,  highly  magnified,  after  Wagner,  .  176] 

48.  Apparatus  for  Investigating  Blood-pressure, 178 

49.  Tracing  of  Arterial  Pressure  with  a  Mercury  Manometer,  ....  180 

50.  Diagram  illustrating  Pick's  Spring  Manometer, 182 

[51.  Tracing  obtained  with  the  Spring  Manometer,  after  Carpenter,        .        .  183] 

52.  Large  Kymograph,  with  contiiiuous  roll  of  paper, 184 

[•53.  Volkmann's  Hfemodrometer,  after  Dalton, 185] 

54.  Diagrammatic  Representation  of  Ludwig's  Stromuhr,        ....  186 

[55.  HjEmatochometer  of  Vierordt,  after  Longet, 187] 

[56.  Lortet's  Hsemotochonieter,  after  Lortet, 188] 

[57.  Anastomosing  Muscular  Fibres  of  the  Heart,  after  Eberth,        .        .        .  198] 

[58.  Interior  of  Right  Side  of  the  Heart,  from  Quain's  Anatomy,       .        .        .  199] 

[59.  Interior  of  Left  Side  of  the  Heart,  from  Quain's  ^wt'omy,         .        .        .  200] 
[60.  View  of  the  Base  of  the  Ventricles,  showing  the  Valves,  from  Quain's 

Anatomy, 202] 

[61.  Diagram  of  the  Circulation  through  the  Heart,  after  Dalton,      .        .        .  203] 

62.  Tracings  of  the  Variations  of  Pressure  in  the  Right  Auricle  and  Ventri- 

cle, and  of  Cardiac  Impulse,  after  Marey, 207 

63.  Marey's  Tambour,  with  cardiac  sound, .  208 

64.  The  Maximum  Manometer  of  Goltze  and  Gaule, 212 

65.  Curve  of  Pressure  in   Aorta  and  Left  Ventricle  of  the  Dog,  taken  with 

the  Manometer  of  Goltze  and  Gaule, 213 

[66.  Diagram  of  the  Valves  of  the  Heart,  after  Dalton, 214] 

[67.  Diagram  of  the  Valves  of  the  Heart,  after  Dalton, 215] 

68.  Diagrammatic  Ref)resentation  of  Movements  and  Sounds  of  the  Heart 

during  a  Cardiac  Period, 220 

[69.  Marey's  Sphygmograph,  after  Longei, 226] 


LIST    OF    ILLUSTRATIONS.  XIX 


PAGE 

[70.  Apparatus  of  ^[arey  for  showing  Mode  of  the  Propagation  of  the  Pulse, 

after  Longet, 227] 

71.  Pulse-curves  described  by  a  series  of  Sphygmographic  Levers,  at  inter- 

vals on  an  elastic  tube,  into  which  a  fluid  is  forced  by  a  sudden  pump,  .  228 

72.  (a)  Sphygmograph  Tracing  from  the  Ascending  Aorta  (Aueurisraal  Dila- 

tation); (fe)  from  Carotid  Artery  of  a  Healthy  Man;  (c)  from  Ra- 
dial Artery  of  same  person  ;  (d)  from  Radial  Artery  of  a  Healthy  Man 
less  athletic  than  in  (c);  (e)  from  Dorsaiis  Pedis  of  same  person  as  (6) 
and(c);  (/)  Tracing  of  Pulse  fully  Dicrotic;  Predicrotic-wave  also 
shown  (Typhoid  Fever  (?));  c<7)  Pulse  fully  Dicrotic,  and  Dicrotic-wave 
very  large,  Typhoid  Fever;  (k)  Pulse  with  very  large  Predicrotic-wave, 
Acute  Albuminuria;  (k)  Hyperdicrotic  Pulse,  the  Dicrotic-wave  becom- 
ing lost  on  succeeding  beat ;  after  Hteniorrhage  in  Typhoid  Fever,      233,  234 

[73.  Diagram  of  the  Nerves  of  the  Heart,  after  Carpenter, 244] 

74.  Inhibition  of  the  Frog's  Heart  by  Stimulation  of  the  Vagus,       .        .        .  246 

75.  The  last  Cervical  and  first  Thoracic  Ganglia  in  a  Rabbit,     ....  252 

76.  The  last  Cervical  and  first  Thoracic  Ganglia  in  a  Dog, 253 

77.  Tracing  showing  the  influence  of  Cardiac  luhibition  on  Blood-pressure,  .  257 

78.  Blood-pressure  during  Cardiac  Inhibition, 258 

79.  Tracing  showing  the  effect  on  Blood-pressure  by  Stimulating  the  Central 

End  of  the  Depressor  Nerve, 267 

[80.  Epithelium  from  a  Serous  Membrane,  after  Henle, 299] 

[81.  Epithelium  from  a  Mucous  Membrane,  after  Henle,      .        .        .        .        .  299] 

[82.  Cylindrical  Epithelium,  after  Kolliker, .'  300] 

[83.  Ciliated  Epithelium,  after  Kolliker, 300] 

[84.  Section  of  a  Villus  from  the  lutestine  of  a  Rabbit,  after  Klein   and 

Yerson, 302] 

[85.  Lobule  of  the  Parotid  Gland  of  a  New-born  Infant,  after  Wagner,    .        .  304] 

[86.  Submaxillary  Gland  of  a  Dog,  after  Frey, 304] 

[87.  Modes  of  Terminations  of  Nerves  in  Salivary  Glands,  after  Pfluger,  .        .  305] 

[88.  Salivary  Corpuscles,  Epithelium  Scales,  and  Granules,  after  Carpenter,   .  306] 
[89.  Capillary  Network  of  the  Lining  Membrane  of  the  Stomach,  after  Kolli- 

ker 312] 

[90.  Vertical  Section  of  the  Mucous  Membrane  of  the  Stomach,  after  Wagner,  312] 

[91.  Peptic  Gastric  Gland,  after  Kolliker 313] 

[92.  Portion  of  one  of  the  Cceca  more  highly  magnified,  after  Kolliker,    .        .  313] 

[93.  Mucous  Gastric  Gland,  alter  Kolliker, 313] 

[94.  Hepatic  Column,  after  Leidy, 324] 

[95.  Cross-section  of  a  Lobule  of  Human  Liver,  after  Sappey,      ....  325] 

[96.  Longitudinal  Section  of  a  small  Portal  Vein  and  Canal,  after  Kiernau,    .  326] 

[97.  Longitudinal  Section  of  a  large  Hepatic  Vein,  after  Kiernan,     .        .        .  327] 

[98.  Injected  Biliary  Capillaries:,  after  Irmiuger  and  Frey, 328] 

[99.  Diagram  to  show  Bile-passages,  after  Hering, 328] 

[100.  Ty  rosin,  after  Frey, 336] 

[101.  Brunner's  Gland,  after  Thompson, 341] 

[102.  Glands  of  Lieberkuhn,  after  Kirke, 341] 

[103.  Agminate  Follicles,  after  Boehm, 342] 

[104.  Side  View  of  the  Intestinal  Mucous  Membrane,  after  Bendz,      .        .        .  342] 

[105.  Solitary  Gland  of  Small  Intestine,  after  Boehm, 342] 

[106.  Villi  of  Intestine,  after  Teichmann, 343] 

107.  Diagrammatic  Representation  of  the  Submaxillary  Gland  of  the  Dog,      .  348 


XX  LIST    OF    ILLUSTRATIONS. 


lOS.  Diagram  ilhistratinK  the  Influence  of  Food  on  the  Secrotiou  of  Pancreatic 

Juice,  after  Bernstein, 'M) 

109.  Pancreas  of  tlie  Rabbit  in  States  of  Rest  and  Activity,  after  Kuhue  and  Lea,  ;3()3 

110.  Mucous  Cihind  in  States  of  Rest  and  Activity,  after  Ladowsky,    .        .        .  368 

111.  Serous  (iland  in  States  of  Rest,  and  after  Stimulation  of  the  Cervical  Sym- 

pathetic, after  Ileidenliain,     370 

[112.  Diagram  of  tlie  Portal  System  or  Circulation,  after  Marshall,      .        .        .  40«] 

[113.  Transverse  Section  of  a  Bronchial  Tube  of  a  Pig,  after  Schultze,        .        .  417] 

[114.  System  of  Alveolar  Passages  and  lufundibuhi,  alter  Waters,       .        .        .  41HJ 

[115.  Pulmonary  Lobules,  after  Kolliker, 41Hj 

[116.  Capillary  Network  of  Bloodvessels  of  Human  Lung,  after  Carpenter,        .  41i»l 

117.  Tracing  of  Thoracic  Respiratory  Movements 423 

118.  Apparatus  for  Taking  the  Movements  of  the  Columns  of  Air  in  Respi- 

ration   424 

[119.  Apparatus  to  show   the  Mechanism  of  the  Diaphragm  in  Respiration, 

after  Eberth, 428J 

[120.  Rib  Articulated,  showing  its  Axis  of  Rotation,  from  Kirke,        .        .        •  429] 
[121.  Diagrams  showing  the  Mechanism  of  the  Internal  and  External  Inter- 
costal Muscles  in  Respiration,  after  Huxley,       431] 

122.  Diagrammatic  Illustration  of  Ludwig's  Mercurial  Gas  Pump,      .        .        .  440 

123.  Spectra  of  Haemoglobin  and  some  of  its  Derivatives, 444 

[124.  Haemoglobin  Crystals  from  the  Blood  of  the  Pig,  after  Kirke,     .        .        .  446] 

[12.5.  Hiemoglobin  Crystals  from  the  Blood  of  the  Squirrel,  after  Funke,    .        .  446] 

[126.  Haemoglobin  Crystals  from  the  Blood  of  Man,  alter  Kirke,  .        .        .        .  447] 

127.  Comparison  of  Blood-pressure  Curve  with  Intrathoracic  Pressure,    .        .  483 

128.  Traube's  Curves, 486 

[129.  Vertical  Section  of  Skin,  magnified,  after  Sharpey, oOl] 

[130.  Simple  Papillae  of  Skin,  after  Breschet, 502] 

[131.  Compound  Papillae  from  Palm  of  Hand,  after  Kolliker,       ....  502] 
[132.  Portion   of  Skin  from  Palmar  Surface  of  the  End   of  the   Thumb,  after 

Marshall, 503] 

[133.  End  bulbs  of  Krause,  after  Kolliker, 503] 

[1.34.  Tactile  Coipuscles,  after  Kolliker, 504] 

[135,  Pacinian  Corpuscles,  after  Todd  and  Bowman, 505] 

[136.  Transverse  Section  of  the  Nail  and  Matrix,  after  Marshall,         .        .        .  506] 

[137.  Hair  in  its  Follicle,  after  Kolliker, 507] 

[1.38.  Root  of  the  Hair,  after  Kohlrausch 507] 

[139.  Sudoriparous  Gland,  after  Wagner, 509] 

[140.  Vertical  Section  through  the  Kidney,  after  Henle, 519] 

[141.  Diagram  of  the  Course  of  the  Renal  Tubules,  after  Hertz,  .        .        .        .  520] 

[142.  Transverse  Section  of  a  Renal  Papilhe,  after  K()lliker,         ....  521] 

[143.  Plan  of  the  Renal  Circulation  in  Mammals,  from  Kirke,      ....  522] 

[144.  Semi-diagrammatic  Representation  of  a  Malpighian  Body, from  Kolliker,  522] 

[145.  Urinary  Sediment  of  Trii)le  Phosphates,  from  Kirke, 524] 

[146.  Diagram  showing  the  Points  of  Puncture  of  the  Floor  of  the  Fourth  Ven- 
tricle to  produce  Glycosuria,  Polyuria,  and  Albuminuria,        .        .        .  5.52] 

[147.  Lobule  of  the  Mammary  Gland,  after  Cooper, 561] 

[148.  Distribution  of  the  Milk-ducts  in  tbe  Human  Female,  after  Cooper,         .  562] 
[149.  Microscopic  Appearance  of  Human  Milk,  after  Cooper,        ....  564] 
[150.  Branch  of  Splenic  Artery  and  its  Ramifications  with  Malpighian  Corpus- 
cles, after  Kolliker,   566] 

[151.  Malpighian  t  orpuscles,  after  Mulier, 567] 


LIST    OF    ILLUSTRATIONS.  XXI 


PAGE 

[152   Cerebro-spinal  Axis,  showing  Origin  of  Cranial  and  Spinal  Nerres,  after 

Marshall, 626] 

[153.  Various  Forms  of  Ganglionic  Vesicles,  after  Kirke, 628] 

[154.  Structure  of  Pyrifonu  Nerve-cells,  after  Beale  and  Arnold,         .        ,        .  629] 

[155.  Stellate  Nerve-cell,  after  Beale 629] 

[156.  Funiculus  of  Nerve,  after  Ranvier, 630] 

[157.  Nerve-fibre  from  Sciatic  Nerve,  after  Ranvier, 630] 

[158.  Nerve-tubules  showing  Effects  of  Post-mortem  Changes,  after  Wagner,  631] 

[159.  Diagram  of  Structure  of  Nerve-fibre,  after  Carpenter,         ....  631] 

[160.  Piimitive  Nerve-fibrils,  after  Schultze, 632] 

[161.  Diagram  of  a  Horizontal  Section  of  the  Eyeball,  after  Ellis,       .        .        .  645] 

[162.  Vertical  Section  of  Cornea,  alter  Ellis, 646] 

[163.  Inner  View  of  the  Front  of  the  Choroid  Coat,  the  Ciliary  Processes,  and 

the  Back  of  the  Iris,  after  Ellis, 647] 

[164.  Section  of  the  Ciliary  Region  of  the  Eye  of  Man,  after  Iwauoff,        .        .  648] 

[165.  Muscular  Structure  of  the  Iris,  after  KoUiker, 647] 

[166.  Pigment-cells  of  the  Eyeball,  after  Kolliker, 650] 

[167.  Diagrammatic  Representation  of  the  Connection  of  the  Nerve-fibres  of 

the  Retina,  after  Schultze, 651] 

[168.  Rod  and  Cone  from  the  Retina  of  Man,  after  schultze 651] 

[169.  Diagrammatic  Representation  of  the  Connective  Tissue  of  the  Retina, 

after  Schultze,    .........        ^        •.        ■  651] 

[170.  Inner  Surface  of  the  Retina,  showing  Macula  Lutea,  Entrance  of  Optic 

Nerve,  and  Arteria  Centralis  Retina,  after  Soemmering,    .        .        .        .  653] 

[171.  Magnified  Vertical  Seciion  of  Retina,  after  Ellis, 653] 

[172.  Representation  of  the  Laminge  of  a  Hardened  Lens,  after  Ellis,         .        .  654] 

173.  Diagram  of  Scheiner's  Experiment, 660 

[174.  Diagram  showing  the  Course  of  Parallel  Rays  in  the  Myopic  Eye,  after 

Carpenter, 661] 

[175.  Diagram  showing  the  Course  of  Parallel  Rays  in  the  Hypermetropic 

Eye,  after  Carpenter, 662] 

[176.  Diagram  showing  the  Course  of  Parallel  Rays  in  the  Emmetropic  Eye, 

after  Carpenter, 662] 

[177.  Diagram  showing  how  the  Accommodation  of  the  Lens  is  affected  for  Di- 
verging Rays  of  Near  Objects,  after  Carpenter,  ......  664] 

178.  Diagram  illustrating  Chromatic  Aberration, 675 

[179.  Diagram  of  Method  for  Finding  the  Situation  of  the  Blind  Spot,      .        .  678] 

180.  Diagram  illustrating  the  Formation  of  Purkinje's  Figures  when  the  Illu- 

mination is  directed  through  the  Sclerotic, 680 

181.  Diagram  illustrating  the  Formation  of  Purkiuje's  Figures  when  the  Illu- 

mination is  directed  through  the  Cornea,     680 

182.  Diagram  of  the  Three  Primary  Color  Sensations 698 

183.  Diagram  illustrating  the  Appreciation  of  Apparent  Size,    ....  708 

184.  Diagram  illustrating  Corresponding  Points  in  the  Retina,   .        .        .        .710 

185.  Diagram  of  the  Attachment  of  the  Muscles  of  the  Eye,  after  Frick,         .  714 

186.  Diagram  illustrating  a  Simple  Horopter, 718 

187.  Diagram  illustrating  Monocular  and  Binocular  Perception  of  an  Object,  .  721 
[188.  Vertical  Section  of  the  Meatus  Auditorius   Externus  and  Tympanum, 

after  Scarpa, 726] 

[189.  Inner  View  of  Membrana  Tympani  and  Tympanic  Bone,  after  Ellis,  .  728] 
[190.  Plan  of  Ossicles  in  Position  in  the  Tympanum,  with  their  Muscles,  from 

Ellis, 728] 


XXU  LIST    OF    ILLUSTRATIONS. 


PAOK 

f  191.  Interior  of  Osseous  Labyrinth,  after  Siemmerin?:, 729] 

[192.  Osseous  Labyrinth,  natural  size,  after  S(£mmerins 729] 

[193.  Representation  of  the  Seniitireuiar  Canals,  enlarged,  from  Ellis,        .        .  730] 

[194.  Seetion  tbroiij,'b  the  Cochlea,  after  Breschet, 731] 

[19").  Diasram  of  a  Section  of  the  Tube  of  the  Cochlea,  from  Ellis,  modified 

from  HenlH, 7.32] 

[196.  Petrous  Bone  partly  removed  to  show  Membranous  Labyrinth  in  place, 

after  Breschet, 733] 

[197.  Distribuiion  of  Nerves  to  the  Meml)rnnous  Lal)yriiith,  after  Breschet,     .  734] 
[198.  Diagram  of  the  Mode  of  Termination  o"  the  Auditory  Nerve  in  Ampnihe 

and  Sacculi,  after  RiidinRcr 7:!')] 

[199.  Vertical  section  of  Ri;,'bt  Nasal  Fos-a,  after  Arnold, 748] 

[200.  Cells  of  the  Olfactory  Mucous  Membrane,  after  Schultze  and  Clark,  .        .  748] 

[201.  Vertical  Section  of  the  Circumvailate  Papillse,  from  Kolliker,    .         .        .  752] 
[202.  Surface  and  Section  of  Fungiform  PapiiUe,from  Kolliker,  after  Todd  and 

Bowman, 953] 

[203.  Vertical  Section  of  Filiform   Papilke,  also  showing   Hairs  of  Tongue, 

after  Todd  and  Bowman, 754] 

[204.  Gustatory  Bulbs  from  the   Lateral  Gustatory  Organ  of  the   Rabbit,  after 

Engelmann, 755] 

[205.  Transverse  Section  of  the  Spinal  Cord,  after  Clarke,    .        .        .        •        .  770] 

[200.  Median  Portion  of  a  Transv.rse  Section  of  the  Spinal  Cord,  after  Gerlach,  772] 

207.  Diagram  showing  the  Relative  Sectional  Areas  of   the  Spinal   Nerves, 

as  they  join  the  Spinal  Cord, 788 

208.  Diagraiu  showing  the  United  Sectional  Areas  of  the  Spinal  Nerves,  pro- 

ceeding from  below  upwards, 788 

209.  Diagram  showing  the  Variations  in  the  Sectional  Area  of  the  Gray  Mat- 

ter of  the  Spinal  Cord,      788 

210.  Diagram  showing  the  Variations  in   the  Sectional  Area  of  the  Lateral 

Columns 75=9 

211.  Diagram  showing  the  Variations  in  the  Sectional  Area  of  the  Anterior 

Columns, 789 

212.  Diagram  showing  the  Variations  in  the  Sectional  Area  of  the  Posterior 

Columns, 789 

[213.  Diagram  showing  the  Course  of  Motor  and  Sensory  Fibres  in  the  Spinal 

Cord  and  Medulla  Oblongata,  after  Brown-Sequard, 791] 

[214.  View  of  the  Anterior  Surface  of  the  Pons  Varolii  and  Medulla  Oblongata, 

from  Kirke, 799] 

[215.  View  of  the  Posterior  Surface  of  the  Pons  Varolii  and  Medulla  Oblongata, 

from  Kirke, 799] 

[216.  Under  Surface  of  Base  of  the  Encephalon  freed  from  its   Membranes, 

from  Kirke 800] 

[217.  Dissection  of  Brain,  from  above,  exposing  the  Third,  Fuurth,  and  Fifth 

Ventricles,  after  Hirsehfeld  and  Leveille, 803] 

[218.  View  of  the  Cerebellum  in  Section,  and  of  Fourth  Ventricle,  with  Neigh- 
boring Parts,  from  Sappey,  after  Hirsehfeld  and  Leveille,  .       .        .        .    803] 

[219.  Brain  of  Man 807] 

[220.  Diagram  of  the  Distribution  of  the  Fibres  in  the  Brain,  after  Meynert,    .    809] 

221.  The  Areas  of  the  Cerebral  Convolutions  of  the  Dog,  according  to  Hilzig 

and  Fritsch, 829 

222.  The  Areas  of  the  Cerebral  Convolutions  of  the  Dog,  according  to  Fcrricr,    830 


LIST    OF    ILLUSTRATIONS.  XXlll 


PAGE 

223.  Side  and  Upper  Views  of  the  Brain  of  Man,  with  the  Areas  of  the  Cere- 

bral Convolutions,  according  to  Ferrier, 831 

224.  Side  and  Upper  Views  of  the  Brain  of  ^[an,  with  the  Areas  of  the  Cere- 

bral Convolutions,  according  to  Ferrier, 832 

[225.  Course  of  Fibres  in  the  Optic  Commissure,  after  Bowman,  .        .        .        .  861] 

[226.  The  Nerves  of  the  Orbit  seen  from  the  Outer  Side,  after  Arnold,        .        .  8G2J 

[227.  General  Plan  of  the  Branches  of  the  Fifth  Pair,  after  Charles  B.^11, .        .  86o] 

[228.  The  Distribution  of  the  Facial  Nerve,  after  Erasmus  Wilson,      .        .        .  867] 
[229.  The  Distribution  of  the  Pneumogastric  Nerve,  after  Hirschftld  and  Le- 

veille 870] 

[230.  Median  Section  of  the  Mouth,  Nose,  Pharynx,  and  Larynx,  after  Quain,  874] 

[231.  View  of  the  Larynx  and  part  of  the  Trachea  behind,  after  Quain,     .        .  87G] 

[232.  View  of  the  Larynx  from  above,  after  Quain, 876] 

[233.  View  of  Upper  Part  of  the  Larynx,  as  seen  by  means  of  tiie  Laryngo- 
scope, during  the  Utterance  of  a  Grave  Note,  after  Quain,       .        .        .  876] 
234.  The  Larynx  as  seen  by  means  of  the  Laryngoscope  in  Different  Condi- 
tions of  the  Glottis,  from  Quain,  after  Czermak, 878 

[235.  Illustration  of  Third  Kind  of  Lever,  after  Kirke, 889] 

[236.  Diagram   illustrating   Movements  of  Legs  and  Feet  in  Walking,  after 

Kirke,  ....  - 890] 

[237.  Diagrammatic  View  of  the  Uterus  and  its  Appendages,  after  Quain,          .  895] 

[238.  Section  of  the  Liuins:  Membrane  of  Uterus,  after  Weber,    ....  896] 

[239.  View  of  a  Section  of  a  Prepared  Ovary  of  a  Cat,  after  Sehron,    .        .        .  897] 
[240.  The  Base  of  the  Male  Bladder,  with  VesiculieSeminales  and  Prostate  Gland, 

after  Ilaller, 898] 

[241.  View  of  a  Section  of  the  Testicle  and  Epididymis,  after  Kirke,          .        .  898] 

[242.  Spermatozoa  and  Spermatic  Ceils,  after  Kolliker, 900] 

[243.  Section  of  a  Graafian  Follicle,  after  Vcn  Baer 901] 

[244.  Ovum  of  a  Sow,  after  Barry, 901] 

[245.  Successive  Stages  of  the  Formation  of  the  Corpus  Luteum,  after  Pouchet,  903] 
[246.  Diagram  of  the  Various  Stages  of  the  Cleavage  of  the  Yolk,  after  Dalton,  907] 
[247.  Impregnated  Egg,  with  the  Commencement  of  the  Formation  of  the  Em- 
bryo, after  Dalton 908] 

[248.  Diagrammatic  Section  of  Ovum,  at  Fifteenth  or  Seventeenth  Day,     .        .  909] 
[249.  Diagrammatic  Section  of  Ovum,  with  Chorion  and  Villi,  after  Todd  and 

Bowman, 910] 

[250.  Diagrammatic  Section  of  Ovum,  with  Chorion  and  Villi,  after  Todd  and 

Bowman, 910] 

[251.  Diagram  of  Fecundated  Egg,  after  Dalton, 911] 

[252.  Diagramof  Fecundated  Egg,  with  Aliantois  nearly  complete,  after  Dalton,  911] 

[253.  Human  Ovum,  at  eighth  week, showing  Tufts  of  the  Chorion,  after  Ecker,  912] 

[254.  Portion  of  one  of  the  Foetal  Villi,  after  Ecker, 912] 

[255.  First  Stage  of  the  Formation  of  the  Decidua  Refiexa,  after  Coste,      .        .  913] 

[256.  More  Advanced  Stagp  of  the  Decidua  Reflexa,  after  Coste,  ....  913] 

[257.  Section  of  a  Fully  Formed  Placenta,  after  Ecker, 914] 

[258.  Diagram  of  the  Foetal  Circulation,  after  Erasmus  Wilson,   ....  921] 

[259.  Cbolesterii.,  after  Dalton 988] 


ERRATA. 

P.  173,  for  Figs.  41  and  42,  read  descriptions  under  Figs.  43 

and  44,  and  vice  versa. 
P.  301,  1.  23,  for  "  physical"  read  "  mechanical  or  physical." 
P.  314,  1.  19,  read  ''  spheroidal  or  ovoidal." 
P.  627,  1.  18,  for  "  the  "  read  "  each." 
PP.  941,  942,  for  ''ovum"  read  "ovule." 


A  TEXT  BOOK  OF  PHYSIOLOGY. 


INTRODUCTORY. 

Among  the  simpler  organisms  known  to  Biologists,  per- 
haps the  most  simple  as  well  as  the  most  comm.on  is  that 
which  has  received  the  name  of  Amoeba.  There  are  many 
varieties  of  Amcrba,  and  probably  many  of  tlie  forms  which 
have  been  described  are,  in  reality,  merely  amoebiform 
phases  in  the  lives  of  certain  animals  or  plants  ;  but  they  all 
possess  the  same  general  characters.  Closely  resembling 
the  white  corpuscles  of  vertebrate  blood,  they  are  wholly  or 
almost    wholly   composed    of    undifferentiated    protoplasm 


[Fig 


Amoeba  princpps,  shown  in  difiFerent  forms  (a,  b,  c)  assumed  liy  the  same  animal  ] 


in  the  midst  of  which  lies  a  nucleus,  though  this  is  sometimes 
absent.  (Fig.  1.)  In  many  a  distinction  ma}'  be  observed  be- 
tween a  more  solid  external  la3er  or  ectosarc^  and  a  more  fluid 


14  INTRODUCTORY. 

granular  interior  or  <'/?c/osrt?7',-  but  in  others  even  tliis  primary 
difforentiation  is  wanting.  IJy  means  of  a  continually  occur- 
ring tlux  of  its  [)r()to|)lasmic  substance,  tl>e  auKeiia  is  enal)led 
from  moment  to  moment  not  only  to  change  its  form  but  also 
to  shift  its  position.  By  flowing  round  the  substances  which 
it  meets,  it,  in  a  way, swallows  them  ;  and  having  digested  and 
absorbed  such  i)arts  as  are  suitable  for  food,  ejects  or  rather 
flows  away  from  the  useless  remnants.'  It  thus  lives,  moves, 
eats,  grows,  and  after  a  time  dies,  having  been  during  its 
whole  life  hardly  anything  more  than  a  minute  himp  of  pro- 
toplasm. Hence  to  the  Physiologist  it  is  of  the  greatest 
interest,  since  in  its  life  the  [)roblems  of  physiology-  are  re- 
duced to  their  simi)lest  forms. 

Now  the  stud}'  of  an  ama?ba,  with  the  help  of  knowledge 
gained  by  the  examination  of  more  complex  l)odies,  enables 
us  to  state  that  the  undifferentiated  protoplasm  of  which  its 
body  is  so  largely  composed  possesses  certain  fundamental 
vital  properties. 

1.  It  is  contractile.  There  can  be  little  doubt  that  the 
changes  in  the  protoplasm  of  an  amoeba  which  bring  about 
its  peculiar  "  am(jeb()id  "  movements,  are  identical  in  their 
fundamental  nature  with  those  which  occurring  in  a  muscle 
cause  a  contraction  :  a  muscular  contraction  is  essentially  a 
regular,  an  amojboid  movement  an  irregular  flow  of  proto- 
plasm. The  substance  of  the  amoeba  may  therefore  be  said 
to  be  contractile. 

2.  It  is  irritable  and  automatic.  When  any  disturbance, 
such  as  contact  with  a  foreign  body,  is  brought  to  bear  on 
the  amoeba  at  rest,  movements  result.  These  are  not  passive 
movements,  the  etfects  of  the  push  or  pull  of  the  disturb- 
ing body  proportionate  to  the  force  employed  to  cause  them, 
but  active  manifestations  of  the  contractility  of  the  proto- 
plasm ;  that  is  to  sa}',  the  disturbing  cause,  or  "stimulus," 
sets  free  a  certain  amount  of  energy  previously  latent  in  the 
protoplasm,  and  the  energy  set  free  takes  on  the  form  of 
movement.  Any  living  matter  which,  when  acted  on  by  a 
stimulus,  thus  suffers  an  explosion  of  energy,  is  said  to  be 
^'  irritable."  The  irritability  may,  as  in  the  anKpba,  lead  to 
movement ;  but  in  some  cases  no  movement  follows  the  ap- 
plication of  the  stimulus  to  irritable  matter,  the  energy  set 

'  Huxley  and  Martin,  Elementary  Biology,  lesson  iii. 


PROPERTIES    OF    PROTOPL  ASxM .  !5 

free  bj'  the  explosion  taking  on  some  other  form  tlian  move- 
ment, ex  gr..  heat.  Thus  a  substance  may  be  irritable  and 
yet  not  contractile,  though  contractility  is  a  very  common 
manifestation  of  irritability. 

The  amoeba  (except  in  its  prolonged  quiescent  stage)  is 
rarely  at  rest.  It  is  almost  continually  in  motion.  The 
movements  cannot  always  be  referred  to  changes  in  sur- 
rounding circumstances  acting  as  stimuli ;  in  many  cases 
the  energy  is  set  free  in  consequence  of  internal  changes, 
and  the  movements  which  result  are  called  spontaneous  or 
automatic'  movements.  We  may  therefore  speak  of  the 
protoplasm  of  the  amoeba  as  being  irritable  and  automatic. 

3.  It  is  receptive  and  assimilative.  Certain  sul)stances 
serving  as  food  are  received  into  the  body  of  the  amosba, 
and  there  in  large  measure  dissolved.  The  dissolved  por- 
tions are  subsequently  converted  from  dead  food  into  new 
living  protoplasm,  and  become  part  and  parcel  of  the  sal> 
stance  of  the  amoeba. 

4.  It  is  metabolic-  and  secretory.  Foti  pa^m  with  the 
reception  of  new  material,  there  is  going  on  an  ejection  of 
old  material,  for  the  increase  of  the  amai!)a  by  the  addition 
of  food  is  not  indefinite.  In  other  words,  the  protoplasm 
is  continually  undergoing  chemical  change  (metaboiism), 
room  being  made  for  the  new  protoplasm  by  the  breaking- 
up  of  the  old  protoplasm  into  products  which  are  cast  out 
of  the  body  and  got  rid  of.  These  products  of  metabolic  ac- 
tion have,  in  man}'  cases  at  all  events,  subsidiary  uses.  Some 
of  them,  for  instance,  we  have  reason  to  think,  are  of  value 
for  the  purpose  of  dissolviug  and  effecting  other  preliminary 
changes  in  the  raw  food  introduced  into  the  body  of  the 
amoel)a;  and  hence  are  retained  within  the  body  for  some 
liltle  time.  Such  products  are  generally  spoken  of  as  ''se- 
cretions."    Others  which  pass  Qiore  rapidl}'  away  are  gen- 


'  This  word  has  recently  aa|uii"ed  a  meaning  almost  exactly  opposite 
to  that  -R'hicli  it  originally  l3ore,  and  aii  autwmatie  action  is  now  by  many 
understood  to  mean  nothing  more  than  an  action  produced  by  some  ma- 
fliinery  or  other.  In  tills  work  I  use  it  in  the  older  sense,  as  denoting 
an  action  of  a  body,  the  causes  of  wliic)]  appear  to  lie  in  the  body  itself. 
It  seems  preferalde  to  "  spontaneous,'"  inasmuch  as  it  does  not  necessa- 
rily carry  with  it  tlie  idea  of  irregularity,  and  bears  no  reference  to  a 
"  will."  ■ 

*  This  term  was  introduced  by  Schwann  (1839).  Mircros,  Unter- 
such.,  p.  2:2*J. 


1()  INTRODUCTORY. 

orally  called    "excretions."     The   distinclioii    between   the 
two  is  an  unimportant  and  fre(iuenlly  accidental  one. 

Tiie  energy  expended  in  the  movements  of  the  amceha  is 
snpi)lied  by  the  chemical  chanucs  goini;  on  in  the  proto- 
plasm, by  the  breaking  np  of  bodies  possi'ssing  much  latent 
energy  into  bodies  possessing  less.  Thus  the  metabolic 
changes  wiiich  the  food  (as  distinguished  from  the  undi- 
gested stulf  mechanically  lodged  for  awiiile  in  the  body) 
undergoes  in  passing  through  the  protoplasm  of  the  amceiia 
are  of  three  classes:  those  prei)aratory  to  and  culminating 
in  the  conveision  of  tiie  food  into  protf)|)lasm,  tlujse  con- 
cerned in  the  discharge  of  energy,  and  those  tending  to 
economize  the  immediate  products  of  the  second  class  of 
changes  by  rendering  them  more  or  less  useful  in  carrying 
out  the  first. 

5.  It  is  respiratory.  Taken  as  a  whole,  the  metabolic 
changes  are  pre-ennnently  processes  of  oxidation.  One 
article  of  food,  i.  e.,one  substance  taken  into  the  body,  viz., 
oxygen,  stands  apart  from  all  the  rest,  and  one  product  of 
metabolism  peculiarly  associated  with  oxidation,  viz.,  car- 
bonic acid,  stands  also  somewhat  apart  from  all  the  rest. 
Hence  the  assumption  of  oxygen  and  the  excretion  of  car- 
bonic acid,  together  with  such  of  the  metabolic  processes  as 
are  more  especially  oxidative,  are  frequently  spoken  of  to- 
gether as  constituting  the  respirator}'  j)rocesses. 

6.  It  is  reproductive.  The  ijidividual  amo?ba  represents 
a  unit.  This  unit,  after  a  longer  or  shorter  life,  having  in- 
creased in  size  l»y  the  addition  of  new  i)r()to})lasm  in  excess 
of  that  which  it  is  continually  using  np,  may,  by  fission  (or 
by  other  means),  resolve  itself  into  two  (or  more)  parts, 
each  of  which  is  ca])able  of  living  as  a  fresh  unit  or  indi- 
vidual. 

Such  are  the  fundamental  vital  qualities  of  the  protoplasm 
of  an  amoeba;  all  the  facts  of  the  life  of  an  amneba  are  man- 
ifestations of  these  protoplasmic  qualities  in  varied  sequence 
and  sul)ordination. 

The  higher  animals,  we  learn  from  morphological  studies, 
may  be  regarded  as  groups  of  amoebaj  i)eculiarly  asso- 
ciated togetlier.  All  tlie  physiological  jjhenomena  of  the 
higher  animals  are  similarly  tlie  results  of  these  fundamental 
qualities  of  protoplasm  peculiarly  associated  together.  The 
dominant  princii)le  of  this  association  is  the  physiological 


THE    FUNDAMENTAL    TISSUES.  17 

division  of  labor  corresponding  to  tlie  morphological  differ- 
entiation of  structure.  Were  a  larger  or  "  higher"  animal 
to  consist  simply  of  a  colony  of  undifferentiated  amoeba?, 
one  animal  differing  from  another  merely  in  the  number  of 
units  making  up  the  mass  of  its  body,  witliont  any  differ- 
ences between  the  individual  units,  progress  of  function 
woidd  be  an  impossibility.  The  accumulation  of  units 
would  be  a  hindrance  to  welfare,  rather  than  a  help.  Hence, 
in  tlie  evolution  of  living  beings  througli  past  times,  it  has 
come  about  that  in  the  higher  animals  (and  plants)  certain 
groups  of  the  constituent  amoebiform  units  or  cells  have,  in 
company  with  a  cliange  in  structure,  been  set  apart  for  the 
manifestation  of  certain  only  of  the  fundamental  properties 
of  protoplasm,  to  the  exclusion  or  at  least  to  the  complete 
subordination  of  the  otlier  properties. 

These  groups  of  cells,  thus  distinguished  from  each  other 
at  once  by  the  differentiation  of  structure  and  by  the  more 
or  less  marked  exclusiveness  of  function,  receive  the  name 
of  "  tissues.''  Thus  the  units  of  one  class  are  characterized 
by  the  exaltation  of  the  contractility  of  their  prot(;plasm, 
their  automatism,  metabolism,  and  reproduction  being  kept 
in  marked  abeyance.  These  units  constitute  the  so-called 
muscular  tissue.  Of  another  tissue,  viz.,  the  nervous,  the 
marked  features  are  irritabilicy  and  automatism,  with  an 
almost  complete  al)sence  of  contractility  and  a  great  restric- 
tion of  the  other  qualities.  In  a  third  group  of  units,  the 
activity  of  the  protoplasm  is  largely  contined  to  the  chem- 
ical clianges  of  secretion,  contractility  and  automatism  (as 
manifested  by  movement)  being  either  absent  or  existing  to 
a  very  slight  degree.  Such  a  secreting  tissue,  consisting  of 
epithelium  cells,  forms  the  basis  of  the  mucous  membrane  of 
the  alimentar}'  canal.  In  the  kidney,  the  substances  se- 
creted by  the  cells,  being  of  no  further  use,  are  at  once 
ejected  from  the  body.  Hence  the  renal  tissue  may  be 
spoken  of  as  excretory.  In  the  epithelium  cellsof  the  lungs, 
the  protoplasm  plays  an  altogether  suboi'diriate  part  in  the 
assumption  of  oxygen  and  the  excietion  of  carbonic  acid. 
Still  we  may,  perhaps,  be  permitted  to  speak  of  the  pul- 
monary e[)ithelium  as  a  respiratory  tissue. 

In  addition  to  these  distinctly  secretory  or  excretory  tis- 
sues, there  exist  groups  of  cells  sijecially  reserved  for  the 
carrying  on  of  chemical  changes,  the  i)roducts  of  which  are 
neither  cast  out  of  the  body,  nor  collected  in  cavities  for 
digestive  or  other  uses.     The  work  of  these  cells  seems  to 


18  INTRODUCTORY. 

be  of  an  intermediate  character;  tiiey  are  engaged  eitlier  in 
elaborating  llie  material  of  food  that  it  may  l)e  the  more 
easily  assimilated,  or  in  preparing  used-up  material  for  final 
excretion.  They  receive  their  materials  fi'om  the  blood,  and 
return  their  products  back  to  the  blood.  They  ma}'  be 
called  the  metabolic  tissues  par  excellence.  Such  are  the 
fat-cells  of  adipose  tissue,  the  hepatic  cells  (as  far  as  the 
work  of  the  liver  other  than  the  secretion  of  bile  is  con- 
cerned), and  probably  many  other  cellular  elements  in  va- 
rious regions  of  the  body. 

p]ach  of  the  various  units  retains  to  a  greater  or  less  de- 
gree the  power  of  re})roducing  itself,  and  the  ti^-sues  gener- 
ally are  capable  of  regeneration  in  kind.  But  neither  units 
nor  tissues  can  reproduce  other  parts  of  the  organism  than 
themselves,  much  less  the  entire  organism.  For  the  repro- 
duction of  the  complex  individual,  certain  units  are  set  apart 
in  the  form  of  ovary  and  testis.  In  these  all  the  properties 
of  protoplasm  are  distinctly  subordinated  to  the  work  of 
growth. 

Lastly,  there  are  certain  groups  of  units,  certain  tissues, 
w  hich  are  of  use  to  the  body  of  which  they  form  a  part,  not 
by  reason  of  their  manifesting  any  of  the  fundamental  qual- 
ities of  protoplasm,  but  on  account  of  the  physical  and  me- 
chanical properties  of  certain  substances  which  their  proto- 
plasm has  been  able  by  virtue  of  its  metabolism  to  manu- 
facture and  to  deposit.  Such  tissues  are  bone,  cartilage, 
connective  tissue  in  large  part,  and  the  greater  portion  of 
the  skin. 

We  may,  therefore,  consider  the  complex  body  of  a  higher 
animal  as  a  compound  Qi'  so  many  tissues,  each  tissue  cor- 
responding to  one  of  the  fundamental  qualities  of  protoi)lasm, 
to  the  development  of  which  it  is  specially  devoted  by  the 
division  of  labor.  It  must,  however,  be  remembered  that 
there  is  a  distinct  limit  to  the  division  of  labor.  In  each 
and  every  ti^rsue,  in  addition  to  its  leading  quality,  there 
are  more  or  less  pronounced  remnants  of  all  the  other  pro- 
toplasmic qualities.  Thus,  though  we  may  call  one  tissue 
par  e-rcellence  metabolic,  all  the  tissues  are  to  a  greater  or 
less  extent  metabolic.  The  energy  of  each,  whatever  be  its 
particular  mode,  has  its  source  in  the  breaking-up  of  the 
protoplasm.  Chemical  changes,  including  the  assumption 
of  oxygen  and  the  production,  complete  or  partial,  of  car- 
bonic acid,  and,  therefore,  also  entailing  a  certain  amount 
of  secretion  and   excretion,  must   take   place  in   each   and 


INTEGRATION.  19 

every  tissue.  And  so  with  all  the  other  fundamental  prop- 
erties of  protoplasm  ;  even  contractility,  which  for  obvious 
mechanical  reasons  is  soonest  reduced  where  not  wanted,  is 
present  in  many  other  tissues  besides  muscle.  And  it  need 
hardly  be  said  that  each  tissue  retains  the  power  of  assimi- 
lation. However  thoroughly  the  material  of  food  be  pre- 
pared b}'  digestion  and  subsequent  metabolic  action,  the 
last  stages  of  its  conversion  into  living  protoplasm  are 
effected  directly  and  alone  by  the  tissue  of  which  it  is  al)Out 
to  form  a  part. 

Bearing  this  qualification  in  mind,  we  may  draw  up  a 
physiological  classification  of  the  body  into  the  following 
fundamental  tissues: 

1.  The  eminently  contractile  ;  the  muscles. 

2.  "  "  irritable  and  automatic  ;  the  nervous  system. 

3.  "  "  secretory  or  excretory  ;   digestive,  urinary, 

and  puhnonary,  etc.,  epithelium. 

4.  "  "  metabolic  :  fat-cells,  hepatic  cells,  lymphatic 

and  ductless  glands,  etc. 

5.  '•  "  reproductive ;  ovary,  testis. 

6.  The  inditferent  or  mechanical ;  cartilage,  bone,  etc. 

All  these  separate  tissues,  with  their  individual  characters, 
are,  however,  but  parts  of  one  body  ;  and  in  order  that  they 
may  be  true  members  working  harmoniously  for  the  good 
of  the  whole,  and  not  isolated  masses,  each  serving  its  own 
ends  only,  they  need  to  be  bound  together  by  co-ordinating 
bonds.  Some  means  of  communication  must  necessarily 
exist  between  them.  In  the  mol)ile  homogeneous  body  of 
the  amceba,  no  special  means  of  communication  are  required. 
Simple  dilfusion  is  sufficient  to  make  the  material  gained  by 
one  part  common  to  the  whole  mass,  and  the  native  proto- 
plasm is  ph3'siologically  continuous,  so  that  an  explosion 
set  up  at  any  one  point  may  be  immediately  propagated 
throughout  the  whole  irritable  substance.  In  the  higher 
animals  the  several  tissues  are  separated  by  distances  far 
too  great  for  the  slow  process  of  dilfusion  to  serve  as  a  suf- 
ficient means  of  communication,  and  their  primary  physio- 
logical continuity  is  broken  by  their  being  imbedded  in 
masses  of  formed  material,  the  product  of  the  indiflferent 
tissues,  wliich,  being  devoid  of  irritability,  present  an  effec- 
tual barrier  to  the  propagation  of  molecular  explosions.  It 
thus  becomes  necessary  that  in  the  increasing  complexity 


20  INTRODUCTORY. 

of  animal  forms,  the  process  of  differentiation  should  be  ac- 
companied hy  a  correspondintr  integration,  tliat  the  isolated 
tissues  should  be  made  a  whole  by  bonds  uniting  them  to- 
gether.    These  bonds,  moreover,  must  be  of  two  kinds. 

In  tiie  first  i)lace  tiiere  must  be  a  ready  and  rapid  distri- 
bution and  interciiange  of  material.  The  contractile  tissues 
must  be  abundantly  supplied  with  material  best  adapted  by 
previous  elaboration  for  direct  assimilation,  and  the  waste 
jjroducts  arising  from  their  activity  must  be  at  once  carried 
away  to  tlie  metabolic  or  excretory  tissues.  And  so  with 
all  the  other  tissues.  There  must  be  a  free  and  speedy 
intercourse  of  material  between  each  and  all.  Tiiis  is  at 
once  and  most  easily  effected  b}'  the  regular  circulation  of 
a  common  fluid,  the  blood,  into  which  all  the  elaborated  food 
is  discharged,  from  which  each  tissue  seeks  what  it  needs, 
and  to  which  eacii  returns  that  for  which  it  has  no  longer 
any  use.  Such  a  circulation  of  fluid,  being  in  large  measure 
a  mechanical  matter,  needs  a  machiner}^  and  calls  forth  an 
expenditure  of  energy.  The  machinery  is  supplied  by  a 
s[)eclal  construction  of  the  primary  tissues,  and  the  energy 
is  arranged  for  by  the  presence  among  these  of  contractile 
and  irritable  matter.  Thus  to  the  fundamental  tissues  there 
is  added,  in  the  higher  animals,  a  vascular  l)ond  in  tlie  shape 
of  a  mechanism  of  circulation. 

In  the  second  place,  no  less  important  tlian  the  inter- 
change of  material  is  the  interchange  of  energy.  In  the 
amoiba  the  irritable  surface  is  physiologically  continuous 
with  the  more  internal  protoplasm,  while  eacii  and  every 
part  of  tlie  body  has  automatic  powers.  In  the  higher  ani- 
mal, portions  onl}'  of  the  skin  remain  as  eminently  irrital)le 
or  sensitive  structures,  while  automatic  actions  are  chiefly 
confined  to  a  central  mass  of  irritable  nervous  matter.  Both 
forms  of  irritable  matter  are  separated  b^^  long  tracts  of  in- 
different material,  from  those  contractile  tissues  through 
which  they  chiefly  manifest  the  changes  going  on  in  them- 
selves. Hence  the  necessity  for  long  strands  of  eminently 
irritable  tissue  to  connect  the  skin  and  contractile  tissues  as 
well  with  each  other  as  witli  the  automatic  centres.  Similar 
strands  are  also  needed,  though,  perliaps,  less  urgently,  to 
connect  the  other  tissues  with  tiiese  and  with  each  other. 
To  the  vascular  bond  there  must  be  added  an  irritable  bond, 
along  the  strands  of  wliich  impulses,  set  up  by  clianges  in 
one  or  another  part,  may  travel  in  determinate  courses  for 
the  regulation   of  the  energy  of  distant  spots.     In  other 


CENTRAL    NERVOUS    MECHANISxM.  21 

words,  part  of  the  irritable  tissues  must  be  specially  ar- 
raniJ:ed  to  form  a  co-ordinating  nervous  system. 

Still  further  complications  have  yet  to  be  considered.  In 
the  life  of  a  minute  homogeneous  amoE3ba,  possessing  no  spe- 
cial form  or  structure,  there  is  little  scope  for  purely  me- 
chanical operations.  As  however  we  trace  out  tlie  gradual 
development  of  the  more  complex  animal  forms,  we  see 
coming  forvN-ara  into  greater  and  greater  prominence  the 
arrangement  of  the  tissues  in  definite  ways  to  secure  me- 
chanical ends.  Thus  the  entire  body  acquires  particular 
shapes,  and  parts  of  the  body  are  built  up  into  mechanisms, 
the  actions  of  which  are  to  the  advantage  of  the  individual. 
Into  the  composition  of  these  mechanisms  or  ''organs  "  the 
active  fundamental  tissues  as  well  as  the  i)assive  or  indif- 
ferent tissues  enter;  and  the  working  of  each  mechanism, 
the  function  of  each  organ,  is  dependent  partly  on  the  me- 
chanical conditions  offered  by  the  passive  elements,  partly 
on  the  activity  of  the  active  elements.  The  vascular  mech- 
anism, of  which  we  have  just  spoken,  is  such  a  mechanism. 
Similarly  the  urgent  necessity  for  the  access  of  oxygen  to 
all  parts  of  the  body,  has  given  rise  to  a  complicated  respi- 
ratory mechanism  ;  and  the  needs  of  copious  alimentation 
to  an  alimentary  or  digestive  mechanism. 

Further,  inasmuch  as  muscular  movement  is  one  of  the 
chief  ends,  or  the  most  important  means  to  the  chief  ends 
of  animal  life,  we  find  ti»e  animal  body  abounding  in  motor 
mechanisms,  in  which  the  prime  mover  is  muscular  contrac- 
tion, while  the  machinery  is  supplied  by  complicated  ar- 
rangements of  muscles  with  such  indifferent  tissues  as  bone, 
cartilage,  and  tendon.  In  fact,  the  greater  part  of  the 
animal  body  is  a  collection  of  muscular  machines,  some 
serving  for  locomotion,  otliers  for  special  manaMivres  of  par- 
ticular members  and  parts,  others  as  an  assistance  to  the 
senses,  and  yet  others  for  tiie  production  of  voice,  and,  in 
man,  of  speech. 

Lastly,  the  simple  automatism  of  the  ama^ba.  with  its 
simple  responses  to  external  stimuli,  is  replaced  in  the 
higher  animals  by  an  exceedingly  complex  volition  affected 
in  multitudinous  ways  by  influences  from  the  world  without, 
and  there  is  a  correspondingly  complex  central  nervous  sys- 
tem. And  here  we  meet  with  a  new  form  of  differentiation 
unknown  elsewhere.  While  the  contractility' of  the  amo^bal 
l)rotoplasm  differs  but  slightly  from  the  contractility  of  the 
vertebrate  striated  muscle,  there  is  an  enormous  difference 


22  INTRODUCTORY. 

between  the  simple  irritability  of  the  amrjeba  and  the  com- 
plex action  of  the  vertebrate  nervons  system.  Excepting 
the  nervous  or  irritable  tissues,  the  fundamental  tissues 
have  in  all  animals  the  same  properties,  being,  it  is  true, 
more  acute  and  perfect  in  one  than  in  another,  but  remain- 
ing fundamentally  the  same.  The  elementary  muscular 
fibre  of  a  mammal  is  a  mass  of  but  slightly  differentiated 
protoplasm,  forming  a  whole  physiologically  continuous, 
and  in  no  way  constituting  a  mechanism.  Each  fibre  is  a 
counterpart  of  all  others;  and  the  muscle  of  one  animal 
differs  from  that  of  another  in  such  particulars  only  as  are 
wholly  subordinate.  In  the  nervous  tissues  of  the  higher 
animals,  on  the  contrar}',  we  find  properties  unknown  to 
those  of  the  lowev  ones  ;  and  in  proportion  as  we  ascend 
the  scale  we  observe  an  increasing  differentiation  of  the 
nervous  system  into  unlike  parts.  Thus  we  have,  what  does 
not  exist  in  any  other  tissue,  a  mechanism  of  nervous  tissue 
itself,  a  central  nervous  mechanism  of  complex  structure  and 
complex  function,  the  complexity  of  which  is  due  not  pri- 
marily to  any  mechanical  arrangements  of  its  parts,  but  to 
the  further  differentiation  of  that  fundamental  qualit}^  of 
iiritability  and  automatism,  which  belongs  to  all  irritable 
tissues,  and  to  all  native  protoplasm. 

In  the  following  pages  I  propose  to  consider  the  facts  of 
physiology  very  much  according  to  the  views  which  have 
been  just  sketched  out.  The  fundamental  properties  of 
most  of  the  elementary  tissues  will  first  be  reviewed,  and 
then  the  various  special  mechanisms.  It  will  be  found  con- 
venient to  introduce  early  the  account  of  the  vascular  mech- 
anism, and  of  its  nervous  co-ordinating  mechanism,  while 
the  mechanisms  of  respiration  and  alimentation  will  be  best 
considered  in  connection  with  the  respiratory  and  secretory 
tissues.  Tiie  description  of  the  pur^y  motor  mechanisms 
will  be  brief;  and,  save  in  a  few  instances,  confined  to  a 
statement  of  general  principles.  The  special  functions  of 
the  central  nervous  system,  including  the  senses,  must  of 
necessity  be  considered  by  themselves.  The  tissues  and 
mechanism  of  reproduction  and  the  phenomena  of  the  decay 
and  death  of  the  organism  will  naturally'  form  the  subject  of 
the  closing  chapters. 


BOOK  I. 

BLOOD— THE  TISSUES  OF  MOVEMENT— THE 
VASCULAR  MECHANISM. 


CHAPTER    L 

BLOOD. 

Blood,  when  flowing-  in  a  noi-mal  condition  throngli  the 
bloodvessels,  consists  of  an  almost  colorless  fluid,  the  plasma, 
in  which  are  suspended  a  number  of  more  solid  bodies,  the 
red  and  white  cor[)uscles.  Were  we  anxious  to  give  a  formal 
completeness  to  the  classification  of  the  various  parts  of  the 
body  into  tissues,  we  might  speak  of  the  blood  as  a  tissue 
of  which  the  corpuscles  are  the  essential  cellular  elements, 
while  the  plasma  is  a  liquid  matrix.  We  might  compare  it 
to  a  cartilage,  the  firm  matrix  of  which  had  become  com- 
pletely liciueficd  so  that  the  cartilage  corpuscles  were  per- 
fectly free  to  move  about. 

In  regarding  blood  as  tissue,  however,  we  come  upon  the 
difficulty  that  it,  unlike  all  the  other  tissues,  possesses  no 
one  characteristic  property.  The  protoplasm  of  the  white 
corpuscles  is  native  undilferentiated  protoplasm,  in  no  re- 
spect fitted  for  any  special  dut}';  and  though,  as  we  shall 
see,  the  red  corpuscles  have  a  definite  respirator}-^  function, 
inasmuch  as  they  are  carriers  of  ox3'gen  from  the  lungs  to 
the  several  tissues,  still  this  respiratory  work  is  only  one  of 
the  verv  man}'  labors  of  the  blood.  It  will  be,  therefore, 
far  more  profitable,  indeed  necessary,  to  treat  of  the  blood, 
not  as  a  tissue  by  itself,  but  as  the  great  means  of  commu- 
nication of  material  between  the  tissues  properly  so  called. 


24  BLOOD. 

Its  real  nscfnlness  lies  not  so  mncli  in  any  one  property  of 
eitiier  its  corpuscles  or  its  plasma,  as  in  its  nature  fitting;  it 
to  serve  as  the  ijreat  medium  of  excluino;e  between  all  paits 
of  the  body.  The  receptive  tissues  pour  into  it  the  material 
which  they  have  received  from  without,  the  excr«.'tiniJ:  tissues 
withdraw  from  it  the  thiuirs  which  are  no  lonijerof  any  use, 
and  tlie  irrital>le,  tlie  contractile,  and  indeed  all  the  tissues, 
seek  in  it  the  substances  (includin<j:  oxy;^en)  whicli  tliey 
need  for  the  manifestation  of  eneriry  or  for  the  storino;  up 
of  dirterentiatcd  material,  and  return  to  it  the  waste  prod- 
ucts resulting. from  their  activitv.  All  over  the  body  every- 
where there  is  so  long  as  life  lasts  a  double  current,  here 
rapid,  there  slow,  of  material  from  the  l)lood  to  the  tissues, 
and  from  the  tissues  to  the  blood. 

It.  togetlier  with  lymph  (whether  in  the  lymph  canals  or 
in  the  interstices  of  the  tissues),  may.  as  Bernard  has  sug- 
gested, be  regarded  as  an  internal  medium  bearing  the  same 
relations  to  the  constituent  tissues  that  the  external  medium, 
the  world,  does  to  tiie  whole  individual.  Just  as  tiie  whole 
organism  lives  on  tlie  tilings  around  it,  its  air  and  its  food, 
so  the  several  tissues  live  on  the  complex  fluid  iiy  which 
they  are  all  bathed,  and  which  is  to  them  tiieir  immediate 
air  and  food. 

From  this  it  follows,  on  the  one  hand,  that  the  composi- 
tion and  characters  of  the  blood  must  be  forever  vai'yins^" 
in  different  parts  of  the  body  and  at  different  times;  and, 
on  the  other  hand,  that  the  united  action  of  all  tlie  tissues 
must  tend  to  establisii  and  maintain  an  average  uniform 
com|)osition  of  the  whole  mass  of  blood.  Tlie  special 
changes  which  blood  is  known  to  undergo  while  it  passes 
through  the  several  tissues  will  best  be  dealt  with  when  the 
individual  tissues  and  organs  come  under  our  considera- 
tion. At  present  it  will  be  sufficient  to  study  the  main  fea- 
tures, which  are  presented  by  blood,  brought  so  to  speak 
into  a  state  of  ecpiilibrium  by  the  common  action  of  all  the 
tissues. 

Of  all  these  main  features  of  blood,  the  most  striking  if 
not  the  most  important  is  the  property  it  possesses  of  clot- 
ting or  coagulating  when  shed. 

Section  1.  The  Coagulation  of  Blood. 

Blood,  when  shed  from  the  bloodvessels  of  a  living  body, 
is   perfectly  fluid.     In   a  short  time  it  becomes  viscid  ;  it 


COAGULATION    OF    BLOOD, 


25 


The  viscidit}'  in- 

[FiG.  2. 


Bow]  of  recently  Coapu- 
hited  Blood,  showing  the 
whole  mass  uniformly  solidi- 
lied.    After  Daltox.] 


[Fi'i.  3. 


flows  loss  readily  from  vessel  to  vessel 
creases  rapidly  until  the  whole  mass 
of  blood  under  observation  becomes  a 
complete  jelly.  The  vessel  into  which 
it  has  i)een  shed  can  at  tiiis  stage  be 
inverted  without  a  drop  of  the  l)lood 
being  spilt.  The  jelly  is  of  the  same 
bulk  as  the  previously  fluid  blood,  and 
if  forcil)ly  removed  presents  a  com- 
pletemouldof  the  interiorof  the  vessel. 
(Fig.  2.)  If  the  blood  in  this  jel'y  stage 
be  left  untouched  in  a  glass  vessel,  a 
few  drops  of  an  almost  colorless  fluid 
soon  make  their  appeai'ance  on  the 
surface  of  the  jelly.  Increasing  in 
number,  and  running  together,  the 
drops  after  awhile  form  a  superficial  layer  of  pale  straw- 
colored  fluid.  Later  on,  similar  layers  of  the  same  fluid  are 
seen  at  the  sides,  and  finally  at  the  bottom  of  the  jelly, 
which,  shrunk  to  a  smaller  size  and  of 
firmer  consistency,  now  foinis  a  clot 
or  cra.s.s'o??ie??/zn7?,  floating  in  a  perfect 
fluid  serum.  (Fig.  3.)  The  shrinking 
and  condensation  of  the  clot,  and  the 
corresponding  increase  of  the  serum 
continue  for  some  time.  The  upper 
surface  of  the  clot  is  generally  cup[)ed. 
A  portion  of  the  clot  examined  under 
the  microscope  is  seen  to  consist  of  a 
feltwork  of  fine  granular  fiiuils,  in 
the  meshes  of  which  are  entangled 
the  red  and  white  corpuscles  of  the 
blood.  In  the  serum  nothing  can  be 
seen  but  a  few  stray  corpuscles.  The 
fibrils  are  composed  of  a  sul)stance  called  fibrin.  (Fig.  4.) 
Hence  we  may  speak  of  the  clot  as  consisting  of  fibrin  and  cor- 
puscles ;  and  the  act  of  clotting  or  coagulation  is  obviously 
a  conversion  of  the  naturally  fluid  portion  of  the  blood  or 
plasma  into  fibrin  and  serum,  followed  by  separation  of  the 
serum  from  the  fibrin  and  cor{)uscles. 

In  man,,  blood  when  shed  becomes  viscid  in  about  two  or 
three  minutes,  and  enters  the  jelly  stage  in  about  five  or  ten 
minutes.  After  the  lapse  of  another  few  minutes  the  first 
drops  of  serum  are  seen,  and  coagulation  is  generally  com- 


Bowl  of  Coagulated  Blood 
after  twelve  hours,  showing 
the  clot  contracted  and  float- 
ing in  the  fluid  serum.  After 
Daltun.] 


26 


BLOOD. 


pletc  in  from  one  to  several  iioiii's.  The  times,  however,  will 
l)e  found  to  vary  according  to  the  condition  of  the  iiidi- 
vidiial,  the  temi)erature  of  the  air,  and  the  size  and  form  of 
the  vessel  into  which  the  blood  is  shed.  Among  animals  the 
rapidit}' of  coagulation  varies  exceedingly  in  ditlerent  species. 
The  hlood  of  the  horse  coagulates  with  remarkalile  slow- 
ness ;  so  slowly,  indeed,  that   many  of  tiie   red   corpuscles 


Coagulated  Fibrin,  showing  its  fibrillated  condition.    After  Daltox.] 

(these  being  specifically  heavier  than  the  plasma)  have  time 
to  sink  before  viscidity  sets  in.  In  consequence  there  ap- 
pears on  the  surface  of  the  blood  an  upper  layer  of  colorless 
l)lasma,  containing  in  its  deeper  portions  many  colorless 
corpuscles  (which  are  lighter  than  the  red).  This  layer  clots 
like  the  other  parts  of  the  blood,  forming  the  so-called 
"  buffy  coat."  A  similar  butfy  coat  is  sometimes  seen  in  the 
blood  of  man  in  inflammatory  conditions  of  the  body. 

This  buflfy  coat  makes  its  appearance  in  horse's  l»lood  even 
at  the  ordinary  temperature  of  the  air.  If  a  portion  of 
horse's  blood  be  surrounded  by  a  cooling  mixture  of  ice 
and  salt,  and  thus  kept  at  about  0^  C,  coagulation  may  be 
almost  indefinitely  postponed.  Under  these  circumstances 
a  more  complete  descent  of  the  corpuscles  takes  plac3,  and 
a  considerable  quantity  of  colorless  transparent  plasma  free 
from  blood-corpuscles  may  be  obtained.  A  portion  of  this 
plasma  removed  from  the  freezing  mixture  clots  exacth'  as 


COAGULATION    OF    BLOOD.  27 

does  the  entire  blood,  It  first  becomes  viscid  and  then 
forms  a  jelly,  which  subsequently  separates  into  a  colorless 
shrunken  clot  and  serum.  This  shows  that  the  corpuscles 
are  not  an  essential  part  of  the  clot. 

If  a  few  cubic  centimeters  of  tiie  same  plasma  be  diluted 
with  fifty  times  its  bulk  of  a  75  per  cent,  solution  of  sodium 
chloride^  coagulation  is  much  retarded,  and  the  various 
stages  may  be  more  easily  watched.  As  the  fluid  is  becom- 
ing viscid  fine  fibrils  of  fil)rin  will  be  seen  to  be  developed 
in  it,  especially  at  the  sides  of  the  containing  vessel.  As 
these  fibrils  multiply  in  number  the  fluid  becomes  more  and 
more  of  the  consistence  of  a  jelly,  and  at  the  same  time 
somewhat  opaque.  Stirred  or  pulled  about  with  a  needle, 
the  fibrils  shrink  up  into  a  small  opaque  stringy  mass;  and 
a  very  considerable  bulk  of  the  jolly  may,  by  agitation,  be 
resolved  into  a  minute  fragment  of  shrunken  fibrin  floating 
in  a  quantity  of  what  is  really  diluted  serum.  If  a  speci- 
men of  such  diluted  plasma  be  stirred  from  time  to  time,  as 
soon  as  coagulation  begins,  with  a  needle  or  glass  rod,  the 
fibrin  may  be  removed  piecemeal  as  it  forms,  and  the  jelly 
stage  may  be  altogether  done  away  with.  When  fresh  blood 
which  has  not  yet  had  time  to  coagulate  is  stirred  or  whip- 
ped with  a  bundle  of  rods  (or  anything  presenting  a  large 
amount  of  rough  surface),  no  jellylike  coagulation  takes 
place,  but  the  rods  become  covered  with  amass  of  shrunken 
fibrin.  Blood  tiius  whipped  until  fibrin  ceases  to  be  de- 
posited is  found  to  have  entirelj^  lost  its  power  of  coagula- 
tion. 

Putting  all  these  facts  together,  it  is  very  clear  that  the 
phenomena  of  the  coagulation  of  blood  are  caused  by  the 
appearance  in  the  plasma  of  fine  fibrils  of  fibrin.  As  long 
as  tliese  are  scanty  the  blood  is  simply  viscid.  When  they 
become  sufficiently  numerous  they  give  the  blood  the  firm- 
ness of  a  jell}'.  Soon  after  their  formation  they  begin  to 
shrink,  and  in  their  shrinking  inclose  in  their  meshes  the 
corpuscles,  but  squeeze  out  the  fluid  parts  of  the  blood. 
Hence  the  appearance  of  the  shrunken  colored  clot  and  the 
colorless  serum. 

Fibrin,  whether  obtained  by  wdiipping  freshly-shed  blood, 
or  by  washing  either  a  normal  clot,  or  a  clot  obtained  from 
colorless  plasma,  exhibits  the  same  general  characters.     It 

^  A  solution  of  sodium  chloride  of  this  strength  will  liereafter  be 
spoken  of  as  "  normal  .saline  solution." 


28  BLOOD. 


belongs  to  tliat  class  of  complex  unstable  nitrogenous  bodies 
called  prot('i(h,  which  form  a  large  portion  of  all  living 
bodies,  and  an  essential  |)nrt  of  all  protoi)lasm.^  It  gives 
the  ordinary  i)roteid  reactions.  It  is  insolul>le  in  water  nnd 
in  dilute  saline  solutions;  and  though  it  swells  up  in  dilute 
hydrochloric  acid,  it  is  not  thereby  appreciably  dissolved.^ 

]Minor  difterences  have  been  stated  to  exist  in  the  characters  of 
fibrin  o])tainc!d  in  various  Avays  and  from  various  sources, f;r  f/r., 
by  whipping,  or  by  Avashing  a  blood-clot  from  venous  or  from 
arterial  blood.  liut  these  ditfercnces  are  unimportant.  The 
characters  are  said  to  vary  also  in  difterent  animals. 

Coagulation  then  is  brought  about  by  the  introduction 
into  the  blood-i)lasma  of  a  substance,  fibrin,  which  previously 
did  not  exist  there  as  such.  Such  a  substance  must  have 
antecedents,  or  an  antecedent — what  are  they,  or  what  is  it  ? 

If  blood  be  received  direct  from  the  bloodvessels  into  one- 
third  its  bulk  of  a  saturated  solution  of  some  neutral  salt 
such  as  magnesium  sulphate,  and  the  two  gently  but  thor- 
oughly mixed,  coagulation,  especially  at  a  moderately  low 
temperature,  will  be  deferred  for  a  very  long  time.  If  the 
mixture  be  allowed  to  stand,  the  corpuscles  will  sink,  and  a 
colorless  plasma  will  be  obtained  similar  to  the  plasma  gained 
from  horse's  blood  by  cold,  except  that  it  contains  an  excess 
of  the  neutral  salt.  The  presence  of  the  neutral  salt  has 
acted  in  the  same  direction  as  cold;  it  has  prevented  the 
occurrence  of  coagulation.  It  has  not  destroyed  the  fibrin, 
for  if  some  of  the  plasma  be  diluted  with  ten  times  its  bulk 
(or  even  a  less  quantity)  of  water,  it  will  coagulate  speedily 
in  quite  a  normal  fashion,  with  the  production  of  quite 
norujai  fibrin. 

If  some  of  the  colorless  transparent  plasma,  obtained 
either  by  the  action  of  neutral  salts  from  any  blood,  or  by 
the  help  of  cold  from  horse's  blood,  be  treated  with  some 
solid  neutral  salt,  such  as  sodium  chloride,  to  saturation,  a 
white  flaky,  somewhat  stick}-  precipitate  will  make  its  ap- 
pearance. If  this  precipitate  be  removed  the  fluid  is  no 
longer  coagulable  (or  ver}'  slightly  so),  even  though  the 
neutral  salt  present  be  removed  by  dialysis,  or  its  influence 
lessened  by  dilution.  With  the  removal  of  the  substance 
precipitated,  the  plasma  has  lost  its  power  of  coagulating. 

^  See  Appendix.  ^  Yov  further  details  see  Appendix. 


COAGULATION    OF    BLOOD.  29 

If  the  precipitate  itself,  after  being  washed  with  a  satu- 
rated solution  of  the  neutral  salt  (in  which  it  is  insoluble) 
so  as  to  get  rid  of  all  serum  and  other  constituents  of  the 
plasma,  be  treated  with  a  small  quantity  of  water,  it  readily 
dissolves,^  and  the  solution  rapidh*  filtered  gives  a  clear 
colorless  filtrate,  w^hich  is  at  first  perfectly  fluid.  Soon,  how- 
ever, the  fluidity  gives  way  to  viscidity,  and  this  in  turn  to 
a  jelly  condition,  and  finally  the  jelly  shrinks  into  a  clot  float- 
ing in  a  clear  fluid  ;  in  other  words,  the  filtrate  clots  like 
plasma.  Thus  there  is  present  in  cooled  plasma,  and  in 
plasma  kept  from  clotting  by  the  presence  of  neutral  salts, 
a  something,  precipital)le  by  saturation  with  neutral  salts, 
a  something  which,  since  it  is  solidile  in  very  dilute  saline 
solutions,  cannot  be  fibrin  itself,  but  which  in  solution 
speedily  gives  rise  to  the  ai)pearance  of  fibrin.  To  this  sub- 
stance its  discoverer,  Denis,-  gave  the  name  of  jylaHinine. 
We  are  justified  in  saying  that  the  coagulation  of  blood  is 
the  result  of  the  conversion  of  plasmine  into  fibrin. 

The  question  now  arises.  What  is  the  exact  nature  of 
plp.smine?  Is  it,  for  instance,  a  mixture  of  two  or  more 
substances  which  by  their  interaction  produce  fibrin  ?  This 
view  is  suggested  by  the  fact  that  plasmine  cannot  be  kept 
ill  solution  for  any  length  of  time  without  changing  into 
fibrin,  except  when  submitted  to  certain  influences,  such  as 
cold.     It  is  moreover  supported  by  tiie  following  facts : 

The  disease  known  as  hydrocele  is  characterized  by  the 
presence  in  the  tunica  vaginalis  (or  serous  sac  of  the  testis) 
of  an  abnormal  and  often  very  considerable  quantity  of  a 
clear,  colorless,  or  faintly  yellow  fluid,  very  similar  in  appear- 
ance to  the  serum  of  clotted  blood.  This  secretion,  when 
drawn  from  the  living  bod}'  without  admixture  of  blood, 
will  in  the  great  majority  of  cases  remain  perfectly  fluid,  and 
enter  into  decomposition  without  having  shown  any  tendency 
whatever  to  clot.  In  a  few  exceptional  cases  a  coagulation, 
generally  slight,  but  quite  similar  to  that  of  colorless  blood- 
plasma,  may  be  observed. 

If  a  small  quantity  of  hydrocele  fluid  which  has  been  ob- 
served not  to  clot  spontaneously  be  mixed  with  some  serum 
or  whipped  blood,  the  mixture  will  after  a  longer  or  shorter 

^  The  substance  itself  is  not  soluble  in  distilled  water,  but  a  quantity 
of  the  neutral  salts  always  clings  to  the  precipitate,  and  thus  the  addition 
of  water  virtually  gives  rise  to  a  dilute  saline  solution,  in  which  the  sub- 
stance is  readily  soluble. 

2  Ann.  d.  Sci'.  Nat.  (iv),  x,  p.  25. 

3 


30  BLOOD. 

time  clot  in  a  coniplclcly  normal  manner.  That  is  to  say, 
two  fluids  neither  of  wliieh  apart  clot  spontaneously,  will 
clot  spojitaneously  when  mixed  together.  (In  some  cases 
no  clot  is  formed  ;  specimens  of  hydrocele  fluid  are  occa- 
sionally met  with  in  which  coagulation  cannot  he  thus  i)ro- 
duced. ) 

If  serum  be  treated  to  saturation  with  solid  sodium  chlo- 
ride or  magnesium  sulphate,  a  flaky  precipitate,  ver}'  similar 
in  general  a|)pearance  to  plasmine,  will  make  its  ai)pearance. 
Like  plasmine,  this  i)recipitate  is  soluble  in  very  dilute 
neutral  saline  vsolutions,  and  in  consequence  as  thus  pre- 
pared readily  dissolves  when  treated  with  distilled  water, 
since  a  certain  amountof  sodium  cldoride  clings  to  it.  Un- 
like plasmine,  its  (iltered  solution  will  not  clot.  If,  however, 
some  of  the  solution  be  added  to  hydrocele  fluid,  a  clotting 
takes  plac^  just  as  when  serum  itself  is  added.  The  rest  of 
the  serum  from  which  this  substance  has  been  removed  will 
not,  after  the  removal  by  dial\sis  of  the  excess  of  salt,  cause 
clotting  in  hydrocele  fluid.  Evidently  it  is  the  presence  of 
this  constituent,  not  coagulable  of  itself,  which  gives  to  serum 
its  power  of  producing  a  coagulation  in  hydrocele  fluid. 
The  substance  in  question  may  also  be  prepared  by  diluting 
blood  serum  with  ten  or  twenty  times  its  bulk  of  water  and 
passing  a  brisk  stream  of  carbonic  acid  through  it.  The 
mixture  speedil}'  becomes  turbid,  and  if  left  to  stand  a 
copious  white  amorphous  somewhat  granular  precipitate 
settles  down.  The  substance  so  thrown  down  has  received 
the  name  of  pararjlobulin^  or  fibrinoplaM'tc  globulin,  or 
jibrinopladin.  It  may  also  be  thrown  down  b}'  very  cau- 
tiously adding  dilute  acetic  acid  to  dilute  serum.  It  is,  like 
fil)rin.a  proteid ;  but  it  differs  in  many  respects  from  fibrin. 
It  does  not  occur  in  the  form  of  fiin'ils.  and  though  insoluble 
in  distilled  water  is  very  readily  soluble  in  dilute  neutral 
saline  solutions.  There  are  many  proteids  very  closely 
allied  to  it ;  and  these  are  frequently  classed  together  as 
globulins} 

If,  on  the  other  hand,  hydrocele  fluid,  specimens  of  which 
have  been  observed  to  coagulate  on  the  addition  of  serum 
or  paraglobulin.  be  treated  in  the  same  way  either  with 
carbonic  acid  or  with  sodium  chloride  to  saturation,  a 
precipitate  is  obtained  similar  to,  but  more  flak}^  and  less 
granular  in   nature  than    that  produced   in  serum.     When 

*  For  further  details  see  Appendix. 


PARAGLOBULIN    AND    FIBRINOGEN.  31 

this  precipitate,  to  which  the  name  of  Jihrinocjen  has  Ijeeii 
given,  is  dissolved  in  dihite  neutral  saline  solution,  and  the 
solution  added  to  serum,  the  mixture  coagulates  spontane- 
ously, while  the  hydrocele  fluid  from  which  the  subslance 
has  been  removed  no  longer  causes  coagulation  in  serum. 
Tims  paraglohulin  from  serum  causes  coagulation  of 
hydrocele  fluid,  and  fibrinogen  from  hydrocele  fluid  causes 
coagulation  of  serum,  though  neither  alone  coagulates 
spontaneously.  And  serum  deprived  of  its  paraglobulin, 
and  hydrocele  fluid  deprived  of  its  fibrinogen,  have  lost  all 
power  of  coagulating  each  other. 

Lastly,  if  solid  paraglobulin  and  fibrinogen,  prepared  by 
the  soiliuni  chloride  method,  be  together  dissolved  in  dilute 
saline  solution,  the  fluid  mixture  will  coagulate  spontane- 
ously with  the  production  of  quite  normal  fibrin. 

These  facts  seem  to  show  that  plasmine  is  a  mixture  of 
fibrinogen  and  paraglobulin;  indeed,  an  artificial  mixture  of 
the  two  latter,  obtained  from  serum  and  hydrocele  fluid 
respectively,  would  be  undistinguishable  from  the  former 
obtained  from  plasma.  It  must,  however,  be  remembered 
that  no  one  has  \  et  succeeded  in  separating  natural  plasmine 
into  fibrinogen  and  fibrinoplastin.^ 

There  are,  moreover,  facts  which  show  that  the  above  state- 
ments do  not  cover  the  whole  ground  ;  there  is  evidence  of 
the  existence  of  yet  another  factor  in  the  process. 

1.  If  fihrinogen  and  paraglobulin  be  isolated  by  the  car- 
bonic acid  metliod,  their  mixture  in  a  saline  solution  clots 
with  great  ditiiculty  or  not  at  all ;  when  they  are  prepared 
by  the  saturation  metUod.  their  mixture  gives  a  good  firm 
clot.  This  suggests  tiiat  something  retained  by  the  latter 
method  is  lost  by  the  former. 

2.  Xorraal  blood-plasma  must  naturally  contain  an  excess 
of  paraglobulin.  since  after  coagulation  the  serum  still  con- 
tains a  considerable  quantit}'  of  that  body.  Yet  even  in 
blood-plasma,   paraglobulin,   under  certain  circumstances, 

'  AVe  ow«  tlie  disctivery  of  fihrinoj>la.stin  and  .fihrinowen  to  A. Schmidt, 
whose  earlier  pajjers  will  \ye  found  in  Eeicliert  aiid  Du  Bois-Reymond's 
Archiv,  1861^  p.  545,  and  1862,  p.  428.  Schmidt's  lat<?r  results,  which 
are  discussed  in  the  succeedins;  portions  of  this  section,  are  contained  in 
pa})ers  puhlislied  in  Pfliiiier's  Archiv,  vi  (1872),  p.  4145;  xi  (1875),  ]>i>. 
291  and  515;  xiii  (1876),' pp.  93  and  146. 


82  BLOOD. 

will  favor  coaoiiliition.  If  tliree  parts  of  i)lasnia  1)C  mixed 
with  one  part  of  a  solution  of  niagnesiinn  sulphate  (one  of 
the  salt  to  three  and  a  half  of  water),  the  mixture  diluted 
with  eight  parts  of  water  will  afford  a  dilute  plasma,  in 
which  spontaneous  coagulation  will  either  not  occur  at  all 
or  come  on  ver}'  slowly  indeed.  In  this  dilute  plasma  the 
paraglobulin  is  still  in  excess.  Nevertheless  the  addition 
of  a  further  (pKnitity  of  paraglobulin.  prei)nred  by  satura- 
tion with  sodium  chloride,  will  speedil\  cause  coagulation. 
Froni  this  it  may  he  inferred  that  in  adding  tiie  paraglobulin 
thus  prepared  something  else  is  added  as  well. 

3.  If  l)lood  serum  or  defilirinated  blood  he  poured  into 
abouttwenty  times  its  bulk  of  strong  s|)irit,  and  the  mixture 
allowed  to  stand  for  some  three  weeks,  or  longer,  all  the 
proteid  matters,  including  the  paraglobulin,  become  coagu- 
lated and  almost  wholly  insoluble  in  water.  Hence  if  tiie 
si)irit  be  filtered  of!*  from  the  co[)ious  precipitate,  and  the 
latter  dried  at  a  low  temperature  (below  40^;  and  extracted 
with  distilled  water,  the  aqueous  extract  contains  no  palpa- 
ble amount  of  i)roteid  material  and  gives  but  slight  reactions 
with  proteid  tests.  A  small  quantity  of  this  aqueous  extract 
of  blood,  however,  though  fiee  fiom  pai-aglobulin,  will  when 
added  to  the  dilute  plasma,  spoken  of  above,  bring  about  a 
ra[)id  coagulation. 

4.  If  the  pericardial  cavity  of  a  large  mammal  (ox,  horse, 
sheep)  l)e  laid  open  immediately  after  death,  the  fluid  re- 
moved will  coagulate  spontaneousl}^  and  rapidly.  The  clot 
will  on  examination  be  found  to  consist  of  a  uieshwork  of 
normal  fibrin  in  which  are  entangled  a  multitude  of  white 
corpuscles.  If  the  opening  of  the  body  be  deferred  to  some 
twenty  or  more  hours  after  tleath.  the  pericardial  fluid  will 
be  found  either  not  to  coagulate  at  all  or  to  coagulate  very 
slowly  and  feeb.ly. 

When,  however,  paraglobulin  prepared  by  the  saturation 
method  is  added  to  such  a  pericardial  fluid  a  rapid  and 
complete  coagulation  is  generally  brought  about.  13ut  pre- 
cisely the  same  coagulation  may  in  many  cases  be  brought 
about  by  the  simple  addition  of  the  arjueous  extract  just 
described.  Most  pericardial  fluids  in  fact  behave  extremely 
like  the  dilute  plasma  spoken  of  above.  Moreover  i^ome 
specimeuii  of  hydrocele  fluid  will  clot  spontaneously  on  the 


FIBRIN     FERMENT.  33 

addition  of  the  aqueous  extract  without  au}-  paraglobulin 
being  added  at  all. 

Here  then  are  indications  of  the  existence  of  a  substance 
which  is  neither  fibrinogen  nor  paraglobulin.  but  which  nev- 
ertheless appears  to  be  as  necessar}'  as  either  of  the  other 
two  for  the  occurrence  of  coagulation.  This  third  substance 
will  not  bring  about  coagulation  with  fibrinogen  alone  or 
with  paraglobulin  alone.  It  will  not  bring  about  coagula- 
tion in  fluids  such  as  many  hydrocele  fluids,  from  which 
paraglobulin  is  apparently  absent,  nor  serum,  from  wdiich 
fibrinogen  is  absent.  It  is  efficacious  only  in  such  cases 
where  there  are  reasons  for  thinking  that  both  paraglobulin 
and  fibrinogen  are  present.  But  its  most  important  feature 
is  the  following:  In  the  cases  in  which  coagulation  is 
brought  about  by  the  addition  of  paraglobulin  to  fibrino- 
genous  liquids,  the  quantity  of  fibrin  produced  certainl}' 
depends  on  the  quantity  of  fibrinogen  present,  and  appears 
also  to  be,  to  a  certain  extent,  determined  by  the  quantity 
of  paraglobulin  added;  whereas  the  addition  of  the  aqueous 
extract  only  aff"ects  the  rap'dily  with  which  coagulation  sets 
in,  and  not  at  all  the  quantit}-  of  fibrin  produced.  In  other 
words,  the  aqueous  extract  docs  not  contribute  to  the  sub- 
stance of  the  fibrin,  but  favors,  or  is  essential  to,  the  union 
of  the  two  fibrin  factors.  That  is  to  say,  the  substance  in 
the  aqueous  extract  which  thus  effects  coagulation  belongs 
to  that  class  of  substances  which  promote  the  union  of  other 
bodies,  or  cause  changes  in  other  bodies,  without  themselves 
entering  into  union  or  undergoing  change.  These  sub- 
stances we  shall  hereafter  learn  to  speak  of  as  "  ferments  ;" 
and  this  particular  substance  has  been  called  by  its  discov- 
erer, A.  Schmidt,^  filnin  ferment.  Obviously  the  ferment  is 
present  in  blood-plasma,  in  plasmine.  and  in  paraglobulin  as 
prepared  by  the  saturation  method,  but  is  ai)parently  in 
large  measure  lost  when  paraglobulin  is  prepared  hy  the 
carbonic  acid  method. 

In  conclusion,  then,  we  may  sa}',  that  coagulation  is  the 
result  of  the  interaction  of  two  bodies,  paraglobulin  and 
fibrinogen,  brought  about  b}'  the  agency  of  a  third  body, 
fibrin  ferment.  Where  these  three  bodies  are  all  present, 
as  in  blood  plasma,  in  plasmine,  in  pericardial  fluid  taken 
from  the  body  immediately  after  death,  spontaneous  coagu- 
lation is   witnessed;  where   the   ferment  is   absent,  but  the 

'  Op.  cit. 


34  BLOOD. 

other  factors  are  present,  as  in  inMiiy  cases  of  i)ericar(]ial 
fluid  removed  some  time  after  death,  coa<i!;iilation  will  take 
place  on  the  addition  of  ferment  alone  ;  where  hotli  ferment 
and  paraglobulin  are  absent,  us  in  many  cases  of  hydrocele 
fluid,  both  these  must  be  added  defore  coagulation  can 
come  on. 

The  exact  nature  of  the  process  by  which  the  presence  of  all 
three  factors  leads  to  the  formation  of  fibrin  cannot  be  at  present 
detiued  more  closely  than  by  the  phrase  ''  interaction."  Beyond 
the  broad  fact  that  the  quantity  of  fibrin  formed  is  aflccted  by 
the  quantity  of  paraglobulin  and  fibrinogen  present,  we  have  no 
knowledge  of  quantitative  relations  between  the  two  constituents. 
That  thc'y  do  not  unite  simply  together,  as  a  base  with  an  acid, 
seems  to  be  clearl}^  shown  by  the  fact,  that  in  artificial  coagula- 
tions the  quantity  of  fibrin  formed  is  by  weight  always  less  than 
that  of  the  paraglobulin  used  ;  indeed  is  frecjuently  less  than  that 
of  the  fibrinogen  calculated  to  be  present.  Ilammarsten'  argues 
that  the  paraglobulin  does  not  enter  in  any  way  into  the  fibrin, 
the  latter  being  simply  transformed  fibrinogen.  lie  explains  the 
fibrinoplastic  properties  of  paraglobulin  as  due  to  that  substance 
obviating  certain  hindrances  to  the  formation  of  the  fibrin,  for 
instance,  preventing  the  solution  by  saline  or  other  bodies  of  the 
fibrin  while  it  is  in  what  may  be  called  a  nascent  condition,  ^.  e., 
in  a  stage  intermediate  between  llljrinogen  and  fibrin.  Accord- 
ing to  him  the  quantity  of  paraglobulin  present  in  a  coagulating 
fluid,  though  of  marked  effect  on  the  quantity  of  fibrin  produced, 
has  no  effect  on  the  total  quantity  of  fibrinogen  used  up,  i.  e., 
transformed  into  fibrin  or  into  something  else. 

Some  authors  go  so  far  as  to  believe  that  paraglobulin  in  itself 
has  no  share  in  the  matter,  and  that  its  apparent  fibrinoplastic 
qualities  are  always  due  to  a  quantity  of  the  ferment  being  en- 
tangled in  it  during  its  preparation.  The}'  regard  the  formation 
of  fibrin  as  being  simply  a  transformation  of  fibrinogen  by  means 
of  the  fibrin  ferment.  But  this  view  is  clearly  untenable  so  long 
as  the  statement  that  the  quantity  of  fibrin  formed  is  affected  by 
the  presence  of  paraglo1)ulin  is  not  disproved.  The  assertion  of 
Hammarsten,2  that  paraglobulin  may  be  deprived  of  its  fibrino- 
plastic powers  by  exposure  to  a  temperature  of  56^^  or  58^  C. 
without  any  change  in  its  ordinary  characters  points  it  is  true  in 
that  direction,  but  his  further  statement  that  specimens  of  hydro- 
cele fluid  which  refuse  to  clot  on  the  simple  addition  of  the 
ferment,  but  do  so  on  the  further  addition  of  paraglobulin,  may 
yet  contain  a  considerable  quantity  of  a  body  apparently  iden- 
tical with  paraglobulin,  show  that  further  study  of  the  whole 
subject  is  still  required. 

*  Pfliiger's  Archiv,  xiv  (1877),  211. 
'  I)j.,  xviii  (1878),  p.  38. 


INFLUENCE  OF  THE  LIVING  BLOODVESSELS.   35 

This  conception  of  coaoulation  as  a  cheinical  process 
between  certain  factors  renders  easy  of  comprehension  the 
influence  of  various  conditions  on  the  coagulation  of  blood. 
The  quickening  influence  of  heat,  the  retarding  effect  of 
cold,  the  favorable  action  of  motion  and  of  contact  with 
surfaces,  and  hence  the  results  of  whipping  and  the  influence 
exerted  by  the  form  and  surface  of  vessels,  become  intelli- 
gible. The  greater  the  number  of  points,  that  is  the  larger 
and  rougher  tiie  surface  presented  by  the  vessel  into  which 
blood  is  shed,  the  more  quickly  coagulation  comes  on,  for 
contact  with  surfaces  favors  chemical  union.  So  also  the 
presence  of  S|)ongy  platinum,  or  of  an  inert  powder  like 
charcoal,  quickens  the  coagulation  of  tardily  clotting  fluids, 
such  as  many  cases  of  pericardial  fluid. 

The  action  of  neutral  salts  is  still  obscure.  Schmidt  has 
shown  that  the  presence  of  a  neutral  salt,  such  as  sodium  chlo- 
ride, is  essential  to  the  process,  coagulation  not  occurring  even 
where  all  three  factors  are  present,  if  no  neutral  salt  accompany 
them  ;  thus  bringing  flbiin  coagulation  after  all  into  the  same 
category  as  the  coagulation  of  albumin  by  heat  :  see  Appendix. 
The  presence  of  hfemoglobin  also,  independently  of  the  flbrino- 
plastin  which  may  be  present  in  the  red  corpuscles,  appears  to 
favor  coagulation. 

Having  thus  arrived  at  an  approximate  knowledge  of  the 
nature  of  coagulation,  we  are  in  a  better  position  for  dis- 
cus ing  the  question,  Why  does  blood  remain  fluid  in  the 
vessels  of  the  living  body  and  yet  clot  when  shed  ? 

The  older  views  may  be  at  once  summarily  dismissed. 
The  clotting  is  not  due  to  loss  of  temperature,  for  cold 
retards  coagulation,  and  the  blood  of  cold-blooded  animals 
behaves  just  like  that  of  warm-blooded  animals  in  clotting 
when  shed.  It  is  not  due  to  loss  of  motion,  for  motion 
favors  coagulation.  It  is  not  due  to  exposure  to  air, 
whereby  either  an  increased  access  of  oxygen  or  an  escape 
of  volatile  matters  is  facilitated,  for  on  the  one  hand  the 
blood  is  fully  exposed  to  the  air  in  the  lungs,  and  on  the 
other  shed  blood  clots  when  received,  without  any  exposure 
to  the  atmosphere,  in  a  closed  tube  over  mercury. 

All  the  facts  known  to  us  point  to  the  conclusion,  that 
when  blood  is  contained  in  healthy  living  bloodvessels,  a 
certain  relation  or  equilibrium  exists  between  the  blood  and 
the  containing  vessels  of  such  n  nature,  that  as  long  as  this 
equilibrium  is  maintained  the   l)lood  remains  fluid,  but  that 


86  liLooi). 

when  this  equilibi-iiun  is  distui-bed  by  events  in  the  blood  or 
in  the  bloodvessels,  or  by  the  removal  of  the  l)lood,  the 
blood  undergoes  ehanijes  vvhieh  result  in  coagulation.  The 
most  salient  I'aets  in  support  of  this  conclusion  are  as  fol- 
lows : 

1.  After  death,  when  all  motion  of  the  blood  has  ceased, 
the  blood  remains  for  a  long  time  fluid.  It  is  not  till  some  time 
afterwards,  at  an  epoch  when  post-mortem  changes  in  the 
l)lood  and  in  the  bloodvessels  have  iiad  time  to  develop 
themselves,  that  coagulation  begins.  Thus  some  hours  after 
death  tlie  blood  in  the  great  veins  may  he  found  perfectly 
fluid.  Yet  such  blood  has  not  lost  its  power  of  coagulating  ; 
it  still  clots  when  removed  from  the  body,  and  clots  too 
when  received  over  mercury  without  exposure  to  air,  show- 
ing that  the  fluidity  of  the  higldy  venous  blood  is  not  due 
to  any  excess  of  carl)onic  acid  or  absence  of  oxygen. 
Eventually  it  does  clot  even  within  the  vessels,  but  never 
so  firmly  and  completely  as  when  shed.  It  clots  first  in  the 
larger  vessels,  remaining  for  a  very  long  time,  for  many 
hours  in  fact,  fluid  in  the  smaller  veins,  where  the  same 
bulk  of  blood  is  exposed  to  the  influence  of,  and  recipro- 
cally exerts  an  influence  on,  a  larger  surface  of  the  vascular 
walls  than  in  the  larger  veins.  Thus  if  the  foot  of  a  slieep 
be  ligatured  and  amputated,  the  l>lood  in  the  small  veins 
will  be  found  fluid  and  yet  coagulable  for  many  hours. 

2.  If  the  vessels  of  the  heart  of  a  turtle  (or  any  other 
cold-blooded  animal)  be  ligatured,  and  the  heart  be  cut  out 
and  suspended  so  that  it  n)ay  continue  to  beat  for  as  long  a 
period  as  possible,  the  blood  will  remain  fluid  within  the 
heart  as  long  as  the  pulsations  go  on,  z.  ^.,  for  one  or  two 
days  (and,  indeed,  for  some  time  afterwards),  though  a  por- 
tion taken  away  at  any  period  of  the  experiment  will  clot 
very  speedily.^ 

3.  If  the  jugular  vein  of  a  large  animal,  such  as  an  ox  or 
horse,  be  ligatured  when  full  of  l)lood,and  the  ligatured  por- 
tion excised,  t'lie  blood  in  many  cases  remains  perfectl}'  tluid 
along  the  greater  part  of  the  length  of  the  piece  for  twenty- 
four,  or  even  forty-eight  hours.  The  piece  so  ligatured  may 
be  suspended  in  a  framework  and  opened  at  the  top  so  as  to 


1  Brucke,  Brit,  and  For.  Med.-Chir.  Keview,  xix,  p.  183  (1857). 


SOURCES  OF  THE  FIBRIN  FACTORS.        37 

imitate  a  livinjr  test- lube,  and  yet  the  blood  will  often  remain 
Ions:  fluid,  thouojh  a  portion  removed  at  any  time  into  an- 
other vessel  will  clot  in  a  few  minutes.  If  two  such  living 
test-tuiies  be  prepared,  tiie  blood  may  be  poured  from  one 
to  the  other  without  coagulation  taking  place. ^ 

The  above  facts  illustrate  the  al)sence  of  coagulation  in 
intact  or  slightly  altered  living  bloodvessels;  the  following 
show  that  coagulation  may  take  place  even  in  the  living 
vessels. 

4.  If  a  needle  or  piece  of  wire  or  thread  be  introduced 
into  the  living  bloodvessel  of  an  animal,  either  during  life 
or  immediately  after  death,  the  piece  will  be  found  incrusted 
with  fibrin. 

5.  If  in  a  living  animal  a  bloodvessel  be  ligatured,  the 
ligature  being  of  such  a  kind  as  to  injure  the  inner  coat, 
coagulation  takes  place  at  the  lii^ature  and  extends  for  some 
distance  from  it.  Thus  if  the  jugular  vein  of  a  rabbit  be 
ligatured  roughU'  in  two  places,  clots  will,  in  a  few  hours, 
be  found  in  the  ligatured  portion,  reaching  upwards  and 
downwards  from  each  ligature,  the  middle  i)ortion  being  the 
least  congulated.  Clots  will  also  be  found  on  the  far  side  of 
each  ligature.  The  clot^;  will  still  appear  if  the  ligature  be 
removed  immediately  after  being  applied,  provided  that  in 
the  process  the  inner  coat  has  been  wounded.  If  the  liga- 
tures be  applied  in  such  a  way  as  not  to  injure  the  inner 
coat,  coagulation  will  not  take  place,  tiiough  the  blood  may 
remain  for  many  hours  pei'fectly  at  rest  between  the  liga- 
tures. 

fi.  When  an  artery  is  ligatured  a  conspicuous  clot  is 
formed  on  the  cardiac  side  of  the  ligature.  The  clot  is 
largest  and  firmest  in  the  immediate  neighborhood  of  the 
ligature,  gradually  thinning  away  from  thence,  and  reaching 
usually  as  far  as  where  a  branch  is  given  otf.  Between  this 
brancii  and  the  ligature  there  is  stasis  ;  the  walls  of  the  artery 
sutler  from  the  want  of  renewal  of  Idood,  and  thus  favor  the 
propagation  of  the  coagulation.  On  the  distal  side  of  the 
ligature,  where  the  artery  is  much  siirunken,  the  clot  which  is 
formed,  though  naturally  small  and  inconspicuous,  is  similar. 

^  Lister,  Proc.  Koy,  Soc,  xii,  p.  580  (1858). 
4 


38  BLOOD. 

7.  Any  iiijurv  of  the  inner  eoat  of  a  bloodvessel  causes  a 
C(Ki<rulatioii  at  the  spot  of  injury.  Any  treatment  of  a  blood- 
vessel tending  to  injure  its  normal  condition  causes  local 
coagulation. 

8.  Disease  involving  the  inner  eoat  of  a  bloodvessel  causes 
a  coagulation  at  the  part  diseased.  Thus  inllammation  of 
the  lining  membrane  of  the  valves  of  the  heart  in  endocar- 
ditis is  frequently  accompanied  by  the  deposit  of  fibrin.  In 
aneurism  the  inner  coat  is  diseased,  and  layers  of  fibrin 
are  commonly  deposited.  So  also  in  fatty  and  calcareous 
degeneration  without  any  aneurismal  dilatation  there  is  a 
tendency  to  the  formation  of  clots. 

9.  Similar  phenomena  are  seen  in  the  case  of  serous  fluids 
which  coagulate  spontaneously.  If,  as  soon  after  death  as 
the  body  is  cold,  and  the  fat  is  soliditied,  the  pericardium  l)e 
carefully  removed  from  a  sheep  by  an  incision  round  the 
base  of  the  heart,  the  pei'icardial  fluid  may  be  kept  in  the 
pericardial  bag  as  in  a  living  cup  for  many  hours  without 
clotting,  and  yet  a  small  portion  removed  with  a  ))ipette 
clots  at  once,  and  a  thread  left  hanging  into  the  fluid  soon 
becomes  covered  with  flbrin. 

The  only  interpretation  which  embraces  these  facts  is  that 
so  long  as  a  certain  normal  relation  between  the  lining 
surfaces  of  the  bloodvessels  and  the  blood  is  maintained, 
coagulation  does  not  take  place;  but  when  this  relation  is 
disturbed  by  the  more  or  less  gradual  death  of  bloodvessels, 
or  by  their  more  sudden  disease  or  injury,  or  by  the  presence 
of  a  foreign  body,  coagulation  sets  in.  Two  additional 
points  may  here  be  noticed.  1.  Stagnation  of  blood  favors 
coagulation  within  the  bloodvessels,  api)arenth'  because  the 
bloodvessels,  like  other  tissues,  demand  a  renewal  of  the 
blood  on  which  they  depend  for  the  maintenance  of  their 
vital  powers.  2.  The  influence  of  surface  is  seen  even  in 
the  coagulation  within  the  vessels.  In  cases  of  coagulation 
from  gradual  death  of  the  liloodvessels,  as  in  the  case  of  an 
excised  jiigidar  vein,  the  fibrin,  when  its  deposition  is  suf- 
ficiently slow,  is  seen  to  appear  first  at  the  sides,  and  from 
thence  gradually,  frequently  in  layers,  to  make  its  way  to 
the  centre.  So  in  aneurism,  the  deposit  of  fibrin  is  fre- 
quently laminated.  In  cases  where  coagulation  results  from 
disease  of  the  lining  membrane,  the  rougher  the  interior  the 
more  speedy  and  complete  the  clotting.     So  also  a  rough 


SOURCES  OF  THE  FIBRIN  FACTORS.       39 


foreign  body,  prepeiiting  a  large  number  of  surfaces  and 
points  of  attacliment,  more  readily  produces  a  clot  when  in- 
troduced into  the  living  bloodvessels  than  a  perfectly  smooth 
one. 

Clear  as  it  seems  to  be  that  some  vital  relation  of  blood 
to  bloodvessel  is  the  dominant  condition  affecting  coagula- 
tion, it  is  by  no  means  easy  to  state  distinctly  wliat  is  the 
exact  nature  of  that  relation.  Some  authors'  speak  of  the 
bloodvessels  as  exercising  a  restraining  influence  on  the 
natural  tendency  of  the  blood  to  coagulate.  Others'  regard 
the  living  bloodvessel  (and  indeed  living  matter  in  general) 
as  being  wholly  inert  towards  the  fibrin  factors.  These 
the}-  consider  need  the  presence,  the  contact  influence  of 
some  body,  in  order  that  they  ma\'  act  on  each  other  to 
form  fibrin  ;  thus  contact  with  the  sides  of  the  vessel  into 
which  blood  is  shed,  or  with  the  surface  of  a  foreign  body 
introduced  into  a  living  vessel  is.  according  to  them,  the 
determining  cause  of  coagulation.  The}'  sup[)ose  tliat  living 
matter  exercises  no  such  contact  influence. 

Before  this  point  can  be  decided,  further  knowledge  is  needed 
concerning  the  exact  condition  of  the  fibrin  factors  in  living  blood 
within  the  body.  AVhile  the  blood  is  flowing  micoagulated 
through  the  vessels,  are  all  the  three  fibrin  factors,  paraglobulin, 
fibrinogen,  and  ferment,  already  present  in  plasma  V  Or  are  they 
all,  or  is  one  or  two,  absent,  and  if  so  is  the  appearance  of  them, 
or  of  one  of  then,  in  the  plasma,  the  necessary  invisible  forerun- 
ner of  coagulation  V  Our  scanty  information  on  this  point  may 
be  summarized  as  follows  : 

1.  In  all  spontaneous!}'  coagulable  fluids  white  corpuscles  are 
present,  and  the  more  alnmdant  they  are  the  more  pronounced 
is  the  coagulation.  Thus  the  spontaneously  coagulating  peri- 
cardial fluid  is  exceedingly  rich  in  white  corpuscles,  and  the  clot 
formed  seems  under  the  microscope  to  be  almost  entirely  com- 
posed of  them,  so  completely  do  they  hide  the  threads  of  fibrin. 
In  the  specimens  of  pericardial  and  of  hydrocele  fluid  which  do 
not  coagulate  spontaneously  white  corpuscles  are  absent,  or  at 
least  scanty. 

2.  The  deposition  of  fibrin  round  a  thread  if  dipped  into  a  co- 
agulable fluid  or  drawn  through  a  bloodvessel  and  left  there,  is 

^  Briicke,  op.  cit.  ^  leister,  op.  cit. 


40  BLOOD. 


preceded  by  an  accutiuilation  of  white  corpuscles.  These  cluster 
ill  greater  numbers  round  the  thread,  and  when  the  mass  is  ex- 
amined under  the  microscope  the  corpuscles  seem  to  serve  as 
starting-points  for  the  development  of  tibrin. 

3.  In  the  experiment  of  keeping  blood  fluid  but  coagulable  in 
an  excised  jugular  vein  (of  the  horse),  it  is  observed  that  when, 
as  m  course  of  time  happens,  the  corpuscles  have  sunk  to  the  bot- 
tom of  the  piece  of  vein,  the  upper  layers  of  clear,  corpuscle-free 
plasma  clot  very  feebly  indeed  when  removed  from  the  vein, 
whereas  the  lower  layers,  rich  in  corpuscles,  clot  most  firmly. 

4.  When  horse's  blood  is  received  from  a  bloodvessel  into  an  ice- 
cold  dilute  solution  of  chloride  of  sodium,  and  the  mixture  kept 
just  short  of  actually  freezing,  the  whole  mass  of  corpuscles  sinks 
rapidly.  It  is  then  observed  that  the  dilute  plasma  free  from 
corpuscles  clots  feebly,  whereas  the  lower  layers  of  the  same  di- 
lute plasma,  containing  all  the  corpuscles,  give  an  abundant 
coagulation.  Plasma  of  horse's  blood  may  be  diluted  with  twelve 
times  its  bulk  of  distilled  water  and  filtered  without  coagulation 
setting  in,  provided  that  the  whole  operation*  is  conducted  at  a 
temperature  just  short  of  freezing.  The  filtered  diluted  plasma, 
which  is  found  to  be  exceedingly  free  from  white  corpuscles,  these 
being  left  on  the  filter,  clots  feebly  ;  the  amount  of  fibrin  it  pro- 
duces is  less  than  half  that  obtainable  from  the  same  diluted 
plasma  unfiltered.' 

These  facts  point  very  decidedly  to  the  conclusion  that  the 
white  corpuscles  have  some  share  in  bringing  about  coagulation  ; 
they  moreover  suggest  that  one  or  more  of  the  fibrin  fjictors  have 
their  source  in  the  white  corpuscles,  and  that  coagulation  is  due 
to  the  passage  of  these  elements  from  the  body  of  the  corpuscle 
into  the  plasma.  The  latter  view  is  corroborated  by  the  following 
facts  : 

5.  In  defibrinated  blood  or  blood-serum  a  certain  amount  of 
fibrin  ferment  is  present.  If,  however,  blood  be  treated  with  al- 
cohol immediately  on  leaving  the  bloodvessels,  very  little  ferment 
indeed  is  found  to  be  present.  The  quantity  is  found  to  increase 
from  the  moment  of  leaving  the  vessels  to  the  onset  of  coagula- 
tion. The  fibrin  ferment,  therefore,  is  developed  from  some  part 
of  the  blood. 

If  horse's  blood  be  kept  at  freezing  temperature,  the  formation 
of  ferment  is  arrested.  If  after  the  corpuscles  have  sunk  the  un- 
dermost layers  of  the  blood,  containing  almost  exclusively  red 
corpuscles,  be  removed,  little  or  no  ferment  can  be  obtained  from 
this  portion,  either  when  examined  immediately,  or  after  being 

^  A.  Schmidt,  op.  cit. 


SOURCES  OF  THE  FIBRIN  FACTORS.       41 


allowed  to  clot  at  an  ordinary  temperature.  In  a  portion  taken 
from  the  upper  layers  (colorless  plasma)  of  the  same  blood,  while 
there  is  little  or  no  ferment  present  before  the  coagulation  of  the 
specimen,  there  is  abundance  afterwards.  If  a  similar  portion  of 
the  same  colorless  plasma  be  filtered  in  the  cold,  the  filtrate, 
which  is  nearly  frse  from  white  corpuscles,  is  very  poor  in  fer- 
ment both  before  and  after  the  feeble  and  slow  coagulation  which 
the  fiuid  undergoes  ;  the  material  on  the  filter,  consisting  almost 
entirely  of  white  corpuscles,  is  very  rich  in  ferment.  These  facts 
seem  to  show  that  the  fibrin  ferment  which  is  present  in  blood- 
serum  has  its  source,  not  in  the  red  but  in  the  white  corpuscles, 
and  that  the  passage  of  the  ferment  from  the  white  corpuscle  into 
the  plasma  is  a  precursor  of  coagulation. 

6.  The  coagulation  of  filtered  diluted  plasma  has  been  said  to 
be  both  feeble  and  slow.  The  tardiness  of  the  coagulation  is  due 
to  the  paucity  of  ferment ;  the  feebleness,  i.  e.,  the  small  quantity 
of  fibrin  produced,  must  he  due  to  the  scantiness  of  one  or  both 
of  the  fibrin  factors.  On  adding  paraglobulin  the  quantity  of 
fibrin  produced  is  the  same  as  that  given  by  tlie  same  quantity 
of  unaltered  plasma.  The  filtered  plasma  is  therefore  deficient 
in  paraglobulin.  The  material  left  on  the  filter  is  rich  in  para- 
globulin. The  inference  which  A.  Schmidt  draws  from  these 
facts,  is  that  paraglobulin,  like  the  fibrin-ferment,  has  its  origin 
in  the  white  corpuscles,  but  that  fibrinogen  is  a  normal  constitu- 
ent of  the  plasma. 

7.  If  a  drop  of  horse's  plasma  kept  from  coagulating  by  cold 
be  examined  under  the  microscope,  it  will  be  found  to  contain  a 
large  number  of  white  corpuscles,  mixed  with  which,  according 
to  A.  Schmidt,  are  corpuscles  of  an  intermediate  character  be- 
tween white  and  red,  /.  e.,  nucleated  cells  whose  protoplasm  is 
loaded  with  colored  haemoglobin  granules.  As  the  drop  is 
watched,  a  large  number  of  the  white  corpuscles  and  all  the  in- 
termediate forms  are  seen  to  break  up  into  a  granular  detritus. 
This  breaking  up  of  the  white  corpuscles  is  the  precursor  of  co- 
agulation, the  threads  of  fibrin  seeming  to  start  from  the  remains 
of  the  corpuscles.  Putting  all  these  facts  together,  Schmidt  con- 
cludes that  when  blood  is  shed,  a  number  of  white  and  interme- 
diate corpuscles  fall  to  pieces,  by  which  act  a  quantity  of  fibrin 
ferment  and  of  paraglobulin  is  discharged  into  the  plasma.  These 
meeting  there  with  the  alread}^  present  fibrinogen  give  rise  to 
fibrin,  and  coagulation  results.  In  other  mammals  coagulation, 
even  at  low  temperatures,  is  too  rapid  to  permit  of  the  changes  in 
the  corpuscles  being  watched  as  satisfactorily  as  in  the  horse, 
but  even  in  these  evidences  of  the  existence  of  intermediate  forms 
may  be  met  with. 

This  view  excludes  the  red  corpuscles,  as  far  as  mammals  are 
concerned,  from  any  direct  share  in  coagulation.  A\^hether  this 
ultimately  proves  to  be  correct  or  not,  there  are  facts  which  show 


42  BLOOD. 


that  the  nucleated  red  corpuscles  of  other  vertebrates,  which  it 
must  be  remembered  are  the  homoloixues  of  the  intermediate 
forms,  have  a  much  clearer  conut'ctiou  with  the  process.  If  the 
defibrinated  blood  of  the  fro<2;  or  the  Ijird  be  allowed  to  stand 
until  the  cori)uscles  have  suljsided,  the  latter,  separated  as  much 
as  possible  from  the  serum,  and  treated  with  a  considerable  quan- 
tity of  distilled  water,  yield  a  tiltrate  which  coagulates  si)onta- 
neously.  That  is  to  say,  the  water  breaks  up  the  red  corpuseles 
and  sets  free  a  quantity  of  fibrin  factors  which  otherwise  would 
have  remained  latent.  The  amount  of  fibrin  thus  obtained  may 
be  considerably  greater  than  the  quantity  originally  appearing  in 
the  blood.  It  is  worth}'  of  notice,  that  in  this  case  the  corpuscle 
is  the  source,  not  onl v  of  the  librin  ferment  and  paraglobulin,  but 
also  of  the  librinogen. 

Accepting  this  view  as  approximately  correct,  the  coagulation 
of  shed  blood  may  be  referred  to  the  circumstance,  that  even  the 
comparatively  slight  changes  which  must  take  place  in  the  blood 
on  its  leaving  the  vessels  are  sutlicient  to  entail  the  death,  and  so 
the  breaking  up,  of  a  number  of  the  delicate  white  corpuscles. 
The  formation  of  clots  within  the  body  is  not  so  easy  to  explain. 
We  are  driven  in  these  cases  to  suppose  that  injured  and  diseased 
spots  or  foreign  bodies  first  attract,  and  then,  as  it  were  by  irri- 
tation, cause  the  death  of  a  certain  number  of  corpuscles. 

But  in  any  case,  if  this  view  be  admitted,  it  must  also  be 
granted  that  the  bloodvessels  do  in  some  manner  or  other  exer- 
cise a  restraining  influence  on  the  formation  of  fibrin.  For  many 
of  these  corpuscles  must,  in  the  natural  course  of  events,  die 
and  break  up  in  the  blood-stream,  without  causing  coagulation. 
Further,  defibrinated  blood  contains  both  fibrin-ferment  and 
paraglobulin  ;  it  ought,  therefore,  when  injected  into  vessels 
which  already  in  the  natural  blood  contain  fibrinogen,  to  occasion 
a  rapid  and  speedy  general  coagulation.  This  it  does  not.  The 
coagulations  which  occur  after  transfusion  of  defibrinated  blood 
are  partial  and  uncertain.  We  might  infer  from  this  that  the 
system  has  some  power  of  rapidly  either  destroying  ferment  or 
changing  the  properties  of  paraglobulin.  In  support  of  this  it 
has  been'stated  that  a  quantity  of  fibrin-ferment  injected  into  the 
system  may  be  detected  in  the  blood  immediately  afterwards 
(and  is  present  then  without  causing  coagulation),  but  speedily 
disappears.  The  loss  of  spontaneous  coagulability  in  pericardial 
fluid  might  be  attributed  to  an  escape  b}^  migracion  of  the  white 
corpuscles  away  from  the  pericardial  cavity,  but  this  is  incon- 
sistent with  the  fact  that  in  the  majority  of  cases  the  ferment 
alone  disappears  while  the  paraglobulin  remains.  According  to 
the  facts  given  above,  the  white  corpuscles  in  eseaping  would 
carry  away  both  ferment  and  paraglobulin,  leaving  the  fibrinogen 
alone.  Moreover,  it  must  be  rememljered  that,  as  was  men- 
tioned on  p.  3-1,  Schmidt's  view  of  the  fibrinoplastic  function  of 
paraglobulin  is  not  accepted  by  all  investigators ;   and  some 


CHEMICAL    COMPOSITION    OF    BLOOD.  43 


authors'  while  agreeing:  with  Schmidt  that  the  white  eorpiiseles 
are  the  source  of  the  librin  factors,  differ  from  him  in  so  far  that 
they  beheve  that  the  fibrinogen  as  well  as  the  fibrin-ferment  arise 
from  these  bodies,  paragiol)uUn  according  to  them  having  nothing 
to  do  with  the  matter. 

Lastl}-,  we  should  remember  that  all  the  above,  even  if  correct, 
is  only  an  approximative  solution.  The  coagulation  of  muscle- 
plasma  is  a  coagulation  in  which  white  corpuscles  cannot  serve 
as  dei  ex  machina;  moreover,  as  we  shall  see  later  on,  the  rigor 
mortis  of  the  white  corpiLscle  itself  is  a  coaguUition  ;  and  for  this 
its  own  subsequent  disintegration  cannot  be  regarded  as  an  ade- 
quate cause. 


Sec.  2.   The  Chemical  Composition  of  Blood. 

The  average  specific  gravity  of  human  blood  is  1055.  va- 
rying from  1045  to  1075  witbin  the  limits  of  health.  The 
reaction  of  blood  as  it  flows  from  the  bloodvessels  is  found 
to  be  distinctly  alkaline. 

According  to  Zuntz,^  the  alkalescence  of  shed  blood  rapidly 
diminishes  up  to  the  oiLset  of  coagulation.  Other  observers  have, 
however,  maintained  that  the  serum  is  more  alkaline  than  the 
uncoagulated  blood,  or  cruor. 

Blood  may,  in  general  terms,  be  considered  as  consisting 
by  weight  of  from  about  one-third  to  somewhat  less  than 
one-half  of  corpuscles,  the  rest  being  plasma,  the  corpuscles 
being  supposed  to  retain  the  amount  of  water  proper  to 
tiiem. 

Hoppe-Seyler  gives,  in  1000  parts  of  the  venous  blood  of  the 
horse;  Corpuscles,  32(3 ;  plasma,  074. ^  As  will  be  seen  in  the 
succeeding  sections,  the  number  of  corpuscles  in  a  specimen  of 
blood  is  found  to  vary  considerably,  not  onh'in  different  animals 
and  in  difterent  individuals,  but  in  the  same*^ individuals  at  differ- 
*ent  times.  [The  proportion  of  corpuscles  in  the  plasma  of  arterial 
blood  exceeds  that  in  the  venous.     In  the  venous  blood  the  pro- 


'  Fredericq  L.,  Eecberches  sur  la  coagulation  du  Sang.     Bruxelles, 
1877. 

•^  Centralbt.  f.  med.  Wiss.,  1867,  p.  801. 
-    '  For  th^  various  methods  of  determmation  see  Hop|)e-Seyler,  Hdb. 
Physiul.  Chein.  Analyse,  p.  327. 


44  BLOOD. 


jiortion  varies  considorably,  it  being  the  greatest  in  the  splenic, 
and  .smallest  in  the  hepatic  veins.] 

Consi)icnons  and  striking  as  are  the  results  of  coagida- 
tion,  massive  as  appears  to  be  the  clot  which  is  formed,  it 
must  be  remembered  that  by  far  tiie  greater  part  of  the  clot 
consists  of  corpuscles,  'I'jje  amount  l)y  weight  of  rii)rin 
required  to  bind  together  a  number  of  corj^Mscles  in  oi-dcr 
to  form  even  a  large  firm  clot  is  exceedingly  small,  Tiius 
tlie  average  quantity  by  weight  of  fibrin  in  human  blood  is 
said  to  be  .2  per  cent.,  but  the  amount  whicii  can  be  obtained 
from  a  given  quantity  of  plasma  varies  extremely;  the  va- 
riation being  due  not  only  to  circumstances  tiffecting  the 
blood,  liut  also  to  tlie  method  employed. 

The  difliculties  indeed  of  acquiring  an  exact  knowledge 
of  the  chemical  constitution  of  the  plasma,  whicli  as  we 
have  seen  from  the  foregoing  section  is  probably  undergoing 
changes  from  tiie  moment  of  being  shed,  are  very  great ; 
our  infoimation  concerning  the  composition  of  the  serum 
and  of  the  corpuscles  is  much  more  trustworthy. 

Composition  of  Serum. — In  100  parts  of  serum  there  are 
in  round  numbers 

Water, 90  parts. 

Proteid  substances, 8  to  9     " 

Fats,  extractives,'  and  saline  matters,      .      2  to  1     " 

The  proteid  substances  present  in  serum  are  :  (1)  Tiie 
so-called  ne rum-albumin^  (2j  paraglobulin.  Tlie  paraglob- 
ulin,  as  has  been  stated  in  the  preceding  section,  may  be 
removed  from  the  serum  in  several  ways,  viz.,  by  passing 
cari)onic  acid  through,  or  by  cautiously  adding  dilute  acetic 
acid  to  tlie  diluted  serum,  or  by  saturating  the  undiluted 
serum  with  sodium  chloride  or  magnesium  sulphate.  When 
this  has  been  done  a  considerable  quantitj'  of  proteid  mate- 
rial is  still  left  in  the  serum  in  the  form  known  as  serum 
albumin,  distinguished  from  [jaraglobulin,  among  other  char- 
acters, b}^  its  being  soluble  in  distilled  water,  and  therefore 

^  This  Avord  is  used  to  denote  soluble  substances  of  varied  origin  and 
nature,  occurring  in  small  quantities,  and  therefore  requiring  to  be  ''  ex- 
tracted "  by  special  means. 


COMPOSITION    OF    SERUM.  45 

not  requiring  for  its  solution  the  presence  of  a  neutral  salt.^ 
Wlien  seium,  after  the  cautious  addition  of  acetic  acid,  in 
order  to  neutralize  its  alkalinity,  is  heated  to  about  75^  C, 
both  the  serum  albumin  and  paraglobulin  are  thrown  down 
in  the  form  known  as  coagulated  proteids^  substances  char- 
acterized b}' their  great  insolubility.  This  "  coagulation  " 
by  heat  of  these  and  other  proteids  is,  it  perha[)s  need 
hardly  be  said,  not  to  be  confounded  with  the  coiigulation 
of  plasma  due  to  the  appearance  of  fibrin, 

Man}-  authors  have  distinguished  between  the  deposit  caused 
by  the  passage  of  carbonic  acid  through  the  dilute  serum,  and 
the  further  precipitate  of  proteid  material,  which  may  be  gained 
by  the  subsequent  addition  of  dilute  acetic  acid.  The  former  is 
general!}'  hbrinoplnstic,  i  e.,  will  give  rise  to  fibrin  when  added 
to  fibrinogenous  liquids.  The  latter  will  not  do  so,  and  has,  on 
this  account,  and  for  the  reason  that  it  is,  or  speedily  becomes 
insoluble  in  diUite  neutral  saline  solution,  been  distinguished 
from  paraglobulin  under  the  name  of  .^crum-casein  or  alkaU  al- 
bumin J  The  presence  or  absence  of  tibrinoplastic  powers  appears 
in  the  present  state  of  our  knowledge,  at  all  events,  to  be  an 
unsatisfactory  character  by  which  to  distinguish  one  form  of 
proteid  from  another,  and  it  seems  on  the  whole  the  best  to 
recognize  only  one  proteid  as  existing  in  serum  besides  serum 
albumin,  and  to  call  it  paraglobulin .^  Hammarsten^  finds  that 
saturation  with -magnesium  sulphate  is  a  more  trustworthy 
means  of  throwing  down  paraglobulin  than  the  saturation  with 
sodium  chloride  generally  employed  ;  and  by  the  use  of  this 
method  has  come"  to  the  conclusion  that  the  quantity  of  para- 
globulin present  in  serum  has  been  greatly  underrated.  It  has 
hitherto  been  generally  spoken  of  as  existing  in  small  quantities 
only,  but  Hammarsten  has  estimated  it  as  varying  in  difierent 
animals  from  1.788  per  cent,  (rabbit)  to  4.565  per  cent,  (horse), 
the  serum  albumin  ranging  from  4.43(3  per  cent,  (rabbit)  to  2.677 
per  cent,  (horse).  In  human  blood  he  found  3.103  per  cent,  par- 
aglobulin, and  4.516  per  cent,  serum  albumin. 

Tile  fats,  which  are  scanty,  except  after  a  meal  or  in  cer- 
tain i)athological  conditions,  are  the  neutral  fats,  stearin, 
palmitin,  and  olein,  with  a  certain  quantity  of  their  respec- 
tive alkaline  soaps.     Lecithin^  and  cholesterin  occur  in  very 

^  For  furtlier  details  see  Appendix. 

2  See  Appendix. 

3  Cf.  Weyl,  Zt.  f.  physioloo-.  Chem.,  i  (1877),  p.  72. 
*  Pthiger's  Arcliiv,  xvii  (1878),  p.  413. 

^  For  detailed  acconnts  of  the  characters  of  the  several  chemical  sub- 
stances mentioned  in  tills  and  succeeding  chapters,  consult  the  Appendix 
under  the  appropriate  headings. 


40  BLOOD. 

small  quantities  only.  Among-  the  extractives  present 
in  serum  may  be  put  down  all  the  nitro<^enous  and  other 
substances  which  form  the  extractives  of  the  body  and  of 
food,  such  as  urea,  kreatin,  sugar,  lactic  acid.  etc.  A  very 
large  numl)er  of  these  have  been  discovered  in  tlie  blood 
under  various  circumstances,  the  consideration  of  which 
must  be  left  for  the  present.  The  peculiar  odor  of  blood- 
serum  is  prolmbly  due  to  the 'presence  of  volatile  bodies  of 
the  fatty  acid  series.  The  faint-yellow  color  of  serum  is 
due  to  a  special  yellow  pigment.  The  most  characteristic 
and  important  chemical  feature  of  the  saline  constitution  of 
the  serum  is  the  preponderance  of  sodium  salts  over  those 
of  potassium.  In  this  respect  the  serum  otters  a  marked 
contrast  to  the  corpuscles  (see  below).  Less  marked,  but 
still  striking,  is  the  abundance  of  chlorides  and  the  poverty 
of  phosphates  in  the  serum  as  compared  with  the  corpuscles. 
The  salts  may,  in  fact,  briefly  be  described  as  consisting 
chiefly  of  sodium  chloride,  with  small  quantities  of  sodium 
carbonate,  sodium  suli)liate,  sodium  phosphate,  calcium 
phosphate,  and  magnesium  phosphate. 

[Physical  Properties  of  the  Red  Corpuscles. — When  ob- 
served under  the  stage  of  a  microsco[)e,  the  red  corpuscles 
appear  as  minute,  circular,  flattened,  biconcavo-convex 
bodies,  depressed  in  the  centre,  and  surrounded  by  an  ele- 
vated rounded  margin.  If  seen  a  little  beyond  the  focus  of 
the  instrument,  the  centre  appears  as  a  dark  spot  surrounded 
by  an  annular  light  ring  ;  wliile  if  the  corpuscle  is  brought 
a  little  within  focus,  the  converse  is  observed.  This  optical 
effect  is  due  to  the  impossibility  of  getting  both  the  bicon- 
cave and  biconvex  portions  in  focus  at  the  same  time. 
The  appearance  of  the  central  dark  spot  was  supposed  to 
indicate  the  existence  of  a  nucleus,  but  this  supposition 
has  been  shown  to  be  erroneous,  from  what  has  already 
been  said.  These  corpuscles  are  further  observed  to  be 
soft,  transparent,  and  ductile.  By  virtue  of  their  elastic  and 
ductile  properties  they  are  capable  of  adapting  themselves 
to  sudden  changes  in  the  direction  of  the  blood-current, 
or  to  modifications  in  the  calibre  of  the  capillaries.  Thus  in 
their  passnge  through  capillary  anastomoses  they  will  often 
be  observed  to  become  bent  nearly  at  right  angles  in  going 
from  one  capillary  to  another  ;  occasionall}'  they  become 
lodged  in  the  middle  of  the  blood  current  on  an  intracapil- 


PHYSICAL  PROPERTIES  OF  THE  RED  CORPUSCLES.   47 


dislodged.     In    tlie   minutest 


lary  septum,  and  are  bent  nearly  double,  resuming  again 
their  original  outline  when 
vessels  they  will  often  appear 
elongated,  so  as  to  be  enabled 
to  pass  through  the  constrict- 
ed channel. 

The  color  of  the  corpuscles 
if  en  mas.<e  is  a  bright  red  ; 
if  seen  singly  they  appear  of 
a  pale  amber  coloi.  After 
the  blood  is  drawn  from  the 
vessels  the}^  exhibit  a  re- 
markable tendency  to  aggre- 
gate by  approximating  their 
sides,  and  thus  form  irregular 
rows,  which,  from  tiieir  ap- 
pearance to  rolls  of  money, 
iiave  been  termed  rouleaux. 
If  the  amount  of  plasma  l*e 
quite  small,  so  that  the  cor- 
puscles cannot  be  floated 
sntKciently  to  allow  of  the 
approximation  of  their  entire 
sides,  they  will  overlap  or 
adhere  by  their  edges. 

Another  interesting  fact  observed  after  the  blood  is 
drawn,  is  that  tlieir  outline  becomes  much  changed  bv  the 
development  of  small  nodular  projections  on  their  edges. 
If  the  corpuscles  are  now  allowed  to  be  somewhat  desic- 
cated, they  become  shrunken  and  assume  a  stellate  or 
crenated  appearance. 

In  different  animals  these  corpuscles  vary  both  in  size 
and  form.  In  mammalia  (excluding  the  camel  tribe)  they 
exist  as  circular  disks,  relatively  small,  possessing  no  nu- 
cleus. In  aves  they  are  oval,  nucleated,  and  larger  ;  while 
in  reptilia  they  possess  the  same  features  as  in  aves,  but 
are  still  larger.  The  different  forms  and  sizes  of  these  cor- 
puscles are  beautifully  exhibited  in  the  accompanying 
figure.     (Fig.  6.) 

The  size  of  the  corpuscles  seems  to  bear  no  relation  to 
tlie  size  of  the  bod}',  but,  as  has  been  pointed  out  by  ]\[ilne- 
Edwards,  there  occasionally  exists  a  relation  between  the  size 
and  the  muscular  activity  of  the  animal.  Thus  it  was  found 
that  in  deer  and  other  fleet-footed  animals  the  corpuscles 


Rod  Corpuscles  of  Man,  At  a,  the  cor- 
puscles are  seen  fiat,  on  edge,  and  in 
rolls;  the  first  two  curpuscles  show  the 
central  spot  or  concavity  dark  and  light; 
next  are  shown  the  biconcave  and  con- 
cavo-convex forms;  among  the  rolls,  one 
corpuscle  is  drawn  out,  by  virtue  of  its 
viscidity,  and  would  resume  its  circular 
shape  by  virtue  of  its  elasticity. 


48 


BLOOD. 


were  relatively  small  ;  in  aini)liil)ia,  wliicli  arc  comparatively 
sluggish,  the   corpuscles   were  relativel}'  larger.    The   rela- 


FiG.  G. 
Mammals.        Birds.        Reptiles.  Ampliiliia. 


Fish. 


The  measurements  in  the  figure,  which  are  of  the  average  diameters,  represent, 
fractions  of  an  inch.  In  the  oval  corpuscles  the  measurements  of  the  long  diameters 
are  indicated. 

tion  then  that  the  diameter  of  the  corpuscle  would  bear  to 


COiMPOSITION    OF    THE    RED    CORPUSCLES.  49 

the  muscular  activity  would  be  iu  au  inverse  ratio.  It  has 
also  been  found  that  the  higher  the  scale  of  life  is  advanced 
the  smaller  the  diameter  of  these  bodies  become. 

The  action  of  different  substances  on  the  corpuscles  is 
very  interesting.  Water  causes  them  to  swell  and  become 
gloljular.  Acetic  acid  and  alkalies  cause  tliem  to  swell  and 
become  decolorized.  Ether,  when  added  to  l)lood  outside  of 
the  vessels,  dissolves  the  stroma,  setting  the  coloring  matter 
free.  Tannic  acid  causes  a  nodule  to  project  from  the  cir- 
cumference. Electric  shocks  temporarily  crenate  them,  which 
state  is  followed  by  their  becoming  round  and  decolorized. 
In  fever  they  are  diminished  in  size,  and  may  be  restored 
by  quinine  or  other  antipyretics.  Cari)onic  acid  gas  renders 
them  biconvex.  Sodium  chloride  causes  numerous  thorn- 
like projections  to  appear  on  their  circumference.] 

Composition  of  the  red  corpuscles. — The  corpuscles  con- 
tain less  water  liian  the  serum.  In  100  parts  of  wet  cor- 
puscles there  are  of 

Water,     ....     56.5  parts. 
Solids,      ....     43.5     " 

The  solids  are  almost  entireh'  organic  matter,  the  inorganic 
salts  in  the  corpuscles  amounting  to  less  tlian  1  p.  c.  Of 
the  organic  matter  again  by  far  the  larger  part  consists  of 
haemoglobin.  In  100  parts  of  the  dried  organic  matter  of 
the  corpuscles  of  human  blood,  JiidelF  found,  as  the  mean 
of  two  observations. 

Hremoglobin,     .     .     .     90.54        Lecithin,    .     .     .     .54 
Proteid  Substances,   .       8.67        Cholesterin,     .     .     .25 

The  composition  and  properties  of  haemoglobin  will  be  con- 
sidered in  connection  with  respiration.  Of  the  proteid  sub- 
stances which  form  the  stroma  of  the  non-nucleated  red 
corpuscles  this  mucii  may  be  said,  that  they  belong  to  the 
globulin  family.  The  amount  of  filu'inoplastic  paraglobuliu, 
a!ul  the  exact  nature  of  the  other  members  of  the  group 
present,  must  be  considered  as  yet  undetermined.  As  re- 
gards the  inorganic  constituents,  the   corpuscles  are  distin- 


Hoppe-Seyler,  Untei*snch.,  ill,  390. 


50 


BLOOD. 


ouished  hy  the  relative  abundance  of  the  salts  of  [)otassium 
and  of  [)h()sphates. 

The  distribution  of  inori^anic  salts  in  blood  ma}''  be  seen  from 
the  followinj^  analysis  by  C.  Schmidt  of  the  ash  of  plasma  and 
coriHiscles  respectively  (tlie  iro)i  which  bcloni^s  almost  exclusively 
to  the  hi\imoglobin'  of  the  red  corpuscles  and  exists  in  mere  tra(xs 
only  in  the  serum  or  plasma  being  omitted). 


I.\  lOM  Parts  Corpvsclks. 


In  1000  Parts  Plasma. 


Potassium  chloride, 

3.679 

Potassium  chloride, 

.359 

"         sulphate, 

.1:52 

"         sulphate, 

.281 

"         phosphate, 

2,343 

Sodium                '' 

.G3IJ 

Sodium  phosphate, 

.271 

Calcium              " 

.091 

Calcium         " 

.298 

Magnesium        " 

.060 

Magnesium  " 

.218 

Soda                    " 

.341 

Soda, 

1.532 

Sodium  chloride. 

5.546 

7.282 

8.50.5 

It  must  be  remembered  that  the  arrangement  of  bases  and  acids 
in  such  an  analysis  is  an  artilicial  one,  and,  moreover,  that  the 
ash  does  not  represent  the  inorganic  salts  present  in  a  natural 
condition  in  the  blood.  Thus,  for  instance,  the  phosjihates  in  the 
ash  are  largely  derived  by  oxidation  from  the  phosphorus  present 
in  the  lecithin,  and  the  sulphates  similarly  from  the  sulphur  of 
proteid  substances.  On  the  other  hand,  carbonic  anhydride  is 
absent  from  the  above  table,  though  carbonates  undoubtedly  exist 
in  the  serum.  Free  soda  is  put  down  as  a  constituent  of  the  ash, 
because  in  the  ash  the  bases  preponderate  over  the  acids  (even 
when  carbonic  anhydride  is  reckoned  with  them)  ;  this  alone 
shows  how  little  the  salts  of  the  ash  correspond  to  those  really 
present  in  the  blood.  Among  the  natural  saline  constituents  of 
serum  may  be  enumerated  sodium  chloride,  calcic  phosphate, 
which  is  enabled  to  exist  in  a  state  of  solution  in  the  alkaline 
blood  by  reason  of  its  being  combined  in  some  way  or  other  with 
the  proteids,  and  sodium  carbonate. 

[Properties  of  the  White  Corpuscles. — The  white  corpus- 
cles exist  in  the  blood  as  free  masses  of  i^rotoplasm.  They 
appear  as  globules  with  granular  contents,  frequently  con- 
taining a  nucleus  or  nuclei.  As  observed  in  the  stage  of 
the  microscope  the}^  are  irregularly  shaped  masses,  and  are 


^  Haemoglobin  contains  .4  to  .5  per  cent,  of  Fe,  and  the  quantity  of 
iron  in  the  blood  will  depend  on  the  quantity  of  haemoglobin. 


PROPERTIES    OF    WHITE    CORPUSCLES. 


51 


remarkable  for  their  pseudopod  prolongations  and  move- 
ments, which,  from  their  resendilance  to  those  of  the  amoeba, 
have  been  termed  '•  the  amoeboid  movements." 

In  the  bloodvessels  they  snstain  their  globular  form,  and 
have  a  tendency  to  adhere  to  the  sides  of  the  vessels — a 
tendency  directly  oi)posite  to  that  of  the  red  corpuscles. 
The}    possess    a   very    remarkable    property-  of   migi'ating 


Fig.  7. 


a.  Common   white  corpuscle  soon  after  its  withdrawal  from  the  vessels  (magni- 
fied). 

b.  The  surface  become  prickly,     h.  Protrusion  of  larger  processes  and  apparition 
of  nuclei. 


through  the  intercellular  interstices  of  the  capillaries  into 
the  adjacent  tissues.  In  tiiis  act  of  migration  a  prolonga- 
tion is  sent  out,  which,  penetrating  the  intercellular  sub- 
stance of  the  vessel  wall,  continues  to  urge  its  way  through, 
more  and  more,  until  the  whole  mass  of  protoplasm  has 
passed. 

Through  the  intervention  of  vital  processes,  the  corpus- 
cles, after  reaching  the  extra-vascular  tissues,  undergo  such 
changes  in  the  ditt'erentiatiou  of  the  amceljiform  units  and 
differentiation  of  structure  that  they  become  component 
parts  of  the  tissues,  and  we  have  "  the  manifestation  ol  cer- 
tain only  of  the  fundamental  properties  of  protoplasm,  to 
the  exclusion  or  complete  subordination  of  others." 

The  corpuscles,  as  free  protoplasm,  possess  all  ihe  fun- 
damental proi)erties  of  protoplasm.  As  fixed  j)rotoplasm 
they  lose  certain  of  the  amo3l)if()rm  units.  Free  protoplasm 
is  automatic ;  fixed  protoplasm  is  suliservient  to  the  intlu- 
ences  exerted  through  the  nervous  system.  This  is  prob- 
ably true  of  all  fixed  protoplnstn,  and  we  find  in  rising  the 
scale  of  life,  that  the  more  differentiated  and  fixed  the  pro- 


62  BLOOD. 

toplasm,  the  o^reater  proportionate!}^  is  the  development  of 
the  nervous  svstem. 

The  niii^ration  of  these  corpuscles  is  best  seen  in  points 
of  inrtamniation,  where  vast  numbers  are  seen  cong^regjated 
in  the  bloodvessels  and  extra  vascular  tissues.  Professor 
Binz  and  other  investigators  have  proven  that  quinine  has 
the  very  interesting  power  of  preventing  this  migration.  He 
exposed  tiie  mesentery  of  a  frogon  the  stage  of  a  microscope, 
and  found,  that  after  a  hypodermic  injection  of  quinine,  the 
migration  was  immediately  checked.  He  also  found  that 
in  areas  of  inflammation,  wlien  the  migration  was  most  active, 
it  at  once  ceased  after  the  administration  of  the  drug. 

In  size  they  are  somewhat  larger  than  the  red  corpus- 
cles, measuring  about  1 1.  mmm.  in  diameter.  Although  the 
red  corpuscles  vary  exceedingly  in  size  in  different  species 
of  animals,  the  white  corpuscles  always  retain  about  the 
same  measui'ement.] 

Composition  of  the  White  Corpuscles. — If  it  be  permitted 
to  infer  the  composition  of  the  white  corpuscles  from  that 
of  the  pus-corpuscles,  which  they  so  closely  resemble,  they 
would  seem  to  consist  of  :^ 

1.  Several  proteid  substances,  viz.,  ordinary  albumin,  an  albu- 
min like  that  of  muscle  coagulating  at  48^,  an  alkali  albumin,  a 
substance  closely  resembling  myosin,  and  yet  ditferinix  from  it, 
and  a  peculiar  form  of  proteid  material  soluble  with  difficulty  in 
hydrochloric  acid.     The  nuclei  contain  nuclein.     See  Appendix. 

2.  Lecithin,  extractives,  glycogen,  and  inorganic  salts,  there 
being  in  the  ash  a  preponderance  of  potassium  salts  and  of  phos- 
phates ;  after  the  death  of  the  corpuscle  the  glycogen  appears  to 
be  converted  into  sugar. 

Both  the  corpuscles  and  the  plasma  (or  serum)  contain 
gases.  These  will  be  considered  in  connection  with  respira- 
tion. 

The  main  facts  of  interest,  then,  in  the  ciiemical  compo- 
sition of  the  blood  are  as  follows  :  The  red  corpuscles  consist 
chiefly  of  hiemoglobin.  The  solids  of  serum  consist  chiefly 
of  serum  albumin,  the  quantity  of  flbrin  factors  and  of  alkali 
albuminate  being  small.  The  serum  or  plasma  contrasts 
with  the  corpuscles,  inasmuch  as  the  former  contains  chiefly 

^  Miescher.     Hoppe-Seyler,  Untersuchungen,  iv,  441. 


HISTORY    OF    THE    CORPUSCLES.  53 

chlorides  and  sodium  salts,  while  tlie  latter  are  richer  in 
phosphates  and  potassium  salts.  The  extractives  of  tiie 
blood  are  reraarl^able  rather  for  their  number  and  variability 
than  for  their  abundance,  the  most  constant  and  important 
being  perhaps  urea,  kreatin,  sugar,  and  lactic  acid. 

Sec.  3.    The  History  of  the  Corpuscles. 

In  the  living  body  red  blood-corpuscles  are  continually 
being  destroyed,  and  new  ones  as  continuallj'  being  pro- 
duced.    The  proofs  of  this  are : 

1.  The  number  of  the  red  corpuscles  in  the  blood  at  any 
given  time  varies  much. 

The  number  of  corpuscles  in  a  specimen  of  l)lood  is  determined 
b}^  mixing  a  small  but  carefull}^  measured  quantity  of  the  blood 
with  a  large  quantit}'  of  some  indifferent  fluid,  and  then  actually 
counting  the  corpuscles  in  a  known  minimal  bulk  of  the  mixture. 

This  may  be  done  either  by  Vierordt's'  plan  (somewhat  modi- 
fied bj'  Gowers^),  in  wdiich  a  minimal  quantity  of  the  diluted 
blood,  measured  in  a  fine  capillary  tube,  is  spread  on  a  surface 
marked  out  in  square  areas,  and  the  number  of  corpuscles  in  each 
square  area  counted  under  the  microscope,  or  by  Malassez,-^  in 
which  the  diluted  blood  is  drawn  into  a  capillary  tube  of  flattened 
sides,  and  the  number  of  corpuscles  counted  in  situ  in  the  tube 
by  means  of  an  ocular  marked  out  in  squares,  the  microscope 
being  so  adjusted  that  each  area  of  the  ocular  corresponds  to  a 
certain  capacity  of  the  capillarj-  tube. 

The  average  number  of  red  corpuscles  in  human  blood  is 
about  five  millions  in  a  cubic  millimeter  :  in  mammals  gen- 
erally it  ranges  from  three  to  eighteen  millions.  The  num- 
ber varies  in' different  parts  of  the  vascular  system,  being 
greater  in  the  capillaries  and  in  the  veins  than  in  the  arte- 
ries. It  is  increased. by  meals,  and  diminished  by  fasting  ; 
of  course  the  number  of  corpuscles  present  in  any  given 
bulk  of  blood  being  merely  the  expression  of  the  proportion 
of  corpuscles  to  the  amount  of  plasma,  variations  in  the 
number  counted  might,  and  in  certain  cases  are,  probably, 
caused  by  an  increase  or  decrease  in  the  quantity  of  plasma, 
occurring  while  the  actual  number  of  corpuscles  is  station- 
ar3\     But   many  of  the  variations  cannot  be  so  accounted 

^  Grundriss  der  Physiologic,  p.  9. 

2  Lancet,  1877,  ii,  p.  497." 

■^  Archives  de  Physiologie,  1874,  p.  32. 


64  I3L00D. 

for ;  they  nnist  l)e  due  to  an  increase  or  decrease  of  the  total 
number  of  corpuscles  in  the  body.  After  a  very  large  re- 
duction of  the  total  number  of  red  corpuscles,  as  by  hnemor- 
rhage  or  disease  (an.iimia),  the  normal  proportion  may  be 
regained  even  within  a  very  sliort  time. 

2.  There  are  reasons  for  thinking  that  tlie  urinary  and 
bile  pigments  are  derivatives  of  luvmoglobin.  If  this  be  so, 
an  immense  number  of  corpuscles  must  be  destroyed  daily 
(and  replaced  !)y  new  ones)  in  order  to  give  rise  to  the 
amount  of  urinary  and  bile  pigment  discharged  daily  from 
the  body. 

3.  When  the  blood  of  one  animal  is  injected  into  the  ves- 
sels of  another  [ex.  gr.^  that  of  a  bird  into  a  mammal),  the 
corpuscles  of  the  first  may  for  some  time  be  recognized  in 
blood  taken  from  the  second  ;  but  eventually  they  wholly 
disappear.  This,  of  course,  is  no  strong  evidence,  since  the 
destruction  of  foreign  corpuscles  might  take  place  even 
though  the  proper  ones  had  a  permanent  existence. 


Origin  of  the  Bed  Corpuscles. 
In  the  embryo  red  corpuscles  are  produced  : 

1.  From  metamorphosis  of  certain  mcsoblastic  cells  in  the 
vascular  area.     (Fig.  8.) 

2.  B}'  division  of  the  corpuscles  thus  formed. 

3.  In  a  somewhat  later  stage,  b}'  the  transformation  of 
nucleated  white  corpuscles,  which  probably  arise  in  the  liver 
and  spleen,  and  pass  thence  into  the  blood.  The  cell-sub- 
stance l>ecomes  impregnated  with  haemoglobin,  and  the 
nucleus  breaks  up  and  disappears. 

4.  By  the  direct  transformation  of  the  protoplasm  of  undif- 
ferentiated connective  tissue  corpuscles/  the  red  corpuscle  ap- 
pearing first  as  a  minute  speck  in  the  protoplasmic  cell-substance, 
and  subsequently  enlarging  very  much  after  the  fashion  of  an 
oil-ojlobule. 


Schiifer,  Proc.  Eov.  Soc,  xxii,  243. 


THE    RED    CORPUSCLES.  55 

In  the  adult,  division  of  existiiior  corpuscles  is,  at  least, 
exceedingly  rare,  if  it  occurs  at  all.  In  the  spleen  pulp 
small  nucleated  colored  corpuscles  have  been  oi)served, 
similar  to  those  met  with  in  the  embryo  ;  transitional  forms, 
showing  the  presence  of  haemoglobin  in  the  cell-substance 
and  degeneration  of  the  nucleus  have  been  seen.     In  the 


[Fio.  8. 


^ 


i 


Development  oi  uic  iirst  set  of  tilocMi-enriiUi^cles  ia  the  niaminalian  embryo,  a.  A 
dotted,  uncleated  eiubryo-cell  in  process  of  conversion  into  a  blood-corpuscle;  the 
nucleus  jjrovided  with  a  nucleolus,  b.  A  i^iniilar  cell  with  a  dividing  nucleus;  at  c, 
the  division  of  the  nucleus  is  complete  ;  at  D,  the  cell  also  is  dividing.  K.  A  blood- 
corpuscle  almost  complete,  but  still  containing  a  few  granules.  F.  Perfect  blood- 
corpuscle  of  embryonic  "life.  These  embryonic  corpuscles  are  gradually  replaced  by 
the  corpuscles  of  adult  life,  and  entirely  disappear  by  the  fourth  or  fifth  month 
of  foetal  life.] 

wide  capillaries  of  the  red  medulla  of  bones  similar  transi- 
tional forms  have  been  observed,  and  they  have  also  been 
noticed  in  circulating  blood. 

According  to  Alex.  Schmidt,^  in  living  unchanged  blood 
these  forms  are  abundant ;  they  break  up  and  disappear,  how- 
ever, immediately  that  the  blood  is  shed,  unless  special  precau- 
tions (applications  of  cold,  etc.)  be  used. 

■  From  these  several  facts  it  is  concluded  that  the  red  cor- 
puscles take  origin  from  colorless  nucleated  corpuscles 
similar  to,  if  not  identical  with,  the  ordinary  white  corpus- 
cles of  the  blood. 

In  the  case  of  animals  with  nucleated  red  corpuscles  the  change 
consists  chiefly  in  a  transformation  of  the  native  protoplasm  of 
the  white  corpuscle  into  haemoglobin  and  stroma.  In  the  case 
of  animals  with  non-nucleated  red  corpuscles,  most  observers^ 

^  Op.  tit.  2  Kolliker,  Neumann,  Schmidt. 


56  BLOOD. 


aujrce  in  the  opinion  that  the  nucleus  of  the  white  corpuscle  breaks 
up  and  (lisa])pcai\s,  so  that  the  red  corpuscle  represents  only  the 
modi  lied  cell-substance  of  its  progenitor.  Wharton  Jones,  sup- 
ported by  Huxley,  resting  chieliy  on  the  parallelism  in  size  and 
form  between  the  nuclei  of  the  white  corpuscles  and  the  entire 
red  corpuscles  in  different  orders  and  families  of  mammals,  con- 
cludes that  the  latter  is  in  realit}^  the  naked  colored  nucleus  of 
the  former. 

Hayem'  describes  the  red  corpuscles  as  arising  from  a  kind  of 
uncolored  corpuscle  quite  distinct  from  the  ordinary  white  cor- 
puscles. To  thase,  which  have  been  overlooked  on  account  of 
their  great  transparency,  and  which  are  jis  numerous,  or  even 
more  numerous  than  the  ordinary  white  corpuscles,  he  proposes 
to  give  the  name  of  Iwiiaat/Masts. 

There  are  reasons  for  believing  that  not  only  may  the 
numl)er  of  red  corpuscles  vary,  but  also  the  quantity  of 
ha3moglol)in  present  in  the  individual  corpuscles  ditfer  under 
different  circumstances.  Malassez,^  by  comparing  the  tint 
of  a  quantity  of  hlood  the  numbers  of  whose  corpuscles 
had  been  estimated,  with  that  of  a  graduated  solution  of 
picrocarminate  of  ammonia,  has  been  able  to  estimate  the 
amount  of  lisemoglobin  present  in  the  corpuscles  under  dif- 
ferent circumstances.  He  finds  that  in  anjemia  the  poverty 
of  tiie  corpuscles  in  haimoglobin  is  even  more  striking  than 
the  scantiness  of  the  corpuscles,  and  is  sooner  affected  by 
the  administration  of  iron. 


Origin  of  White  Corpusclefi. 

That  the  white  corpuscles  are  continually  being  removed 
is  evident  from  the  fact  that  they  var}-  extremely  in  number 
at  different  times  and  under  various  circumstances.  They 
are  very  largely  increased  by  taking  food.  Thus  during 
fasting  tliey  may  be  seen  in  a  drop  of  ])lood  to  bear  to  the 
red  the  proportion  of  1  in  800  or  1000.  After  a  meal  this 
proportion  rises  to  1  in  300  or  400. 

The  fact  that  in  the  lymphatic  glands,  and  other  adenoid  struc- 
tures, corpuscles,  similar  to  if  not  identical  with  white  blood- 
corpuscles,  are  to  be  seen  of  very  various  sizes,  many  with  double 
nuclei,  and  some,  indeed,  actually  dividing  into  two  corpuscles, ^ 

1  Cornpt.  Eend.,  t.  So  (1877),  p.  1285. 

-  Archives  de  Physiologie,  1877,  p.  1.     Cf.  also  H^^yem,  ibid.,  p.  649. 

^  Ranvier,  Traite  d'histologie,  p.  161. 


THE    RED    CORPUSCLES.  oV 

suggests  that  these  organs  are  the  birthplaces  of  the  white  cor- 
puscles. The  lymph  is  continually  pouring  into  the  blood  a 
crowd  of  white  corpuscles,  which,  for  the  most  part,  make  their 
appearance  in  the  hmph-vessels  after  the  latter  have  traversed 
the  Ij-mphatic  glands.  And  this  view  is  further  supported  by 
the  fact  that  in  the  disease  leucferaia,  where  the  white  corpus- 
cles maj'  be  so  abundant  as  to  number  as  many  as  1  to  10  red, 
the  spleen,  the  lymphatic  glands,  and  other  forms  of  adenoid 
tissue,  are  enlarged.  (The  phenomena  are,  however,  capable  of 
a  converse  interpretation,  viz.,  that  the  wdiite  corpuscles,  failing 
to  become  converted  into  red  corpuscles,  are  crowded  into  the 
lymphatic  organs.) 

At  the  same  time  it  is  open  for  us  to  suppose  that  any  pro- 
liferating tissue  may  give  rise  to  new  corpuscles  ;  and  Klein'^ 
states  that  he  has  seen  them  budded  otf  from  the  reticulum  of  the 
spleen.     The  white  corpuscles  have  also  been  observed  to  divide .^ 

We  may  conchKle,  therefore,  that  the  white  corpuscles 
probabl}'  arise,  by  division  cliiefly,  from  the  leucocytes  of 
adenoid  tissue,  but  that  other  sources  may  exist. 

Fate  of  the  White  CorpUi<cles. 

As  we  have  seen,  it  is  extremely  probable  that  a  large 
number  of  the  white  corpuscles  end  by  giving  birth  to  red 
corpuscles;  but  it  is  only  possible  that  a  not  inconsiderable 
number  die  in  the  blood  and  are  tliere  broken  up  and,  disap- 
pear. 

On  the  other  hand  we  know  that  in  an  inflamed  area  the 
white  corpuscles  migrate  in  large  numbers  into  the  extravas- 
cular  portions  of  the  tissues,  and  there  are  reasons  for  think- 
ing that  not  only  the  pus-corpuscles  and  ''  exudation  "  cor- 
puscles, which  are  the  common  products  of  inflammation, 
but  even  the  new  tissue  elements  (connective  tissue  cells  and 
fibres,  bloodvessels,  etc.),  which  make  their  appearance  as 
the  result  of  tiie  so-palled  ''productive"  inflammations,  are 
tlie  descendants,  immediate  or  remote,  of  such  migrator}'- 
corpuscles.  But  a  discussion  of  this  question  would  lead  us 
too  far  awa\'  from  the  purpose  of  this  w^ork. 

Fate  of  the  Red  Cor^puscles. 

In  the  spleen  we  find,  as  Kolliker  long  since  pointed  out, 
large  protoplasmic  cells,  in  which  are  included  a  number  of 

^  Q.  J.  Micros.  Sci.,  xv  ( 1875),  p.  370. 
2  Klein,  Hdb.  Phys.  Lab.,  p.  8. 


58  BLOOD. 

red  corpuscles  ;  and  these  red  corpuscles  may  he  observed 
in  various  stages  of  apparent  disintegration.  Jt  is  probable, 
therefore,  that  the  spleen  is  the  grave  of  many  of  the  red 
corpuscles. 

•Since  serum  of  fresh  blood  contains  no  dissolved  luemo- 
globin,  it  is  clear  that  the  luemoglobin  of  tlie  broken-up 
corpuscles  must  speedily  i)e  transformed  into  some  other 
body.  Into  what  other  body  ?  In  old  blood  clots  (as  in 
those  of  cerebral  haemorrhage)  there  are  frequently  found 
minute  crystals  of  a  body  which  has  received  the  name 
haemaloidln.  There  can  be  no  doubt  that  the  hsematoidin 
of  these  clots  is  a  derivative  from  the  luTmoglobin  of  the 
escaped  blood.  We  know  ^  that  iiittmoglobin  contains,  be- 
sides a  proteid  residue,  a  residue  not  proteid  in  nature, 
called  hicmatin.  We  know,  further,  tliat  hiiematin  may  lose 
the  iron  which  it  contains  (and  which  appears  to  be  loosely 
attached),  and  yet  remain  a  colored  body.  So  that  there  is 
no  ditticulty  in  the  passage  from  the  proteid  and  iron  contain- 
ing haemoglobin  to  the  proteid-and-iron  free  lu\}matoidin. 
But  luematoidin,  not  only  in  the  form  and  ap})earance  of  its 
crystals,  but  also,  as  far  as  can  be  ascertained  by  the  analy- 
sis of  the  small  quantities  at  disposal,  in  its  chemical  com- 
position, is  identical  with  hilirubm^  the  primary-  i)igment  of 
bile.  Moreover,  the  injection  of  haemoglobin,  or  of  dissolved 
red  corpuscles,  into  the  vessels  of  a  living  animal,  gives  rise 
to  a  large  amount  of  bile  pigment  in  the  urine,  and  at  the 
same  time  increases  enormously  the  relative  quantity  of 
bilirubin  in  the  bile.  Thus  though  no  one  has  yet  succeeded 
in  producing  bilirubin  artificially  from  haemoglobin,  facts 
point  very  strongly  to  the  view  that  the  red  corpuscles  are 
used  up  to  supply  bile  pigment. 

It  must  be  added,  however,  that,  according  to  Preyer,^  the 
spectra  of  haematoidin  and  bilirubin  are  quite  distinct,  and  that 
many  observers  have  failed  to  obtain  bile  pigment  in  the  urine  as 
the  result  of  injection  of  a  solution  of  haemoglobin.  Blood 
clots  frequently  -contain,  besides  or  in  place  of  haematoidin,  a 
yellow  substance  named  lutein,  which  is  certainly  distinct  from 
bilirubin.  Lutein  is  the  substance  which  gives  to  corporea  lutea 
their  characteristic  color. 

Our  knowledge  of  urinary  pigments  is  so  imperfect  that  little 
can  be  said  as  to  their  relation  to  haemosrlobin.     We  cannot  at 


^  See  chapter  on  Changes  of  Blood  in  Respiration. 
^  Die  Bhit-Krvstalle. 


QUANTITY    OF    BLOOD    IN    THE    BODY.  59 

present  definitely  trace  the  normal  urinary  pigment  back  to 
haemoglobin,  however  probable  such  a  source  may  seem  ;  but 
Jaffe  finds  in  many  urines,  especially  those  of  fever  patients,  a 
body  called  urobilin^  identical  with  hi/drohiliruhi7i  obtained  from 
bilirubin  by  reduction  with  sodium  amalgam.^ 

Sec.  4.    The  Quantity  of  Blood,  and  its  Distribution 
IN  THE  Body. 

The  total  quantity  of  blood  present  in  an  animal  body  is 
estimated  in  the  following  way.  As  much  blood  as  possible 
is  allowed  to  escape  from  the  vessels  ;  this  is  measured  di- 
rectly. The  vessels  are  then  washed  out  with  water  or 
normal  saline  solution,  and  the  washings  carefnll}' collected, 
mixed,  and  measured.  A  known  quantity  of  blood  is  diluted 
with  water  or  normal  saline  solution  until  it  possesses  the 
same  tint  as  a  measured  specimen  of  the  washings.  This 
gives  the  amount  of  blood  (or  rather  of  htemoglobin)  in  the 
measured  specimen,  from  which  the  total  quantity  in  the 
whole  washings  is  calculated.  Lastly,  the  whole  body  is 
carefully  minced  and  washed  free  from  blood.  The  wash- 
ings are  collected  and  filtered,  and  the  amount  of  blood  in 
them  estimated  as  before  by  comparison  with  a  specimen  of 
diluted  blood.  The  quantity  of  blood  in  the  two  washings, 
together  with  the  escaped  blood,  gives  the  total  quantit}^  of 
blood  in  the  body.  Estimated  in  this  vvay,  the  total  quan- 
tity of  blood  in  the  human  body  may  be  said  to  be  about 
yVth  of  the  body  weio^ht. 

There  are  several  sources  of  error  in  the  above  method.  One 
is  that  venous  blood  has  less  coloring  power  than  arterial  blood. 
This  has  been  met  by  Gscheidlen  by  poisoning  the  animal  with 
carbonic  oxide,  by  which  all  the  haemoglobin  is  reduced  to  one 
state,  and  therefore  has  throughout  the  same  coloring  power. 
The  quantity  of  haemoglobin  in  the  muscular  fibre  itself  is  a 
source  of  error,  but  probably  a  very  slight  one.  The  difiiculty  of 
getting  a  clear  infusion  of  the  minced  tissues  is  more  serious. 
According  to  Ranke^  the  total  blood  in  the  body  of  a  rabbit 
amounts  to  i^th  of  the  body  weight,  in  a  dog  to  x'^th,  in  a  cat  to 
5',  st,  in  a  frog  to  x'^th. 

The  blood^  is  distributed  as  follows  in  round  num!)ers: 


^  Cf.  Liebermann,  Pflii2:er's  Archiv,  xi  (1875),  p.  181  ;  Disque,  Ztschr, 
f.  Physiol.  Chem.,  ii  (1878),  p.  259. 

2  Blut-vertlieilung,  1871.  ^  Ranke,  op.  cit. 


60 


BLOOD. 


About  one-fourth  in  the  heart,  lungs,  large  arteries,  and  veins. 
"      liver. 
"  "  "      skeletal  muscles. 

"  "  "      other  organs. 

Since  in  the  heart  and  great  bloodvessels  the  blood  is 
simply  in  transit,  without  undergoing  any  great  changes 
(and  in  the  lungs,  as  far  as  we  know,  the  changes  are  lim- 
ited to  respiiatory  changes),  it  follows  that  the  changes 
which  take  place  in  passing  through  the  liver  and  skeletal 
muscles  far  exceed  those  wliich  take  place  in  the  rest  of  the 
body. 

Kanke  found  the  distribution  to  be  as  follows  : 


IN  THE  VISCKRA. 


IN  THE  CARCASE. 


Per  cent,  of 
total  blood. 

-DoKKu    (Living,  63.4 

^^^^'^  1  Dead,  rigid,   01.23 
Dog, 59.0 


Per  cent,  of 
organ  weight. 

18.0 
20.6 
24.0 


Per  cent,  of 
total  blood. 

30.6 

38.77 
41.0 


Per  cent,  of 
organ  weight. 

2.7 
2.7 
3.4 


In  the  various  oro-ans  of  the  rabbit: 


Per  cont.  of  organ  weight. 


Per  cent,  of  total  blood. 

Spleen,     . 
Brain  and  cord. 
Kidneys, 

Skin,        .... 
Intestines, 

Bones,  etc.,      .        .         .     8.24    Kidneys, 
Heart,  lungs,  great  blood-  Spleen, .... 

vessels,  .  .  .  22.70  Liver,  .... 
Skeletal  muscles,  .  .  29.20  (Heart,  lungs,  and  great 
Liver,      ....  29.30       vessels,       .         .        .  03.11). 


.23  Skin,     . 

1.24  Bones,  . 

1.03  Alimentary  canal, 

2.10  Muscles, 

0.30  Brain  and  cord,    . 


1.07 

2.30 

3.40 

5.14 

5.52 

11.80 

12.50 

28.71 


THE    CONTRACTILE    TISSUES.  '61 

CHAPTER  ir. 

THE  COXTRACTILE  TISSUES. 

The  greater  number  of  the  movements  of  the  complex 
animal  body  are  carried  on  by  means  of  the  skeletal  striated 
muscles.  A  skeletal  muscle  when  subjected  to  certain  influ- 
ences contracts,  i.  e.,  shortens,  bringing  its  two  ends  nearer 
together;  and  the  shortening  acting  upon  various  bony 
levers  or  l>y  help  of  other  mechanical  arrangements,  pro- 
duces a  movement  of  some  part  of  the  body.  The  striated 
tissue  of  which  the  skeletal  muscles  are  composed  is  the 
chief  contractile  tis-siie.  The  peculiar  muscular  tissue  of  the 
heart  is  another  contractile  tissue;  under  certain  influences 
the  fibres  into  which  it  is  arranged  shorten,  and  thus  give 
rise  to  the  beat  of  the  iieart.  A  similar  shortening  or  con- 
traction of  the  fusiform  fibre-cells  of  plain  muscular  tissue, 
gives  rise  to  movements  or  to  changes  of  calibre,  etc.,  of  the 
alimentary  canal,  the  urinary  bladder,  the  uterus,  the  arte- 
ries, and  the  like. 

At  first  sight  ''  contraction"  of  any  one  of  these  forms  of 
difterentiated  muscular  tissue  seems  wholly  unlike  an  amoe- 
boid movement  of  an  amoeba  or  of  a  white  corpuscle  of  the 
lilood.  And  yet  tlie  transition  from  the  one  to  the  other  is 
very  slight.  A  typical  amoeba  may  be  regarded  as  spherical 
in  form,  and  when  it  is  executing  its  movements  the  pseu- 
dopodic  bulging  of  its  protoplasm  may  be  seen  to  occur  now 
on  this  now  on  that  part  of  its  circumference,  and  to  take 
now  this  and  now  that  direction.  The  fibre-cell  of  plain 
muscular  tissue  is  a  nucleated  protoi)lasmic  juasss  of  a  dis- 
tinctly fusifoim  shai)e,  and  when  it  executes  its  movements, 
i.  e.,  contracts,  tlie  l)ulgiug  of  its  protoplasm  is  always  a 
lateral  bulging  in  a  direction  at  right  angles  to  the  long  axis 
of  the  fibre-cell.  Since  as  we  shall  see  there  is  no  change  of 
total  bulk,  this  thickening  of  the  fibre  by  means  of  the  lat- 
eral bulging  is  necessarily  accom.panied  by  a  shortening  of 
its  length.  The  contraction  of  muscular  tissue  is  in  fact  a 
limited  and  definite  amoeboid  movement  in  which  intensity 
and  rapidity  are  gained  at  the  expense  of  variety. 

Besides  these  movements  which  are  carried  out  in  the 
bod}'  by  means  of  diflferentiated  muscular  tissue,  there  are 
others  brought  about  by  the  peculiar  structures  known  as 
cilia,  among  which  we  ma}'  include  the  motile  tails  of  sper- 
matozoa ;  and  ordinary  amoeboid  movements  are  not  waut- 

6 


62  THE    CONTRACTILE    TISSUES. 

iiig,  being  conspicuously  siiown  by  the  so-called  migi'atinf*; 
cells.  We  may  incliule  both  these  under  the  heading  of 
coutraclile  tissues. 

or  all  these  various  forms  of  contractile  tissue  the  skeletal 
striated  muscles,  on  account  of  the  more  complete  develoi)- 
ment  of  their  functions,  will  be  lietter  studied  first ;  the 
others,  on  account  of  their  very  simplicity,  are,  in  many 
respects,  less  satisfactorily  understood. 

AH  the  oi-dinary  striated  skeletal  muscles  are  connected 
with  nerves.  We  have  no  reason  for  thinking  that  their 
contractility  is  called  into  play,  under  normal  conditions, 
otherwise  than  by  the  agency  of  nerves. 

Muscles  find  nerves  being  thus  so  closely  allied,  and  having 
besides  so  many  properties  in  common,  it  will  conduce  to 
clearness  and  brevity  if  we  treat  them  together. 

\_Phy biological  Anatomy  of  the  Skeletal  or  Voluntary  MaaeleH. 

The  skeletal  muscles  compose  that  portion  of  the  body 
which  is  commonly  termed  flesh.  They  are  made  up  of 
bundles,  which  are  subdivided  through  several  gradations  into 

Fic  9. 

a 


Transverse  section  of  a  portion  of  a  muscle  (magnified),  showing  smallf^r  bundles 
with  secondary  and  primitive  fasciculi,  a,  e.Kterual  periinj'sium ;  c,  internal  perimy- 
sium. 

smaller  bundles.  These  in  their  turn  consist  of  secondary 
fasciculi,  closely  bound  together,  and  inclosed  in  a  fibro 
areolar  tissue,  called  the  '*  internal  perimysium."  (Fig.  9,  c.) 
The  internal  perimysium  is  formed  by  prolongations  from  the 
"external  perim3'sium,"  which  envelops  the  muscle.  (Fig. 
9,  a.) 

These  fasciculi  are  made  up  of  a  number  oi prinufire  fas- 


THE    SKELETAL    OK    VOLUNTARY    MUSCLES. 


63 


cicnli  or  fihrex,  i^l-icerl  parallel  with  each  other,  inclosed 
and  separated  Ity  a  delicate  structureless  membrane  called 
the  sarcolemma.  They  are  more  or  less  flattened  on  their 
sides  owing  to  the  pressure  of  adjacent  fihres.  Tiiese 
filtres,  which  are  the  contractile  substance  of  the  organ, 
are,  in  their  turn,  comjjosed  of  numerous  long,  cylindri- 
torm,  threadlike  bodies  (^'aWq^X  fihriUse  (Fig.  10),  which  have 

Fig.  10. 


A,  a  muscular  fibre  showing  longitudinal  and  transverse  lines  of  separation ;  c, 
individual  fihrillse,  which  have  been  separated  in  the  longitudit  al  lines;  B,  showing 
the  transverse  lines  of  separation  ;  b',  plate  detached  and  more  highly  magnified, 
showing  sarcous  elements  more  distinctly ;  c',  c",  sarcous  elements  more  highly  mng- 
nified,  showing  different  appearances. 

distinct  longitudinal  lines  of  se[)aration,  and  are  marked 
b}'  transverse  striae,  giving  them  an  appearance  which  has 
been  likened  to  a  number  of 
strings  of  beads  closely  bound 
together.  The  transverse 
strife  mark  the  divissions  be- 
tween the  cells  composing 
the  fibrilhe.  These  cells, 
which  are  called  the  '•  sarc- 
ous elements,"  arc  rectan- 
gular in  outline,  and  i)Os- 
sess  a  dark  centre,  which 
indicates  the  presence  of  a 
nucleus. 

When  these  fibres  are  torn,  the  sarcolemma  l\v  virtue  of 
its  greater  tenacity,  often  remains  intact,  and  forms  a  deli- 
cate, transparent  tube,  in  which  are  inclosed  the  ruptured 
ends  of  the  fi'u-e.     (Fig.  11.) 

When  the  muscular  fibre  is  attached  to  the  skin  or  mucous 
membrane,  it  is  continuous  with  the  areolar  tissue  ;  when 
attached  to  a  tendon,  the  sarcolemma  becomes  joined  to  the 


>ruseular  fibre  torn  across;  the  sarco- 
lemma still  connecting  the  two  parts  of 
the  fi  hie.— After  Todd  and  Bo  war  ax. 


64  THE    CONTRACTILE    TISSUES. 

tissue  of  tlic  tendon,  nnd  the  fibre  ends  in  a  conical  extrem- 
ity, which  is  received  into  a  depression  in  the  tendon,  or  else 
is  connected  to  an  adjoining  fibre  hy  means  ofthe  sarcolemma. 
The  skeletal  muscles  are  abundantly  sn|)i)lied  with  nerves 
and  bloodvessels.  The  nerves  are  j)rinci|)ally  supplied  by 
the  cerebro-spinal  system.  The  ca[)illaries  form  elongated 
meshes  outside  of  the  sarcolemma.] 

Sec.  1.   The  Phenomena  of  Muscle  and  Nerve. 

Muiicular  and  Nervous  Irritability. 

The  skeletal  muscles  of  a  frog,  the  brain  and  spinal  cord 
of  which  have  been  destroyed,  do  not  exhibit  any  spontane- 
ous movements  or  contractions,  even  though  the  nerves  be 
otherwise  quite  intact.  Left  untouched  the  whole  body  may 
decompose  without  any  contraction  of  any  of  the  muscles 
having  been  witnessed.  Neither  the  skeletal  muscles  nor 
the  nerves  distributed  to  them  possess  any  power  of  auto- 
matic action. 

If,  however,  a  muscle  be  laid  bare  and  be  more  or  less 
violently  disturbed,  if  for  instance  it  be  pinched,  or  touched 
with  a  hot  wire,  or  brought  in  contact  with  certain  chemical 
substances,  or  subjected  to  the  action  of  galvanic  currents, 
it  will  contract  whenever  it  is  thus  disturbed.  Though  not 
possessing  any  automatism,  the  muscle  is  (and  continues 
for  some  time  after  the  general  death  of  the  animal  to  be) 
irritahle.  Though  it  remains  quite  quiescent  when  left  un- 
touched, its  powers  are  then  dormant  only,  not  absent. 
These  require  to  be  roused  or  "  stimulated  "  by  some  change 
or  disturbance  in  order  that  the}-  may  manifest  themselves. 
The  substances  or  agents  which  are  thus  able  to  evoke  the 
activity  of  an  i;ritable  muscle  are  spoken  of  as  dimuli. 

But  to  produce  a  contraction  in  a  muscle  the  stimulus 
need  not  be  applied  directly  to  the  muscle  ;  it  ma}^  be  ap- 
plied indirectly  by  means  of  the  nerve.  Thus  if  the  trunk 
of  a  nerve  be  pinched,  or  subjected  to  sudden  heat,  or  dipped 
in  certain  chemical  substances,  or  acted  upon  by  various 
galvanic  cm  rents,  contractions  are  seen  in  the  muscles  to 
wdiich  branclK  s  of  the  nerve  are  distributed. 

The  nerve,  like  the  muscle,  is  irritable,  it  is  thrown  into  a 
state  of  activity  by  a  stimulus;  but  unlike  the  muscle  it 
does  not  itself  contract.  The  changes  set  up  in  the  nerve 
by  the  stimulus  are  not  visible  changes  of  form  ;  but  that 
changes  of  some  kind  or  other  are  set  up  and  propagated 


MUSCULAR    AND    NERVOUS    IRRITABILITY.  65 

along  the  nerve  down  to  the  muscle  is  shown  by  the  fact 
that  the  muscle  contracts  when  a  part  of  the  nerve,  even  at 
some  distance  from  itself,  is  stimulated.  Both  nerve  and 
muscle  are  irritable,  but  only  the  muscle  is  contractile,  ?'.  e., 
ninnifests  its  irritability  by  a  coutraction.  Tlie  nerve  mani- 
fests its  irritability  bv  transmitting  along  itself,  without  any 
visible  alteration  of  form,  certain  molecular  changes  set  up 
by  the  stimulus.  We  shall  call  these  changes  tiuis  ])ropa- 
gated  along  a  nerve,  ^-nervous  impulses." 

We  have  stated  aliove  that  the  muscle  is  irritable  in  the 
sense  that  it  may  be  thrown  into  contractions  by  stimidi  ap- 
plied directly  to  itself.  But  it  might  fairl}'  be  urged  that 
the  contractions  so  produced  are  in  reality  due  to  the  fact 
that,  although  the  stimulus  is  apparently  applied  directly  to 
the  muscle,  it  is,  after  all,  the  fine  nerve  branches,  so  abun- 
dant in  the  muscle,  which  are  actually  stimulated.  The  fol- 
lowing facts,  however,  go  far  to  prove  that  the  muscular 
fibres  themselves  are  capal»le  of  being  directly  stimulated 
without  the  intervention  of  any  nerves.  When  a  frog  (or 
other  animal)  is  poisoned  with  urari,the  nerves  may  be  sub- 
jected to  the  strongest  stimuli  without  cnusing  any  contrac- 
tions in  the  muscles  to  which  they  are  distributed  ;  yet  even 
ordinary  stimuli  ai^plied  directly  to  the  muscle  readily  cause 
contractions.  If  before  introducing  the  urari  into  the  sys- 
tem a  ligature  be  passed  underneath  the  sciatic  nerve  in  one 
leg,  for  instance  the  right,  and  drawn  tightly  round  the 
wiiole  leg  to  the  exclusion  of  the  nerve,  it  is  evident  that 
the  urari,  when  injected  into  the  back  of  the  animal,  will 
gain  access  to  the  right  sciatic  nerve  above  the  ligature,  but 
not  below,  wliile  it  will  have  free  access  to  the  whole  left 
sciatic.  If,  as  soon  as  the  urari  has  taken  etfect,  the  two 
sciatic  nerves  be  stimulated,  no  movement  of  the  left  leg 
v*ill  be  produced  by  stimulating  the  left  sciatic,  whereas 
strong  contractions  of  the  muscles  of  the  right  leg  below 
the  ligature  will  follow  stimulation  of  the  right  sciatic, 
whether  the  nerve  be  stimulated  above  or  below  the  lii^ature. 
Now  since  the,ui)per  parts  of  both  sciati(  s  are  ecpially  ex- 
posed to  tlie  action  of  the  i)oison,  it  is  clear  that  tlie  failure 
of  the  left  nerve  to  cause  contraction  is  not  attributable  to 
any  change  having  taken  place  in  the  upper  j)ortion  of  the 
nerve,  else  why  should  not  the  right,  which  has  in  its  uj^per 
portion  been  equally  exp(;scd  to  the  action  of  the  poison, 
also  fail?  Evidently  the  i)oison  acts  on  some  parts  of  the 
nerve  lower  down.  If  a  single  muscle  be  removed  from 
the  circulation  (b}'  ligaturing  its  bloodvessels  ,  la-evious  to 


66  THE    CONTRACTILE    TISSUES. 

tlie  poisoning  with  nrari,  tiiat  muscle  will  contract  when  any 
l)art  of  the  nerve  goin^r  to  it  is  stimidated,  though  no  otiier 
muscle  in  the  body  will  contra(;t  when  its  nerve  is  stimu- 
lated. Here  the  whole  nerve  right  down  to  the  muscle  has 
been  exposed  to  the  action  of  the  poison  ;  and  yet  it  has 
lost  none  of  its  power  over  the  muscle.  On  the  other  hand, 
if  the  muscle  be  allowed  to  remain  in  the  body,  and  so  be 
exposed  to  the  action  of  the  poison,  but  the  nerve  be  divided 
high  up  and  the  lower  part  connected  with  the  muscle  gently 
lifted  up  and  kept  sei)arate  from  the  rest  of  the  tissues  of 
the  body  before  the  urari  is  introduced  into  the  system,  so 
as  to  be  protected  from  the  intluence  of  the  poison,  it  is 
found  that  stimulation  of  the  nerve  produces  no  contractions 
in  the  muscle,  tiiough  stimuli  applied  directly  to  the  muscle 
at  once  cause  it  to  contract.  From  these  fads  it  is  clear 
that  urari  poisons  the  ends  of  the  nerve  within  the  muscle 
long  before  it  affects  the  trunk,  and  it  is  exceedingly  proba- 
blethat  it  is  the  very  extreme  ends  of  tlie  nerves  (possibly 
the  end  plates,  for  urari  poisoning,  at  least  when  profound, 
causes  a  slight  but  yet  distinctly  recognizable  effect  in  the 
microscopic  appearance  of  these  structures)^  which  are 
affected.  The  phenomena  of  urari  poisoning,  therefore,  go 
far  to  i)rove  that  muscles  are  capable  of  being  made  to  con- 
tract by  stimuli  applied  directly  to  the  muscular  tibres  them- 
selves ;  and  there  are  other  facts  which  support  this  view. 

This  question  of  "  independent  muscular  irritability  "  was  once 
thought  to  be  of  impoi'tance.  In  old  times,  the  swelling  of  a 
muscle  during  contraction  was  held  to  be  caused  by  the  animal 
spirits  descending  into  it  along  the  nerves  ;  and  when  the  doc- 
trine of  ''spirits  '^  was  given  up,  it  was  still  taught  that  the  vital 
activity  of  the  nmscle  was  something  bestow^ed  upon  it  by  the  ac- 
tion of  the  nerve,  and  not  properly  belonging  to  itself.  We  owe 
to  Haller  the  establishment  of  the  truth, Ihat  the  contraction  of 
a  muscle  is  a  manifestation  of  the  muscle's  own  energy,  excited 
it  may  be  by  nervous  action,  but  not  caused  by  it.  Haller  spoke 
of  the  nuiscle  as  possessing  a  vis  insita^  while  he  called  the  ner- 
vous action,  which  excites  contraction,  the  vis  nervosa.  He  used 
the  word  irritability  as  almost  synonymous  with  contractility,  a 
meaning  which  is  still  adopted  by  many  authors.  In  this  work 
we  have  used  it  in  the  wider  sense,  first  employed  by  Glisson, 
which  includes  other  manifestations  of  energy  than  the  change  of 
form  which  constitutes  a  contraction.  Since  Haller's  time  the 
question  whether  muscles  possess  an  independent  irritability  has 
shifted  its  ground  ;  it  now^  means,  not  whether  muscles  are  irri- 
table or  not,  but  simply  whether  their  irritability  can  be  called 

^  Kiihne,  Untersuch.  Pl.ysiol.  Inst.  Heidelberg,  Bd.  ii  (1878),  p.  LS7. 


MUSCULAR    CONTRACTION.  '67 


into  action  in  other  ways  than  by  the  mediation  of  nerves.  In 
addition  to  the  urari  argument  just  described,  we  may  state  that 
portions  of  muscular  fibres,  entirely  destitute  of  nerves,  such  as 
the  lower  end  of  the  sartorius  of  the  frog,  ma}'  be  stimulated  di- 
rectly, with  contractions  as  a  result ;  that  the  chemical  substances 
which  act  as  stimuli  when  applied  directly  to  muscles,  differ 
somewhat  from  those  which  act  as  stimuli  to  nerves  ;  and  lastly, 
that  a  portion  of  muscle  fibre  quite  free  from  nerves  may  be  seen 
under  the  microscope  to  contract.  In  the  succeeding  portions  of 
this  work  abundant  evidence  will  be  afibrded  that  the  activity  of 
contractile  protoplasm  is  in  no  wa}'  essentially  dependent  on  the 
presence  of  nervous  elements. 

The  Fhenomena  of  a  Simple  3Iuscular  Contraction. 

If  the  far  end  of  the  nerve  of  a  muscle-nerve  preparation 
(the  gastrocnemius  for  instance  of  the  frog  with  the  attached 
sciatic  nerve  dissected  out)  :  Figs.  12  and  13)  be  laid  on  the 
electrodes  of  an  induction-machine,  the  passage  of  a  single 
induction  shock  (either  making  or  breaking)  will  produce 
no  visible  change  in  the  nerve,  but  the  muscle  will  give  a 
short  sharp  contraction,  ?.  e.,  will  for  an  instant  shorten 
itself,  becoming  thicker  the  while,  and  then  return  to  its 
previous  condition.  If  one  end  of  the  muscle  be  attached 
to  a  lever,  while  the  other  is  fixed,  the  lever  will  by  its 
movement  indicate  the  extent  and  duration  of  the  shorten- 
ing. If  the  point  of  the  lever  be  brought  to  bear  on  some 
rapidly  travelling  surface  on  which  it  leaves  a  mark  (being 
for  this  purpose  armed  with  a  pen  and  ink  if  tlse  sni-lace  l»e 
plain  i)a])er,  or  with  a  bristle  or  needle  if  the  surface  be 
smoked  glass  or  i>aper).  so  long  as  the  muscle  remains  at 
rest  the  lever  will  describe  an  even  line.  When,  iiowever, 
a  contraction  takes  place,  as  when  a  single  induction-shock 
is  sent  through  the  nerve,  some  such  curve  as  that  shown 
in  Fig.  14  will  Ise  described,  the  lever  rising  with  the  shoit- 
ening  of  the  muscte,  and  descending  as  the  muscle  returns 
to  its  natural  length.  This  is  knowi]  as  the  ''muscle-curve." 
In  order  to  make  the  ''  muscle-curve  "  comi)lete,  it  is  necs- 
sary  to  mark  on  the  recording  surface  the  exact  time  at 
which  the  induction-shock  is  sent  into  the  nerve,  and  also 
to  note  the  speed  at  which  the  recording  surface  is  travel- 
ling. These  points  are  best  effected  by  means  of  the  pendu- 
lum myograph.     (Fig.  15.) 

In  this  instrument  a  smoked-glass  plate,  on  which  a  lever 
writes,  swings  with  a  pendulum.  The  pendulum  with  the  glass 
plate  attached  being  raised  up,  is  suddenly  let  go.     It  swings  of 


(5S 


TllK    CONTRACTILE    TISSUK 

Fj(;.  12. 


Biagiain  Illiislrntiiitr  Apparatus  arranged  for  Experiments  with  Muscle  and  Nerve. 


MUSCULAR    CONTRACTION. 


69 


A.  The  moist  chamber  containing  the  muscle-nerve  preparation.  (The  muscle-nerve 

and  electrode-holder  are  shown  on  a  larger  scale  in  Fig.  13.)  The  muscle  vi, 
supported  by  the  clamp  cl,  which  firmly  grasps  the  end  of  the  femur/,  is  con- 
nected by  means  of  the  S  hook  5  and  a  thread  with  the  lever  I,  placed  below 
the  moist  chamber.  The  nerve  ?!,  with  the  portion  of  the  spinal  column  n' 
still  attached  to  it,  is  placed  on  the  electrode-holder  e?,  in  contact  wiih  the 
wires  x,  y.  The  whole  of  the  interior  of  the  glass  case  gl,  is  kept  saturated  with 
moisture,  and  the  electrode-holder  is  so  constructed  that  a  piece  of  moistened 
blotting-paper  may  be  placed  on  it  without  coming  into  contact  with  the  nerve. 

B.  The  revolving  cylinder  bearing  the  smoked  paper  on  which  the  lever  writes. 

C.  Du  Bois-Reymond's  key  arrang<-d  for  short-circuiting.    The  wires  x  and  y  of  the 

electrode-holder  are  connected  through   binding  screws  in  the  floor  of  the 
moist  chamber  with  the  wires  x',  y',  and  these  are  secured  in  the  key,  one  on 
either  side.    To  the  same  key  are  attached  the  wires  x"  2/"  coming  from  the 
secondary  coil  s.  c.  of  the  induction  machine  D.    This  secondary  coil  can  be 
made  to  slide  up  and  down  over  the  primary  coil  j^r.  c,  with  which  are  con- 
nected the  two  wires  x'"  and  y'".    x'"  is  connected  directly  with  one  pole,  for 
instance  the  copper  pole  c.  p.  of  the  battery^.  y"'h  carried  to  a  binding  screw 
a  of  the  Morse  key  F,  and  is  continued  as  i/iv  from  another  binding  screw  6  of 
the  key  to  the  zinc  pole  z.  p.  of  the  battef  y. 
Supposing  everything  to  be  arranged,  and  the  battery  charged,  on  depressing  the 
handle  ha,  of  the  Morse  key  F,  a  current  will  be  made  in  the  ^primary  coil  pr.  c, 
passing  from  c.p-  through  x'"  to  pr.  c,  and  thence  through  y'"  to  a,  thence  to  b,  and 
so  through  ^'iv  to  s.  p.    On  removing  the  finger  from  the  handle  of  7'"",  a  spring  thrusts 
up  the  handle,  and  the  priiaary  circuit  is  in  consequence  immediately  broken. 

At  the  instant  that  the  primary  current  is  either  made  or  broken,  an  induced  cur- 
rent is  for  the  instant  developed  in  the  secondary  c>iil  s.  c.  If  the  cross-bar  A,  in  the 
Du  Bois-Reymond's  key  be  raist-d  (as  shown  in  the  thick  line  in  the  figure),  the  wires 
x",  x',  X,  the  nerve  between  the  electrodes,  and  the  wires  y,  y',  y",  form  the  com- 
plete secondary  circuit,  and  the  nerve  consequently  experiences  a  making  or  break- 
ing induction-shock  whenever  the  jirimary  current  is  made  or  broken.  If  the  cross- 
bar of  the  Du  Bois-Reymond  key  be  shut  down,  as  in  the  dotted  line  /t'in  the  figure, 
the  resistance  of  the  cross-bar  is  so  slight  compared  with  that  of  the  nerve  and  (jf 
the  wires  going  from  tlie  key  to  the  nerve,  that  the  wlxjle  secondary  (induced)  cur- 
rent passes  from  x"  to  y"  (or  from  y"  to  x")  along  the  cross-bar,  and  none  passes  into 
the  nerve.    The  nerve  being  thus  short-circuited,  is  not  affected  by  any  changes  in 

the  current. 

Fig.  13. 


Fig.  13.— The  muscle-nerve  preparation  of  Fig.  12,  with  the  clamp,  electrodes,  and 
electrode-holder,  are  here  shown  on  a  larger  srale.  The  letters  as  in  Fig.  12  The 
form  of  electrode-holder  figured  is  a  convenient  one  for  general  i)urposes,  but  many 
other  forms  are  in  use. 


70 


THE    CONTRACTILE    TISSUES. 


course  to  the  opposite  side,  the  »iiass  plate  travels  throu<T;h  an  arc 
of  a  circle,  and,  the  lever  being  stationary,  the  point  of  the  lever 
describes  an  arc  on  the  glass  plate.  The  rate  at  which  the  glass 
plate  travels,  i  <'.,  the  time  it  takes  for  the  lever-point  to  describe 
a  line  of  a  given  length  on  the  glass  plate,  may  be  calculated 
from  the  length  of  the  pendulum,  but  it  is  simpler  and  easier  to 
phice  a  vibrating  tuning-fork  immediately  under  the  point  of  the 
lever.  If  the  vibrations  of  the  tuning-fork  are  known,  then  the 
number  of  vibrations  which  are  marked  on  the  plate  between 


Cf   h 


A  Muscle-Curve  obtained  by  means  of  the  Penduhim  Myogrnph. 
To  be  read  from  left  to  right. 

a  indicates  the  moment  at  which  the  induction-shock  is  S"nt  into  the  nerve  :  h  the 
commencement,  c  the  maximum,  and  d  the  close  of  the  contraction.    The  two 
smaller  curves  succeeding  the  larger  one  are  due  to  oscillations  of  the  lever. 
Below  the  muscle-curve  is  the  curve  drawn  by  a  tuning-foik  making  180  double 

vibrations  a  second,  each  complete  curve  representing  therefore  ys^o^  o'  a  second. 

It  will  be  observed  that  the  plate  of  the  myograph  was  travelling  more  rapidly 

towards  the  close  than  at  the  beginning  of  the  contraction,  as  shown  by  the  greater 

length  of  the  vibration  curves. 

any  two  points  on  the  line  described  by  the  lever  gives  the  time 
taken  by  the  lever  in  passing  from  one  point  to  the  other.  An 
easy  arrangement  permits  the  exact  time  at  which  the  shock  is 
sent  through  the  nerve  to  be  marked  on  the  line  of  the  lever.  To 
avoid  too  niany  markings  on  the  plate  the  pendulum  after  de- 
scribing an  arc  is  caught  b}-  a  spring  catch  on  the  opposite  side. 

A  complete  muscle-curve,  such  as  that  shown  in  Fig.  14, 
taken  from  the  gaslrocnemins  of  a  frog,  teaches  us  the  fol- 
io win  o-  facts : 


1.   That  altlu)iigh  the  passage  of  the  induced  current  from 
electrode  to  electrode  is  practicall}'  instantaneous,  itsetfect, 


THE    MUSCLE-CURVE. 
Fig.  15. 


71 


-    ~N 


The  Pendulum  Myograph. 


THE    CONTRACTILE    TISSUES. 


Tlie  fifjurc  is  diapriiniiuiitic,  the  essentials  only  of  the  insi  iinnent  heing  shown. 
The  sniokeil-glass  plate  A  swinj^s  on  the  "  seconds  "  pendulum  B  by  means  of  care- 
fully adjusted  bearings  at  C.  The  contrivances  by  whieh  the  glass  plate  can  be 
removed  and  replaced  at  j)leasure  are  not  sliown.  A  second  glas>  plate  so  arranged 
that  tlie  (list  glass  i>hite  may  be  moved  up  and  down  without  altering  the  swing  of 
the  pendulum  is  also  omitted.  Before  commencing  an  experiment  tiie  pendulum  is 
raised  up  (in  the  figure  to  the  right),  and  is  kept  in  that  position  by  the  tooth  a 
catching  on  the  spring-catch  b.  On  depressing  the  catch  h  the  glass  plate  isset  free, 
swings  into  the  new  position  indieattd  by  the  dotted  lines,  and  is  held  in  that  posi- 
tion by  the  tooth  a'  catching  on  thecatch  b'.  In  the  course  of  its  swing  the  tooth  «' 
coming  into  contact  with  the  projecting  steel  rod  c,  knocks  it  on  one  side  into  tiie 
position  indicated  by  the  dotted  line  c'.  The  rod  c  is  an  electric  continuity  with 
the  wire  X  of  the  primary  ci>il  of  an  induction-machine.  The  screw  dissimilarly 
in  electric  continuity  with  the  wire  ?/ of  the  same  i)rimHry  coil.  The  screw  tZ  and 
the  rod  c  are  armed  with  platinum  at  the  points  in  whieh  they  are  in  contact,  and 
both  are  insulated  by  means  of  the  ebonite  block  e.  As  long  as  c  and  d  are  in  con- 
tact the  circuit  of  the  primary  coil  to  whieh  x  and  y  belong  is  closed.  When  in  its 
swing  the  tooth  a'  knocks  c  away  from  d,  at  that  in.stant  the  circuit  is  broken,  and 
a  "breaking"  shock  is  sent  through  the  electrodes  connected  with  the  secondary 
coil  of  the  machine,  and  so  through  the  nerve.  The  lever/,  the  end  only  of  which 
is  shown  in  the  figure,  is  brought  to  bear  on  the  glass  pl-tte,  and  when  at  rest  de- 
scribes a  straight  line,  or  more  exactly  an  arc  of  a  circle  of  large  radius.  The 
tuning-fork  /,  the  ends  only  of  the  two  limbs  of  whieh  are  shown  in  the  figure 
placed  immediately  below  the  lever,  serves  to  mark  the  time. 

measured  from  the  entrance  of  tlie  shock  into  the  nerve  to 
tlie  return  of  the  muscle  to  its  natural  length  alter  the  short- 
ening, takes  an  appreciable  time.  In  the  figure,  the  whole 
curve  from  a  to  d  takes  up  al)out  the  s  iine  time  as  eighteen 
double  vibrations  of  the  tuning-fork.  Since  each  doul)le 
vibration  represents  jI,,  of  a  second,  the  duration  of  the 
whole  curve  was  y'^  second. 

2.  In  the  first  portion  of  this  period,  from  a  to  6,  there  is 
no  visible  change,  no  shortening  of  the  muscle,  no  raising 
of  the  lever. 

21 

8.   It  is  not  until  Ij,  that  is   to  say  after  the   lapse  of   — ^ 
'  *  180 

i.  e.^  about  ^K  sec,  that  the  shortening  begins.  The  short- 
ening ns  shown  by  the  curve  is  at  first  slovv,  but  soon  l)e- 
comes  more  rapid,  and  tiien  slackens  ngain  until  it  reaches 
a  maximum  at  c ;  the  whole  shortening  occupying  about 
7,'jj  sec, 

4.  Arrived  at  the  maximum  of  shortening,  the  muscle  at 
once  begins  to  relax,  the  lever  descending  at  first  slowly, 
then  veiy  rapidly,  and  at  last  more  slowly  again,  until  at  d 
the  muscle  has  reo-ained  its  natural  lenijth  ;  the  whole  return 


THE    MUSCLE-CURVE. 


73 


from   the   raaxiimim   of  contraction   to   the   natural  length 
occupying  ,|^,  i.  e.,  about  -j^  sec. 

Thus  a  simple  muscular  contraction,  a  simple  spasm  as  it 
is  sometimes  called,  produced  by  a  momentary  stimulus, 
such  as  an  instantaneous  iuduclion-shock,  consists  of  three 
main  phases : 

1.  A  i)]iase  antecedent  to  any  visible  alteration  in  the 
muscle.  This  i)hase,  during  wliich  in  visit 'le  preparatory 
changes  are  taking  place  in  the  nerve  and  muscle,  is  often 
called  the  '*  latent  period." 

2.  A  phase  of  shortening  or  contraction,  more  strictly 
so  called. 

3.  A  phase  of  relaxation  or  return  to  the  original  length. 

In  the  case  we  are  considering,  the  electrodes  are  sup- 
posed to  be  applied  to  the  nerve  at  some  distance  from  the 


Fig. 


ct    66 


Curves  illustrating  the  Measurement  of  the  Velocity  of  a  Nervous  Impulse.  (Dia- 
grammatic.)   To  be  rfad  from  left  to  right. 

The  same  muscle-nerve  fireparation  is  stimulated  (1)  as  far  as  possible  from  the 
muscle,  (2)  as  near  as  possible  to  the  .nuscle  ;  buth  contractions  are  registered  by  the 
pendulum  inyographion  exactly  in  the  same  way. 

In  (1)  the  stimulus  enters  the  nerve  at  the  time  indicated  by  the  line  a,  the  con- 
traction shown  by  the  dotted  line  begins  at  h' ;  the  whole  latent  period,  therefore,  is 
indicated  by  the  distance  from  a  to  b' . 

In  '2)  the  stinuilus  enters  the  nerve  at  exactly  the  same  time  a ;  the  contraction, 
shown  by  the  unbroken  line,  begins  at  b  ;  the  latent  period,  therefore,  is  indicated 
by  the  distance  between  a  and  ft. 

The  time  taken  up  by  the  nervous  impulse  in  passing  along  the  longth  of  nerve 
between  1  and  2  is  therefore  indicated  by  the  distance  between  b  and  b',  which  may 
be  measured  by  the  tuning-fork  curve  below.  N.B. — No  value  is  given  in  the  figure 
for  the  vibrations  of  the  tuning-fork,  since  the  figure  is  diagrammatic,  the  distance 
between  the  two  curves,  as  compared  with  the  length  of  either,  having  been  pur- 
posely exaggerated  for  the  sake  of  simplicity. 

muscle.     Consequently  the  latent  period  of  the  curve  com- 
prises not  only  the  preparatory  actions  going  on  in  the  mus- 


74  THE    CONTRACTILE    TISSUES. 

cle  itself,  hut  also  the  chanoes  necessary  to  conduct  the  im- 
mediate ert'ect  of  the  induction-shock  from  tiie  part  of  the 
nerve  hetween  the  electrodes,  along  a  considerahle  lenii,tli 
of  nerve  down  to  the  muscle.  It  is  obvious  tiiat  these  latter 
changes  might  he  eliminated  by  placing  the  electrodes  on 
the  muscle  itself  or  on  the  nerve  close  to  the  muscle.  If 
this  were  done,  the  muscle  and  lever  being  exactly  as  before, 
and  care  were  taken  that  the  induction-sliock  entered  into 
the  nerve  at  tlie  new  spot,  at  the  moment  vviien  the  point  of 
the  lever  had  reached  exactly  thesiune  point  of  the  travelling 
surfjice  as  before,  a  curve  like  that  shown  by  the  plain  line 
in  Fig.  IG  would  be  gained.  It  resembles  ti»e  firstcurve  (in- 
dicated in  the  figure  by  a  dotted  line)  in  all  points,  except 
that  the  latent  i)eri()d  is  shortened  ;  the  contraction  begins 
rather  earlier.     From  this  we  learn  two  facts: 

1.  The  greater  part  of  the  latent  period  is  taken  up  by 
changes  in  the  muscle  itself,  preparatory  to  the  actual  visi- 
ble shortening,  for  the  two  latent  periods  do  not  dilfer  much. 
Of  course,  even  in  the  second  case,  the  latent  period  in- 
cludes the  changes  going  on  in  the  short  piece  of  nerve  still 
lying  between  the  electiodes  and  the  muscular  fibres.  To 
eliminate  this  with  a  view  of  determining  the  latent  period 
in  the  muscle  itself,  the  electrodes  should  be  placed  directh' 
on  the  muscle  poisoned  with  urari.  If  this  were  clone,  it 
would  still  be  found  that  the  latent  period  was  chiefly  taken 
up  by  changes  in  the  muscular  as  distinguished  from  the 
nervous  elements. 

2.  Such  difference  as  does  exist  indicates  the  time  taken 
up  by  the  proijagation,  along  the  piece  of  nerve,  of  the 
changes  set  up  at  the  far  end  of  tlie  nerve  by  the  induc- 
tion-shock. These  changes  we  shall  hereafter  speak  of  as 
constituting  a  nervous  impulse  ;  and  the  above  experiment 
show^s  that  it  takes  some  appreciable  time  for  a  nervous 
impulse  to  travel  along  a  nerve.  In  the  figure  the  differ- 
ence between  tlie  two  latent  periods,  the  distance  between 
b  and  h' ^  seems  almost  too  small  to  measure  accurately  ;  but 
if  a  long  piece  of  nerve  be  used  for  the  experiment,  and  the 
recording  surface  be  made  to  travel  very  fast,  the  difference 
between  the  duration  of  the  latent  period  when  the  induc- 
tion-shock is  sent  in  at  a  point  close  to  the  muscle,  and  that 
when  it  is  sent  in  at  a  point  as  far  away  as  possible  from 
the  muscle,  may  be  satisfactorily  measured  in  fractions  of  a 


TETANIC    CONTRACTIONS.  75 

second.  If  the  length  of  nerve  between  the  two  points  be 
accurately  measured,  the  rate  at  which  a  nervous  impulse 
travels  along  the  nerve  to  a  muscle  can  be  easily  calculated. 
This  has  been  found  to  be  in  the  frog  about  twenty-eight, 
and  in  man  about  thirty-three  meters  per  second. 

Thus  when  a  momentary  stimulus,  such  as  a  single  in- 
duction-shock, is  sent  into  a  nerve  connected  with  a  muscle, 
the  following  events  take  place  : 

1.  The  generation  at  the  spot  stim.ulated  of  a  nervous 
impulse,  and  the  propagation  of  the  impulse  along  the  nerve 
to  the  muscle.  The  time  taken  up  by  this  varies  according 
to  the  length  of  the  nerve.  For  the  same  length  of  nerve 
it  is  tolerablj'  constant. 

2.  The  setting-up  of  certain  molecular  changes  in  the 
muscle,  unaccompanied  by  any  visible  alteration  in  its  form, 
constituting  the  latent  period,  and  occupying  on  an  average 
about  y^o^th  second.  The  time  taken  up  by  the  latent 
period  varies  somewhat  according  to  circumstances. 

3.  The  shortening  of  a  muscle  up  to  a  maximum,  occu- 
pying about  j-Q-Q^tli  second. 

4.  The  return  of  a  muscle  to  its  former  length,  occupying 
about  jfijth  second.  Both  these  last  events  varj'  much  in 
duration  according  to  circumstances.^ 

Ti'tam'c  Contractions. 

If  a  single  induction  shock  be  followed  at  a  sufficiently 
sliort  interval  by  a  second  shock  of  the  same  strengtli,  the 
first  simple  contraction  or  spasm  will  be  followed  by  a 
second  spasm,  the  two  bearing  such  relation  to  each  other 
as  that  shown  by  the  curve  in  Fig.  IT,  where  the  interval 
between  the  two  shocks  was  just  long  enough  to  allow  the 
first  spasm  to  have  passed  its  maximum  before  the  latent 
period  of  the  seond  was  over.  It  will  be  observed  that 
the  second  curve  is  almost  in    all  respects  like  the  first,  ex- 

^  The  measurements  here  stated  are  those  ordinarily  given.  The  curve 
described  in  the  previous  text  happened  to  have  a  rather  long  latent 
period,  and  the  lengthening  to  be  of  shorter  instead  of  longer  duration 
than  the  shortenina:. 


7G 


THE    CONTRACTILE    TISSUES. 


CH'pt,  tliat  it  st.nj-ts,  so  to  speak,  fVom  the  first  curve  instead 
of  tVoiii  the  l){ise-liiic.  The  second  nervous  impulse  has 
acted  on  the  already  contracted  muscle,  and  made  it  con- 
tract a<{ain  just  as  it  would  have  done  if  there  had  been  no 
Hist  impulse  and  tlie  muscle  had  heen  at  rest.  The  two 
contractions  are  added  toi^ether  and  the  lever  raised  nearly 
double  the  height  it  would  have  been  by  either  alone.  A 
more  or  less  similar  result  would  occur  if  the  second  con- 
traction i)egan   at  any  other  [)hase  of  the  first.     The  C(jm- 

F\>:.   17. 


Tracing  of  a  Double  Muscle-Curve.    To  be  read  fro;ii  left  to  rl;,'ht. 

Wliile  the  muscle^  was  engaged  in  tlie  first  cmtraction  (whose  complete  course, 
had  nothing  intervened,  is  indicated  bj-  the  dotti  d  line),  a  second  induction-shocl^ 
was  thrown  in,  at  such  a  time  that  the  srcond  contraction  began  just  as  the  first  was 
beginning  to  decline.  The  second  curve  is  seen  to  start  from  the  first,  as  does  the 
first  from  the  base-line, 

l)ined  effect  is,  of  course,  greatest  when  the  second  contrac- 
tion begins  at  the  maximum  of  the  first,  being  less  both 
before  and  afterwards.  If,  in  the  same  wa}',  a  third  shock 
follows  the  second  at  a  sutliciently  short  interval,  a  third 
curve  is  piled  on  the  lop  of  the  second.  The  same  with  a 
fourth,  and  so  on. 

When,  however,  repeated  shocks  are  given,  it  is  found 
that  the  height  of  each  contraction  is  rather  less  than  the 
preceding  one,  and  this  diminution  becomes  more  marked 
fhe  greater  the  nuud)er  of  shocks.  Hence,  after  a  certain 
number  of  shocks,  the  succeeding  impulses  do  not  cause 
any  further  shortening  of  the  muscle,  any  further  raising  of 
the  lever,  but  merely  keep  up  the  contraction  alread}'  exist- 
ing. The  curve  thus  reaches  a  maximum,  which  it  main- 
tains, subject  to  the   depressing  effects  of  exhaustion,  as 


In  this  and  the  other  curves  of  this  section  the  tracings  figured  were 
taken  from  frog's  muscle. 


TETANIC    CONTRACTIONS. 


77 


long  as  the  shocks  are  repeated.  Wlien  these  cease  to  be 
given,  the  muscle  returns,  in  the  usual  way,  at  first  very 
raj)idh',  and  then  more  slowly,  to  its  natural  length.  When 
tlie  shocks  do  not  succeed  each  other  too  rapidly,  the  indi- 
vidual contractions  may  readily  be  traced  along  the  whole 
curve,  as  is  seen  in  Fig.  18,  where  the  primary  current  of  the 
induclion-machine   was   repeatedly   broken  at  intervals   of 


Muscle  thrown  inlo  Tetanus,  when  the  Primary  Current  of  an  Induction-Macliine 
is  repeatedly  broken  at  intervals  of  sixteen  in  a  second. 
To  be  read  from  left  to  right. 
The  upper  line  is  that  described  by  the  muscle.  The  lower  marks  time  the  inter- 
vals between  the  elevations  indicating  seconds.  The  intermediate  line  shows  when 
the  shocks  were  sent  in,  each  mark  on  it  corresponding  to  a  shock.  The  lever, 
which  describes  a  straight  line  before  the  shocks  are  allowed  to  fall  into  the  nerve, 
rises  almost  vertically  (the  recording  surface  travelling  in  this  case  slowly)  as  soon 
as  the  first  shock  enters  the  nerve  at  a.  Having  risen  to  a  certain  height,  it  begins 
to  fall  again,  but  in  its  fall  is  raised  once  more  by  the  second  shock,  and  that  to  a 
greater  height  than  before.  The  third  and  succeeding  shocks  have  similar  eflfect, 
the  muscle  continuing  to  become  shorter,  though  the  shortening  at  each  shock  is 
less.  After  awhile  the  increase  in  the  total  shortening  of  the  muscle,  though  the 
individual  contractions  are  still  visible,  almost  ceases.  At  h  the  shocks  cease  to  be 
sent  into  the  nerve  ;  the  contractions  almost  immediately  disappear,  and  the  lever 
forthwith  commences  to  descend.  The  muscle  being  lightly  loaded,  the  descent  is 
very  gradual ;  the  uiuscle  had  not  regained  its  natural  length  when  the  tracing  was 
stopped. 

sixteen  in  a  second.  When  the  shocks  succeed  each  other 
more  rapidly,  the  individual  contractions,  visible  at  first, 
may  becomie  fused  together  and  lost  to  view  as  the  tetanus 
continues  and  the  muscle  becomes  tired.  When  the  shocks 
succeed  each   other  still  more  rapidly  (the  second  contrac- 


78 


THE    CONTRACTILE    TISSUES. 


tioii  ht'i^imiiiii^  in  tlie  asccMulinir  portion  of  the  first),  it 
becomes  ditlieult  or  impossible  to  traee  out  the  single  con- 
tractions. The  curve  then  desL-rihed  by  the  lever  is  of  the 
kind   shown    in    Fig.    lU,  where  the   primary-  current  of  an 

Fx(i.  19. 


Tetanus  produced  with  liie  ordinary  Magnetic  Interruptor  of  an  Induction-Machine. 
(Recording  surface  travelling  slowly.)    To  be  read  from  left  to  right. 

The  interrupted  current  iieing  thrown  in  at  a  the  lever  rises  rapidly,  but  at  b  the 
muscle  reaches  the  niaxiuium  of  contraction.  Tliis  is  continued  till  c,  when  the 
current  is  shut  oflF  and  rela.xation  commences. 

induction-machine   was   rapidly   made  and   broken    by   the 
magnetic  interruptor,  Fig.  20.  The  lever,  it  will  be  observed, 


The  Magnetic  Inlenuptor, 


TETANIC    CONTRACTIONS.  '79 


The  figure  is  introduced  to  illustrate  the  action  of  this  instrument  as  commonly 
used  by  physiologists. 

The  two  wires  J- and  y  from  the  battery  are  connected  with  the  two  brass  pillars  a 
and  d  by  meanr;  of  screws.  Directly  contact  is  thus  made  the  current,  indicated  in 
the  figure  by  the  thick  interrupted  line,  passes  in  the  direction  of  the  arrows,  up  the 
pillar  a,  along  the  steel  spring  b,  as  far  as  the  screw  c,  the  point  of  which,  armed 
with  platinum,  is  in  contact  with  a  small  platinum  plate  on  b.  The  current  passes 
from  0  through  c  and  a  connecting  wire  into  the  primary  coil  p.  Upon  its  entering 
into  the  primary  coil,  an  induced  (making)  current  is  for  the  instant  developed  in 
the  secondary  coil  (not  shown  in  the  figure).  From  the  primary  coil  p  the  current 
passes,  by  a  connecting  wij-e,  through  the  double  spiral,  m,  and,  did  nothing  happen, 
would  continue  to  pass  from  in  by  a  connecting  wire  to  the  pillar  d,  and  so  by  the 
wire  y  to  the  battery.  The  whole  of  this  course  is  indicated  by  the  thick  inter- 
rupted line  with  its  arrows. 

As  the  current  however  passes  through  the  spirals  m,  the  iron  cores  of  these  are 
made  magnetic.  They  in  consequence  draw  down  the  iron  bar  e,  fixed  at  the  end  of 
the  spring  b,  the  flexibility  of  the  spring  allowing  this.  But  when  e  is  drawn  down, 
the  platinum  plate  on  the  upper  surface  of  b  is  also  drawn  away  from  the  screw  c, 
and  a  similar  platinum  plate  on  the  under  surface  of  b  is  brought  into  contact  with 
the  platinum-armed  point  of  the  screw  /,  the  screws  being  so  arranged  that  this 
takes  place.  In  consequence  of  this  change  the  current  can  no  longer  pass  from  b 
to  c.  On  the  contrary,  it  passes  from  b  to/,  and  so  down  the  pillar  d,  in  the  direc- 
tion indicated  by  the  t/iin  interrupted  line,  and  out  to  the  battery  by  the  wire  y. 
Thus  the  current  is  "  short-circuited."  from  the  primary  coil ;  and  the  instant  that 
the  current  is  thus  cut  off  from  the  primarj'  coil,  an  induced  (breaking)  current  is 
for  the  moment  developed  in  the  secondary  coil.  But  the  current  is  cut  off  not  only 
from  the  primary  coi!,  but  also  from  the  spirals  /«  ;  in  consequence  their  cores  cease 
to  be  magnetized,  the  bar  e  ceases  to  be  attracted  by  them,  and  the  spring  6,  by 
virtue  of  its  elasticity,  resumes  its  former  position  in  contact  with  the  screw  c. 
This  return  of  the  spring,  however,  re-establishes  the  current  in  the  primary  coil 
and  in  the  spirals,  and  the  spring  is  di'awn  down,  to  be  released  once  more  in  the 
same  manner  as  before.  Thus  as  long  as  the  current  is  passing  along  x,  the  contact 
of  b  is  constantly  alternating  between  e  and  /,  and  the  current  is  constiantly  passing 
into  and  being  shut  off  from  p,  the  periods  of  alternation  being  determiiit-d  liy  the 
periods  of  vibration  of  the  spring  b.  With  each  passage  of  the  current  into  or 
withdrawal  from  the  primary  coil,  an  induced  (making  and,  respectively,  breaking) 
shock  is  developed  in  the  secondary  coil. 

rises  at  a  after  the  latent  i)ei'iorl  (which  is  not  marked^,  first 
rapidly,  and  then  .more  slowly,  in  an  apparently  unbroken 
line  to  a  maximum  at  about  6,  maintains  the  maximum  so 
lon<i;  as  the  shocks  continue  to  be  given,  and  when  these 
cease  to  be  given,  as  at  c,  gradually  descends  to  the  base- 
line. This  condition  of  muscle,  brought  al)out  by  rapidly 
repeated  shocks,  this  fusion  of  a  number  of  simple  spasms 
into  an  apparently  smooth,  continuous  effort,  is  known  as 
tetanus^  OY  tetanic  contraction.  The  above  facts  are  most 
clearly  shown  when  induction-shocks,  or  at  least  galvanic 
currents  in  some  form  or  other,  are  employed.  The}-  are 
seen,  however,  whatever  be  the  form  of  stimulus  employed. 


80  TIIK    CONTRACTILE    TISSUES. 

Tlius  in  the  cnse  of  meclinnicnl  stimuli,  while  a  single  hlow 
niav  eaiise  a  siiii^le  spasm,  a  iironoimced  tetanus  may  be 
obtained  by  rapidly  strikin<j:  snccessi\'ely  fresh  portions  of 
a  nerve.  With  ehemical  stimulation,  as  when  a  nerve  is 
dipped  in  acid,  it  is  impossil)le  to  secure  a  momentary  ap- 
plication ;  hence  tetanus,  generally  irregular  in  character, 
is  the  normal  result  of  this  mode  of  stimulation.  In  the 
living  body,  the  contractions  of  the  striated  muscles, 
brought  ar)Out  either  by  the  will  or  by  reflex  action,  are 
generally  tetanic  in  character.  Even  very  short  sharp 
movements,  such  as  a  sudden  jerk  of  the  limbs,  are  in  real- 
ity examples  of  tetanus  of  short  duration. 

When  it  has  once  been  realized  that  an  ordinary  tetanic 
muscular  movement  is  essentially  a  vibratory  movement, 
that  the  apparently  rigid  and  firm  muscular  mass  is  really 
the  subject  of  a  whole  series  of  vibrations,  a  series  namely 
of  simple  spasms,  it  will  be  readily  undeistood  why  a  tetan- 
izcd  muscle,  like  all  other  vibrating  bodies,  gives  out  a 
sound.  That  a  contracting  (tetanizedj  muscle  does  give 
out  a  sound,  the  so-called  muscular  sound,  is  easily  proved 
by  listening  with  a  stethoscope  to  a  contracted  biceps,  or 
by  stopping  the  ears  and  listening  to  the  contractions  of 
one's  own  masseter  and  temporal  muscles. 

When  a  muscle  is  thrown  into  tetanus  by  interrupted 
shocks  applied  directly  to  the  nerve  or  to  the  muscle,  the 
note  is  the  same  as  that  of  the  interruptor  determining  the 
number  of  the  shocks.  This  is  naturally  the  case,  since 
the  note  of  the  muscle-sound  is  determined  by  the  rapidity 
of  the  spasms  or  vibrations  which  go  to  make  up  the  teta- 
nus, ancl  these  are  determined  by  the  rapidity  with  which 
the  stimulus  is  rei)eated. 

AVhen  a  muscle  is  thrown  into  tetanus  l»y  the  will  or  by 
reflex  action  or  by  direct  stimulation  of  the  spinal  cord,  in 
fact,  in  any  way  through  the  action  of  the  central  nervous 
system,  the  same  note  is  always  heard,  viz.,  one  indicating 
19.5  vibrations  per  second. 

The  note  actually  heard  is  one  indicating  39  (36  to  40)  vibra- 
tions per  second.  This  is,  however,  an  harmonic  of  the  primary 
note  of  the  whole  sound. 

It  need  hardly  be  said  that  a  single  muscular  contraction, 
a  single  vil)ration,  cannot  cause  a  uiuscular  sound. 

The   i^eneral  observations  which   have  been  described   in 


THE    CHANGE    IN    FORM.  81 

this  section  may,  when  proper  precautions  are  taken,  he 
carried  out  on  a  muscle-nerve  preparation  from  a  frog  for  a 
very  considerable  time  after  its  removal  from  the  body. 
After  some  hours,  however,  or  it  maybe  days,  the  length  of 
lime  varying  according  to  circumstances,  it  will  be  found 
that  no  stimulus,  however  powerful,  will  cause  any  contrac- 
tion when  applied  either  to  the  nerve  or  to  the  muscle.  Both 
muscle  and  nerve  are  then  said  to  have  lost  their  irritability; 
and  a  short  time  afterwards  the  muscle  may  be  observed  to 
pass  into  a  peculiar  condition  known  as  rigor  mortifi^  in 
wiiich  it  loses  all  the  suppleness  and  exterisibility  character- 
istic of  the  living  irrital)le  muscle.  The  causes  of  this  loss 
of  irritability,  as  well  as  the  features  and  nature  of  this  rigor 
mortis,  we  shall  study  in  detail  presently. 

The  muscles  and  nerves  of  a  mammal,  or,  indeed,  of  any 
warm  blooded  animal,  lo'^e  their  irritability,  and  the  muscles 
become  rigid  in  a  very  short  time  {\l  may  be  a  few  minutes) 
after  removal  from  tlie  body.  Hence  these  are  less  suitable 
for  experiments  than  the  muscles  and  nerves  of  the  frog, 
though  their  general  phenomena  are  exactly  the  same. 

We  must  now  attemi)t  to  study  in  greater  detail  the 
changes  which  take  [)lace  in  a  muscle  and  nerve  during  the 
contraction  of  the  former  and  the  passage  of  an  impulse 
along  the  latter,  with  a  view  to  the  better  understanding  of 
both  events. 


Sec.  2.     The  Changes  in  a  Muscle  during  Muscular 
Contraction. 

The  Change  in  Form. 

We  have  seen  that,  at  the  close  of  the  latent  period,  tlie 
muscle  shortens  :  that  is,  each  fibre  shortens,  at  first  slowly, 
then  more  rapidly,  and  lastly,  more  slowly  again.  The 
shortening  (which,  in  severe  tetanus,  may  amount  to  three- 
fifths  of  the  length  of  the  muscle)  is  accompanied  by  an 
almost  exactly  corresponding  thickening,  so  that  there  is 
hardly  any  actual  change  in  bulk.  [A  very  delicate  and  etti- 
cient  mode  of  determining  that  the  muscle  does  not  change 
in  bulk  b}'  contracting  is  by  suspending  a  muscle  and  nerve 
preparation  by  electrodes  in  a  tightly  stoppered  bottle,  having 
a  graduated  capillary  tube  projecting  above  the  cork.  Tlie 
bottle   is  filled   with  water,  and   the    tube   but  partially  so. 


82  THE    CONTRACTILE    TISSUES. 

Stimulus  is  then  a|)i)li(Mltotlie  noive,  whicli  causes  llie  muscle 
to  coiitiact.  If  the  water-Hue  iu  the  tube  is  observed,  no 
chanire  will  be  appreciable.  (Marey.)]  If  a  muscle  be  placed 
horizontally,  and  a  lever  laid  upon  it,  the  thickening  of  the 
muscle  will  raise  up  the  lever,  and  cause  it  to  describe  on  a 
recording  surface  a  curve  exactly  like  that  described  by  a 
lever  attached  to  the  end  of  the  muscle.  There  appears  to 
be  a  minute  diminulion  of  bulk  not  amounting  to  more  than 
one-thousandth. 

If  a  long  muscle  of  par.illel  fibres,  poisoned  with  urari,  so 
as  to  eliminate  the  action  of  its  nerves,  be  stimulated  at  one 
end,  the  contraction  may  be  seen,  almost  with  the  naked 
eye,  to  start  from  the  end  stimulated,  and  to  travel  along 
the  muscle.  If  two  levers  be  made  to  rest  on,  or  be  sus- 
pended from,  two  points  of  such  a  muscle  placed  horizon- 
tally, the  points  being  at  a  known  distance  from  each  other 
and  from  the  point  stimulated,  the  progress  of  the  contrac- 
tion may  be  studied.  It  is  found  that  the  contraction  start- 
ing from  the  spot  stimulated  passes  along  the  muscle  in  the 
form  of  a  wave,  diminishing  in  vigor  as  it  proceeds.  The 
velocity  with  which  this  contraction-wave  travels  in  the 
muscles  of  the  frog  is  about  three  or  four  meters  a  second  ; 
and  since  it  takes,  in  round  numbers,  from  about  .05  to  .1 
second  for  the  contraction  to  pass  over  any  point  of  the 
fibre,  the  wave-length  of  the  contraction-wave  must  be  from 
about  200  to  400  mm. 

Bernstein'  o;ives  the  velocity  of  the  contraction-wave  in  the 
fro<?  as  about  three  to  four  (3.809),  its  duration  as  .0533  to  .0894 
seconds,  and  hence  its  wave-length  as  from  198  to  200  mm.  In  the 
dog,  Bernstein  and  Steiner^  tind  the  velocity  of  the  wave  about 
the  same,  viz.,  3.589,  but  the  duration  much  longer,  viz.,  .27  to 
.4975  second,  indicating  a  much  uKjre  extended  wave  ;  but  this 
was  probably  due  to  the  abnormal  condition  of  the  muscle,  since 
the  duration  of  the  wave  in  the  untouched  muscles  of  the  rabbit 
more  nearly  agreed  with  that  of  the  frog.  Hermann^  makes  the 
rate  in  the  frog  about  three  meters,  or  rather  less.  Aeby  had 
previously  given  .8 — 1.2  meters  per  second,  and  Engelmann  1.17 
m.  per  second  as  the  velocity. 

The  velocity  is  increased  by  an  elevation,  and  diminished  by  a 


1  Untersuch.  ii.  d.  Erregungsvorgang  in  Nerven-  und  Muskelsysteme, 
1871,  p.  84. 

2  Pfiuger's  Archiv,  x  (1875),  48. 

«  Archiv  f.  Anat.  u.  Phvs.,  1875,  p.  526. 


CHANGES    IN    MICROSCOPIC    STRUCTURE. 


83 


lowering  of  temperature,  but  is  not  affected  by  variations  in  the 
load. 

Seeing-  that  the  extreme  limit  of  the  length  of  a  muscular 
fibre  is  about  30  or  40  mm.,  it  is  evident  that,  even  when  the 
stimulation  begins  at  one  end,  the  whole  fibre  is  not  only  in 
a  state  of  contraction  at  the  same  time,  but  almost  in  the- 
same  phase  of  the  contraction-wave.  In  an  ordinary  con- 
traction occurring-  in  "the  living  body  the  stimulus  is  never 
applied  to  one  end  of  the  fibre;  the  nervous  itnpulse,  which 
in  such  cases  acts  as  the  stimulus  to  the  nuiscle,  falls  into 
the  fibre  at  aliout  its  middle,  where  the  nerve  ends  in  an  encT- 
plate  (  Fig.  21),  and  the  contraction-wave  starting-  from  the 
end-plate  travels  along  the  muscular  fibre  in  both  directions. 

[Fig  21. 


Muscular  Fibre,  with  termination  of  Motor  Xerve,  from  the  Gastrocnemius  of  the 
Rana  esculenta.  a,  terminal  pencil  of  a  dark-bordered  nerve-fibre;  ft,  intramuscular 
naked  axis  cylinder;  c,  uucleus  of  the  neurilemma;  d,  clavate  extremities  of  the 
nerve;  e,  spaces  of  the  muscle-nuclei ;  /,  terminal  knob  of  nerve,  with  central  fibre 
and  vesicular  dilation  of  the  nerve. — After  Cohnheim.] 


In  such  a  case,  therefore,  still  more  even  than  in  the  urarized 
muscle  stimulated  artificiallj'  at  one  end,  must  the  whole  fibre 
be  occupied  at  the  same  time  b}'  the  wave  of  contraction. 


Changes  in  Microscopic  Structure. — When  portions  of  living 
irritable  muscle  are  examined  under  the  microscope,  con- 
traction-waves similar  to  those  just  described,  but  feebler 
and  of  shorter  length,  may  be  observed  passing  along  the 


81 


THE    CONTRACTILE    TISSUES. 


Flu.  22. 


lihres.  By  appropriate  treatment  witli  osinic  acid  or  other 
reagents,  tiiese  sliort  contraction-waves  may  he  fixed,  and 
the  structure  oi'  the  contracted  portion  compared  at  leisure 
with  that  of  the  i)ortions  of  tlie  fil)re  at  rest.  In  Fig  22, 
representing  a  fibre  of  tlie  muscle  of 
an  insect  (in  wiiich  these  clianges 
can  be  more  satisfactorily  studied 
than  in  vertebrate  muscle),  the  con- 
traction-wave begins  near  a,  and  has 
reached  about  its  maximum  at  6, 
while  at  c  the  fibre  is  at  rest,  the 
con  traction -wave  not  having  reached 
it  (or  having  passed  over  it,  for  the 
Iteginning  and  end  of  the  wave  are 
exactly  alike).  It  will  be  seen  that 
at  b  each  disk  of  the  fibre  is  shorter 
and  broader  than  at  c.  Further, 
while  at  c  the  dim  band  x  is  con- 
spicuous, and  the  light  band  ^,  with 
its  accessory  markings  y%  is  to- 
gether lighter  than  the  dim  band  .r, 
at  b  in  the  fully  contracted  part  of 
the  fil)re  the  dim  band  appears  light 
as  comi)ared  with  the  black  line  y' 
occupying  the  middle  of  the  previ- 
ously light  band.  In  the  contracted 
muscle,  then,  there  is  a  reversal  of 
the  state  of  things  in  the  resting 
muscle,  the  light  band  (or  part  of 
tlie  light  baudj  of  the  latter  in  con- 
tracting becomes  dark,  and  the  dim 
band  of  the  latter  becomes  by  com- 
parison light.  Between  rest  and  full 
contraction  there  is  an  intermediate 
stage,  as  at  d^  in  which  the  distinc- 
tion between  dim  and  bright  bands 
seems  to  he  largely  lost.  The  subject,  however,  is  one  offer- 
ing pecnliar  ditficulties  in  the  wa}'  of  investigation  ;  and, 
while  most  observers  agree  in  the  broad  facts  which  have 
just  been  stated,  there  is  great  diversity  of  opinion  concern- 
ing further  details,  and  especially  as  to  the  interpretation 
of  the  various  appearances  observed.  The  accessory  mark- 
ings in  the  middle  of  the  light  band  have,  in  particular,  been 
the  subject  of  controversies  into  which  we  cannot  enter  here. 


Muscular  Fibro  undergoing 
Contraction. 

The  inusrle  is  that  of  Tehph- 
orus  meianurns  treated  with  os- 
niic  acid.  The  fibre  at  e  is  at 
rest,  at  o  the  contraction  begins, 
at  b  it  has  reached  its  maxi- 
mnin.  The  right  hand  side  of 
the  figure  shows  the  same  fibre 
as  seen  in  polarized  light. — After 
Enoelmann. 


RELAXATION.  85 


When  the  fibre  is  exarahied  in  polarized  light  it  is  seen  that  the 
dim  band  is  anisotropic,  and  the  light  band  Avholh"  isotropic, 
the  accessory  markings  //'  of  the  light  band  not  being"^ recogniza- 
ble in  polarized  light.  This  is  the  case  dnring  all  the  phases  of 
the  contraction.  At  no  period  is  there  an}'  confusion  between 
the  anisotropic  and  isotropic  material;  these  maintain  their  rela- 
tive positions,  both  become  shorter  and  broader  ;  but  it  will  be 
observed  that  the  isotropic  substance  diminishes  in  height  to  a 
much  greater  extent  than  does  the  anisotropic  substance.  The 
latter  in  fact  appears  to  increase  in  bulk  at  the  expense  of  the 
former.^ 

Relaxation. — The  shortening  as  we  have  seen  is  followed 
by  a  relaxation,  the  muscle  returning  to  its  original  length. 
This  is  brought  about  by  the  elastic  reaction  of  the  muscular 
substance  itself.  The  application  of  an  extending  force, 
though  useful,  is  not  necessary. 

The  muscles  in  their  natural  position  in  the  body,  where  they 
are  to  a  certain  extent  on  the  stretch,  return  completely  and 
rapidl}'  to  their  former  length,  even  after  a  powerful  and  pro- 
longed contraction.  Out  of  the  body  the  return,  especially  in 
muscles  which  are  not  loaded,  is  slower,  and  is  frequently  incom- 
plete. The  amount  of  this  deficiency  of  relaxation  depends  on 
the  nutritive  condition  of  the  muscle.  AVhen  a  muscle  is  stimu- 
lated by  induction-shocks  repeated  with  a  certain  rapidity  this 
deficiency  of  relaxation  or  "contraction  remainder,"  as  it  has 
been  called,  becomes  very  conspicuous.^ 

A  muscular  contraction  appears  then  to  be  essentiall}"  a 
translocation  of  molecules.  If  we  were  to  represent  a  por- 
tion of  muscular  substance  at  rest  by  four  rows  of  molecules 
four  abreast  as  in  Fig.  23.  the  contraction  might  be  repre- 
sented by  the  four  rows  of  four 
shiftins?  into  two  rows  of  eisfht :  ^        ^^^-  -^- 

A  A  A  A 

and   the    subsequent  relaxation      JJJJ^^^^Afi^ft 

by  a  return  into  four  rows.     We      ??552J^a  &  aS  a 

cannot  at  present  give  any  satis-      ©  ®  9  9 
factory  molecular  explanation  of 

tiiis  translocation,  even  when  we  have  studied  the  chemical 
and  other  events,  to  be  described  immediately,  which  accom- 
pany and  are  doubtless  the  cause  of  the  change  of  form. 
And  there  is  a  remarkable  physical  characteristic  of  the 
contracted  state  wliich  shows  how  complex  and  peculiar  is 

^  Enaelmann,  Pfliiger's  Archiv,  xviii  (1878),  p.  1. 
2  Cf.  Tiegel,  PfliigeVs  Archiv,  xiii  (1876),  p.  71. 


86  THE    CONTRACTILE    TISSUES. 

the  act  of  contraction.  Living  muscle  at  rest  is  very  ex- 
tensible, Ijut  a  stretched  muscle  after  the  extending  cause 
has  lieen  removed  returns  rapidly  and  completely  to  its 
former  length.  In  physical  language  muscle  is  spoken  of  as 
possessing  slight  hut  }jerfect  elasticity.  It  might  be  imag- 
ined that  during  a  contraction  this  extensibility  would  he 
diminished  in  oi"der  that  none  of  the  resistance  which  the 
muscle  had  to  overcome,  no  part  of  the  weigiit  for  instance 
which  had  to  be  lifted,  should  be  wasted  in  stretching  the 
muscle  itself.  On  the  contrary,  we  lind  that  during  a  con- 
traction there  is  a  marked  increase  of  extensibility  ;  thus,  if 
a  muscle  at  rest  be  loaded  with  a  given  weiglit,  say  50  grams, 
and  its  extension  observed,  and  be  then  while  unloaded 
thrown  into  tetanus,  and  the  load  applied  during  the  teta- 
nus, the  extension  in  the  second  case  will  be  distinctly 
greater  than  in  the  first.  During  the  contraction  there  is  so 
to  speak  a  greater  mobility  of  the  muscular  molecules,  and 
the  loaded  muscle  has  in  contracting  to  overcome  its  own 
tendency  to  lengthen  on  extension  before  it  can  i^roduce 
any  eflect  on  the  weight  which  it  has  to  lift. 

When  a  muscle  is  extended  by  a  series  of  w^eights  increasing  in 
magnitude,  the  curve  (obtained  by  making  the  weights  abscissae 
and  the  extensions  ordinates)  is  not  a  straight  line,  as  is  the 
case  with  dead  elastic  bodies,  but  a  hyperbola. 

The  elasticity  or  extensibility  of  the  muscidar  substance 
is  essentially  a  vital  propert}^  i.  e.,  is  dependent  on  the  same 
nutritive  factors  as  the  irritability  of  the  muscular  substance. 
As  the  muscular  substance  becomes  wear}'  with  too  much 
w'ork  or  impoverished  by  scanty  nutrition,  its  elasticity  suf- 
fers pari  2)a^su  with  its  irritai^ilit}-.  The  exhausted  muscle 
when  extended  does  not  return  so  readily  to  its  proper  length 
as  the  fresh  active  muscle,  and,  as  we  shall  see,  the  dead 
muscle  does  not  return  at  all. 


Electrical  Changes. 

Muscle-Currents. — If  a  muscle  be  removed  in  an  ordinary 
manner  from  the  body,  and  two  non-polarizable  electrodes,^ 

^  These  (Fig.  24)  consist  essentially  ofa  slip  of  thoroughly  amalgamated 
zinc  dipping  into  a  saturated  solution  of  zinc  sulphate,  wliich  in  turn  is 
brought  into  connection  with  the  nerve  or  muscle  by  means  of  a  phig  or 
bridge  of  china-clay  moistened  with  dilute  sodium  chloride  solution  ;  it 


MUSCLE-CURREXTS. 


87 


connected  with  a  delicate  galvanometerof  many  convolutions, 
be  placed  on  two  points  of  the  surface  of  the  muscle,  a  de- 
flection of  the  galvanometer  will  take  place  indicating  the 
existence  of  a  current  passing  through  the  galvanometer 
from  the  one  point  of  the  muscle  to  the  other,  the  direction 
and  amount  of  the  deflection  varying  according  to  the  posi- 
tion of  the  points.  The  '' muscle-ciirrents  "  thus  revealed 
are  seen  to  the  best  advantage  when  the  muscle  chosen  is  a 
cylindrical  or  prismatic  one  with  j^arallel  fil^res,  and  when 
the  two  tendinous  ends  are  cut  ofl[*  by  clean  incisions  at  right 
angles  to  the  long  axis  of  the  muscle.  The  muscle  then 
presents  an  (artificial;  transverse  section  at  each  end  and  a 
longitudinal  surface.  We  may  speak  of  the  latter  as  being 
divided  into  two  equal  parts  by  an  imaginary  transverse 
line  on  its  surface  called  the  "equator,"  containing  all  the 


is  important  that  the  zinc  should  be  thoroughly  amalgamated.  This  form 
of  electrodes  gives  rise  to  less  polarization  than  do  simple  platinum  or 
copper  electrodes.     The  clay  affords  a  connection  between  the  zinc  and 

Fig.  24. 


JLi2^ 


Non-polarized  Electrodes. 

a,  the  glass  tube;  z,  ihe  amalgamated  zinc  slips  connected  with  their  respective 
■wires  ;  z.  s.,  the  zinc  sulphate  solution  ;  cfi.  c,  the  plug  of  china-clav  ;  c',  the  portion 
of  the  china-clay  plug  projecting  from  the  end  of  the  tube  ;  this  can  be  moulded 
into  any  required  form. 


the  tissue  which  neither  acts  on  the  tissue  nor  is  acted  on  by  the  tissue. 
Contact  of  any  tissue  with  copper  or  platinum  is  in  itself  sufficient  to 
develop  a  current. 


88 


THE    CONTRACTILE    TISSUES. 


points  of  the  surface  midway  between  tlie  two  ends.  Fio-. 
25  is  a  diairi'finiHiatic  representation  of  such  a  muscle,  the 
line  ah  being  the  equator.  In  such  a  muscle  the  develop- 
ment of  the  muscle-currents  is  found  to  be  as  follows: 

The  greatest  deflection  is  observed  when  one  electrode  is 
placed  at  the  mid-point  or  equator  of  the  muscle,  and  the 


Diagram  Illustrating  the  Electric  Currents  of  Nerve  and  Muscle. 

Being  purely  diagrammatic,  it  may  serve  for  a  piece  either  of  nerve  or  of  muscle, 
except  that  the  currents  at  the  transverse  section  cannot  be  shown  in  a  nerve.  The 
arrows  show  the  direction  of  the  current  through  the  galvanometer. 

a  b,  the  equator.  The  strongest  currents  are  those  shown  by  the  dark  lines,  as  from 
«,  at  equator,  to  x  or  to  y  at  the  cut  ends.  The  current  from  a  to  c  is  weaker  than 
from  a  toy,  though  both,  as  shown  by  the  arrows,  have  the  s'ame  direction.  A  current 
is  shown  from  e,  which  is  near  the  equator,  to/,  which  is  farther  from  the  equator. 
The  current  (in  muscle)  from  a  point  in  the  circumference  to  a  point  nearer  the 
centre  of  the  transverse  section  is  shown  at  g  h.  From  a  to  6  or  from  xto  y  there  is 
no  current,  as  indicated  by  the  lines. 


other  at  either  cut  end;  and  the  deflection  is  of  such  a  kind 
as  to  show  that  positive  currents  are  continually  passing 
from  the  equator  through  the  galvanometer  to  the  cut  end, 
that  is  to  say,  the  cut  end  is  negative  relativel}'  to  the  equa- 
tor. The  currents  outside  the  muscle  may  be  considered  as 
completed  by  currents  in  the  muscle  from  the  cut  end  to  the 
equator.  In  the  diagram,  Fig.  25,  the  arrows  indicate  the 
direction  of  the  currents.  If  the  one  electrode  be  placed 
at  the  equator  a  6,  the  eflTect  is  the  same  at  w'hichever  of 
the  two  cut  ends  x  or  y  the  other  is  placed.     If,  one  elec- 


MUSCLE-CURRENTS.  89 

trode  remaining  at  the  equator,  the  other  be  shifted  from  the 
cut  end  to  a  spot  c  nearer  to  the  equator,  the  current  con- 
tinues to  have  the  same  direction,  but  is  of  less  intensit}-  in 
l^roportion  to  the  nearness  of  the  electrodes  to  each  other. 
If  the  two  electrodes  be  placed  at  unequal  distances  e  and 
/,  one  on  either  side  of  the  equator,  there  will  be  a  feeble 
current  from  the  one  nearer  the  equator  to  the  one  farther 
off,  and  the  current  will  be  the  feebler  tlie  more  nearly  they 
are  equidistant  from  the  equator.  If  thej^  are  quite  equidis- 
tant, as  for  instance  when  one  is  placed  on  the  cut  end  a:, 
and  the  other  on  the  other  cut  end  y.  there  will  be  no  cur- 
rent at  all. 

If  one  electrode  be  placed  at  the  circumference  of  the 
transverse  section  and  the  other  at  the  centre  of  tlie  trans- 
verse section,  there  will  be  a  current  througli  the  galvanom- 
eter from  the  former  to  the  latter:  there  will  be  a  current  of 
similar  direction  ])ut  of  less  intensity  when  one  electrode  is 
at  the  circumference  g  of  the  transverse  section  and  the 
other  at  some  point  h  nearer  the  centre  of  the  transverse 
section.  In  fact,  the  jjoints  which  are  relatively  most  posi- 
tive and  most  negative  to  each  other  are  points  on  the 
equator  and  the  two  centres  of  the  transverse  sections;  and 
the  intensity  of  the  current  between  any  two  points  will 
depend  on  the  respective  distances  of  those  points  from  the 
equator  and  from  the  centres  of  the  transverse  sections. 

Similar  currents  may  be  observed  when  the  longitudinal 
surface  is  not  the  natural  but  an  artificial  one  ;  indeed  they 
may  lie  witnessed  in  even  a  [)iece  of  muscle  provided  it  be 
of  cylindrical  shape  and  composed  of  parallel  fibres. 

These  natural  •'  muscle-currents"  are  not  mere  transitor}^ 
currents  disappearing  as  soon  as  the  circuit  is  closed;  on 
the  contrary  they  last  a  very  consideral)le  time.  They  must 
therefore  be  maintained  by  some  changes  going  on  in  the 
muscle,  by  continiicd  chemical  action  in  fact.  They  disap- 
pear as  the  irritability  of  the  muscle  vanishes,  and  therefore 
may  be  su[)posed  to  be  connected  with  those  nutritive,  so- 
called  vital  changes  which  maintain  the  irritability  of  the 
muscle. 

Muscle-currents  such  as  have  just  been  described  may, 
we  repeat,  be  observed  in  an}'  cylindrical  muscle  suitably 
prepared.,  and  similar  currents,  with  variations  which  need 
not  be  described  here,  may  be  seen  in  muscles  of  irregular 
shape  with  obliquel}'  or  otherwise  arranged  fibres.  And  Da 
Bois-Reyraond,  to  whom   chiefly  we   are  indebted  for  our 


90  THE    CONTRACTILE    TISSUES. 

knowle(lii:e  of  these  currents,  has  been  led  to  regard  them  as 
essential  and  important  properties  of  living  muscle.  He 
has  moreover  advanced  the  theory  that  muscle  may  be  con- 
sidered as  composed  of  electro-motive  particles  or  mole- 
cules, each  of  whicii  like  the  muscle  at  large  has  a  positive 
equator  and  negative  ends,  tiie  whole  muscle  being  made  up 
of  these  molecules  in  somewhat  the  same  wa}^  (to  use  an 
illustration  which  must  not  however  be  strained  or  consid- 
ered as  an  exact  one)  as  a  magnet  may  be  supposed  to  i)e 
made  up  of  magnetic  particles  each  with  its  north  and  south 
pole. 

There  are  reasons,  however,  for  thinking  that  these  mus- 
cle-currents have  no  such  fundamental  origin,  that  they  are 
in  fact  of  surface  and  indeed  of  artificial  origin.  Without 
entering  largely  into  the  controvers}^  on  this  question  (some 
details  of  which  will  be  found  in  a  subsequent  section  in 
small  print),  the  following  important  facts  may  be  men- 
tioned. 

1.  When  a  muscle  is  examined  while  it  still  retains  un- 
touched its  natural  tendinous  terminations,  the  currents  are 
much  less  than  when  artificial  transverse  sections  have  been 
made.  The  natural  tendinous  end  is  less  negative  than  the 
cut  surface.  In  some  cases  it  may  be  even  positive  rela- 
tivel}^  to  the  longitudinal  surface.  But  the  tendinous  end 
becomes  at  once  negative  when  it  is  dipped  in  water  or  acid, 
indeed  when  it  is  in  any  way  injured.  The  less  roughly  in 
fact  a  muscle  is  treated  the  less  evident  are  the  muscle-cur- 
rents, and  Hermann  has  shown  that  if  proper  care  be  taken 
a  muscle  may  be  so  removed  from  the  body  as  to  give  only 
currents  which  are  hardly  appreciable. 

2.  Engelmann^  lias  shown  that  the  surface  of  the  unin- 
jured inactive'^  ventricle  of  the  frog's  heart  is  isoelectric,  i.  e., 
that  no  current  is  obtained  when  the  electrodes  are  placed 
on  any  two  points  of  the  surface.  If,  however,  any  part  of 
the  surface  be  injured,  or  if  the  ventricle  be  cut  across  so  as 
to  expose  a  cut  surface,  the  injured  spot  or  the  cut  surface 
becomes  at  once  most  powerfully  negative  towards  the  un- 
injured surface,  a  strong  current  being  developed,  which 
passes  through  the  galvanometer  from  the  uninjured  surface 
to  the  cut  surface  or  to  the  injured  spot.     The  negativity 

'  Pfliiger's  Arcliiv,  xv  (1877),  p.  166. 

^  The  necessity  of  its  being  inactive  will  be  seen  subsequently. 


NEGATIVE  VARIATION   OF   THE    MUSCLE  -  CURRENT.     91 

thus  developed  in  a  cut  siirface  passes  off  in  the  course  of 
some  liours.  but  may  be  restored  b\'  making  a  fresh  cut  and 
exposing  a  fresh  surface. 

Xow,  when  a  muscle  is  cut  or  injured  the  substance  of  the 
fibres  dies  at  the  cut  or  injured  surface.  And  certain  au- 
thorities, auiong  whom  the  most  prominent  is  Hermann, 
have  been  led  by  the  above  and  other  facts  to  the  conclusion 
that  muscle-currents  do  not  exist  naturally  in  untouched 
muscles,  that  the  muscular  substance  is  naturally,  when 
living,  isoelectric,  but  that  whenever  a  portion  of  the  mus- 
cular substance  dies,  it  becomes  while  di/wg  negative  to  the 
living  substance,  and  thus  gives  rise  to  currents.  They  ex- 
plain the  typical  currents  (as  they  might  be  called)  mani- 
fested by  a  muscle  with  a  natural  longitudinal  surface  and 
artificial  transverse  sections,  by  the  fact  that  the  dying  cut 
ends  are  negative  relatively  to  the  rest  of  the  muscle. 

Du  Bois-Heymond  and  tliose  with  him  offer  special  expla- 
nations of  the  above  facts  and  of  other  objections  which 
have  been  urged  against  the  theory  of  naturally  existing 
electro-motive  molecules.  Into  these  we  cannot  enter  here. 
We  must  rest  content  with  the  statement  that  in  an  ordi- 
nary muscle  currents  such  as  have  been  described  may  be 
witnessed,  but  that  strong  arguments  may  be  adduced  in 
favor  of  the  view  that  these  currents  are  not  '"natural" 
plienomena,  but  essentially  of  artificial  origin.  It  will  tliere- 
fore  be  best  to  speak  of  them  as  "currents  of  rest." 

Ifegative  Variation  of  the  Muscle-Current  — The  contro- 
versy whether  the  '^  currents  of  rest"  ol)servable  in  a  muscle 
be  of  natural  origin  or  not,  does  not  affect  the  truth  or  the 
importance  of  the  fact  that  an  electrical  change  takes  place 
in  a  muscle  whenever  it  enters  into  a  contraction.  When 
currents  of  rest  are  observable  in  a  muscle  these  are  found 
to  undergo  a  diminution  at  tiie  onset  of  a  contraction,  and 
this  diminution  is  spoken  of  as  "the  negative  variation  "  of 
the  currents  of  rest.  The  negative  variation  may  be  seen 
when  a  muscle  is  thrown  into  a  single  contraction,  but  is 
most  readily  shown  when  tiie  muscle  is  tetanized.  Thus  if 
a  pair  of  electrodes  be  placed  on  a  muscle,  one  at  the  equa- 
tor and  the  other  at  or  near  tlie  transverse  section,  so  that 
a  considei'able  deflection  of  the  galvanometer  needle,  indi- 
cating a  considerable  current  of  rest,  be  gained,  the  needle 
of  the  galvanometer  will,  when  the  muscle  is  tetanized  b}' 


92  TUE    CONTRACTILE    TISSUES. 

an  inteiTiii)ted  current  sent  tbrougli  its  nerve  (at  a  point 
too  far  from  the  mnsckto  allow  any  eseai)e  of  the  current 
into  the  electrodes  connected  with  the  galvanometer),  swing 
back  towards  z&ro;  it  retuins  to  its  original  deflection  when 
the  tetaniziiig  current  is  shut  off. 

This  negative  variation  may  not  only  be  shown  Iw  the 
galvanomeUn',  but  it,  as  well  as  the  current  of  rest,  may  be 
used  as  a  galvanic  shock  and  so  employed  to  stimulate  a 
muscle,  as  in  tlie  experiment  known  as  "  the  rheoscopic 
frog."  For  this  purpose  very  irritable  muscles  and  nerves 
in  thoroughly  good  condition  are  required.  Two  muscle- 
nerve  preparations,  A  and  Z?,  having  been  made,  and  each 
placed  on  a  glass  plate  for  the  sake  of  insulation,  the  nerve 
of  the  one,  Z>,  is  allowed  to  fall  on  the  muscle  of  the  other, 
A,  in  such  a  way  that  one  point  of  the  nerve  comes  in  con- 
tact with  the  equator  of  the  muscle,  and  another  point  with 
one  end  of  the  muscle  or  with  a  point  at  some  distance  from 
the  equator.  At  the  moment  tlie  nerve  is  let  fall  and  con- 
tact made,  a  current,  viz.,  the  "current  of  rest"  of  the 
muscle  A  passes  through  the  nerve  ;  this  acts  as  a  stimulus 
to  the  nerve,  and  so  causes  a  contraction  in  the  muscle  con- 
nected with  the  nerve.  Thus  the  muscle  A  acts  as  a  bat- 
tery, the  completion  of  the  circuit  of  which  b}-  means  of  the 
nerve  of  B  serves  as  a  stimulus,  causing  the  muscle  B  to 
contract. 

If  while  the  nerve  of  B  is  still  in  contact  with  tlie  muscle 
of  A,  the  nerve  of  the  latter  is  tetanized  with  an  interrupted 
current,  not  only  is  the  muscle  of  A  thrown  into  tetanus, 
but  also  that  of  B  ;  the  reason  being  as  follows  :  At  each 
spasm  of  which  the  tetanus  of  A  is  made  up,  there  is  a  nega- 
tive variation  of  the  muscle-currrent  of  A.  Each  negative 
variation  in  the  muscle-current  of  A  serves  as-  a  stimulus  to 
the  nerve  of  /i,  and  is  hence  the  cause  of  a  spasm  in  the 
muscle  of  B  ;  and  the  stimuli  following  each  other  rapidly, 
as  being  i)ruduced  t)y  tetanus  of  A  the}'  must  do,  the  spasms 
in  B  to  which  they  give  rise  are  also  fused  into  a  tetanus 
in  A.  B  in  fact  contracts  in  harmony  with  B.  This  ex- 
periment shows  that  the  negative  variation  accompanying 
the  tetanus  of  a  muscle,  though  it  causes  only  a  single  swing 
of  the  galvanometer,  is  really  made  up  of  a  series  of  nega- 
tive variations,  each  single  negative  variation  corresponding 
to  the  single  spasms  of  which  the  tetanus  is  made  up. 

But  an  electrical  change  may  be  manifested  even  in  cases 
when  no  currents  of  rest  exist.     We  have  stated  (p.  90) 


KEGATIVE    VARIATION    OF    THE   M  USCLE  -  C  U  R  RENT.     93 

that  the  surfnce  of  the  uninjured  inactive  ventricle  of  the 
frog's  heart  is  isoelectric,  no  currents  being  observed  when 
the  electrodes  of  a  galvanometer  are  placed, on  two  points 
of  the  surface.  Nevertheless  a  most  distinct  current  is  de- 
veloped whenever  the  ventricle  contracts.  This  may  be 
shown  either  by  the  galvanometer  or  by  the  rheoscopic  frog. 
If  the  nerve  of  an  irritable  muscle-nerve  preparation  be  laid 
over  a  pulsating  ventricle,  each  beat  is  responded  to  by  a 
spasm  of  the  muscle  of  the  preparation.  In  the  case  of  or- 
dinary muscles  two  instances  occur  in  which  it  seems  im- 
possible to  regard  the  electrical  change  manifested  during 
the  contraction  as  the  mere  diminution  of  a  pre-existing 
current. 

Accordingly  Hermann  and  those  who  with  him  deny  the 
existence  of  ''natural"  muscle-currents,  speak  of  a  muscle 
as  developing  during  a  contraction  a  '"current  of  action," 
occasioned,  as  they  believe,  b^^  the  muscular  substance  as  it 
is  entering  into  the  state  of  contraction  becoming  negative 
towards  the  muscular  substance  which  is  still  at  rest,  or  has 
returned  to  a  state  of  rest.  In  fact,  they  regard  tiie  nega- 
tivity of  muscular  substance  as  characteristic  alike  of  a  be- 
ginning death  and  of  a  beginning  contraction.  And  they 
believe  that  in  a  muscular  contraction  a  wave  of  negativity 
starting  from  the  end-plate  wlien  indirect,  or  frojn  the  point 
stimulated  when  direct  stimulation  is  used,  passes  along 
the  muscular  substance  to  the  ends  or  end  of  the  fibre.  We 
cannot  enter  more  fully  here  into  a  discussion  of  this  diffi- 
cult subject,  but  some  account  of  the  various  facts  and  ar- 
guments brought  forward  by  the  advocates  of  the  contlicting 
views  will  be  found  in  a  subsequent  section  in  small  print. 

Whichever  view  be  taken  of  the  nature  of  these  muscle- 
currents,  and  of  the  electric  change  during  contraction, 
whether  we  regard  that  change  as  a  ''  negative  variation  ''  or 
as  a  "current  of  action,"  it  is  important  to  remember  that 
it  takes  place  entirely  during  the  latent  period.  It  is  not 
in  any  way  the  result  of  the  change  of  form;  it  is  the  fore- 
runner of  that  change  of  form.  Just  as  a  nervous  impulse 
passes  down  the  nerve  to  the  muscle  witiiout  any  visible 
changes,  so  a  molecular  change  of  some  kind,  unattended 
b}'  an}'  visible  events,  marked  only  by  an  electrical  change, 
runs  along  the  muscular  fibre  from  the  end-phites  to  the  ter- 
minations of  the  fibre,  preparing  the  way  for  the  visible 
change  of  form  which  is  to  follow.  This  molecular  invisible 
change  is  the  work  of  the  latent  period,  and  careful  obser- 


94  THE    CONTRACTILE    TISSUES. 

vation  lias  sliown  us  that  it,  like  tiie  visible  contraetion 
whicli  follows  at  its  heels,  travels  alon^  the  fii)re  from  a  spot, 
stiimilatecl  (from  the  end-plates  when  the  stimiibis  isapplied 
indirectly  throngh  a  nerve,  or  from  the  point  touched  hy 
the  electrodes  when  the  stimulus  is  a  direct  one)  towards 
the  ends  of  the  fibres,  in  the  form  of  a  wave  having  about 
the  same  velocity  as  the  contraction,  viz.,  about  three  meters 
a  second. 

Chemical   Change.'^. 

Before  we  attack  the  important  problem.  What  are  the 
chemical  changes  concerned  in  a  muscular  contraction?  we 
must  study  in  some  detail  the  chemical  features  of  muscle 
at  rest.  And  here  we  are  brought  face  to  face  with  the 
chemical  differences  between  living  and  dead  muscles.  All 
muscles,  within  a  certain  time  after  removal  from  the  body, 
or  while  still  within  the  bod\',  after  '"general"  death  of  the 
body,  lose  their  irritabilit3'.  The  loss  of  irritability,  even 
when  rapid,  is  gradual,  but  is  succeeded  hy  an  event  of  some 
suddenness,  the  entrance  into  the  condition  known  as  rigor 
morli.s,  the  occurrence  of  which  is  marked  by  the  following 
features:  The  muscle,  previously  possessing  a  certain  trans- 
lucency,  becomes  much  mora  opaque.  Previously  very  ex- 
tensible and  elastic,  it  becomes  rigid  and  inextensible,  an<l 
at  the  same  time  loses  its  elasticity  ;  the  muscle  now  re- 
quires considerate  force  to  stretch  it,  and  when  the  force 
is  removed,  does  not,  as  before,  return  to  its  natural  length. 
To  the  touch  it  has  lost  much  of  its  former  softness,  and 
becomes  firmer  and  more  resistant.  The  entrance  into  rigor 
mortis  is  characterized  by  a  shortening  or  contr;!Ction  whicii 
maj',  under  certain  circumstances,  be  considerable.  The 
energy  of  this  contraction  is  not  great,  so  that  when  opposed, 
no  actual  shortening  takes  place.  When  rigor  mortis  has 
been  fully  developed  no  muscle-currents  whatever  are  ob- 
served. The  onset  of  this  rigidity  may  be  considered  as 
the  token  of  the  death  of  the  muscle  itself.  As  we  shall 
see,  the  chemical  features  of  the  dead  rigid  muscle  are 
strikingly  ditferent  from  those  of  the  living  muscle. 

If  a  dead  muscle,  from  which  all  fat,  tendon,  fascia,  and 
connective  tissue  have  been  as  much  as  possible  removed, 
and  which  has  been  freed  from  blood  by  the  injection  of 
saline  solution,  be  minced  and  repeatedly  washed  with  water, 
the  washings  will  contain  certain  forms  of  al'Dumin  and  cer- 
tain extractive   bodies,  of  which    we   shall  speak   directly. 


CHEMICAL    CHANGES.  95 

When  the  washing  has  been  coiitinuerl  until  tlie  wash-water 
gives  no  proteid  reaction,  a  large  portion  of  muscle  will  still 
remain  undissolved.  If  this  be  treated  with  a  10  per  cent, 
solution  of  sodium  chloride,  a  large  portion  of  it  will  be- 
come imperfectly  dissolved  into  a  viscid  fluid  which  filters 
with  difficulty.  If  tlie  viscid  filtrate  be  allowed  to  fall  drop 
by  drop  into  a  large  quantity  of  distilled  water,  a  white 
flocculent  matter  will  be  precipitated.  This  flocculent  pre- 
cipitate is  myosin.  It  is  a  proteid,  giving  the  ordinary 
proteid  reactions,  and  having  the  same  general  elementary 
composition  as  otlier  proteids.  It  is  soluble  in  dilute  saline 
solutions,  especially  those  of  sodium  chloride,  and  may  l)e 
classed  in  the  globulin  family,  though  it  is  not  so  soluble  as 
paraglobulin.  Dissolved  in  saline  solutions  it  readily  coagu- 
lates when  heated,  2.  e.,  is  converted  into  coagulated  proteid,^ 
and  it  is  worthy  of  notice  that  it  coagulates  at  a  lower 
temperature,  viz.,  55°-60^  C,  than  does  serum-albumin, 
paraglobulin,  and  many  other  proteids:  it  is  precipitated 
and  after  long  action  coagulated  by  alcohol,  and  is  precipi- 
tated by  an  excess  of  the  sodium  chloride.  By  the  action 
of  dilute  acids  it  is  very  readily  converted  into  what  is  called 
syntonin  or  acid-albumin,-'  by  the  action  of  dilute  alkalies 
into  alkali-albumin.  S[)eaking  generally  it  may  be  said  to 
be  intermediate  in  its  character  between  fibrin  and  globulin. 
On  keeping,  and  especially  on  drying,  its  solubilit}'  is  much 
diminished. 

Of  the  substances  which  are  left  in  washed  muscle  from 
which  the  myosin  has  thus  been  extracted  by  sodium  chlo- 
ride solution  little  is  known.  If  washed  muscle  be  treated 
directly  with  dilute  hydrochloric  acid,  the  greater  part  of 
the  material  of  the  muscle  passes  at  once  into  syntonin. 
The  quantity  of  syntonin  thus  obtained  may  be  taken  as 
representing  the  quantity  of  myosin  previously  existing  in 
the  muscle.  The  portion  insoluble  in  dilute  hydrochloric 
acid  consists  in  part  of  the  sul)stance  of  the  sarcolemma,  of 
the  nuclei,  and  of  the  tissue  between  the  bundles,  and  in 
part  probabl}^  of  certain  elements  of  the  fibres  themselves. 

If  living  contractile  frog's  muscle,  freed  as  before  as  much 
as  possible  from   blood,  be  frozen,^  and  while  frozen  minced 

^  See  Appendix.  2  ibij], 

^  Since,  as  we  shall  presently  see,  a  muscle  may  be  frozen  and  thawed 

again  withont  losing  any  of  its  vital  powers,  we  are  at  liberty  to  regard 

the  frozen  muscle  as  a  still  livino^  muscle. 


9G  TUE    CONTRACTILE    TISSUES. 

an<l  ruhbed  up  in  a  mortar  witli  four  times  its  wciorht  of 
snow  eontaininir  1  per  cent,  of  sodium  chloride,  a  mixture 
is  obtained  whicii,  at  a  temperature  just  below  0°  C,  is  suf- 
ficiently fluid  to  be  filtered,  though  with  difficulty.  The 
slightly  opalescent  filtrate,  or  mui-<lrplai<ma  as  it  is  called, 
is  at  first  quite  fluid,  but  will  when  ex-jmsed  to  the  ordinary 
temperature  become  a  solid  jelly,  and  afterwards  separate 
into  a  clot  and  serum.  It  will,  in  fact,  coagulate  like  blood- 
plasma,  with  this  difference,  that  the  clot  is  not  firm  and 
fibrillar,  but  loose,  granular,  and  flocculent.  During  the 
coagulation  the  fluid,  which  before  was  neutral  or  slightly 
alkaline,  becomes  distinctly  acid. 

The  clot  is  myosin.  It  gives  all  the  reactions  of  myosin 
obtained  from  dead  muscle. 

The  serum  contains  albumin  and  extractives. 

Besides  ordinary  serum  albumin  coagulating  at  75^,  Kiihne' 
(to  whom  we  owe  our  knowledge  of  the  above)  found  a  peculiar 
form  of  albumin  or  soluble  proteid  coagulating  at  45-,  irrespec- 
tive of  the  degree  of  acidity  acquired  by  the  serum.  There  is 
present  also  a"  proteid  substance  whose  coagulation-point  varies 
widely  (sometimes  as  low  as  25-),  being  dependent  on  the  acidity 
of  the  serum  ;  this  latter  appears  to  be  a  form  of  alkali  albumin, 
its  coagulation-point  being  probably  connected  with  the  salts 
present  in  the  serum  (see  Appendix).  Such  muscles  as  are  red 
also  contain  a  small  quantity  of  haemoglobin,  to  which  indeed 
their  redness  is  due. 

Thus  while  dead  muscle  contains  mj-osin.  serum  allmmin, 
and  extractives  with  certain  insoluble  matters  and  certain 
gelatinous  elements  not  referable  to  the  muscle-substance 
itself,  living  muscle  contains  no  myosin,  but  some  substance 
or  substances  which  bear  somewhat  the  same  relation  to 
myosin  that  the  fibrin  factors  do  to  fibrin,  and  which  be- 
comes or  become  myosin  on  the  death  of  the  muscle. 

We  may  in  fact  speak  of  rigor  mortis  as  characterized  by 
a  coagulation  of  the  muscle-plasma,  com.parable  to  the  coag- 
ulation  of  blood-plasma,  but  ditfering  from  it  inasmuch  as 
the  product  is  not  fibrin  l)ut  myosin.  The  rigidity,  the  loss 
of  suppleness,  and  the  diminished  transluceucy  appear  to 
be  at  all  events  largely,  though  probably  not  wholly,  due  to 
the  change  from  the  fluid  plasma  to  the  solid  myosin.  We 
might  compare  a  living   muscle  to  a   number  of  fine  trans- 

Protoplasma,  Leipzig,  18G4. 


CHEMICAL    CHANGES.  97 

parent  raemln'anons  tubes  filler]  with  Itlood-plasma.  When 
this  blood-i)lasma  entered  into  the  "jelly"  stage  of  coagu- 
lation, the  system  of  tubes  would  present  many  of  the 
phenomena  of  rigor  mortis.  They  would  lose  mucli  of  their 
suppleness  and  translucency,  and  acquire  a  certain  amount 
of  rigidity. 

But  there  is  one  very  marked  and  important  difference 
between  rigor  mortis  of  muscle  and  the  coagulation  of  blood  : 
blood  during  its  coagulation  undergoes  only  a  slight  change 
in  its  reaction  ;  muscle  during  the  onset  of  rigor  mortis  be- 
comes distinctly,  it  might  be  said  intensely,  acid. 

A  living  muscle  at  rest  is  in  reaction  neutral,  or,  from 
some  remains  of  13'mph  adhering  to  it,  faintly  alkaline. 
Tested  by  litmus-paper  it  is  frequently  amphicroitic,  i.  e.,  it 
will  turn  blue  litmus  red  and  red  litmus  blue, — but  the 
change  from  red  to  blue  is  more  marked  than  that  from 
blue  to  red.  If,  on  the  other  hand,  the  reaction  of  a  thor- 
oughl}'  rigid  muscle  be  tested,  it  will  be  found  to  be  most 
distinctly  acid.  This  development  of  acid  is  witnessed  not 
only  in  the  solid  untouched  fibre  but  also  in  expressed  mus- 
cle-plasma. The  red  coloration  of  the  blue  litmus  thus 
obtained  is  permanent,  and  cannot  therefore  be  due  to  car- 
bonic acid. 

From  rigid  muscle  there  may  be  obtained  a  quantity  of 
lactic  acid,  or  rather  of  a  variet}'  of  lactic  acid  known  as 
sarcolactic  acid.^  It  is  probable  that  the  change  in  the 
reaction  is  due  to  tlie  formation  of  this  acid. 

The  appearance  of  rigor  mortis  is  characterized  then  b}" 
the  occurrence  of  a  nitrogenous  proteid  body,  myosin,  not 
previously  existing  as  such  in  the  living  irritable  fibr-e,  and 
of  a  carbon  acid,  sarcolactic  acid.  But  there  is  another 
most  important  acid,  which  is  developed  at  the  same  time. 
Irritable  living  muscular  suV)stance  like  all  living  protoplasm - 
is  continually  respiting,  continually  consuming  oxygen  and 
giving  out  carbonic  acid.  In  the  body,  the  arterial  blood 
going  to  the  muscle  gives  up  some  of  its  oxygen,  and  gains 
a  quantity  of  carbonic  acid,  thus  becoming  venous  as  it 
passes  through  the  muscular  capillaries.  After  removal 
from  the  body,  the  living  muscle  continues  to  take  up  from 
the  surrounding  atmosphere  a  certain  quantitv  of  oxygen 
and  to  give  out  a  certain  quantity  of  carbonic  acid. 

At  the   onset  of  rigor  mortis  there  is   a  very  large  and 

*  See  Appendix. 


98  THE    CONTRACTILE    TISSUES. 

sudden  increase  in  this  production  of  cnrhonic  acid,  in  fact 
a  burst  as  it  were  of  that  gas.  This  is  a  phenomenon  de- 
serving special  attention.  Knowing  that  the  carbonic  acid 
which  is  the  outcome  of  the  respiration  of  the  whole  body 
is  the  result  of  the  oxidation  of  carbon-holding  substances, 
we  might  very  naturally  suppose  that  tiie  increased  produc- 
tion of  carbonic  acid  attendant  on  the  development  of  rigor 
mortis  is  due  to  the  fact  that  durir)g  that  event  a  certain 
quantity  of  the  carbon-holding  constituents  of  the  muscle 
are  suddenly  oxidized.  But  such  a  view  is  negatived  by 
the  following  facts.  In  the  first  i)lace,  the  increased  pro- 
duction of  carbonic  acid  during  rigor  mortis  is  not  accom- 
panied b}'  any  corresponding  increase  in  the  consumption 
of  oxygen.  In  the  second  place,  a  muscle  Cof  a  frog  for 
instance;  contains  in  itself  no  free  or  loosely^  attached 
oxygen  ;  when  subjected  to  the  action  of  a  mercurial  air- 
pump  it  gives  off  no  oxygen  to  a  vacuum,  offering  in  this 
respect  a  marked  contrast  to  blood,  and  yet,  when  placed  in 
an  atmosphere  free  from  oxygen,  it  will  not  only  continue 
to  give  otf"  carbonic  acid  while  it  remains  alive,  but  will  also 
exhibit  at  the  onset  of  rigor  mortis  the  same  increased  pro- 
duction of  carbonic  acid  that  is  shown  by  a  muscle  placed 
in  an  atmosphere  containing  oxygen.  It  is  obvious  that  in 
such  a  case  the  carbonic  acid  does  not  arise  from  the  direct 
oxidation  of  the  muscle  substance,  for  there  is  no  oxygen 
present  at  the  time  to  carry^  on  that  oxidation.  We  are 
driven  to  suppose  that  during  rigor  mortis  some  complex 
body,  containing  in  itself  ready-formed  carbonic  acid  so  to 
speak,  is  split  up  and  thus  carbonic  acid  set  free,  the  process 
of  oxidation  by  which  that  carbonic  acid  was  formed  out  of 
the  carbon-holding  constituents  of  the  muscle  having  taken 
place  at  some  anterior  date. 

It  is  found  moreover  that  there  is  a  certain  amount  of  paral- 
lelism between  the  intensity  of  the  rigor  mortis,  the  degree  of 
acid  reaction  [i.  c,  the  amount  of  sarcolactic  acid  formed),  and  the 
quantity  of  carbonic  acid  given  out.  If  we  suppose,  as  we  fairly 
may  do,  that  the  intensity  of  the  rigidity  is  dependent  on  the 
quantity  of  myosin  deposited  in  the  "fibres,  the  parallelism  be- 
tween the  three  products,  myosin,  sarcolactic  acid,  and  carbonic 
acid,  would  suggest  the  idea  that  all  three  are  the  results  of  the 
splitting-up  of  the  same  highly  complex  substance.  But  we  have 
not  at  present  suceeeded  iii  isolating  or  in  otherwise  definitely 
proving  the  existence  of  such  a  body. 


CHEMICAL    CHANGES.  99 

Living-  resting  muscle  then  is  alkaline  or  neutral  in  reac- 
tion, and  the  substance  of  its  fibres  contains  a  coagulable 
plasma.  Dead  rigid  muscle  on  the  other  baud  is  acid  in  re- 
action from  the  presence  of  sarcolactic  acid  ;  it  no  longer 
contains  a  coagulable  plasma,  but  is  laden  with  the  solid 
myosin.  And  the  change  from  the  living  irritable  condition 
to  tliat  of  rigor  mortis  is  accompanied  by  a  large  and  sudden 
development  of  carbonic  acid. 

We  may  now  return  to  the  question.  What  are  the  chemi- 
cal changes  which  take  place  when  a  living  resting  muscle 
enters  into  a  contraction  ?  These  changes  are  miost  evident 
after  the  muscle  has  been  subjected  to  a  prolonged  tetanus; 
but  there  can  be  no  doubt  that  the  chemical  events  of  a  teta- 
nus are,  like  the  physical  events,  simply  the  sum  of  the  re- 
sults of  the  constituent  single  contractions. 

In  the  first  place  the  muscle  becomes  acid,  not  so  acid  as 
in  rigor  mortis,  i)ut  still  sutliciently  so,  after  a  vigorous 
tetanus,  to  turn  blue  litmus  distinctly  red.  The  reddening 
like  that  of  rigor  mortis  is  permanent,  and,  therefore,  can- 
not be  due  to  carbonic  acid  ;  it  is  probabl}',  as  in  the  case 
of  rigor  mortis,  caused  by  a  development  of  sarcolactic  acid. 

In  the  second  place,  a  considerable  quantity  of  carbonic 
acid  is  set  free  ;  and  the  production  of  carbonic  acid  in  mus- 
cular contraction  runs  altogether  parallel  to  the  production 
of  carbonic  acid  during  rigor  mortis.  It  is  not  accompanied 
by  any  coi  responding  increase  in  the  consumption  of  oxygen. 
This  is  evident  even  in  a  muscle  through  which  the  circula- 
tion of  blood  is  still  going  on,  for  though  the  blood  passing 
through  a  contracting  muscle  gives  up  more  oxygen  than 
the  blood  passing  through  a  resting  muscle,  increase  in  the 
amount  ot  oxygen  taken  up  falls  below  the  increase  in  the 
carbonic  acid  given  out,  but  it  is  still  more  markedly"  shown 
in  a  muscle  removed  from  the  body.  For  in  such  a  muscle 
both  the  contraction  and  the  increase  in  the  production  of 
carbonic  acid  will  go  on  in  the  absence  of  oxygen.  A  frog's 
muscle  suspende  1  in  an  atmosphere  of  nitrogen  will  remain 
irritable  for  some  considerable  time,  and  at  each  vigorous 
tetanus  an  increase  in  the  production  of  carbonic  acid  ma}" 
be  readil}'  ascertained. 

Moreover  there  seems  to  be  a  correspondence  between  the 
energy  of  the  contraction  and  the  amount  of  carbonic  acid 
and  sarcolactic  acid  produced,  so  that  we  are  naturally  led 
to  the  view  that  in  a  muscular  contraction,  as  in  rigor  mortis, 
some   highly  complex  substance   splits  up,  and  thus   gives 


100  TDE    CONTRACTILE    TISSUES. 

rise  to  these  two  acids.  But  here  tlie  resemhlanec  between 
rigor  mortis  and  contraction  ends.  We  have  no  evidence  of 
the  foimation  during  a  contraction  of  any  body  like  myosin. 
Rigor  mortis  and  contraction  are  alii^e  in  so  far  as  they  both 
have  for  their  basis  a  complex  chemical  process  giving  ris'3 
to  the  formation  of  acids,  and  in  both  events  we  have  a  rise 
of  temperature  indicating  that  heat  lias  been  set  free.  But 
the  contracted  and  rigid  muscle  differ  essentially  in  the  fact 
that  while  the  former,  as  compared  with  living  resting  mus- 
cle, increases  in  extensibility  and  loses  none  of  its  translu- 
cenc}',  the  latter  becomes  less  extensible,  less  elastic,  and 
less  translucent.  Corresponding  to  this  marked  dilference, 
we  find  myosin  formed  in  the  rigid  muscle,  but  we  cannot 
find  it  in  tlie  contracted  muscle. 

It  is  stated  by  Hermann  that  in  frog's  muscle  separated  from 
the  body,  the  quantity  of  carbonic  acid  given  out  during  rigor 
mortis  is  in  inverse  proportion  to  the  quantity  given  out  by  the 
contractions  which  have  taken  place  since  the  removal  of  the 
muscle  from  the  blood-current.  The  more  the  muscle  has  con- 
tracted during  this  period  the  less  tlie  amount  of  carbonic  acid 
given  out  in  the  linal  rigor,  and  vice  versa.  From  this  it  is  in- 
ferred that  at  the  moment  of  separation  from  the  body,  the 
muscle  contains  a  certain  capital  of  carbonic  acid-producing  ma- 
terial (to  wit,  the  substance  whose  explosive  decomposition  we 
have  supposed  to  give  rise  to  this  and  other  bodies),  which  may 
be  expended  either  in  rigor  mortis  or  in  contraction,  but  wdiich, 
from  the  absence  of  blood,  cannot  be  replaced.  Consequently 
the  expenditure  in  the  direction  of  contraction  must  come  out  of 
the  share  allotted  to  rigor  mortis.    To  this  point  we  shall  return. 

The  other  chemical  changes  in  muscle  have  not  yet  been 
clearly  made  out.  Indeed  our  whole  information  concerning 
the  other  chemical  constituents  of  muscle  is  at  present  im- 
perfect. 

Fats  are  present  in  considerable  quantities,  and  the  ex- 
tractives are  varied  and  numerous.  The  most  imi)ortant  are 
kreatin,  sarcolactic  or  paralactic  acid  (a  variety  of  lactic 
acid,  differing  from  it  chief!}'  in  the  solubility  of  its  salts, 
and  in  the  amount  of  w-ater  of  crystallization  contained  in 
them),  and  sugar.  To  these  may  be  added  xanthin,  hypo- 
xanthin  (sarkin),  inosit  (especially  in  the  cardiac  muscles), 
inosinic  acid,  and  traces  of  uric  acid.  Except  in  pathologi- 
cal conditions  (and  in  the  plagiostome  fishes)  urea  is  con- 
spicuous by  its  absence.  In  living  muscle  glycogen  is 
frequently  present,  and  is  at  the  death  of  the  muscle  trans- 


CHANGES    DURING    A    NERVOUS    IMPULSE.         101 

formed  into  sugar.  Dextrin  lias  also  been  found  ;  and  a 
special  fermentable  muscle-sugar  has  been  described.  It 
has  been  much  debated  whether  kreatin  or  kreatinin,  or 
both,  are  present  in  muscle  ;  the  evidence  goes  to  show  that 
kreatin  alone  is  present. 

The  ashes  of  muscle,  like  those  of  the  red  corpuscles,  are 
characterized  by  the  preponderance  of  potassium  salts  and 
of  phosphates;  these  form  in  fact  nearly-  80  per  cent,  of  the 
whole  ash. 

The  general  composition  of  human  muscle  is  shown  in 
the  following  table  of  v.  Bibra: 

Water, 744.5 

Solids  : 
Myosin  and  other  matters,  elastic  ele- 
ments, etc.,  insoluble  in  water,         .     155.4 
Soluble  proteids,  .         .         .         .         .19.8 

Gelatin, 20.7 

Extractives,  .         .         .         .         .37.1 

Pats, 23.0 

■ 255.5 

Helmholtz  showed  long  ago  that  by  continued  contraction  the 
substances  in  muscle  which  are  soluble  in  water,  i.  e..  the  aque- 
ous extractives,  are  diminished,  M'hile  those  which  are  soluble  in 
alcohol  are  increased.  In  other  words,  during  contraction  some 
substance  or  substances  soluble  in  water  are  converted  into  an- 
other or  other  substances  insoluble  in  water  but  soluble  in  alco- 
hol. Ranke^  concluded  from  his  observations  that  the  proteids 
are  slightly  diminished,  and  that  sugar  and  fats  are  produced  ; 
but  the  data  for  these  conclusions  are,  at  present  at  all  events, 
insufficient.  It  has  been  suggested  that  the  glycogen  naturally 
present  in  muscle  is  during  contraction  converted  into  sugar. 
The  failure  to  obtain  any  satisfactory  evidence  of  the  production 
of  nitrogenous  crystalline  bodies  as  the  result  of  contraction  is  of 
interest ;  for  though  urea  is  conspicuous  by  its  absence  from  mus- 
cle both  during  rest  and  after  contraction,  some  observers  have 
thought  that  the  kreatin  in  muscle  is  increased  by  contraction  ; 
this  has  not  been  definitely  proved. 

The  Changes  in  a  Nerve  during  the  Passage  of  a  Nervous 
Impulse. 

The  change  in  the  form  of  a  muscle  during  its  contraction 
is  a  thing  which  can  be  seen  and  felt;  but  the  changes  in  a 
nerve  during  its  activit}-  are  invisible  and  impalpable.     We 

'  Tetanus,  1865. 
9 


102  TUE    CONTRACTILE    TISSUES. 

stimulate  one  end  of  a  nerve,  and  since  we  see  tliis  followed 
by  a  contraction  of  tlie  muscle  attached  to  the  other  end, 
we  know  that  some  changes  or  other  constituting  a  nervous 
impulse  have  been  propagated  along  the  nerve,  but  tiiese  are 
changes  which  we  cannot  see.  Xor  have  we  satisfactory 
evidence  of  any  chemical  events  or  of  any  production  of 
heat,  accompanying  a  nervous  impulse.  We  may  fairly  sup- 
pose that  some  cliemical  changes  form  the  basis  of  a  nervous 
impulse,  and  that  these  changes  set  free  a  certain  amount 
of  lieat,  but  these  if  the}'  occur  are  too  slight  to  be  recog- 
nized satisfactorily  b}'  the  means  at  present  at  our  disposal. 
In  fact,  beyond  the  terminal  results  of  a  nervous  impulse, 
such  as  a  muscular  contraction  in  tlie  case  of  a  nerve  going 
to  a  muscle,  or  some  affection  of  the  central  nervous  system 
in  the  case  of  a  nerve  still  in  connection  with  its  nervous 
centre,  there  is  one  event  and  one  event  only  wliicli  we  are  able 
to  recognize  as  the  ol)jective  token  of  a  nervous  impulse,  and 
that  is  the  so-called  negative  variation  of  the  nerve-current. 
For  a  piece  of  nerve  removed  from  the  bod}'  exliibits  nearly 
the  same  electric  phenomena  as  a  piece  of  muscle.  It  has 
an  equator  which  is  electrically  positive  as  compared  to  its 
two  cut  ends.  In  fact,  the  diagram.  Fig.  25,  and  the  descrip- 
tion which  it  was  used  on  p.  88  to  illustrate,  may  be  applied 
to  nerve  as  well  as  to  muscle,  except  that  the  currents  are 
in  all  cases  much  more  feeble  in  the  case  of  nerves  than  of 
muscles,  and  the  special  currents  from  the  circumference  to 
the  centre  of  the  transverse  sections  cannot  well  be  shown 
in  a  slender  nerve;  indeed  it  is  doubtful  if  they  exist  at  all. 

Du  Bois-Eeymond'  found  the  electro-motive  force  of  the  sciatic 
nerve  of  a  frog  to  amount  to  .022  Daniell,  while  that  of  the  rabbit 
did  not  exceed  .026  Daniell.  Engelmann,^  however,  obtained  for 
the  sciatic  of  the  frog  a  value  of  .040  Daniell. 

During^  the  passage  of  a  nervous  impulse  the  "natural 
nerve-current"  undergoes  a  negative  variation,  just  as  the 
"natural  muscle-current"  undergoes  a  negative  variation 
during  a  contraction.  There  are,  however,  difficulties  in 
the  case  of  the  nerve  similar  to  those  in  the  case  of  the  mus- 
cle, concerning  the  pre-existence  of  any  such  "  natural  " 
currents  ;  hence  we  may  say  that  in  a  nerve  during  the  pas- 

^  Gesammelte  Abhandl.  (1877),  ii,  232. 
2  Piiiiger's  Archiv,  xv  (1877),  p.  211. 


CHANGES  DURING  A  NERVOUS  IMPULSE.    103 


sa^re  of  a  nervous  impulse,  as  in  a  muscle  during  a  muscular 
contraction,  a  ''current  of  action"  is  developed. 

This  "current  of  action"  or  "negative  variation"  may 
be  shown  either  by  the  galvanometer  or  by  the  rheoscopic 
frog.  If  the  nerve  of  the  "muscle-nerve  preparation"  B 
(see  p.  92)  be  placed  in  an  appropriate  manner  on  a  thor- 
oughl}'  irritable  nerve  A  (to  which  of  course  no  muscle  need 
be  attached),  i.  e.,  touching  say  the  equator  and  one  end  of 
tlie  nerve,  then  single  imUiction-shocks  sent  into  the  far 
end  of  J[  will  cause  single  spasms  in  the  muscle  of  ^,  while 
tetanization  of  J,  i.e.^  rapidly  repeated  shocks  sent  into  J, 
will  cause  tetanus  of  the  muscle  of  jB. 

That  this  current,  wdiether  it  be  regarded  as  an  indepen- 
dent "current  of  action"  or  as  a  negative  variation  of  a 
"pre-existing"  current,  is  an  essential  feature  of  a  nervous 
impulse  is  shown  by  the  fact  that  the  degree  or  intensity  of 
the  one  varies  with  that  of  the  other.  They  both  travel  too 
at  the  same  rate.  In  descrihing  the  muscle-curve,  and  the 
method  of  measuring  the  muscular  latent  period,  vve  have 
incidentally  shown  (p.  74)  how  the  velocity  of  the  nervous 
impulse  is  measured  also,  and  stated  that  the  rate  in  the 
nerves  of  a  frog  is  about  28  meters  a  second.  Bernstein  by 
means  of  an  apparatus  which  is  descrilied  on  p.  135  finds  that 
the  negative  variation  travels  along  an  isolated  piece  of 
nerve  at  the  same  rate.  He  also  finds  that  it,  like  the  mo- 
lecular change  in  a  muscle  preceding  the  contraction,  and 
indeed  like  the  contraction  itself,  passes  over  any  given  spot 
of  the  nerve  in  the  form  of  a  wave,  rising  rapidly  to  a  max- 
imum and  then  more  gradually  declining  again.  He  has 
been  able  to  measure  the  length  of  the  wave,  and  this  he 
finds  to  be  about  18  mm.,  taking  .0007  sec.  to  pass  over  any 
one  point. 

When  an  isolated  piece  of  nerve  is  stimulated  in  the  mid- 
dle, the  negative  va^-iation  is  propagated  ecpially  well  in  both 
directions,  and  that  wdiether  the  nerve  be  a  chiefl}'  sensory 
or  a  chiefly  motor  nerve,  or,  indeed,  if  it  be  a  nerve-root 
composed  exclusively  of  motor  or  of  sensory  fibres.  Taking 
the  negative  variation  as  the  token  of  a  nervous  impulse, 
we  infer  from  this  that  when  a  nerve  fibre  is  stimulated  arti- 
ficially at  any  part  of  its  course,  the  nervous  impulse  set 
going  travels  in  both  directions. 

We  used  just  novv^  the  phrase  "tetanization  of  a  nerve," 
meaning  the  application  to  a  nerve  of  rapidly  repeated 
shocks  such  as  would  produce  tetanus  in  the  muscle  to  which 


104  THE    CONTRACTILE    TISSUES. 

the  nerve  was  attached,  and  we  shall  have  frecjuent  occasion 
to  employ  the  phrase.  It  will,  however,  of  course  be  under- 
stood that  there  is  in  the  nerve,  as  far  as  we  know,  no  sum- 
mation of  nervous  impulses  comi)aral>le  to  the  summation 
of  muscular  contrncLions.  The  series  of  sliocks  sent  in  at 
the  far  end  of  the  nerve  start  a  series  of  im[)ulses,  these 
travel  down  the  nerve  and  reach  tlie  muscle  as  a  series  of 
distinct  impulses;  and  the  first  changes  in  the  muscle,  the 
molecular  latent  period  changes,  also  form  a  series,  the  mem- 
bers of  which  are  distinct.  It  is  not  until  these  molecular 
changes  become  transformed  into  visible  changes  of  form 
that  any  fusion  or  summation  takes  place. 

Putting  together  the  facts  contained  in  this  and  the  pre- 
ceding sections,  the  following  may  be  taken  as  a  brief  ap- 
proximate histor}^  of  what  takes  place  in  a  muscle  and  nerve 
when  the  latter  is  subjected  to  a  single  induction-shock.  At 
the  instant  that  the  induced  current  passes  into  the  nerve, 
changes  occur,  of  whose  nature  we  know  nothing  certain, 
except  that  they  cause  a  ''  negative  variation "  of  the 
"natural"  nerve-current.  These  changes  propagate  them- 
selves along  the  nerve  in  both  directions  as  a  nervous  im- 
pulse in  the  form  of  a  wave,  having  a  Avave-length  of  about 
18  mm.,  and  a  velocity  (in  frog's  nerve)  of  about  28  m.  per 
second.  Passing  down  the  nerve-fibres  to  the  muscle,  flow- 
ing along  the  branching  and  narrowing  tracts,  the  wave  at 
last  breaks  on  the  end-plates  of  the  fibres  of  the  muscle. 
Here  it  is  transmuted  into  a  muscle-impulse,  with  a  shorter 
steeper  wave,  and  a  greatly  diminished  velocity  (about  8  m. 
per  second).  This  muscle-impulse,  of  which  we  know  hardly 
more  than  that  it  is  marked  by  a  negative  variation  in  the 
muscle-current,  travels  from  each  end-plate  in  both  direc- 
tions to  the  end  of  the  fibre.  What  there  becomes  of  it  we 
do  not  know,  but  it  is  immediately  followed  by  the  visible 
contraction-wave,  travelling  behind  it  at  about  the  same  rate, 
but  with  a  vastly  increased  wave-length.  The  fibre,  as  the 
wave  passes  over  it,  swells  and  shortens,  bringing  its  two 
ends  together,  its  molecules  during  the  change  of  form  ar- 
ranging themselves  in  such  a  way  that  the  extensibility  of 
the  fibre  is  iuereased,  while  at  the  same  time  an  explosive 
decomposition  of  material  takes  place,  leading  to  a  discharge 
of  carbonic  and  sarcolactic  atids,  and  probably  of  other 
unknown  things,  wiih  a  considerable  development  of  heat. 


ACTION    OF    THE    CONSTANT    CURRENT.  105 


Sec.  3.   The  Xature  of  the  Changes  through  which 

AN  Electric  Current  is  able  to  generate  a 

Nervous  Impulse. 

Action  of  the   Constant   Current. 

In  the  preceding  account,  the  stimulus  applied  in  order  to 
give  rise  to  a  nervous  impulse  has  always  been  supposed 
to  be  an  induction-shock,  single  or  repeated.  This  choice 
of  stimulus  has  been  made  on  account  of  the  almost  momen- 
tar}'  duration  of  the  induced  current.  Had  we  used  a  cur- 
rent lasting  for  some  considerable  time,  the  problems  before 
us  would  have  become  more  complex  in  consequence  of  our 
having  to  distinguish  between  the  events  taking  place  while 
the  current  was  parsing  through  the  nerve  from  those  which 
occurred  at  the  moment  when  the  current  was  thrown  into 
the  nerve,  or  at  the  moment  when  it  was  shut  oft'  from  the 
nerve.  These  complications  do  arise  when,  instead  of  em- 
ploying the  induced  current  as  a  stimulus,  we  use  a  constant 
cui^renl,  i.  e.,  when  we  pass  through  the  nerve  (or  muscle)  a 
current  direct  from  the  battery  without  the  intervention  of 
any  iuduction-coil. 

Before  making  the  actual  experiment  we  might,  perhaps, 
naturally  suppose  that  the  constant  current  would  act  as  a 
stimulus  throughout  the  whole  time  during  which  it  was 
applied,  that,  so  long  as  the  current  passed  along  the  nerve, 
nervous  impulses  would  be  generated  and  thus  the  muscle 
thrown  into  something,  at  all  event,  like  tetanus.  And 
under  certain  conditions  this  does  take  place  ;  occasionally 
it  happens  that  at  the  moment  the  current  is  thrown  into 
the  nerve,  the  muscle  of  the  muscle-nerve  preparation  falls 
into  a  tetanus  which  is  continued  until  the  current  is  shut 
oft'.  But  such  a  result  is  exceptional.  In  the  vast  majority 
of  cases  what  happens  is  as  follows.  At  the  moment 
that  the  circuit  is  made,  the  moment  that  the  current  is 
thrown  into  the  nerve,  a  single  spasm,  a  simple  contraction, 
the  so-called  making  contraction  is  witnessed  ;  but  after  this 
has  pa^sed  away  the  muscle  remains  absolutely  quiescent  in 
sj:)ite  of  the  current  continuing  to  pass  through  the  nerve, 
and  this  quiescence  is  maintained  until  the  circuit  is  broken, 
until  the  current  is  shut  off  from  the  nerve,  when  another 
simple  cohtraclion,  the  so-called  breaking  contraction^  is 
observed.  The  mere  passage  of  a  uniform  constant  current 
of  uniform  intensit}'  througli  a  nerve  does  not  act  as  a  stimu- 


106  THE    CONTRACTILE    TISSUES. 

Ins  gonoi'iitinix  a  nervous  imj^ulse  ;  such  an  iinptilso  is  only 
set  up  when  the  current  either  falls  into  or  is  shut  otf  from 
the  nerve.  It  is  the  entrance  or  the  exit  of  the  current,  and 
not  the  continuance  of  the  current  which  is  the  stimulus. 

The  quiescence  of  the  nerve  and  muscle  dui'ing-  the  pas- 
sn*2,e  of  the  current  is  however  dependent  on  the  current 
remaining  uniform  in  intensity  or  at  least  not  being  sud- 
denly increased  or  diminislied.  Any  sulliciently  sudden 
and  large  increase  or  diminution  of  the  intensity  of  the 
current,  will  act  like  the  entrance  or  exit  of  a  current,  and 
by  generating  nervous  impulses  give  rise  to  contractions. 
If  the  intensit}^  of  the  current  however  be  very  slowly  and 
gradually  increased  or  diminished,  a  very  wide  range  of  in- 
tensity' may  be  passed  through  without  any  contraction 
being  seen.  It  is  the  sudden  change  from  one  condition  to 
another,  and  not  the  condition  itself,  which  causes  the  ner- 
vous impulse. 

In  many  cases,  both  a  "  making  "  and  a  "  breaking"  con- 
traction, each  a  simple  spasm,  are  observed,  and  this  is 
perhaps  the  commonest  event ;  but  under  conditions  which 
will  be  discussed  below  either  the  breaking  or  the  making 
contraction  may  be  absent,  i.e.,  there  may  be  a  contraction 
only  when  the  current  is  thrown  into  the  nerve  or  only  when 
it  is  sliut  off  from  the  nerve. 

Under  ordinary  circumstances  the  contractions  witnessed 
with  the  constant  current,  either  at  the  make  or  at  the  break, 
are  of  the  nature  of  a  "  simple"  contraction,  but,  as  has 
already  been  said,  the  application  of  the  current  may  give 
rise  to  a  very  pronounced  tetanus.  Such  a  tetanus  is  seen 
sometimes  when  the  current  is  made,  lasting  during  the 
api)lication  of  the  current,  sometimes  wdien  the  current  is 
broken,  lasting  some  time  after  the  current  has  been  wholly 
removed  from  the  nerve.  The  former  is  spoken  of  as  a 
'*  making,"  the  latter  as  a  ^'  breaking  "  tetanus.  But  these 
exceptional  results  of  the  constant  current  need  not  detain 
us  now. 

The  great  interest  attached  to  the  action  of  the  constant 
current  lies  in  the  fact,  that  during  the  passage  of  the  cur- 
rent, in  spite  of  the  absence  of  all  nervous  impulses  and 
therefore  of  all  muscular  contractions,  the  nerve  is  for  the 
time  both  between  and  on  each  side  of  the  electrodes  pro- 
foundly modified  in  a  most  peculiar  manner.  This  modifi- 
cation, important  both  for  the  light  it  throws  on  the  gener- 


ELECTROTONUS.  107 

ation  of  nervous  impulses  and  for  its  practical  applications, 
is  known  under  the  name  of  electrotonus. 

Electrotonus. — The  marked  feature  of  the  electrotonic 
condition  is  that  the  nerve  though  apparently  quiescent  is 
changed  in  respect  to  its  irritability  ;  and  that  in  a  different 
way  in  the  neighborhood  of  the  two  electrodes  respec- 
tivel}'. 

Suppose  that  on  the  nerve  of  a  muscle-nerve  preparation 
are  placed  two  (non-polarizable)  electrodes   (Fig.  26,  a,  ^^,) 

Fig.  26. 


Muscle-nerve  Preparations,  with  the  nerve  exposed  in  A  to  a  descending  and  in  B 
to  an  a^cendm^' constant  current. 

In  each  a  is  the  anode,  k  the  cathode  of  the  constant  current,    x  represents  the 
spot  where  the  induction-shocks  used  to  test  the  irritability  of  the  nerve  are  sent  in. 

connected  with  a  battery  and  arranged  wnth  a  key  so  that  a 
constant  current  can  at  pleasure  be  thrown  into  or  shut  otF 
from  the  nerve.  This  constant  current,  whose  effects  w^e 
are  about  to  study,  may  be  called  the  "polarizing  current." 
Let  a  be  the  positive  electrode  or  anode,  and  k  the  negative 
electrode  or  kathode,  botli  placed  at  some  distance  from  the 
muscle,  and  also  with  a  certain  interval  between  each  other. 
At  the  point  x  let  there  be  applied  a  pair  of  electrodes  con- 
nected with  an  induction-machine.  Let  the  muscle  further 
be  connected  with  a  lever,  so  that  its  contractions  can  be 
recorded,  and  their  amount  measured.     Before  the  polariz- 


108  THE    CONTRACTILE    TISSUES. 

incr  current  is  tinown  into  the  nerve,  let  a  single  inrUiction- 
sliofk  of  known  intensity  (a  weak  one  being  chosen,  or  at 
least  not  one  wiiich  wonld  cause  in  the  muscle  a  maxinium 
contraction)  be  tinown  in  at  x.  A  contraction  of  a  certain 
amount  will  follow.  That  contraction  may  be  taken  as  a 
measure  of  the  irritability  of  the  nerve  at  the  point  x. 
Now  let  the  polarizing  current  be  thrown  in,  and  let  the 
direction  of  the  current  be  a  de.><ceiuling  one,  with  the  kath- 
ode or  negative  pole  nearest  the  muscle,  as  in  Fig.  2f)  A. 
Jf  while  the  current  is  passing,  the  same  induction-shock  as 
before  be  sent  through  x,  the  contraction  which  results  will 
be  found  to  be  greater  than  on  the  former  occasion.  If  the 
})olarizing  current  be  shut  off,  and  the  point  x  after  a  short 
interval  again  tested  with  the  same  induction-shock,  the 
contraction  will  be  no  longer  greater,  but  of  the  same 
amount,  or  perhaps  not  so  great,  as  at  first.  During  the 
passage  of  the  polarizing  current,  therefore,  the  irritability 
of  the  nerve  at  the  point  x  has  been  temporarily  increased^ 
since  the  same  shock  applied  to  it  causes  a  greater  contrac- 
tion dming  the  presence  than  in  the  alisence  of  the  current. 
But  this  is  onh'  true  so  long  as  the  polarizing  current  is  a 
descending  one,  so  long  as  tiie  point  x  lies  on  the  side  of 
the  katiiode.  On  the  other  hand,  if  the  polarizing  current 
had  been  an  aHcendlng  one,  with  the  anode  or  positive  pole 
nearest  the  muscle,  as  in  Fig.  26  i>,  the  irrital)ility  of  the 
nerve  at  x  would  have  been  found  to  be  diminished  instead 
of  increased  by  the  polarizing  current.  Tiiat  is  to  say, 
when  a  constant  current  is  applied  to  a  nerve,  the  irritability 
of  the  nerve  between  the  polarizing  electrodes  and  the  mus- 
cle is,  during  the  passage  of  the  current,  increased  when 
the  kathode  is  nearest  the  muscle  (and  the  polarizing  cur- 
rent descending),and  diminished  when  the  anode  is  nearest 
the  muscle  (and  the  polarizing  current  ascending).  The 
same  result,  mulatia  mutaiidin,  and  with  some  qualifications 
to  be  referred  to  directly,  would  be  gained  if  x  were  placed 
not  between  the  muscle  and  the  polarizing  current,  but  on 
the  far  side  of  the  latter.  Hence  it  may  be  stated  generally 
that  during  the  passage  of  a  constant  current  through  a 
nerve  the  irritability  of  the  nerve  is  increased  in  the  region 
of  the  kathode,  an(l  diminished  in  the  region  of  the  anode. 
The  changes  in  the  nerve  which  give  rise  to  this  increase  of 
irritability  in  the  region  of  the  kathode  are  spoken  of  as 
katelectrotonuH^  and  the  nerve  is  said  to  be  in  a  katelectro- 
tonic  condition.     Similarlv  the  changes  in  the  region  of  the 


ELECTROTONUS. 


109 


anode  are  spoken  of  as  anelecfrotonus^  and  tlie  neive  is  said 
to  be  in  an  anelectrotonic  condition.  It  is  also  often  usual 
to  speak  of  the  katelectrotonic  increase,  and  anelectrotonic 
decrease  of  irritabilit}'. 

This  law  remains  true  whatever  be  the  mode  adopted  for 
determining  the  irritability.  The  result  holds  good  not  only 
with  a  single  induction-slHJck,  but  also  with  a  tetanizing 
inten-upted  current,  with  chemical  and  with  mechanical 
stimuli.  The  increase  and  decrease  of  irrital)ility  are  most 
marked  in  the  immediate  neighborhood  of  tiie  electrodes, 
but  spread  for  a  considerable  distance  in  either  direction  in 
the  extrapolar  regions.  The  same  modification  is  not  con- 
fined to  the  extrapolar  region,  but  exists  also  in  the  intra- 
polar  region.  In  the  intrapolar  region  there  must  be  of 
course   an   indifferent  point,  where   the  katelectrotonic  in- 


FlG. 


Diagram  Ilhistraling  the  Variations  of  Irritability  during  Elrctrotontis,  witli 
Polarizing  Curreuts  of  Increasing  Intensity.    (From  Pfluger.) 

The  anode  is  supposed  to  be  placed  at  A,  the  kathode  at  B  ;  A  B  is  consequently 
the  intrapolar  district.  In  each  of  the  three  curves,  the  portion  of  the  curve  l>elow 
tlie  base-line  represents  diminished  irritability,  that  above,  increased  irritability. 
Pi  represents  the  effect  of  a  weak  current;  the  indiflerent  point  a-,  is  near  the  anode 
A.  In  ?/o,  a  stronger  current,  the  indifferent  point  5-2  is  nearer  the  kathode  B,  the 
diminution  of  irritability  in  auelectrotonus  and  the  increase  in  kalelectrotonus  be- 
ing greater  than  in  pi]  the  effect  also  spreads  for  a  greater  distance  along  the 
extrapolar  regions  in  both  dirktious.  In  //a  the  ^ame  events  are  seen  to  be  still 
more  marked. 


crease  merges  into  the  anelectrotonic  decrease,  and  where 
therefore  the  irritability  is  unchanged.  When  the  polarizing 
current  is  a  weak  one,  this  indiflerent  point  is  nearer  the 
anode  than  the  kathode,  but  as  the  polarizing  current  in- 
creases in  intensity,  draws  nearer  and  nearer  the  kathode 
(see  Fig.  27). 

10 


110  THE    CONTRACTILE    TISSUES. 

The  katelectrotonic  increase  and  aneleetrotonic  decrease  reach 
a  niaxiniuni  soon  after  the  making  of  thei)olarizing  current,  and 
thenceforward  gradually  diminish.  The  two  effects  however  are 
not  quite  parallel.  The  kati'lectrotonic  increase  is  the  first  to  be 
developed  ;  it  rapidly  rises  to  a  maximum  and  somewhat  ra])idly 
declines.  The  aneleetrotonic  decrease  is  not  manife?,t  at  first ; 
when  it  does  ap]iear  it  increases  slowly,  and  having  reached  a 
maximum  (liminis]i(>s  slowly  again. 

When  the  polarizing  current  is  shut  off  there  is  a  rebound  at 
both  poles  ;  a  temporar}^  increase  of  irritability  in  the  anelee- 
trotonic and  a  temporary  decrease  in  tlie  katelectrotonic  regions. 

The  amount  of  increase  and  decrease  is  dependent:  (1) 
On  the  strength  of  the  current,  the  stronger  current  up  to  a 
certain  limit  producing  the  greater  etfect.  (2)  On  the  irri- 
tabilit}'  of  the  nerve,  tlie  more  irritable,  better-conditioned 
nerve  being  the  more  affected  by  a  current  of  the  same  in- 
tensity- 

The  increase  or  decrease  of  irrital)ility  ai)plies  not  only 
to  the  origination  of  impulses,  but  also  to  their  propagation 
or  conduction.  At  least  anelectrotonus  oflers  an  obstacle 
to  the  passage  of  a  nervous  impulse. 

These  variations  of  irritability  at  the  kathode  and  anode 
respectively,  must  be  the  result  of  molecular  changes, 
brought  al)Out  by  the  action  of  the  constant  current.  They 
are  interesting  because  they  show  that  the  generation  of  a 
nervous  impulse  as  the  result  of  the  makinir  or  breaking  of 
a  constant  current  is  dependent  on  the  change  of  a  nerve 
from  its  normal  condition  into  either  katelectrotonus  or 
anelectrotonus,  or  back  again  from  one  of  these  phases  into 
its  normal  condition.  And  certain  phenomena,  which  will 
be  described  below  under  the  heading  of  the  '^  law  of  con- 
traction," go  far  to  show  that  a  nervous  impulse  is  generated 
only  when  a  nerve  [)ass<'S  suddenly  from  a  normal  condition 
into  the  phase  of  katelectrotonus  (making  contraction ),  or 
returns  from  the  phase  of  anelectrotonus  (breaking  contrac- 
tion)  to  a  normal  condition,  in  other  words,  when  it  passes 
suddenly  from  a  phase  of  lower  to  a  pliase  of  higher  irrita- 
bility. 

An  induction-shock  is  a  current  of  very  short  duration, 
developed  very  suddenly  and  disappearing  more  gradually. 
Hence  when  it  falls  into  a  nerve,  the  nerve  undergoes  a 
sudden  transition  from  its  normal  condition  to  the  katelec- 
trotonic phase,  and  consequently  a  nervous  impulse  giving 
rise  to  a  contraction  is  the  resvdt.  The  return  from  the 
aneleetrotonic  phase  to  the  normal  condition  is  more  gradual, 


LAW    OF    CONTRACTION.  Ill 

and  accordingU'  no  nervous  impulse  is  oreuerated  and  no 
contraction  is  witnessed.  We  might  add  that  the  return 
from  the  anelectrotonic  phase  to  the  normal  condition  ap- 
pears from  a  number  of  considerations  to  be  less  effeclivc 
as  a  generator  of  nervous  impulses  than  the  change  from 
the  normal  condition  to  the  katelectrotonic  phase.  Hence 
in  the  induced  current  we  have  to  deal  with  a  ••  making  " 
contraction  only,  the  breaking  contraction  being  alisent. 
This  is  true  whether  the  induced  current  be  produced  by 
the  making  or  the  breaking  of  a  constant  current. 

Law  of  Contraction. — At  the  making  of  a  constant  current, 
then,  there  is  set  up  a  condition  of  katelectrotonus  and  of  anelec- 
trotonus  ;  on  the  breaking  of  the  current  these  conditions,  w^itli 
more  or  less  rebound,  disappear.  What  have  these  changes  to 
do  with  the  generation  of  nervous  impulses  "? 

It  has  already  been  stated  that  when  a  constant  current  is 
applied  to  a  nerve,  a  contraction  is  caused  iu  the  muscle,  /.  e.,  a 
nervous  impulse  is  started  in  the  nerve,  either  at  the  make  or  at 
the  break,  or  at  both.  On  further  examination  it  is  found  that 
the  occurrence  or  non-occurrence  of  a  contraction  depends  on  the 
direction  (?'.  e.,  whether  descending  with  the  kathode  nearest  the 
muscle,  Fig.  26  A,  or  ascending  with  the  anode  nearest  the  mus- 
cle, Fig,  26  B)  and  the  intensity  of  the  current.  The  results  have 
been  formulated  in  the  followino:  '-law  of  contraction  :'' 


Yerv  weak, . 
Weak, . 
Moderate,    . 


wdiere  C  indicates  a  contraction.  This  law  becomes  intelligible 
if  we  suppose  that  nervous  impulses  are  originated  onl}-  b}^  the 
rise  of  katelectrotonus  and  by  the  fall  of  anelectrotonus,'^  and 
not  at  all  by  the  rise  of  aneleetrotonus,  or  by  the  fall  of  katelec- 
trotonus, or  by  the  steady  maintenance  of  either.  Remembering 
that  in  katelectrotonus  irritability  is  increased  and  in  aneleetro- 
tonus diminished,  we  may  formulate  the  law  as  follows  :  A  ner- 
vous impulse  is  generated  at  any  point  of  a  nerve  wdien  there  is 
a  sudden  change  from  a  phase  of  lower  to  one  of  higher  irrita- 
bility, as  from  the  normal  condition  to  katelectrotonus  or  from 
aneleetrotonus  to  the  normal  condition.  We  must,  however,  fur- 
ther suppose  that  the  rise  of  katelectrotonus  more  readily  gives 
rise  to  an  impulse,  or  gives  rise  to  a  larger  impulse,  than  "does 
the  fall  of  aneleetrotonus,  and  that  the  condition  of  aneleetroto- 
nus, especially  when  pronounced,  is  an  obstacle  to  the  passage 
towards  the  muscle  of  impulses  originating  on  the  side  away  from 


Descend  ins. 

lake.    Break. 
C           — 
C           - 

Asc-etiding. 
Make.     Break. 

C         — 

C           C 

c      c 

C        — 

—      c 

112  THE    CONTRACTILE    TISSUES. 


the  muscle.  Thus,  with  weak  currents,  a  contraction  occurs  only 
at  the  make,  at  the  rise  of  katelectrotonus,  of  l)oth  the  descend- 
iui;  and  ast-cndinu;  currents.  ]5ut  the  contraction  is  easier  to  «;et 
with  the  descending;  than  with  tlie  ascenchnu-  current,  l)ecause  in 
the  latter  the  impulse  started  at  the  kathode  has  to  pass  through 
an  anelectrotonic  region  hefore  it  can  arrive  at  the  nuiscle,  and 
hence  with  ''  very  weak  "  currents  we  iret  a  contraction  with  the 
make  of  the  descending  current  only.  With  a  moderate  currc  nt, 
as  for  instance  with  a  single  Daniell  acting  as  the  source  of  the 
current,  there  is  a  contraction  hoth  at  the  make  and  at  the  hreak 
of  hoth  ascending  and  descending  currents;  the  fall  of  anelectro- 
tonus  here  is  ahle,  as  well  as  the  rise  of  katelectrotonus,  to  origi- 
nate a  nervous  impulse.  Lastly,  when  the  current  is  very  strong, 
as  that  for  instance  of  two  or  more  Groves,  making  the  ascend- 
ing current  produces  no  contraction,  l)ecause  the  anelectrotonus 
round  the  anode  hlocks  the  impulse  starting  from  the  kathode. 
The  fjill  of  anelectrotonus,  however,  at  the  anode,  there  being 
nothing  between  it  and  the  muscle,  does  cause  a  contraction. 
AVith  the  descending  current  the  rise  of  katelectrotonus  produces 
a  making  contraction,  but  there  is  no  breaking  contraction;  the 
absence  of  the  latter  may  be  accounted  for,  i^artly  by  the  strong 
current  depressing  the  irritability  and  especially  the  conductivity 
of  the  intrapolar  nerve,  and  partly  perhaps  by  supposing  that 
the  rebound  on  the  disappearance  of  katelectrotonus  at  the 
kathode,  occurring  as  it  does  in  a  part  lying  between  the  anode 
and  the  nmscle,  serves  to  l)lock  the  downward  progress  of  the  im- 
])ulse  started  by  the  fall  of  anelectrotonus  at  the  anode.  This 
blocking  of  nervous  impulses  by  the  defective  conduction  caused 
in  anelectrotonus,  is  the  reason  why  in  testing  the  variations  of 
irritability  in  anelectrotonus  and  katelectrotonus  it  is  preferable 
to  apply  the  stimulus  between  the  muscle  and  the  polarizing 
current. 

It  has  already  been  stated  that  in  many  cases  the  making  or 
breaking  of  a  constant  current  gives  rise  not  to  a  single  spasm  onl}'^ 
but  to  a  pronounced  tetanus,  often  spoken  of  as  the  making  or 
breaking  tetanus.  Of  these  two  the  most  common  is  the  breaking 
tetanus,  or  Ritter's  tetanus,  which  appears  when  a  strong  cur- 
rent has  been  applied  for  some  time  to  a  nerve.  It  is  developed 
most  readil}'  and  lasts  longest  after  the  application  of  an  ascend- 
ing current,  but  may  also  make  its  appearance  with  a  descend- 
ing current.  When  it  manifests  itself  it  may  be  at  once  dimin- 
ished or  suspended  altogether  by  aj^plying  the  same  current  in 
the  same  direction.  It  is  increased  by  api)lying  the  current  in 
an  opposite  direction.  The  making  tetanus  is  seen  with  cur- 
rents of  a  certain  intensity  only,  being  absent  with  those  of  less 
or  greater  strength.  Both  forms  are  due  to  profound  electrolytic 
changes  in  the  nerve,  those  of  the  making  tetanus  being  of  a 
katelectrotonic,  and  those  of  the  breaking  tetanus  of  an  anelec- 
trotonic character. 

The  constant  current  applied  directly  to  a  muscle  from  which 


THE    MUSCLE-NERVE    MACHINE.  113 


the  piirel}^  nervous  element  has  been  eUmhiated  by  urari  poison- 
ing, has  effects  similar  to  and  yet  somewhat  different  from  those 
which  it  has  upon  a  nerve.  The  efficacy  of  the  rise  of  katelec- 
trotonus  and  the  fall  of  anelectrotonus  respectively  in  producing 
contraction  is  the  same  as  in  a  nerve.  In  one  respect  the  muscle 
is  more  striking,  and  offers  a  support  of  the  h3'pothesis  men- 
tioned above.  The  making  contraction  may  under  favorable  cir- 
cumstances be  seen  to  start  from  the  kathode,  and  the  breaking 
contraction  from  the  anode.  Another  marked  difference  between 
muscle  and  nerve  is  that  in  muscle  the  current  must  act  for  a 
much  longer  time  upon  tlie  tissue  before  it  can  call  forth  a  con- 
traction. This  is  what  we  might  expect  from  the  more  sluggish 
nature  of  the  muscular  impulse- wave.  Hence  muscular  tissue 
which  has  lost  its  nervous  elements  or  does  not  possess  them,  is 
far  less  readily  affected  by  the  almost  momentary  induction- 
shocks  than  are  nerves. 

During  the  passage  of  a  constant  current  the  muscle  is  thrown 
into  a  partial  tetanus,  which,  however,  may  be  sufficiently  weak 
to  permit  the  simple  make  and  break  contractions  to  be  readily 
observed.^  Very  frequently  this  tetanus  changes  into  a  regular 
rhythmic  pulsation  if  the  intramuscular  nerves  be  intact. 


Sec.  4.  The  Muscle-nerve  Preparation  as  a  Machine. 

Tlie  facts  described  in  the  foregoing  sections  show  that  a 
muscle  with  its  nerve  may  be  justly  regarded  as  a  machine 
wdiich,  when  stimulated,  will  do  a  certain  amount  of  work. 
But  the  actual  amount  of  work  which  a  muscle-nerve  prep- 
aration will  do  is  found  to  depend  on  a  large  number  of 
circumstances,  and  consequently  to  vai-y  within  very  wide 
limits.  These  variations  will  be  largely  determined  by  the 
condition  of  the  muscle  and  nerve  in  respect  to  their  nutri- 
tion ;  in  other  words,  by  the  degree  of  irritaldlity  mani- 
fested by  the  muscle  or  by  the  nerve,  or  by  i^oth.  But  quite 
apart  from  the  general  influences  affecting  its  nutrition,  and 
thus  its  irritability,  a  muscle-nerve  preparation  is  affected 
as  regards  the  amount  of  its  work  by  a  variety  of  other 
circumstances,  which  we  may  briefly  consider  iiere,  reserv- 
ing to  a  succeeding  section  the  study  of  variations  in  irri- 
tability. 


1  C"f.  Koinane?;,  Jtnirmd  of  Anat.  and  Phys.,  x,  p.  707. 


114  THE    CONTRACTILE    TISSUES. 


The  Nature  and  Mode  of  Aj)})Uvalion  of  the  iStimvluf^  a.s  af- 
fecting the  Amount  and  Character  of  tlie  Contraction. 

AVilliin  tlie  body,  llie  stiimili  wliich  l)iing  about  natural 
muscular  coutractious  are  nervous  impulses  proceeding  from 
the  central  nervous  system.  As  far  as  we  know,  these  nat- 
ural nervous  impulses  are  identical  in  character  with  the 
nervous  impulses  set  going  in  the  course  of  the  nerve  by 
artificial  stimuli.  Since  in  the  majority  of  cases  natural 
muscular  contractions  are  tetanic  in  nature,  tlie  natural  ner- 
vous imi)ulses  occur,  not  singly,  but  repeated  in  series,  the 
interval  between  successive  impulses  being  always  about 
one-nineteenth  of  a  second  (see  p.  81).  Variations  there- 
fore in  the  energy  and  extent  of  natural  musculnr  contrac- 
tions must  (apart  from  variations  in  the  initability  of  the 
muscles  or  nerves)  depend  on  the  energy  of  the  individual 
nervous  impulses  as  they  leave  the  central  nervous  system, 
and  not  on  any  change  in  the  rapidity  of  their  sequence. 

A  mechanical  stimulus  in  the  shape  of  a  single  tap  or 
blow,  pinch  or  prick,  may  produce  a  single  spasm,  and  slight 
taps  repeated  regularly  and  rapidly  may  be  used  to  produce 
a  tetanus.  As  a  rule,  however,  the  injury  inflicted  by  a 
mechanical  stimulus  destroys  the  irritability  of  the  spot 
stimulated,  and  so  prevents  a  repetition  of  the  spasms. 
On  the  other  hand,  even  a  momentary  injury  may  produce 
changes  leading  to  a  tetanus.  A  chemical  stimulus  pro- 
duces an  irregular  tetanus,  as  does  also  the  sudden  applica- 
tion of  heat. 

The  constant  current  acts,  as  we  have  seen,  as  a  stimulus 
only  when  its  intensity  suddenly  rises  or  falls,  making  and 
breaking  of  the  circuit  being  extreme  cases  of  rise  and  fall. 
If  the  rise  or  fall  be  sudiciently  gradual  a  current  may. 
while  still  passing  through  a  nerve,  be  very  largely  increased 
or  diminished  without  giving  rise  to  any  contraction  ;  where- 
as even  a  very  slight  sudden  rise  or  fall  may  at  once  cause 
one,  the  effect  being  the  greater  the  more  sudden  the  change. 
This  influence  of  the  suddenness  of  the  change  is  also  seen 
in  the  case  of  single  induction-shocks  ;  the  breaking  shock, 
which  is  developed  much  more  rapidly  than  the  making 
shock,  is  by  far  the  more  potent  of  the  two. 

It  is  w^orthy  of  notice,  as  a  matter  of  practical  import- 
ance, that  muscular  substance,  with  its  more  sluggish  im- 
pulse of  stimulation   (see  p.  94),  is  when  devoid  of  nerves 


THE    iMUSCLE-NERVE    MACUINE.  Il5 

more  susceptible  towards  the  more  slowly  acting-  (break  and 
make  of  tlie)  constant  current  than  towards  the  momentary 
induction-shock.  Hence  muscles  which  by  degeneration 
have  lost  tiieir  nervous  suppl}-  respond  to  the  constant  cur- 
rent much  more  readily  tiian  to  an  induction-shock.  By 
this  test  the  condition  of  the  nerves  in  the  muscle  of  cases 
of  paralysis  may  be  ascertained. 

In  order  that  a  galvanic  current  of  any  kind  may  call 
forth  a  contraction,  some  appreciable  length  of  nerve  must 
be  placed  between  the  electrodes.  If  tlie  current  simply  be 
sent  transversely  through  a  nerve,  little  or  no  contraction 
takes  place. 

According  to  Tscbirjew^^  however,  both  muscle  and  nerve  are 
irritable  in  a  transverse  direction  ;  what  ma}'  be  called  the  spe- 
cific irritability,  being  in  the  case  of  muscle  not  at  all  less,  and  in 
the  case  of  nerve  only  slightly  less  in  a  transverse  than  in  a  lon- 
gitudinal direction. 

With  the  same  strength  of  current,  the  longer  the  piece 
of  nerve  the  greater  the  contraction. 

This  when  the  constant  current  is  used  as  a  stimulus  is  said  to 
be  true  of  the  descending  but  not  of  the  ascending  current,  and 
the  results  are  more  constant  with  the  making  than  breaking  of 
the  current. - 

The  amount  of  the  contraction  is,  as  might  be  expected, 
dependent  on  tlie  strength  of  the  stimulus,  but  a  limit  to 
the  increase  of  the  contraction  caused  by  augmenting  the 
stimulus  is  soon  reached.  Thus  if  the  nerve  of  a  muscle- 
nerve  preparation  be  stimulated  at  intervals  by  currents  of 
increasing  intensity,  beginning  with  those  having  no  effect 
at  all,  it  is  found  that  the  effect,  as  measured  by  the  height 
of  the  contra(;tion,  rises  very  rapidly  to  a  maximum,  beyond 
which  it  remains  constant  so  long  as  the  irritability  of  the 
preparation  continues  unchanged. 

We  have  in  a  preceding  section  (p.  IS)  discussed  at  length 
the  manner  in  which  a  stimulus  repeated  sutHcientl}' rapidly 
produces  a  complete  and  uniform  tetanus,  durinir  whicli  the 
constituent  siuijle  contractions  cannot  be  recoonized  either 


'  Archivf.  Anat.  u.  Phvsiol.,  1877,  p,  489. 

2  AVilly,  Pfiiiger  s  Archiv,  v,   1872,  275.     Cf.  Marcuse,  Yerh.  d.  Ph\s. 
Med.  Ges.  in  Wiirzbur^,  x,  1877,  158. 


116  THE    CONTRACTILE    TISSUES. 

by  the  apijcaranco  of  the  muscle  itself  or  by  any  features  in 
the  curve  which  it  may  be  made  to  descril)e,  though  the 
"  muscular  sound  "  shows  that  the  muscle  is  really  in  a  state 
of  vibration.  If  the  frequency  of  the  stimulus  be  reduced 
the  tetanus  l>ccomes  incomplete  and  a  ttickerin^r  of  the 
muscle  becomes  obvious,  and  upon  further  reduction  of  the 
frequency  the  flickering  gives  place  to  a  rhythmic  series  of 
single  contractions.  The  exact  frequency  of  repetition  re- 
quired to  produce  complete  tetanus  varies  according  to  the 
condition  of  the  muscle,  and  is  not  the  same  for  all  muscles, 
])eing  dei)endent  on  the  rapidity  with  which  the  muscle  exe- 
cutes each  single  contraction.  In  tliose  animals  which  pos- 
sess two  kinds  of  skeletal  muscles,  red  and  pale,  tlie  red 
muscles  (the  single  contractions  of  which  are  slow  and  long- 
drawn)  are  thrown  into  complete  tetanus  with  a  repetition 
of  much  less  frequency  than  that  required  for  the  pale  mus- 
cles.' 

Kronecker  and  Stirling-  find  10  stimuli  per  second  quite  suffi- 
cient to  throw  the  red  muscles  of  the  rabbit  into  complete  tetanus, 
while  the  pale  muscles  require  at  least  20  stimuli  per  second. 

When  the  stimulus  is  repeated  more  frequently  than  is  required 
to  bring  about  a  complete  tetanus  the  contractions  are  still  pro- 
portionately increased  in  frequency.  This  is  shown  by  the  in- 
creased pitch  of  the  muscular  sound.  The  interesting  question 
then  arises,  How  far  can  the  increase  in  the  frequency  of  the  con- 
stituent contractions  be  carried  by  increasing  the  frequency  of 
the  stimulus  ?  But  this  question  obviously  involves  two  prob- 
lems :  (1)  How  far  can  the  frequency  of  nervous  impulses  be  car- 
ried ?  What  is  the  limit  to  which  the  duration  of  a  stimulus 
may  be  reduced  without  the  stimulus  ceasing  to  evoke  a  nervous 
impulse  ?  and  (2)  To  what  extent  may  the  frequency  of  nervous 
inqjulses  be  increased  without  the  muscle  ceasing  to  respond  by 
a  contraction  to  each  nervous  impulse  ?  One  w^ould  naturally 
suppose  that  there  is  a  limit  to  the  duration  of  a  stimulus  (of  a 
galvanic  current  for  instance)  necessary  to  efficiency,  and  that 
the  limit  would  vary  with  the  strength  of  the  stimulus,  the 
stronger  stimuli  remaining  effective  with  the  shorter  duration. 
And  the  experience  of  many  observers  confirms  this  view.  Konig^ 
came  to  the  conclusion  that  a  galvanic  current  of  even  maximum 
strength  as  a  stimulus  must  last  at  least  about  .0015  second  in 
order  to  generate  a  nervous  impulse.    And  Bernstein'  found  that 

^  E-anvier,  Archives  de  Phvsiol.,  vi  (1874),  p.  5. 

2  Archiv  Anat.  u.  Phvsiol.,' 1878,  p.  1,  and  Journal  Physiol.,  i  (1878), 
p.  384._  .  "  . 

^  Wien.  Sitzungs-Berichte,  Ixii  (1870). 

*  Nerven- und  Muskel-System,  1871.  See  also  Pfliiger's  Archiv,  xvii 
(1878),  p.  121. 


THE    MUSCLE-NERVE    MACHINE.  117 


when  induction-shocks  of  submaximal  intensity  are  thrown  suffi- 
ciently rapidly  (the  necessary  rapidity  varying  with  the  strength 
of  the  shocks)  into  a  muscle-nerve  preparation,  tetanus  of  "the 
muscle  fails  to  appear  ;  there  is  an  initial  contraction  at  the  com- 
mencement of  the  series  of  shocks,  and  after  that  complete  rest. 
B}'  adequately  increasing  the  strength  of  the  stimulus,  however, 
tetanus  might  always  be  brought  about.  The  absence  of  tetanus 
with  submaximal  stimulation  might  be  interpreted  as  indicating 
the  faihire  not  so  much  of  nervous  impulses  as  of  the  conversion 
of  the  nervous  into  the  muscular  impulse,  i.  c.  the  molecular  fore- 
runner in  the  muscle  of  the  visible  contraction.  Kronecker  and 
Stirling,^  by  using  a  special  instrument  for  rapid  interruption, 
the  so-called  tone-inductorium,  have  been  able  to  obtain  in  all 
cases  a  complete  tetanus  with  alternating  induction-shocks,  even 
when  repeated  they  believe  as  frequently  as  22,000  times  a  second  ; 
and  they  conclude  that  "  the  upper  limit  of  the  frequency  of  elec- 
trical stinnilation  Avhich  can  throw  a  nuiscle  into  tetanus  lies 
near  the  limit  where  variations  in  the  current  can  no  longer  be 
detected  by  the  help  of  other  physical  rheoscopes,"  and  therefore 
far  beyond  Konig's  limit. 

With  regard  to  the  second  question,  the  following  important 
observation  is  worth  attention  :  Helmholtz-  has  shown  that  when 
an  induction-shock  giving  a  maximum  contraction  is  followed  at 
an  interval  of  less  than  .Tootli  second  by  a  second  shock  of  equal 
strength,  no  second  contraction  appears  at  all.  During  p^oth 
second  subsequent  to  the  first  shock  the  muscle  is  absolutely  de- 
void of  irritability  ;  it  is  in  a  ''  refractory  phase  "  similar  to  but 
much  shorter  than  that  which  is  so  conspicuous  in  cardiac  mus- 
cles. Hence  if  a  number  of  maximum  induction-shocks  be  sent 
into  a  muscle  or  nerve  at  intervals  of  a  little  less  than  ,t  i  oth  second 
half  the  shocks  sent  in  would  seem  to  be  without  effect.  But  this 
is  only  true  of  maximum  stimuli.  We  do  not  know  where  to  place 
a  similar  limit  to  submaximal  contractions. 

When  two  pairs  of  electrodes  are  i)laced  on  the  nerve 
of  a  long  and  a  perfectly  fresh  and  successful  nerve-prepa- 
ration, one  near  to  the  cut  end,  and  the  other  nearer  the 
muscle,  it  is  found  that  the  same  stimulus  produces  a  greater 
contraction  when  applied  through  the  former  pair  of  elec- 
trodes than  through  the  latter.  Two  interpretations  of  this 
result  are  possible.  Either  the  nerve  at  the  part  farther 
away  from  the  muscle  is  more  irritable,  i.  e.,  that  the  stimulus 
gives  rise  at  the  spot  stimiitated  to  a  larger  nervous  impulse; 
or  the  impulse  started  at  the  farther  electrodes  gathers 
strength,  like  an  avalanche,  in  its  progress  to  the  muscle. 
The  latter  view  has  been  strongly  urged  bv  Pdiiger,  and  is 

^  Op.  cit.  2  Berlin.  Monatsbericht,  1854. 


118  THE    CONTRACTILE    TISSUES. 

<renerally  known  under  tlie  name  of  the  "  avalanche  theory." 
As  far  as  we  know,  liowever,  the  progress  of  tlie  negative 
variation  along  a  nerve  is  marked  hy  no  such  increase.  It 
is  probable  that  the  larger  contraction  produced  by  stimu- 
lation of  the  })ortions  of  the  nerve  near  the  spinal  cord  is 
due  to  the  stimulus  setting  free  a  larger  impulse^  z.  f?.,  to  this 
part  of  the  nerve  being  more  irritable. 

The  effect  is  not  due  to  the  section  merely,  for  it  may  be  wit- 
nessed in  nerves  still  in  connection  with  the  spinal  cord.  Heiden- 
hain^  states,  however,  that  under  these  circumstances  the  dimi- 
nution of  the  effect  is  not  gradual  from  the  central  to  the  periph- 
eral portions,  as  when  the  nerve  is  cut;  on  the  contrary,  the 
amount  of  contraction  is  at  first  large,  then  becomes  smaller,  and 
finally  increases  somewhat  again  as  the  stimulation  is  carried 
from  the  roots  of  the  nerves  to  the  muscular  periphery. 

Hallstpn  {Arch.  Anat.  P%.s.,  1876,  242)  moreover  found  that  in 
the  case  of  sensory  nerves  also  the  eftect  produced  was  greater 
when  the  stimulus  was  applied  to  the  more  central  than  when  it 
was  applied  to  the  more  peripheral  portions  of  the  nerve  ;  at 
leas'  retlex  actions  were  more  easily  excited. 

It  is  probable  that  the  irritability  of  the  nerve  may  var}-  con- 
siderably at  difierent  points  along  its  course.  And  Fleischl^ 
states  that  an  induction-shock  wdien  applied  as  an  ascending  cur- 
rent has  a  greater  eftect  on  the  more  peripheral,  and  when  applied 
as  a  descending  current  a  greater  effect  on  the  more  central  por- 
tions of  a  nerve. 


The  Influence  of  the  Load. 

It  might  be  imagined  that  a  muscle,  which,  when  loaded 
with  a  given  weight,  say  20  grams,  and  stimulated  by  a  cur- 
rent of  a  given  intensity,  had  contracted  to  a  certain  extent, 
would  only  contract  to  half  that  extent  when  loaded  with 
twice  the  weight  (40  grams)  and  stimulated  with  the  same 
stiniulus.  Such,  however,  is  not  the  case;  the  height  to 
which  the  weight  is  raised  may  be  in  the  second  instance  as 
great,  or  even  greater,  than  in  the  first.  That  is  to  say,  the 
resistance  offered  to  the  contraction  actually  increases  the 
contraction,  the  tension  of  the  muscular  fibre  increases  the 
facility  with  which  the  explosive  changes  resulting  in  a  con- 
traction take  place.     And  it  has  been  observed  by  Heiden- 

^  Stud.  Physiol.  Instit.,  Breslaii,  ii  (1861). 

2  Wien.  Sitz.-Bericht,  Ixxii  (1875),  Ixxiv  (1876).  Compare,  however, 
Tiegel,  Pfiuger's  Archiv,  xiii  (1876),  p.  o98. 


THE    MUSCLE-NERVE    MACHINE.  119 

hain'  that  tension  applied  to  a  nmscle  increases  both  the 
clieraical  products  (carbonic  and  lactic  acids)  and  the  rise  of 
temperature  which  accompany  a  contraction.  There  is,  of 
course,  a  limit  to  this  favorable  action  of  the  resistance.  As 
the  load  continues  to  be  increased,  the  height  of  the  con- 
traction is  diminished,  and  at  last  a  point  is  reached  at 
which  the  muscle  is  unable  (even  when  the  stimulus  chosen 
is  the  strongest  possible)  to  lift  the  load  at  all. 

It  is  said  that  a  muscle,  loaded  be^^ond  its  power,  relaxes  and 
lengthens  when  stimulated  instead  of  shortening,  in  consequence 
of  that  increase  of  extensibility  which  is  a  characteristic  of  the 
contracted  state.  The  occurrence  of  this  lengthening  is  however 
doubtful. 

It  is  obvious  that  the  work  done  (height  to  which  the  load 
is  raised  multiplied  into  the  weight  of  tlie  load)  must,  there- 
fore, be  largely  dependent  on  tlie  weight  itself  Thus  there 
is  a  certain  weight  of  load  with  which  in  any  given  muscle, 
stimulated  b}'  a  given  stimulus,  the  most  work  will  be  done. 

Since  mere  tension  aftects  the  changes  going  on  in  the  muscular 
fibres,  it  is  desirable  in  experiments  in  which  muscles  are  loaded, 
that  the  weight  should  not  bear  upon  the  lever  until  the  contrac- 
tion actually  begins.  This  is  easily  managed  by  interposing  be- 
tween the  end  of  the  muscle  and  the  weiirht  a  lever  with  a  support 
so  arranged  that,  before  contraction  takes  place,  the  weight  only 
extends  the  muscle  to  the  length  natural  to  it  during  rest ;  but 
that  the  muscle  directly  it  shortens  at  once  begins  to  pull  on  the 
weight.     The  muscle  is  then  said  to  be  after-loaded.'^ 

If  the  weight  be  determined  which  will  stop  a  contraction 
when  applied  directly  the  contraction  begins,  and  also  tliat 
wliich  stops  an}'  further  contraction  when  applied  at  a  mo- 
ment when  the  contraction  is  ahead}'  partly  accomplished, 
it  will  be  found  that  the  second  weight  is  much  less  than  the 
first.  It  will  be  found,  in  fact,  that  the  forces  which  produce 
the  change  in  the  form  of  the  m.uscle  are  at  their  maximum 
at  the  beginning  of  the  shortening,  and  thenceforwards  de- 
cline until  the}'  become  nothing  when  the  shortening  is  com- 
plete. 


'  Mechanisclie  Leistiing,  Warmeentwicklnng  und  Stoifumsatz  bei  der 
Mnskelthiitigkeit.    Leipzig,  1864. 

-  This  is  perhaps  the  best  equivalent  of  the  German  iiberlastet. 


120  THE    CONTRACTILE    TISSUES. 


Influence  of  the  Size  and  Form  of  the  Muscle. 

Since  all  known  muscular  fibres  are  mucii  shorter  than  the 
wave-leuiith  of  a  contraction,  it  is  obvious  that  the  longer 
tlie  fibre  the  greater  the  height  of  the  contraction  with  the 
same  stimulus.  Hence  in  a  muscle  of  })arallel  fibres,  the 
heiglit  to  which  the  load  is  raised  as  the  result  of  a  given 
stimulus  applied  to  its  nerve,  will  depend  on  the  length  of  the 
fibres,  while  the  weight  of  the  load  so  lifted  will  depend  on 
the  number  of  the  fibres,  since  the  load  is  distril)uted  among 
them.  Of  two  muscles,  therefore,  of  equal  length  (and  of 
the  same  quality)  the  most  work  will  be  done  by  tiiat  which 
has  the  greater  sectional  area;  and  of  two  muscles  with 
equal  sectional  areas,  t!ie  most  work  will  l)e  done  by  that 
which  is  the  longer.  If  the  two  muscles  are  unequal  both 
in  length  and  sectional  area,  the  work  done  will  be  tiie  greater 
in  the  one  which  has  the  larjjer  bulk,  which  contains  the 
greater  number  of  cubic  units.  In  speaking,  therefore,  of 
the  maximum  of  work  which  can  be  done  by  a  muscle,  we 
may  use  as  a  standard  a  cubic  unit  of  l)ulk,  or,  the  specific 
gravity  of  the  muscle  being  the  same,  a  unit  of  weight. 

In  the  case  of  frog's  muscle,  the  maximum  of  work  which  can 
be  done  under  most  favorable  circumstances  has  been  estimated 
by  Fick^  to  vary  between  3  and  7  grammeters  for  1  grm.  of 
muscle. 

The  weight  which  is  just  sufficient,  but  only  just  sufficient,  to 
keep  a  muscle,  when  stimulated,  from  actually  shortening,  may 
be  taken  as  the  measure  of  the  "absolute  power  "  of  the  muscle. 
It  must,  of  course,  be  taken  only  in  relation  to  the  sectional  area 
of  the  muscle.  The  absolute  power  of  a  square  centimeter  of  a 
frog's  muscle  has  been  in  this  way  estimated  at  about  2800  to 
8000  grms.  :  of  a  square  centimeter  of  human  muscle  at  6000  to 
8000  grms. 


Sec.  5.   The  Circumstances  which  determine  the   De- 
gree OF  Irritability  of  Muscles  and  Nerves. 

A  muscle-nerve  preparation,  at  the  time  that  it  is  removed 
from  the  body,  possesses  a  certain  degree  of  irrital>ility,  it 
responds  b}- a  contraction  of  a  certain  amount  to  a  stimulus 
of  a  certaiu  strength,  applied  to  the  nerve  or  to  the  muscle. 
After  awhile,  the   exact  period   depending  on  a  variety  of 

^  Untersuch.  ii.  Muskelarbeit,  Basel,  1867. 


VARIATIONS    OF    IRRITABILITY.  121 

circumstances,  the  same  stimiilns  produces  a  smaller  con- 
traction, i.  e.,  the  irritability  of  the  preparation  has  dimin- 
ished. In  other  words,  the  muscle  or  nerve,  or  both,  have 
become  partially  "exhausted,"  and  the  exhaustion  subse- 
quently increases,  tlie  same  stimulus  producing  smaller  con- 
tractions until  at  last  all  irritability  is  lost,  no  stimulus 
however  strono^  })roducing  any  contraction  whether  ai)plied 
to  the  nerve  or  directly  to  the  muscle;  and  eventually  the 
muscle,  as  we  have  seen,  becomes  rigid.  The  progress  of 
this  exhaustion  is  more  rapid  in  the  nerves  than  in  the  mus- 
cles ;  for  some  time  after  the  nerve-trunk  has  ceased  to 
respond  to  even  the  strongest  stimulus,  contractions  may 
be  obtained  by  ni)i)lyiiig  the  stimulus  directly  to  the  muscle. 
It  is  much  more  rajnd  in  the  warm-blooded  than  in  the  cold- 
l)looded  animals.  The  muscles  and  nerves  of  the  former 
lose  their  ii-ritability  when  removed  from  the  body  after  a 
jjeriod  varying,  according  to  circumstances,  from  a  few  min- 
utes to  two  or  three  hours  ;  those  of  cold-blooded  animals 
(or  at  least  of  an  amphiliian  or  a  reptile)  may,  under  favor- 
able conditions  remain  irritable  for  two,  three,  or  even  more 
days. 

If  a  sharp  blow  with  some  thin  body  be  struck  across  a  muscle 
which  has  entered  into  the  later  stages  of  exhaustion,  a  wheal 
lasting  for  several  seconds  is  developed.  This  wheal  appears  to 
be  a  contraction-wave  limited  to  the  part  struck,  and  disappear- 
ing very  slowly  without  extending  to  the  neighboring  muscular 
sulostance.  It  has  been  called  an"''  idio-muscular  "  contraction, 
because  it  may  be  brought  out  even  when  ordinary  stimuli  have 
ceased  to  produce  any  effect.  It  may,  however,  be  accompanied 
at  its  beginning  by  an  ordinary  contraction.  It  is  readily  pro- 
duced in  the  living  body  on  the  pectoral  and  other  muscles  of 
persons  suftering  from  phthisis  and  other  exhausting  diseases. 

This  natural  exhaustion  and  diminution  of  irritability  in 
muscles  and  nerves  removed  from  the  body  may  be  modified 
both  in  the  cnse  of  the  muscle  and  of  the  nerve  by  a  variety 
of  circumstances.  Similarly,  wdiile  the  nerve  and  muscle 
still  remain  in  the  body,  the  irritability  of  the  one  or  of  the 
other  may  be  modified  either  in  the  way  of  increase  or  of 
decrease  by  various  events.  AVe  have  already  seen  (p.  107) 
how  the  constant  current  produces  the  variations  in  irrita- 
bility known  as  katelectrotonus  and  anelectrotonus.  We 
have  now  to  study  the  effect  of  moie  general  influences,  of 
which   the   most  important  are  severance  from  the  central 


122  THE    CONTRACTILE    TISSUES. 


nervous  system,   and   variations   in  temperaiure,  in  blood- 
snppl3%  and  in  functional  activity. 

The  EffecU  of  Severance  fr^om  the  Central  Nervous  SyMem. 

When  a  nerve,  such  for  instance  as  the  sciatic,  is  divided 
??i  sifa^  in  tiie  livincr  body,  there  is  first  of  all  observed  a 
slight  increase  of  irritaltilit>\  noticeable  especially  near  the 
cut  end;  hut  after  awhile  the  irritability  diminishes  and 
o^radually  disappears.  Both  the  slitrht  initial  increase  and 
the  subsequent  decrease  begin  at  tiie  cut  end  and  advance 
centrifugally  towards  the  peripheral  terminations.  This 
centrifugal  feature  of  the  loss  of  irrital)ility  is  often  si)oken 
of  as  the  Ritter-Yalli  law.  In  a  mammal  it  may  be  two  or 
tiiree  days  ;  in  a  frog,  as  many,  or  even  more  weeks,  before 
irritability  has  disa|)peared  from  the  nerve-trunk.  It  is 
maintained  in  the  small  (and  especially  in  tiie  intramuscu- 
lar) branches  for  still  longer  periods. 

A  similar  slight  temporary  increase  of  irritability  is  seen  to 
follow  the  section  of  a  nerve  even  when  removed  from  the  body. 
In  the  nei.2;hborhood  of  the  section  the  nerve  is  for  awhile  more 
irritable  after  the  section  than  it  was  before. 

This  centrifugal  loss  of  irritability  is  the  forerunner  in 
the  peripheral  portion  of  the  divided  nerve  of  structural 
changes  whicii  proceed  in  a  similar  centrifugal  manner.  The 
medulla  suffers  changes  similar  to  those  seen  in  nerve-fibres 
after  removal  from  the  body.  Its  double  contour,  and  its 
characteristic  indentations  become  more  marked  ;  it  breaks 
up  into  small  irregular  segments  or  drops,  a  separation  ap- 
parently taking  place  between  its  proteid  and  its  fatty  con- 
stituents. The  latter  are  soon  absorbed,  but  the  former 
remain  for  a  longer  time  within  the  sheath  of  Schwann, 
being  in  some  cases  scarcely,  if  at  all.  to  be  distinguished 
from  the  swollen  axis-cylinder.  Meanwhile  the  nuclei  of  the 
sheath  of  Schwann  divide  and  multiply  rapidly.  If  no  re- 
generation takes  place  the  whole  contents  of  the  sheath  are 
gradually  absorbed,  the  axis-cylinder  disappearing  last. 

In  the  central  portion  of  the  divided  nerve  similar  changes 
may  be  traced  as  far  only  as  the  next  node  of  Ranvier. 
Beyond  this  the  nerve  usually  remains  in  a  normal  condi- 
tion. 

Regeneration,  when  it  occurs,  is  carried  out  by  the  periph- 


VARIATIONS    OF    IRRITABILITY.  123 


eral  growth  of  the  axis-cylinders  of  the  intact  central 
portion.  When  the  cut  ends  of  the  nerve  are  close  together 
the  axis  cylinders  growing  out  from  the  central  portion  run 
into  and  between  tlie  sheaths  of  Schwann  of  the  peripheral 
portion;  but  much  uncertainty  still  exists  as  to  the  exact 
parts  played  by  the  proliferated  nuclei  of  the  sheath  of 
Schwann,  the  proteid  remnants  of  the  medulla,  and  the  old 
axis-cylinders  of  the  peripheral  portion  in  giving  rise  to  the 
new  structures  of  the  regenerated  lihre. 

This  degeneration  may  be  observed  to  extend  down  to 
the  very  endings  of  the  nerve  in  the  muscle,  including  the 
end-plates,  but  does  not  affect  the  muscular  substance  itself. 
The  muscle,  though  it  has  lost  all  its  nervous  elements,  still 
remains  irritable  towards  stimuli  applied  directly  to  itself; 
an  additional  proof  of  the  existence  of  an  independent 
muscnlar  irritability.  As  was  mentioned  before  (p.  115),  it 
is  not  easily  stimulated  by  single  induction-shocks,  but 
responds  readily  to  the  make  or  break  of  a  constant  current. 
If  it  be  thus  artificially  stimulated  from  time  to  time  it  will 
remain  irritable  for  a  ver^^  considerable,  possibly  for  an  in- 
definite time;  but  if  it  be  not  thus  thrown  into  functional 
activity,  its  irritability  ultimately  disappears  and  its  sub- 
stance undergoes  degeneration. 

The  Influence  of  Temperature. 

We  have  already  seen  (p.  64)  that  sudden  heat  applied  to 
a  limited  part  of  a  nerve  or  muscle,  as  when  the  nerve  or 
muf^cle  is  touciied  with  a  hot  wire,  will  act  as  a  stimulus, 
and  the  same  might  be  said  of  cold  when  sutticiently  intense. 
It  is,  however,  much  more  difficult  to  generate  nervous  or 
muscular  impulses  by  exposing  a  whole  nerve  or  muscle  to 
a  gradual  rise  of  temperature.  Thus  according  to  most  ob- 
servers a  nerve  belonging  to  a  muscle^  may  be  either  cooled 
to  0°  C.  or  below,  or  heated  to  50°  or  even  100^  C,  without 
discharging  any  nervous  impulses,  as  shown  b}"  the  absence 
of  contraction  m  the  attached  muscle. 

The  contractions,  moreover,  may  be  absent  even  when  the 
heating  has  not  been  very  gradual.  Several  observers,  however, 
have  found  that  contractions  (of  an  irregular  flickering  tetanic 

'  The  action  of  cold  and  heat  on  sensory  nerves  will  be  considered  in 
the  later  portion  of  the  work. 


124  THE    CONTRACTILE    TISSUES. 


nature)  result  when  a  nerve  is  heated  in  water,  or  in  oil,  or  in  a* 
moist  atmosphere  tor)(Por  even  less.  It  has  heen  su^iiested  that 
the  eontratlions  in  these  cases  are  due  rather  to  s]H)ntane()us  im- 
pulses (whose  tliseharure  was  favored  hy  the  increased  mole(;ular 
activity  caused  hy  the  rise  of  temperature)  than  to  the  heat  act- 
ing as  .a  stimulus,  but  this  seems  hardly  satisfactory.' 

A  muscle  may  be  cfvoled  to  0"^^  Cor  below  without  any  con- 
ti-action  being  caused  ;  but  when  it  is  heated  to  a  limit, 
which  in  the  case  of  frog's  muscles  is  about  45'^,  of  mamma- 
lian muscles  about  50^,  a  sudden  change  takes  place:  the 
muscle  falls,  at  the  limiting  temperature,  into  a  rigor  mortis, 
which  is  initiated  by  a  forcible  coutractiou  or  at  least  short- 
ening. The  rigor  moitis  thus  brought  about  by  heat  is 
often  si)oken  of  as  rigor  caloi-is. 

Moderate  warmth,  e.r.  gr.,  in  the  frog  an  increase  of  tem- 
])e]ature  to  45'^  C.  favors  both  muscular  and  nervous  irrita- 
bility. All  the  molecular  processes  are  hastened  and  facili- 
tated: the  contraction  is  for  a  given  stimulus  greater  and 
more  rapid,  i.  <'.,o\'  shorter  duration,  and  nervous  impulses 
are  generated  moi-e  readily  by  slight  stimuli.  Owing  to  the 
(piickening  of  the  chemical  changes,  the  supply  of  new  ma- 
terial may  prove  insutlicient ;  hence  muscles  and  nerves 
removed  from  the  body  lose  their  irritabilit}^  niore  rapidly 
at  a  high  than  at  a  low  temi)erature. 

The  gradual  application  of  cold  to  a  nerve,  especially 
when  the  temperature  is  thus  brought  near  to  0°,  slackens 
all  the  molecular  processes,  so  that  the  wave  of  nervous  im- 
pulse is  lessened  and  jn-olonged,  the  velocity  of  its  passage 
being  much  diminished,  from  2<S  m.  e.  g.  to  1  m.  per  sec. 
At  about  0°  the  iiritability  of  the  nerve  disai)i)ears  alto- 
gether. 

When  a  muscle  is  exposed  to  similar  cold,  ex.  gr.^  to  a 
temperature  ver3-  little  above  zero,  the  contractions  are 
remaikably  prolonged  ;  they  are  diminished  in  extent  at  the 
same  time,  but  not  in  proj)oi'tion  to  the  increase  of  their 
duiation.  Exposed  to  a  temperature  of  zero  or  lielow, 
muscles  soon  lose  their  irritability,  without  however  under- 
going rigor  mortis.  After  an  exi)osure  of  not  more  than  a 
few  seconds  to  a  temperature  not  much  below  zeio,  they 
may  be  restored,  by  gradual  warmth,  to  an  irritable  condi- 
tion, even  though   they   may  appear  to   have   been  frozen. 

'  Giiilzner,  Pfiiiser's  Archiv,  xvii  (1878),  p.  215.  Cf.  Lautenbach, 
Juurn.  Phys.,  ii  (1879),  p.  1. 


VARIATIONS    OF    IRRITABILITY.  125 

AA^hen  kept  frozen,  however,  for  some  few  minutes,  or  when 
exposed  for  a  less  time  to  temperatures  of  several  degrees 
below  zero,  their  irritability  is  permanently  destroyed. 
AVhen  thawed  they  enter  into  rigor  mortis  of  a  most  pro- 
nounced character. 

The  Influence  of  Blood-supply. 

AA^hen  a  muscle  still  within  the  body  is  deprived  by  any 
means  of  its  proper  blood-supply,  as  when  the  bloodvessels 
going  to  it  are  ligatured,  tlie  same  gradual  loss  of  irritability 
and  final  appearance  of  rigor  mortis  are  observed  as  in 
muscles  removed  out  of  the  body.  Thus  if  the  abdominal 
aorta  be  ligatured,  the  muscles  of  the  lower  limbs  lose  their 
irritability  and  finally  become  rigid.  So  also  in  systemic 
death,  when  the  blood-supply  to  the  muscles  is  cut  off  by 
the  cessation  of  the  circulation,  loss  of  irritability  ensues, 
and  rigor  mortis  eventually  follows.  In  a  human  corpse 
the  muscles  of  the  body  enter  into  rigor  mortis  in  a  fixed 
order:  first  those  of  the  jaw  and  neck,  then  those  of  the 
trunk,  next  those  of  the  arms,  and  lastly  those  of  the  legs. 
The  rajjidity  witli  which  rigor  mortis  comes  on  after  death 
varies  consider;il)ly,  being  rletermined  both  by  external 
circumstances  and  by  the  internal  conditions  of  the  body. 
Thus  external  warmth  hastens  and  cold  retards  the  onset. 
After  g'"eat  muscular  exertion,  as  in  hunted  animals,  and 
wiien  death  closes  wasting  diseases,  rigor  mortis  in  most 
cases  comes  on  rapidly.  As  a  general  rule  it  may  be  said 
that  the  later  it  is  in  making  its  appearance,  the  more  pro- 
nounced it  is,  and  the  longer  it  lasts  ;  but  there  are  many 
exceptions,  and  when  the  state  is  recognized  as  being 
fundamentally  due  to  a  coagulation,  it  is  easy  to  understand 
that  the  amount  ofi-igldity,  i.  e.,the  amount  of  the  coagulum, 
and  the  rapidity  of  tlie  onset,  i.  ^.,  the  quickness  with  which 
coagulation  takes  place,  may  vary  independently.  The 
rapidit}^  of  onset  after  muscular  exercise  and  wasting 
disease  is  apparently  dependent  on  an  excess  of  acid,  which 
seems  to  be  favorable  to  the  coagulation  of  the  muscle, 
plasma  being  produced  under  those  circumstances  in  the 
muscle.  When  rigor  mortis  has  once  become  thoroughly 
established,  in  a  muscle  through  deprivation  of  blood,  it 
cannot  be  removed  by  any  subsequent  suppl}-  of  blood. 
Thus  where  the  al»dominal  aorta  has  remained  ligatured 
until  the  lower  lindjs  have  become  completely  rigid,  untying 

11 


12G  THE    CONTRACTILE    TISSUES. 

tlio  liiiature  will  not  restore  tlje  muscles  to  an  irrital)le  eon- 
ililioii  ;  it  simply  liastens  the  decomposition  of  the  dead 
tissues  l>y  siii)|)lyin*<  them  with  oxygen  and,  in  the  case  of 
ihe  inammai,  with  warmth  also. 

A  muscle,  however,  may  acquire  as  a  whole  a  cartaln  amount 
of  ri^u:;idity  on  account  of  some  of  the  fihres  becomin^i^  I'igid,  while 
the  remainder,  though  they  have  lost  their  irritability,  have  not 
yet  advanced  into  rigor  mortis.  At  such  a  juncture  a  renewal 
of  the  Ijlood  stream  may  restore  the  irritability  of  those  tll)res 
which  were  not  yet  rigid,  and  thus  appear  to  do  away  with  rigor 
mortis  ;  yet  it  appears  that  in  such  cases  the  filjres  which  have 
actually  become  rigid  never  regain  their  irritability,  but  undergo 
degeneration.  It  is  stated  however  by  Preyer'  that  if  the  even  . 
completely  rigid  muscles  of  the  frog  be  washed  out  with  a  10  per 
cent,  sodium  chloride  solution  (which  dissolves  myosin),  and  sub- 
sequently injected  with  blood,  irritability  will  be  restored. 

Mere  loss  of  irritability,  even  though  complete,  if  stop- 
ping short  of  the  actual  coagulation  of  the  muscle-substance 
may  be  with  care  removed.  Thus  if  a  stream  of  blood  be 
sent  artificially  through  the  vessels  of  a  separated  (mam- 
malian) muscle,  the  irritability  may  be  maintained  for  a  very 
considerable  time.  On  stopping  the  artificial  circulation, 
tiie  irritabilit}'  diminishes  and  in  time  entirely  disa|)pears ; 
if  however  the  stream  be  at  once  resumed,  the  irritability 
will  be  recovered.  By  regulating  the  flow,  the  irritability 
may  be  lowered  and  (up  to  a  certain  limit)  raised  at  pleas- 
ure. From  the  epoch  however  of  interference  with  the 
normal  blood  stream  there  is  a  gradual  diminution  in  the 
responses  to  stimuli,  and  ultimately  the  muscle  loses  all  its 
iiritability  and  becomes  rigid,  however  well  the  artificial 
circulati(m  be  kept  up.  This  failure  is  probably  in  great 
part  due  to  the  blood  sent  tiirough  the  tissue  not  being  in  a 
perfectly  normal  condition  ;  but  we  have  at  present  very 
little  information  on  this  point.  Indeed  with  respect  to  the 
quality  of  blood  thus  essential  to  the  maintenance  or  restor- 
ation of  irritability,  our  knowledge  is  definite  witli  regard  to 
one  factor  only,  viz.,  the  oxygen.  If  blood  deprived  of  its 
oxygen  be  sent  through  a  muscle  removed  from  the  l^ody, 
irritability,  so  far  from  being  maintained,  seems  rather  to 
liave  its  disappearance  hastened  In  fact,  if  venous  lilood 
continue  to  be  driven  through  the  muscle,  the  irritability  is 

'  Centrbt.  f.  med.  Wis.^chft.,  1SH4,  p.  769. 


VARIATIONS    OF    IRRITABILITY.  127 

lost  even  more  rapidlv  than  in  the  entire  altsence  of  blood. 
It  would  seem  that  venous  blood  is  more  injurious  than 
none  at  all.  If  exhaustion  be  not  carried  too  far,  the  mus- 
cle may,  however,  be  revived  bj' a  proper  suppl}' of  oxj'gen- 
ated  blood. 

In  a  muscle,  the  irritability  of  which  has  been  suspended  by  a 
current  of  venous  blood,  the  assumption  of  a  minute  fraction  of 
oxygen  is  sufficient  to  restore  irritabilitj^  to  such  an  extent  that 
a  veiy  distinct  amouni;  of  contraction  is  visible  on  the  applica- 
tion of  stimuli.  Much  more  than  this  must  be  taken  up  before 
the  muscle  can  regain  the  standard  at  which  it  was  previous  to 
the  action  of  the  venous  stream.  ^ 

The  influence  of  blood  supply  cannot  be  so  satisfactorily 
studied  in  the  case  of  nerves  as  in  the  case  of  muscles  ; 
there  can  however  be  little  doubt  that  the  elfects  are  analo- 
gous. 

The  Influence  of  Functional  Acticity. 

This  too  is  more  easily  studied  in  the  case  of  muscles 
than  of  nerves. 

When  a  muscle  within  the  body  is  unused,  it  wastes; 
wlien  used  it  (within  certain  limits)  grows.  Both  these 
facts  show  that  the  nutrition  of  a  muscle  is  favorabl}^  affected 
by  its  functional  activity. 

Part  of  this  may  be  an  indirect  effect  of  the  increased  blood- 
supply  which  occurs  when  a  muscle  contracts.  When  a  nerve 
going  to  a  muscle  is  stimulated,  the  bloodvessels  of  the  muscle 
dilate.  Hence  at  the  time  of  the  contraction  more  blood  tlows 
through  the  muscle,  and  this  increased  tlow  continues  for  some 
little  while  after  the  cpntraction  of  the  muscle  has  ceased. 

A  muscle,  even  within  the  body,  after  prolonged  action  is 
fatigued,  i.  e..  a  stronger  stimulus  is  required  to  produce  the 
same  contraction  ;  in  other  words,  its  irritability  is  reduced 
by  functional  activity. 

The  fatigue  of  which,  after  prolonged  or  unusual  exertion,  we 
are  conscious  in  our  own  bodies,  arises  partly  from  an  exhaus- 

'  Ludwig  and  Schmidt,  Ludwig's  Arbeiten,  1868,    p.  1. 


128  THE    CONTRACTILE    TISSUES, 


tion  of  musflos,  jiiirtly  from  nn  cxliniistion  of  motor  nerves,  Init 
cliierty  from  an  exliaii.stion  of  the  central  nervous  system  con- 
cerned in  the  ])rodnction  of  voluntary  impulses.  A  man  who 
says  he  is  ahsolutely  exhausted  may,  under  excitement,  perform 
a  very  lar<re  amount  of  work  with  his  already  wearied  muscles. 
The  will  rarely,  if  ever,  calls  forth  the  greatest  contractions  of 
which  the  muscles  are  capable. 

Absohite  (temporary)  exhaustion  of  the  muscles,  so  that 
the  sti'ongest  stimuli  produce  no  contraction,  may  be  pro- 
duced even  within  the  bo<ly  by  artificial  stimulation  ;  recov- 
ery takes  place  on  rest.  Out  of  the  body  absolute  exhaus- 
tion takes  place  readily.  Here  also  recovery  may  take 
place.  Whether  in  any  given  case  it  does  occur  or  not  is 
determined  l)v  the  amount  of  contraction  causing  the  ex- 
liaustion,  and  by  tlie  previous  condition  of  tiie  muscle.  In 
all  cases  recover}^  is  hastened  by  renewal  (natural  or  artifi- 
cial) of  the  blood-stream.  The  more  rapidly  the  contrac- 
tions follow  each  other,  the  less  the  interval  between  any 
two  contractions,  the  more  rapid  the  exhaustion.  A  certain 
number  of  single  induction-shocks  repeated  rapidly,  say 
every  second  or  oftener,  bring  about  exhaustive  loss  of 
irritability  more  rapidly  than  the  same  number  of  shocks 
repeated  less  ra[)idly,  for  instance,  every  five  or  ten  seconds. 
Hence  tetanus  is  a  ready  means  of  producing  exhaustion. 

There  are  reasons  for  thinking  that  for  each  muscle  it  may  be 
possible  to  choose  such  an  interval  between  successful  stimuli  of 
suitable  strength  as  shall  not  only  not  hasten,  ])ut,  perhaps,  even 
retard  the  gradual  normal  exhaustion  following  upon  removal  from 
the  bod}'.  In  other  words,  it  is  prol)able  that  the  exhaustion 
caused  l)y  a  contraction  is  immediately  followed  by  a  reaction 
favorable  to  the  nutrition  of  the  muscle  ;  and  this  possibly  is  the 
real  reason  why  a  muscle  is  increased  by  use. 

"When  a  muscle  is  subjected  to  a  prolonged  tetanus  the  course 
of  exhaustion,  as  indicated  by  the  varying  heights  to  which  the 
load  is  successively  raised  by  the  repeated  contractions,  is  at  first 
very  slow,  afterwards  more  rapid,  and  finally  slow  again. 

The  amount  of  the  load,  provided  this  be  not  too  great,  has 
no  marked  effect  on  the  course  of  exhaustion.  If  two  muscles 
be  after-loaded,  one  with  a  heavy,  the  other  with  a  light  weight, 
and  stimulated  at  the  same  intervals  with  the  same  stiumlus,  the 
course  of  exhaustion  will  be  parallel  in  the  two  cases,  though  the 
more  heavily  laden  muscle,  responding  at  the  outset  with  smaller 
contractions  than  the  more  highly  laden  one,  will  be  the  first  to 
enter  that  staire  of  exhaustion  at  which  the  contractions  cease  to 


VARIATIONS    OF    IRRITABILITY.  129 


be  visible.^  The  above  is  probably  onl}-  true  for  weights  up  to  the 
standard  Avhich  is  most  favorable  for  the  muscle's  doiug  work. 
See  ante,  p.  118.  Weights  heavier  than  this  quicken  exhaustion, 
and  the  mere  extension  caused  by  loading  with  a  heavy  weight 
(even  when  unaccompanied  by  a  contraction!  is  exhausting. 

"Whether  there  be  a  third  factor,  i.  e.,  whether  muscles,  for 
instance,  are  governed  by  so-called  trophic  nerves,  which  alfect 
their  nutrition  directh-  in  some  other  way  than  by  intiuencing 
either  their  blood-supply  or  activity,  must  at  present  be  left  un- 
decided. 

Muscles  exhausted  by  prolonged  action  may  have  their  irrita- 
bility temporarily  restored  by  passing  through  them  for  some 
time  a  constant  current. 

In  exhausted  muscles  the  elasticity  is  much  diminished  ; 
the  tired  muscle  returns  less  readily  to  its  natural  length 
than  does  the  fresh  one. 

The  exhaustion  due  to  contraction  may  be  the  result :  (1) 
Either  of  the  consumption  of  the  store  of  really  contractile 
material  present  in  the  muscle.  Or  (2)  of  the  accumulation 
in  the  tissue  of  the  products  of  tlie  act  of  contraction.  Or 
(3)  of  both' of  these  causes. 

The  restorative  influence  of  rest  may  be  explained  by 
supposing  that  during  the  repose,  either  tlie  internal  changes 
of  the  tissue  mnnufacture  new  explosive  material  out  of  the 
comparatively  raw  material  already  present  in  the  tihres,  or 
the  directl}'  hurtfid  products  of  the  act  of  contraction  un- 
dergo changes  l)y  wliich  they  are  converted  into  compnra- 
tively  inert  i)odies.  A  stream  of  fresh  blood  may  exert  its 
restorative  influence,  not  onh'  by  quickening  the  above  two 
events,  but  also  b}'  carrying  otf  tlie  immediate  waste  pro- 
ducts, while  at  the  same  time  it  brings  new  raw  material. 
It  is  not  known  to  what  extent  each  of  these  parts  is  played. 
Tiiat  the  products  of  contraction  are  exhausting  in  their 
etiects  is  shown  by-the  fact  that  exhausted  muscles  are  re- 
covered by  tlie  simple  injection  of  inert  saline  solutions  into 
their  bloodvessels  ;  and  that  such  bodies  as  lactic  acid  in- 
jected into  a  muscle  cause  rapid  exhaustion  ;  a  striking 
instance  is  seen  in  the  effect  of  dilute  alkalies  in  restoring 
the  beat  of  tlie  exliausted  frog's  heart.  One  important  ele- 
ment brought  by  fresh  blood  is  oxygen.  This,  as  we  have 
seen,  is  not  necessary  for  the  carrying  out  of  the  actual  con- 
traction, and  yet  is  essential  to  the  maintenance  of  irrita- 

^  Kronecker,  Ludwig's  Arbeiten,  1871. 


130  THE    CONTRACTILE    TISSUES. 


bility.  It  is  probably  of  use  as  wliat  may  be  called  intra- 
molecular oxygen'  in  preparing  the  explosive  material  whose 
decomposition  gives  rise  to  the  carbonic  acid,  and  other 
products  of  contraction. 

It  is  stated  by  Kronecker^  that  oxygen,  not  in  the  form  of 
oxyhsemoglobin,  but  administered  roughly  in  the  form  of  an  in- 
jection of  permanganate  of  potash,  restores  the  irritability  of 
exhausted  muscle. 

After  prolonged  artificial  excitation  of  a  muscle  within  the 
body  the  exhaustion  is  accom[)anied  or  rather  followed  by  histo- 
logical changes  of  the  nature  of  de"eneration. 


Sec.  6.   A  further  Discussion  of  some  points  in  the 
Physiology  of  Muscle  and  Nerve. 

The,  Electrical  Phenomena  of  3Iitscle  and  Nerve. 

The  Natural  Currents — The  Pre-existence  Theory. — As  was 

stated  on  p.  89,  Du  Bois-Reyniond,  and  those  with  him,  believe 
that  electric  currents  naturally  exist  even  in  untouched,  perfectly 
uninjured  muscles  and  nerves;  and  their  view  is  generally  spoken 
of  as  the  "Pre-existence  Theory."  According  to  that  theory, 
the  muscle  (or  nerve)  is  made  up  of  electro-motive  particles  or 
molecules  imbedded  in  an  indifferent  and  imperfectly  conducting 


Fig.  28. 


% 


Diagram  to  Illustrate  Du  Eois-Ueymond  :<  Eli-ciro-;iiut ive  Molecules.    Peripolar 
CouditioD. 

medium.  Each  molecule  is  further  conceived  of  as  presenting  a 
negative  surface  to  the  ends  or  transverse  sections,  and  a  positive 
surface  to  the  longitudinal  surface  or  section  of  the  muscle  ;  the 
molecule,  in  fact,  may  be  regarded  as  a  minute  battery  whose 
positive  and  negative  poles  are  at  the  longitudinal  and  transverse 
surfaces  respectively.  For  reasons  which  will  appear  presently 
the  molecules  are  further  supposed  to  be  not  single  but  double, 
each  half-molecule  consisting,  as  shown  in  Fig.  28,  of  a  positive 

^  Compare  the  section,  in  a  later  portion  of  the  work,  on  the  Kespi- 
ratory  Changes  in  the  Tissues, 
^  Lud wig's  Arbeiten,  1871, 


THE    PRE-EXISTENCE    THEORY.  131 


and  negative  part,  and  the  two  positive  parts  of  the  two  halves 
being  placed  together  so  that  the  double  molecule  still  presents  a 
negative  surface  to  each  end  or  transverse  section,  and  a  positive 
surface  to  the  longitudinal  surface  or  section  of  the  muscle. 

The  presence  of  these  (so-called  peripolar)  molecules  disposed 
throughout  the  substance  of  the  muscle  will  give  rise  to  currents 
in  the^  medium  by  which  they  are  surrounded.  Around  each 
molecule  will  stream  currents  circling  from  the  positive  middle 
to  the  negative  ends  ;  owing  to  the  imperfect  conductivity  of  the 
medium  these  currents  will"  not  only  flow,  as  shown  in  the  dia- 
gram, in  the  immediate  neighborhood  of  each  molecule,  but  will 
extend  in  more  or  less  conceiitric  lines  at  some  distance  from  the 
molecule.  Hence  when  the  electrodes  of  a  galvanometer  are  con- 
nected with  two  points  of  the  surface  of  the  muscle,  the  deflection 
of  the  needle  will  indicate  a  surface  current  which  is  a  resultant 
of  the  numerous  currents  of  the  several  molecules.  And  a  little 
consideration  will  show  that  the  direction  and  intensity  of  the 
currents  passing  through  the  galvanometer  in  dilferent  positions  of 
the  electrodes  will  be  such  as  is  described  on  p.  89  and  illustrated 
by  the  diagram.  Fig.  25.  It  need  hardly  be  added  that  the  hy- 
pothesis of  electro-motive  peripolar  molecules  is  applied  to  nerves 
as  well  as  to  muscles. 

Du  Bois-Reymond  was  led  to  conceive  of  these  molecules  as 
being  double  instead  of  single  in  order  that  he  might  explain  the 
origin  of  the  so-called  electrotonic  currents  which,  as  we  shall 
presently  see,  are  developed  when  a  nerve  is  subjected  to  the  ac- 
tion of  a  constant  current.  For  he  supposed  that  under  certain 
circumstances  (among  these  the  passage  into  the  nerve  of  a  con- 
stant current)  each  half  of  each  molecule  could  be  partially  or,  as 


Diagram  lUiistiatiiig  Du  Bois-Reymoud's  Molecules  iu  their  Bipolar  Con<lition. 

shown  in  Fig.  29,  completely  reverse^t,  so  that  in  each  half-mole- 
cule the  positive  surface  was  directed  to  one  end  and  the  negative 
surface  to  the  other  end  of  the  piece  of  nerve.  The  molecule 
thus,  from  being  peripolar  becomes  bipolar,  and  the  currents  dis- 
charged by  each  molecule  into  the  surrounding  medium  have  all 
the  same  direction. 

In  order  to  explain  the  undoubted  fact  that  ''natural"  cur- 
rents are  either  absent  or  exceediugl}-  feeble  in  untouched  unin- 
jured muscles,  Du  Bois-Reymond  supposes  that  the  ends  of  the 
muscles  in  contact  with  the  tendons  are  composed  of  a  layer  or 
region  in  which  all  the  molecules  have  their  pomtive  instead  of 
their  negative  surfaces  looking  to  the  ends  of  the  muscle.     The 


132  THE    CONTRACTILE    TUSUES. 


molecules  of  this  region,  which  he  calls  the  parelectYonomic  region, 
may  be  looked  upon  as  bipolar,  and  the  arrangement  shown  in 
Fig.  29  may  be  taken  as  illustrating  the  condition  of  the  mole- 
cules in  this  parelectronomic  region.'  Obviously  the  currents 
which  the  electro-motive  molecules  develop  in  this  region  are 
opposed  in  direction  to  those  originating  in  tlie  rest  of  the  muscle, 
and  hence  either  partially  or  wholly  conceal  the  existence  of  the 
latter.  The  development  of  this  parelectronomic  region  is  stated 
by  Du  Bois-Keymond  to  be  greatly  assisted  by  cold,  but  Her- 
mann, who  of  course  wholly  denies  the  existence  of  any  such 
region,  finds  no  electrical  ditferences  in  frogs'  muscles  kept  in  a 
warm  room  from  those  kept  in  an  ice-cold  cellar,  though  when 
currents  are  developed  they  are  increased  by  an  elevation  of  tem- 
perature. 

It  is  obviously  reasonable  to  infer  that  if  this  view  of  Du  Bois- 
lieymond's  be  correct,  if  natural  currents  do  exist  in  muscles  with 
untouched  natural  terminations  but  exist  masked  by  the  parelec- 
tronomic region,  they  would  manifest  themselves  in  full  force 
immediately,  without  loss  of  time,  upon  the  removal  or  destruc- 
tion of  the  parelectronomic  region  ;  whereas  if  Hermann's  view 
be  correct  that  the  currents  do  not  pre-exist  but  are  developed  by 
chemical  changes  due  to  the  injury  (or  commencing  death)  of  the 
ends  of  the  muscle,  it  would  be  expected  that  a  measurable  in- 
terval would  elapse  between,  for  instance,  the  tearing  or  cutting 
ofFof  the  end  of  a  muscle  and  the  appearance  of  the  muscle-currents 
in  their  full  intensity.  And  Hermann  has  attempted  to  show 
that  such  an  interval  does  exist.  For  this  purpose  he  makes  use 
of  the  fall-r he otome^  an  instrument  the  nature  of  which  may  be 
explained  here,  as  it  is  applicable  for  other  purposes  besides  the 
one  in  question. 

A  weight  (Fig.  30)  is  let  fall  from  a  height  of  about  four  feet 
in  a  course  indicated  by  the  arrow  and  the  dotted  lines.  In  fall- 
ing it  comes  in  contact  with  the  exposed  lower  tendinous  expan- 
sion of  the  gastrocnemius  muscle  il/ stretched  over  the  ebonite 
block  Q;  and  tearing  this  off  presumably  removes  to  a  greater  or 
less  extent  the  paralectronomic  region  of  Du  Bois.  The  muscle 
itself  at  two  points  ry  and  r/  is  connected  with  the  galvanometer 
G,  but  in  the  circuit  are  inserted  two  keys  x  and  ?/,  which  are  so 
arranged  that  the  weight  in  falling  catches  a  projecting  part  of 
X,  and  doses  the  galvanometer  circuit  (by  pushing  the  opposite 
end  of  .X  against  the  metal  z) ;  and  theiiopens  the  circuit  by  push- 
ing down  the  projecting  part  of  y. 

Thus  in  certain  definite  successive  times,  which  can  be  calcu- 
lated from  the  rate  with  which  the  weight  falls,  the  tendinous 
end  of  the  muscle  is  torn  otf,  the  galvanometer  circuit  is  closed 


'  Since  in  the  figure  the  positive  surfaces  of  the  molecules  look  to  the 
left-hand  side  of  the  page,  the  end  of  the  muscle,  of  which  they  may  be 
supposed  to  represent  parelectronomic  elements,  must  also  be  considered 
as  directed  to  the  left-hand  side  of  the  page. 


THE    PRE-EXrSTENCE    THEORY. 


183 


SO  that  any  muscle-current  present  passes  into  the  galvanometer, 
and  the  circuit  is  again  opened.  Immetliately  after  such  an  obser- 
vation has  been  made  and  the  deflection  noted,  the  keys  are  re- 
placed, the  weight  is  again  raised  and  again  let  fall,  and  the  deflec- 
tion again  noted  ;  during  this  second  fall  the  muscle,  though  still 
in  connection  with  the  galvanometer  wires,  is  not  aftected  by  the 
weight.  The  first  deflection  is  produced  by  the  current  which  is 
present  in  the  muscle  an  extremely  small  fraction  of  a  second  after 
the  stripping  oft'  the  tendon,  the  second  is  produced  by  the  cur- 


FiG.  30. 


A  Diagram  to  Illustrate  the  Fall-Rheotonie. 

The  explanation  of  most  of  the  figures  of  reference  is  given  in  the  text  s,  the 
space  con)prised  between  tlie  two  first  dotted  horizontal  lines,  serves  as  a  measure 
for  the  time  taken  in  stripping  off  the  tendon,  v  similarly  serves  to  measure  the 
time  claiising  bctwten  the  beginning  of  the  stripping  olf  the  tendon  and  the  closure 
of  the  galvanometer  circuit,  e  is'  a  reversing  key  connected  with  a  com|)ensator,  the 
use  of  wiiieh  is  not  referred  to  in  the  text,  fur  brevity's  sake,  a  the  hook  by  which 
the  gastrocnemius  is  fastened. 


rent  present  in  the  muscle  a  certain  number  of  seconds  later. 
The  currents  pass  through  the  galvanometer  for  the  same  time  i, 
viz.,  that  taken  up  by  the  weight  in  falling  from  x  to  y;  hence 
then,  if  one  deflection  is  greater  than  the  other,  the  current  pro- 
ducing it  is  the  stronger  of  the  two  currents.  In  all  cases,  ac- 
cording to  Hermann,  the  second  deflection  is  stronger  than  the 
first,  i.  e.,  in  the  first  case  the  muscle-current  has  not  reached  its 
full  strength,  or,  in  other  words,  the  current  develops  after  the 


134  THE    CONTRACTILE    TISSUES. 


iiiiurv,  and  is  not  present  in  full  force  a  measurable  time  after 
tlu'  removal  of  the  piireleetronomic  layer. 

The  ari:;ument  based  on  this  is  perhaps  not  very  conclusive, 
but  as  i'ar  as  it  u'oes  it  is  adverse  to  the  pre-existence  theory. 

It  miL!;ht  be  imai^ined  that  the  currents  which  may  be  observed 
when  the  electrodes  connected  with  a  ,i2;alvan()nieter  are  placed  in 
contact  witii  various  points  on  the  surface  of  a  living  body  (hu- 
man or  other)  indicate  the  pre-existence  of  muscle-currents  ; 
but  it  is  impossible  to  prove  that  these  currents  are  anythini:;  but 
cutaneous  currents  ;  and  indeed  in  lislu^s,  according  to  Plermann, 
where  cutaneous  currents  are  absent,  no  such  '■  body  "  currents 
can  be  witnessed. 

As  regards  the  pre-existence  of  a  current  in  nerves,  a  quite 
similar  contention  exists  ;  the  uninjured  nerve  in  the  body  is 
isoelectric  ;  the  proof  of  a  normal  current  here  is,  to  say  the 
least,  no  stronger  than  in  the  case  of  the  muscle. 

The  diagram,  Fig.  25,  p.  KS,  as  was  stated,  illustrates  the 
currents  observable  in  a  cylindrical  muscle  composed  of  parallel 
fibres,  and  with  tolerably  rectangular  terminations.  In  muscles 
not  having  this  form,  the  direction  of  the  currents  is  different. 
Thus  in  a  rhomb  cut  from  a  muscle  with  parallel  fibres  the  most 
positive  portions  instead  of  being  at  the  equator  of  the  longitu- 
dinal surface  are  nearer  the  obtuse  angles  ;  and  the  most  nega- 
tive points  instead  of  being  at  the  centres  of  the  transverse 
sections  are  nearer  the  acute  angles.  In  the  frog's  gastrocnemius, 
in  which  the  fibres  have  a  characteristic  arrangement,  the  direc- 
tions of  the  currents  differ  considerably  from  the  scheme  given 
for  regular  muscles.  The  currents  observed  agree  however  with 
those  theoretically  deduced  from  a  consideration  of  the  currents 
of  a  rhomb  of  muscle  and  of  the  arrangement  of  the  gastrocne- 
mius libres. 

The  Currents  of  Action.— It  was  stated  above,  pp.  94-103, 
that  Bernstein  had  shown  that  the  "negative  variation"  or 
current  of  action  passed  along  a  muscle  or  nerve  from  the  spot 
stimulated  in  the  form  of  a  wave  travelling  in  the  nerve  at  the 
same  rate  as  the  nervous  impulse,  in  the  muscle  at  the  same  rate 
as  the  contraction. 

The  principle  of  the  differential  rheotome  by  which  Bernstein 
was  enabled  to  establish  "this  fact,  is  as  follows  :  A  rod  r  (Fig. 
31)  is  made  to  rotate  with  a  definite  velocity  about  an  axis  a. 
At  one  end  of  the  rod  is  a  steel  pointer  jj  passing  obliquely  down- 
wards, at  the  opposite  end  are  two  other  steel  pointers  p\  p", 
also  passing  obliquely  dowuAvards  and  connected  with  one  an- 
other. As  the  rod  rotates  the  pointer  p  comes  in  contact  at  one 
part  of  its  course  with  a  stretched  wire  lo,  and  the  pointers  p\  p" 
at  one  part  of  their  course  dip  into  two  isolated  mercury  cups 
m,  m'.  The  effect  of  p  coming  in  contact  with  lo  is  to  stiniulate 
the  nerve  7i,  since  it  closes  the  primary  circuit  B  c  a  u\  and  thus 
causes  an  induced  current  in  the  secondary  coil  c'.     The  effect  of 


CURRENTS    OF    ACTION. 


135 


jy'i  p"  dipping  into  ?7i,  m'  is  to  send  into  the  galvanometer  any 
nerve-current  present,  since  it  closes  the  circuit  m  e  t'  G  m'. 
Any  current  of  rest  present  in  the  nerve  is  compensated  by 
an  arrangement  not  shown  in  the  figure,  so  that  in  the  uon- 
stimulated  nerve,  no  detlection  of  the  needle  follows  closure  of 
the  galvanometer  circuit.  It  will  be  seen  that  in  the  position  x 
of  the  wire  id  the  contact  of  p  with  tc^  and  of  p',  p"  with  m^  m' 
is  made  at  the  same  time,  that  is,  the  nerve  is  stimulated  and 
the  galvanometer  circuit  closed  at  the  same  instant.     Accord- 

FlG.  31. 


A  Diagram  to  Illustrate  Bernstein's  Differential  Rlieotoine. 

The  explanation  of  the  figures  of  reference  is  given  in  the  text.  The  letter  ;> 
referring  to  the  pointer  which  strikes  the  wire  w,  is  attached  to  the  rod  only  in  the 
position  X.    Similarly  the  references/)',  p"  are  only  given  in  the  position  y. 


ingly  if  the  rod  7-  be  made  to  rotate  rapidly,  with  to  in  the  posi- 
tion if,  the  nerve  will  be  stimulated,  and  the  galvanometer  circuit 
closed  at  the  same  instant,  a  number  of  times  in  succession  cor- 
responding' to  the  number  of  rotations.  When  this  is  done,  it  is 
found  that  no  detlection  of  the  galvanometer  needle  takes  place, 
though  if  the  galvanometer  circuit  be  kept  closed  by  connecting 
?}z,  tii  without  the  aid  of  jj',  ]/',  the  repeated  contact  of  j;  witli 


136  THE    CONTRACTILE    TISSUES. 


w  as  )•  rotates  docs  jiroduee  a  most  distinct  dcllcction.  Tlie  con- 
clusion from  tliis  is  that  the  electric  clianire  in  the  nerve,  started 
by  each  contact  of  7/  with  vr,  has  not  had  time  to  alfect  the  gal- 
vanonu'ter  before  y/,  j/'  have  left  m,  m\  but  has  passed  away 
before  j/,  7/' come  in  contact  with  m,  vi  at  the  next  rotation; 
in  other  words,  that  the  chanije  of  condition  which  leads  to  the 
current  is  not  estal)lished  instantaneously  in  the  nerve,  but  takes 
some  ai)])rccial)le  time  to  pass  from  the  stimulated  spot  to  the 
electrodes  connected  Avith  the  lu^alvanometcr. 

If  now  the  position  of  the  wire  ir  be  shifted  cm  the  arc  A  a 
short  distance  towards  //,  then  )>  will  touch  w  before  p\  }/'  come 
to  the  mercury  cups  ;  that  is,  there  will  be  a  short  measurable 
interval  between  the  stimulation  of  the  nerve  and  the  closure  of 
the  galvanometer  circuit.  Supjiose  then  a  successi(m  of  experi- 
ments are  made,  in  each  of  which  ?o  is  moved  an  increasintjj  dis- 
tance towards  //,•  it  will  be  found  that  at  a  certain  distance  froni 
X  a  slijiht  dellection  is  obtained,  and  as  the  distance  from  .t  in- 
creases the  deflection  increases,  .iijoes  on  increasing,  reacbes  a 
maximum,  then  diminishes,  and  finally,  when  say  w  is  at  ?/,  dis- 
appears again.  Now  in  all  cases  the  deflection  is  sucli  as  to  in- 
dicate a  current  from  ? '  througb  the  galvanometer  to  f\  that  is  as 
n-  is  moved  towards  //  the  first  effect  observed  is  that  f  becomes 
slightly  negative,  fiie  negativity  then  increases  up  to  a  maximum, 
and  afterwards  diminishes  until  once  more  ;  is  in  the  same  eleit- 
tric  condition  as  f'.  That  is  to  sa}',  wben  a  nerve  is  stimulated 
at  any  point,  a  part  of  the  nerve  at  some  distance  from  the  point 
stimulated  does  not  become  negative  until  a  certain  time,  depen- 
dent on  the  distance  from  the  point  stimulated,  has  elapsed  ;  fur- 
ther the  negativity  is  developed  gradually  with  a  certain  rapidity, 
and  having  reached  a  maximum  declines  and  disappears  ;  in 
other  words,  the  negativity  travels  along  the  nerve  from  the  spot 
stimulated  in  the  form  of  a  wave.  Obviously  by  noting  the  posi- 
tion of  ir  in  the  various  experiments  and  the  rapidity  of  rotation 
of?',  the  rapidity  with  which  this  condition  of  negativity  travels 
down  the  nerve  to  f  and  its  duration  there  can  be  calculated. 
It  was  in  this  Ava}'  that  Bernstein'  obtained  the  results  quoted  at 
the  beginning  of  this  section.  The  same  method  may  be  applied 
to  muscle  by  substituting  a  cnrarized  muscle  for  the  nerve. 

The  necessity  of  employing  a  series  of  rotations,  and  thus  of 
studying  the  etiects,  not  of  a  single  stimulus,  but  of  the  sum  of  a 
series,  arises  from  the  fact  that  though  th(;  current  of  action  de- 
veloped by  a  single  induction-shock  ma}'  be  shown  by  a  suitable 
galvanometer,  the  indications  are  not  sufficientl}^  delicate  to  mark 
the  very  beginning  and  the  very  end  of  the  current,  /.  e. ,  to  give 
the  exact  limits  of  the  wave. 

If  then,  as  seems  clearly  shown  by  the  above,  each  point  of  the 
nerve  or  muscle  becomes  negative  during  the  nervous  or  muscular 

^  Untersncli.  ii.  d.  Erregungsvorgang  im  Nerven-  und  Muskelsvsteme, 
1871. 


CURRENTS    OF    ACTION.  137 


impulse,  several  difficulties  present  themselves.  Thus  it  is  ob- 
vious that  a  nervous  (or  muscular)  impulse,  started  say  b}'  a 
single  induction-shock,  must  give  rise  at  an}'  point  not  to  one 
only  but  to  two  currents,  and  those  in  opposite  directions.  For 
as  the  wave  of  the  impulse  travels  down  the  fibre  (Fig.  32)  in  the 
direction  of  the  arrow,  a  becomes  negative  and  a  current  is  de- 
veloped v.'hich  passes  through  the  galvanometer^  from  h  to  a. 
Almost  immediately  afterwards  h  becomes  negative,  while  the 
negativity  of  a  diminishes  or  disappears.  We  should  accordingly 
expect  to  find  a  second  current  passing  through  the  galvanometer 
from  a  to  h.  And  practically  such  a  double  current  was  observed 
long  ago,^and  has  been  called  by  Du  Bois-lieymond  the  "•  double 
variation."  Indeed  the  prominence  at  times  of  the  one  or  the 
other  current  in  the  hands  of  various  experimenters  gave  rise  to 

Fig.  32. 


a  controversy  as  to  whether  the  variation  caused  by  a  single  in- 
duction-shock was  positive  or  negative  in  character. 

But  if  such  a  double  current  is  develoi)ed  between  any  two  points, 
it  is  obvious  that  when  a  muscle  or  nerve  is  tetanized  and  wave 
after  wave  of  impulse  and  therefore  of  negativity  passes  over  both 
points,  the  current  from  a  to  h  of  one  impulse  will  neutralize,  or, 
at  least,  tend  to  neutralize  the  current  from  h  to  a  of  the  succeed- 
ing impulse.  We  are  driven  to  suppose  that  the  current  which 
is  observed  during  tetanus  as  the  negative  variation  or  current  of 
action  from  h  to  a,  is  able  to  manifest  itself  because  at  each  im- 
pulse it  is  greater  than  the  current  from  a  to  h.  Such  a  difier- 
ence  between  the  opposing  currents  might  arise  either  from  the 
wave  of  impulse  diminishing  along  its  whole  progress,  or  from  its 
diminishing  suddenly  at  the  end  of  the  fibre,  or  from  both  causes 
combined.  If  the  negativity  assumed  by  h  when  the  impulse 
reaches  it  is  less  than  the  negativity  assumed  by  a  when  th.e  im- 
pulse reaches  it,  the  current  from  a  to  b  will  be  less  than  that 
from  h  to  a ;  and  this  will  be  true  whatever  the  position  of  a  and 
h  on  the  fibre. 

Bernstein  found  that  in  muscle  the  "  negative  variation  "  di- 
minished in  its  course.     Du  Bois-Reymond  stated  that  this  was 

^   In  all  the  account  which  follows  the  direction  of  the  current  spoken 
of  U  to  be  suppt>sed  to  be  tliat  of  the  current  through  the  (jalvanometer. 
•^  Mayer,  Archiv  f.  Anat.  u.  Phys.,  1868,  j).  Go". 


138  THE    CONTRACTILE    TISSUES. 


true  of  exhausted  muscle,  but  was  not  true  of  uninjured  muscle 
f»)r  a  short  time  after  removal  from  the  body.  Hermann  finds 
that  in  muscle  removed  from  the  body  and  thus  deprived  of  its 
blood  circulation  there  is  always  a  gradual  diminution  of  the 
current  of  action  as  it  travels  down  the  li])res,  whether  the  mus- 
cle be  urarized  and  stimulated  directly  or  not  urarized  and  stim- 
ulated indirectly  by  means  of  its  nerve.  In  the  latter  case  two 
currents  of  action  proceed  from  ajiproximately  the  middle  of  the 
muscle  (ihe  region  of  the  end-])lates)  towards  the  ends,  dimin- 
ishing as  they  go.  He  found  that  the  diminution  was  greater  as 
the  muscle  became  more  exhausted,  in  this  confirming  Du  Bois- 
Reymond.  Hermann  brings  forward  also  some  experiments  to 
show  that  the  diminution  is  equally  distributed  throughout  the 
course  of  the  current,  so  that  the  diminution  is  equal  for  equal 
distances  of  muscle  traversed. 

Now  in  muscles  in  which  by  cutting  off  one  end  currents  of 
rest  have  become  conspicuous,  Du  Bois-lleymond  has  shown  that 
the  current  of  action  obtained  by  tetanizing  the  muscle  is  greater 
than  that  obtained  by  similarly  tetanizing  an  uninjured  muscle, 
so  that  in  the  former  case  eitlier  the  current  of  action  is  in  itself 
greater  or  the  negativity  diminishes  morci  rapidly  along  the  whole 
or  in  some  part  of  the  course  of  the  fibre  (i.  e.,  the  difference  be- 
tween the  currents  h  to  a  and  a  to  b  becomes  more  marked  in 
favor  of  that  from  h  to  a).  By  comparing  with  the  help  of  the 
fall-rheotome  the  amounts  of  deflection  of  the  galvanometer  in 
the  two  cases  when  single  induction-shocks  are  sent  into  the 
muscle,  Hermann  concludes  that  the  wave  is  not  absolutely  less 
in  the  uninjured  muscle,  so  that  the  greater  deflection  obtained 
in  tetanizing  a  muscle  with  an  artificial  cross-section  nuistbedue 
to  the  current  from  a  to  b  being  less  than  is  the  case  in  the  unin- 
jured nmscle.  This  may  in  part  be  due  to  a  greater  diminution 
of  the  stimulus  wave  as  it  travels,  but  is,  as  we  shall  see,  proba- 
bly in  large  part  due  to  a  rajiid  diminution  or  indeed  extinction 
of  the  wave  when  it  reaches  6. 

Hermann,  with  the  aid  of  the  differential  and  fall-rheotome, 
finds  that  in  all  uninjured  muscle,  whether  stimulated  directly 
or  indirectly,  the  two  currents  from  b  to  a  and  from  a  to  b  may 
be  observed  as  described  above.  This  first  he  calls  ad-terminal^^ 
and  the  second  ab-terminal :  the  two  being  named  phasic  cur- 
rents. The  former  he  finds  always  greater  than  the  latter.  In 
a  muscle  with  an  artificial  cross-section  he  finds  that  as  in  an 
uninjured  muscle  two  currents  are  developed  between  two  points, 
provided  one  be  not  at  the  cross-section,  as  from  b'  to  a'  and 
from  a'  to  b'  (Fig.  32),  but  between  two  points,  one  of  which  is 
at  the  section,  as  a  and  &,  only  one  current  is  observable,  viz., 
that  from  b  to  a,  i.  e.,  the  wave  disappears  at  b ;  the  end  of  the 
muscle,  for  some  reason  or  other,  does  not  become  more  negative. 

'  Since  the  direction  of  the  current  in  the  muscle  completing  the  cir- 
cuit would  be  towards  the  end  of  the  fil)re. 


CURRENTS    OF    ACTION.  139 


From  these  experiments  Hermann  concludes  that  in  uninjured 
muscle,  the  current  of  action  observed  by  the  ordinary  method 
without  a  rheotome  is  due  to  the  diminution  of  the  stimulus 
wave  as  it  travels,  but  that  the  current  of  action  similarly  ob- 
served when  currents  of  rest  are  present  has  an  additional  factor, 
viz.,  the  absence  of  any  power  of  the  wave  to  affect  the  end  of 
the  tibres. 

Hermann  further  states  that  when  two  moistened  threads  are 
passed  rouud  tlie  forearm  of  a  man,  the  one  about  the  middle, 
the  other  at  the  wrist,  and  connected  by  the  usual  electrodes 
with  the  galvanometer,  tetanizing  the  muscles  by  stimulating 
the  nerves  in  the  upper  arm  causes  no  deflection  of  the  galvanom- 
eter ;  no  action  currents  are  in  this  case  perceptible. 

(This  is  in  contradiction  to  the  result  of  the  classical  experi- 
ment of  Du  Bois-Reymond,'  in  which  the  index  lingers  of  the  two 
hands  being  dipped  into  vessels  containing  salt  solutitm  and 
connected  with  a  galvanometer,  a  deflection  of  the  needle  takes 
place  Avhenever  the  muscles  of  the  one  or  the  other  arm  are 
thrown  into  contraction  by  voluntar}-  effort;  the  direction  of  the 
deflection  indicates  the  development  of  an  ascending  current  in 
the  active  arm,  and  the  ascending  current  thus  produced  is  re- 
garded as  the  resultant  of  the  ''negative  variations"  or  cur- 
rents of  action  of  the  various  muscles  thrown  into  contraction. 
But  this  experiment,  tliDUgh  long  looked  upon  as  a  satisfactory 
proof  of  a  "■  current  of  action  "  or  •■•  negative  variation, -  is  re- 
garded b}^  Hermann  as  valueless  in  this  respect,  inasnuich  as 
the  current  observed  is  accorciing  to  him  simply  a  cutaneous  cur- 
rent. ) 

On  the  other  hand,  if  the  rheotome  be  used  so  that  the  ad-  and 
ab-terminal  waves  present  can  be  separated  and  recognized,  the 
two  waves  are  found  to  be  present  but  to  be  of  equal  strength  ; 
thus  in  the  bod}'  in  an  untired  muscle  with  normal  circulation 
the  wave  does  not  diminish  in  its  course,  and  hence  the  two 
waves,  the  ad-terminal  and  the  ab-terminal,  compensate  one 
another  and  cannot  be  detected  in  the  ordinary  manner  of  look- 
ing for  currents  of  action  in  tetanu?.  The  rapidity  of  transmis- 
sion of  the  wave  in  the  above  experiments  was  from  10  to  13 
meters  per  second. 

In  the  case  of  nerves,  since  the  rapidity  of  the  nervous  impulse 
is  much  greater  than  the  rapidity  of  the  stimulus  wave  of  mus- 
cle, the  separation  of  the  ad-  and  ab-terminal  current  is  natu- 
rally more  dithcult.  But  Hermann  by  using  packets  of  the 
sciatic  nerves  (frog's),  and  cooling  them  down  to  0^  in  order  to 
lessen  the  rapidity  of  the  nervous  impulses,  has  obtained  results 
analogous  to  those  just  described  in  reference  to  muscle. 

Since  the  part  of  the  muscle  which  is  at  any  moment  stimu- 
lated becomes  negative,  if  the  whole  of  the  uninjured  muscle 
from  end  to  end  were  stimulated  equally  at  the  same  time,  every 

1800. 


140  TIIK    CONTRACTILE    TISSUES. 


piirt  would  become  equally  negative,  and  no  current  would  occur. 
Hermann  finds  that  under  such  circumstances  no  current  does 
occur.  This  experiment  perhaps  requires  confirmation,  as  it  is 
not  certain  that  it  is  possible  by  the  method  given  to  equally 
stimulate  all  ]>arts  of  the  nniscle. 

To  recapitulate.  Accordiui:  to  the  views  of  Hermann  and  his 
followers,  the  livinu'  untouched  nuiscle  is  isoelectric  and  the  typi- 
cal currents  of  rest  are  developed  in  consequence  of  the  ends  of 
the  muscle  dying  and  therefore  becoming  negative.  To  the  ex- 
perimental evidence  quoted  on  p.  90,  we  ma}' add  that.,  according 
to  Hermann,  parts  of  other  tissues  besides  muscle  and  nerve  be- 
come on  dying  negative  relatively  to  living  parts  of  the  same 
tissue,  and  that  according  to  Engelmann,'  altliough  the  section 
of  a  skeletal  muscle  removed  from  the  body,  unlike  the  section  of 
cardiac  muscle,  remains  negative  for  an  indefinite  time,  the  neg- 
ativity which  appears  at  the  cross-section  of  a  muscle  divided 
subcutaneously  disappears  after  awhile  in  consequenceof  the  cut 
surfaces  l)eing  restored  to  a  living  condition  by  the  help  of  the 
blood-stream.  It  may  be  urged  as  a  difficult}?^  against  Hermann's 
view,  that  if^in  a  muscle  it  is  only  the  negativity  of  the  cut  and 
dying  portion  which  gives  rise  to  the  currents  of  rest,  we  should 
not  expect  the  current  from  the  equator  to  the  cross-section  to 
be  greater  than  one  from  a  point  nearer  the  cross-section,  seeing 
that  the  resistance  is  greater  in  the  former  case. 

According  to  the  same  school  the  current  of  action  is  due  to 
the  sulistanee  of  the  muscle,  which  is  at  any  moment  the  sub- 
ject of  an  impulse  wave  becoming  at  that  time  negative  to- 
wards the  rest  of  the  muscle  ;  hence,  as  the  wave  proceeds  along 
the  librns,  ad-terminal  and  ab-terminal  currents  of  necessity  make 
their  appearance  as  successive  points  of  the  muscle  or  nerve  sub- 
stance reach  their  maximum  of  negativity.  In  the  tetanus  of  an 
uninjured,  unexhausted  muscle  the  ad-terminal  and  ab-terniinal 
currents  neutralize  each  other,  and  no  total  current  can  be  mani- 
fested through  the  galvanometer.  In  exhausted,  but  otherwise 
uninjured  muscle,  the  negativity  of  the  impulse  wave  diminishes 
as  the  wave  proceeds.  Plence,  the  ab-terminal  current  is  weaker 
than  the  ad-terminal,  and  the  excess  of  the  latter  makes  itself 
manifest  as  the  so-called  negative  variation.  In  a  muscle  with 
an  artilicial  cross-section  the  ad-terminal  current  and  so  the  nega- 
tive variation  is  still  more  conspicuous  on  account  of  the  end  of 
the  fibre  not  being  affected  by  the  wave  at  all,  and  the  ab-ter- 
minal current  being  here,  therefore,  whollj'  absent. 

Du  Bois-Reymond,  on  the  oilier  hand,  and  those  with  him, 
regard  the  currents  of  rest  as  due  to  the  electro-motive  molecules, 
and  explain  the  absence  of  currents  in  the  uninjured  muscle  by 
the  presence  of  the  parelectronomic  region  or  layer.  They  regard 
the  negative  variation  as  due  to  an  absolute  diminution  in  the 
energy  of  the  molecules.     In  the  case  of  uninjured  muscles  they 

'  Pfluger's  Archiv,  xv  (1877),  p.  328. 


CURRENTS    OF    ACTION.  141 


suppose  that  while  the  energy,  both  of  the  orclinar}'-  molecules 
constituting  the  chief  substance  of  the  muscle,  and  of  the  mole- 
cules constitutinoj  the  parelectronomic  region,  and  giving  a  cur- 
rent opposed  in  direction  to  the  other,  is  diminished,  the  diminu- 
tion of  the  latter  is  less  than  that  of  the  former,  and  hence  a 
negative  variation  can  make  its  apiiearance  in  a  muscle  showing 
no  currents  of  rest.  In  a  muscle  with  an  artiiicial  cross-section,- 
or  vvitii  the  parelectronomic  region  otherwise  removed,  the  nega- 
tive variation  of  the  natural  electric  molecules  occurs  without  any 
opposition  of  the  molecules  of  the  parelectronomic  region,  and  is, 
consequently,  greater  than  in  the  uninjured  muscle.  They  further 
interpret  the  double  current  (ab-terminal  and  ad-termiiialj  seen 
in  the  gastrocnemius  muscle  with  a  single  induction-shock,  as 
due  to  a  difference  of  time  in  the  development  of  the  negative 
variation  in  the  parelectronomic  regions  of  the  upper  and  of  the 
lower  ends  of  the  muscle. 

Du  Bois-Eeymond  found  that,  in  tetanizing  a  muscle,  the  cur- 
rent of  rest  only  acquired  its  normal  strength  after  some  inter- 
val ;  the  negative  variation  did  not  at  once  disap})ear,  there  was 
an  "after-action."  In  uninjured  muscle  this  "after-action"  he 
found  to  be  considerable,  amounting  to  as  much  as  one-half  or 
two-thirds  of  the  total  negative  variation  ;  in  muscles  with  artifi- 
cial transverse  sections  it  was  much  less,  viz.,  about  one-tenth. 
He  explains  the  difference  by  supposing  that  tlie  removal  of  the 
end  of  the  muscle  does  away  with  one  factor  of  the  after-action, 
for  he  considers  that  there  are  two  kinds  of  after-action  ;  one,  the 
inner  after  action,  affecting  the  whole  of  the  muscle  substance  ; 
the  other,  or  terminal  after-action,  concerning  the  ends  of  the 
muscle  fibres  only.  The  fjrmer  he  believes  to  be  due  to  the  for- 
mation of  lactic  acid  during  contraction,  the  electromotive  force 
of  the  molecules  throughout  the  muscle  substance  being  thereby 
diminished.  The  latter,  on  the  other  hand,  he  considers  to  be 
generated  by  the  several  contraction -waves  as  they  reach  the  ends 
of  the  fibres  changing  some  of  the  peripolar  molecules  into  a 
bipolar  condition,  thereby  temporaril}-  increasing  the  parelectro- 
nomic current.  In  a  muscle  with  an  artificial  transverse  section, 
in  which  no  parelectronomic  current  is  present,  the  tendency  of 
the  contraction-waves  to  establish  such  a  current  by  the  f  )rma- 
tion  of  bipolar  molecules  at  the  ends  of  the  fibres,  is  prevented 
by  the  progressive  death  of  tiie  elements.  Du  Bois-Reymond 
further  thinks  that  the  normal  presence  of  a  parelectronomic  re- 
gion in  an  uninjiu-ed  muscle  within  the  body  is  in  realit}'  a  per- 
manent terminal  after-action,  i.  f. ,  contraction-waves  arriv  ng  at 
the  ends  of  the  muscular  fibres  are  continually  tending  o  convert 
the  peripolar  into  bipolar  molecules.  Hermann  attributes  the 
after-action  to  the  muscle  plasma  not  being  able  under  the  cir- 
cumstances to  return  at  once  to  a  condition  of  full  nutrition,  i.  e., 
to  its  normal  positive  state. 

It  is,  we  venture  to  think,  obvious  that  further  researches  are 
needed  before  either  the  one  view  or  the  other  can  be  regarded  as 
established  beyond  dispute. 


142 


THE    CONTRACTILE    TISSUES. 


Electrotonic  Currpnts. — During  the  passap;e  of  a  constant 
current  throuixh  a  nerve,  variations  in  the  electric  currents  of  the 
nerve,  analogous  in  some  respects  to  the  variations  of  the  irri- 


1^ 


< 


Diagram  Illustrating  Electrotonic  Currents. 


Pi 


le  polarizing  l)attery,  with  k  a  key,  p  the  anode,  and  //  I  lie  kathode.     At  the  left 

end  of  ihe  piece  of  nerve  the  natural  current  flow.s  through  the  galvanometer 

G  from  g  to  7',  in  the  direction  of  tlie  arrows;  its  direction,  therefore,  is  the 

same  as  that  of  the  ))(>!arizii)g  current;  consequently  it  appi-ars  increased,  as 

indicated  hy  the  sign  +•    'i  he  current  at  tl)e  other  einl  of  tiie  piece  of  nerve, 

from  h  to  /*',  through  the  galvanometer  //,  flows  in  a  contrary  direction  to  the 

polarizing  current;  it  consequently  appears  to  be  diminished,  as  indicated  hy 

the  sign  — . 

N.  R. — For  simplicity's  sake,  the  polarizing  current  is  here  supposed  to  he  thrown 

in  at  the  middle  of  a  piece  of  nerve,  and  the  galvanometer  placed  at  the  two  ends. 

Of  course  it,will  be  understood  that  the  former  lyay  be  thrown  in  anywhere,  and  the 

latter  connected  with  any  two  pairs  of  points  which  will  give  currents. 

tahility  of  the  nerve,  may  be  witnessed.  Thus  if  a  constant  cur- 
rent, suppHed  by  the  battery  P  (Fis;.  33),  be  applied  to  a  piece  of 
nerve  by  means" of  two  non-i)olarizable  electrodes,  p,  p',  the  cur- 


ELECTROTONIC    CURRENTS.  143 


rents  obtainable  from  various  points  of  the  nerve  will  be  different 
diu'ing  the  passage  of  the  polarizing  current  from  those  which 
were  manifest  before  or  after  the  current  was  applied  ;  and,  more- 
over, the  changes  in  the  nerve-currents  produced  by  the  polariz- 
ing current  will  not  be  the  same  in  the  neighborhood  of  the 
anl)de  {jj)  as  those  in  the  neighborhood  of  the  kathode  {-p').  Thus 
let  G  and  H  be  two  galvanometers  so  connected  with  the  two 
ends  of  the  nerve  as  to  obtain  good  and  clear  evidence  of  the 
natural  nerve-currents.  Before  the  polarizing  current  is  thrown 
into  the  nerve  the  needle  of  H  will  occupy  a  position  indicating 
the  passage  of  a  current  of  certain  intensity  from  h  to  h'  through 
the  galvanometer  (from  the  positive  longitudinal  surftice  to  the 
negative  cut  end  of  the  nerve),  the  circuit  being  completed  by  a 
current  in  the  nerve  from  h'  to  /^  i.  e.,  the  current  will  flow  in  the 
direction  of  the  arrow.  tSimilarly  the  needle  of  G  will,  by  its 
deflection,  indicate  the  existence  of  a  current  flowing  from  g  to  g' 
through  the  galvanometer,  and  from  g'  to  g  through  the  nerve,  in 
the  direction  of  the  arrow. 

At  the  instant  that  the  polarizing  current  is  thrown  into  the 
nerve  at  pp\  the  currents  at  gg  ,  hh'  will  suffer  a  negative  varia- 
tion corresponding  to  the  nervous  impulse,  which,  at  the  making 
of  the  polarizing"  current,  passes  in  both  directions  along  the 
nerve,  and  may  cause  a  contraction  in  the  attached  muscle.  The 
negative  variation  is,  as  we  have  seen  :p.  104),  of  extremely  short 
duration,  it  is  over  and  gone  in  a  small  fraction  of  a  second.  It 
therefore  must  not  be  confounded  with  a  permanent  effect,  wliich, 
in  the  case  we  are  dealing  with,  is  observed  in  both  galvanom- 
eters. This  effect,  which  is  dependent  on  the  direction  of  the 
polarizing  current,  is  as  follows  :  Supposing  that  the  polarizing 
current  is  flowing  in  the  direction  of  the  arrow  in  the  figure;  that 
is,  passes  in  the  nerve  from  the  positive  electrode,  or  anode  p,  to 
the  negative  electrode  or  kathode  p\  it  is  found  that  the  current 
throug^h  the  galvanometer  G  is  increased,  Avhile  that  through  H 
is  diminished.  AVe  may  explain  this  result  by  saying  that  the 
polarizing  current  has  developed  in  the  nerve  outside  the  elec- 
trodes a  new  current,  the  "  electrotonic  "  current,  having  the 
same  direction  as  itself,  which  adds  to,  or  takes  away  from,  the 
natural  nerve-current,  according  as  it  is  flowing  in  the  same  or 
in  an  opposite  direction. 

The  strength  of  the  electrotonic  current  is  dependent  on  the 
strength  of  the  polarizing  current,  and  on  the  length  of  the  in- 
trapotar  region  which  is  exposed  to  the  polarizing  current.  "When 
a  strong  polarizing  current  is  used,  the  electromotive  force  of  the 
electrotonic  current  may  be  mu(4i  greater  than  that  of  the  natural 
nerve-current.  The  existence  of  an  electrotonic  current  in  the 
intrapolar  regions  between  the  polarizing  electrodes  has  been 
much  disputed,  some  observers  maintaining  that  it  is  in  reality 
absent  from  this  region,  and  confined  entirely  to  the  extrapolar 
districts,  while  others  regard  it  as  existing"  in  the  intrapolar 
region  as  well.     Ah  agree'that  it  spreads,  with  a  diminution  in 


144  THE    CONTRACTILE    TISSUES. 


intensity,  for  some  distance  along  tlie  extrapolar  districts  in  l)oth 
directions. 

When  the  polarizing  current  is  broken  there  is  a  rebound  in 
the  opposite  direction,  the  natural  current  previously  diminished 
or  increased  being  for  a  brief  period  increased  or  diminished. 

The  strenuth  of  the  electrotonic  current  varies  with  tiie  irrita- 
bility, or  vital  condition  of  the  nerv<%  being  greater  with  the 
more  irritable  nerve  ;  and  a  dead  nerve  will  not  manifest  electro- 
tonic  currents.  Moreover,  tbe  propagation  of  the  current  is 
stopped  ])y  a  ligature,  or  by  crushing  the  nerve. 

J^astly,  the  electrotonic  current,  like  the  natural  current,  suffers 
a  negative  variation  during  the  passage  of  a  nervous  impulse.' 

The  application  of  the  constant  current  then  throws  a  nerve, 
during  its  passage,  into  a  peculiar  condition  characterized  by  the 
appearance  of  a  new  (electrotonic)  current.  This  we  may  speak 
of  as  a  phi/sical  electrotonus  analogous  to  that  ]}lnjsioJo(/ical  elec- 
trotonus  which  is  made  known  by  variations  in  irritability.  And 
the  one  set  of  phenomena  are  in  some  respects  so  similar  to  the 
other  that  it  seems  difficult  not  to  suppose  that  they  are  funda- 
mentally connected.  Indeed,  Du  IJois-lieymond,  struck  by  the 
dilferences  observable  between  the  effects  at  the  kathode  and 
those  at  the  anode,  irrespective  of  the  natural  currents,  has  been 
led  to  complete  the  analogy  of  the  physical  with  the  physiological 
electrotonus  by  speaking  of  a  katelectrotonlc  current  and  an  anelec- 
trotonic  current.  The  katelectrotonlc  current,  according  to  him, 
like  the  katelectrotonlc  increase  of  irritability,  rises  very  rapidly 
(almost  immediately)  to  a  maxinunn  and  then  speedily  decliaes. 
The  anelectrotonic  current,  like  the  anelectrotonic  decrease  of 
irritability,  rises  slowly  to  a  maximum  and  slowly  declines.  And 
generally  the  katelectrotonlc  current  is  less  than  the  anelectro- 
tonic. There  are  difficulties  in  the  way  of  estimating  the  force 
exactly,  but  Du  Bois-Reymond-  gives  as  an  instance  an  electro- 
motive force  of  .5  IJaniell  for  the  anelectrotonic,  and  .05  Daniell 
for  the  katelectrotonlc  current. 

Great  ditlicult}'  has  been  experienced  in  obtaining  evidence  of 
the  existence  in  muscles  of  electrotonic  currents  similar  to  those 
observed  in  nerves.  Hermann^  has,  however,  succeeded  in  satis- 
fying himself  of  their  presence. 

The  two  schools  of  whose  views  we  have  so  often  spoken  natu- 
rally offer  totally  different  interpretations  of  the  nature  and  mode 
of  origin  of  the  electrotonic  current. 

Du  BoisReymond  and  those  with  him  explain  the  phenomena 
by  supposing  that  under  the  action  of  the  constant  current,  one- 
half  of  each  electromotive  molecule  is  (partially  or  completely) 
reversed  so  that  every  half  molecule  has  its  positive  portion  di- 
rected to  one  end,  and  its  negative  portion  directed  to  the  other 

^  Bernstein,  Archiv  An=it.  Phys.,  18G6,  p.  590. 

2  Gesaml.  Abhandl.,  ii,  260. 

^  Die  Ergebnisse  neuerer  Unters.  a.  d.  Gebiet  d.  thierisch.  Elect.,  1878. 


ELECTROTONIC    CURRENTS.  145 


end  of  the  nerve.  By  the  action  of  the  constant  current,  in  fact, 
eacli  niokricule  from  beinu'  peripolar  (Fii^.  -S)  lias  become  bipolar 
(Fig.  29),  and  the  currents  disch;iroed  by  the  molecule  into  its 
surrounding  medium  have  all  the  same  direction.  The  half  mole- 
cules thus  (more  or  less)  reversed  by  the  polarizing  current  are 
those  the  currents  issuing  from  which  were  previously  opposed  in 
direction  to  itself;  hence  after  the  conversion  from  the  peripolar 
to  the  bipolar  condition,  the  currents  discharged  by  the  several 
molecules  have  the  same  direction  as  the  polarizing  current.  In 
other  words,  an  electrotonic  current  is  developed.  If  further,  we 
suppose  that  each  (double)  molecule  is  capable  of  acting  on  its 
fellows  in  such  a  way  that  when,  as  in  the  normal  condition,  it 
is  peripolar  it  helps  to  maintain  the  peripolar  condition  of  its 
neighbors  ;  but  when  it  becomes  bipolar,  tends  to  render  them 
bipolar  too,  the  intiuence  dindnishing  at  a  distance,  an  explana- 
tion is  furnished  of  the  spreading  of  the  electrotonic  current 
along  both  extra  polar  regions. 

Hermann  and  his  followers,  rejecting  the  theor}'  of  electromotive 
molecules,  regard  the  electrotonic  current  as  due  to  the  escape  of 
the  polarizing  current  along  the  nerve  under  certain  peculiar  con- 
ditions. Matteucci'  long  ago  showed  that  phenomena  very  simi- 
lar to  those  of  electrotonus  might  be  produced  b}-  surrounding  a 
metal  core  Avith  a  moist  sheath  and  applying  a  constant  current 
to  the  sheath.  Several  writers  have  since  insisted  on  similar  ex- 
periments as  demonstrating  that  the  phenomena  of  electrotonus 
are  not  of  a  physiological  nature,  but  they  were  always  met  with 
the  valid  argument  that  the  electrotonic  current  varied  with  the 
irritability  of  the  nerve,  and  was  stopped  by  a  ligature  or  by  any- 
thing which  destroyed  the  vital  continuity  of  the  nerve.  The 
currents,  simulating  electrotonic  currents,  which  Matteucci  ob- 
served appear  to  have  been  due  to  the  current  escaping  in  a  lon- 
gitudinal direction,  in  consequence  of  the  resistance  offered  by  a 
polarization  taking  place  between  the  core  and  its  sheath.  When 
no  such  polarization  occurs,  when  for  instance  the  core  is  amal- 
gamated zinc  and  the  sheath  a  layer  of  saturated  zinc  sulphate 
solution,  the  escape  of  the  current  in  a  longitudinal  direction  is 
slight.  Under  the  influence  of  polarization  set  up  between  the 
core  and  the  sheath  the  escape  of  the  current  in  longitudinal 
loops  along  the  sheath  becomes  more  and  more  marked,  and  the 
galvanometer  indicates  in  the  extrapolar  regions  extending  to 
some  distance  the  existence  of  currents,  having  the  same  direc- 
tion as  the  constant  current  which  is  being  applied.  The  devel- 
opment of  these  cunents  is  further  dependent  on  an  absolute 
continuity  (mere  contact  of  parts  is  insutiicient)  of  the  core  and 
the  sheath  respectively.  And  Hermann  contends  that  though 
we  may  not  be  justilied  in  assuming  between  the  sarcolemma  of 
a  muscle  and  the  muscle  substance,  or  between  the  primitive 
sheath  of  a  nerve  fibre  and  its  contents,  such  a  difterence  of  con- 

1  Compt.  Eend.,  Ivi  (1863),  p.  7G0,  and  subsequent  papers. 


1-1^)  THE    CONTRACTILE    TISSUES. 


duct  hit}'  as  exists  between  the  core  and  sheath  in  Matteufci's 
experiment,  yet  the  fact  of  the  electrical  resistance  of  liv  n.iz; 
muscle  and  nerve  beinii:  «<>  much  <ijreater  in  a  transverse  than  in  a 
loniiitudinal  direction,  is  due  to  an  inner  j)olarization  takiuij;  i)lace 
between  the  muscle  or  nerve  substance  of  a  muscle  or  nerve  fibre 
and  !ts  resjiective  sheath,  and  hence  the  comparison  of  these 
structures  with  ^Nlatteucci's  experiment  is  valid.  Moreover  this 
inner  polarization  is  (in  the  muscle  wholly,  and  in  the  nerve  in 
larue  jiart)  dependent  on  the  vital  condition  of  the  tissue.  Con- 
sequent! v  ^latteucci's  ex[)eriment  is  really  an  illustration  of  what 
takes  place  in  a  livino;  nerve  (or  nniscle) ;  the  electrotonic  current 
is  simply  an  escape  of  the  polarizing  current.  It  is  absent  or  in- 
si,i2;niticant  in  a  dead  nerve,  because  the  inner  polarization,  which 
determines  the  longitudinal  escape  of  the  current,  is  a  function 
of  the  living  state  ;  and  it  is  stopped  by  ligature  or  crushing,  be- 
cause the  nervous  substance  of  the  fibres  is  thereby  converted 
into  a  dead  and  indifferent  substance,  and  the  functional  conti- 
nuity of  the  nervous  core  thereby  broken. 

lie  further  oflers  an  explanation  why  the  escape  of  the  current 
under  these  circumstances  leads  to  the  physiological  phenomena 
of  katelectrotonus  and  anelectrbtonus,  but  on  this  point  we  must 
refer  the  readers  to  the  oriirinal  Memoirs.  ^ 


The  Energy  of  Mui>cle  and  Nerve,  and  the  Nature  of  the 
Chemical  Changes. 

The  actual  amount  of  energy  developed  by  a  most  powerful 
nervous  impulse  is  exceedingly  slight,  and  hence  chemical  changes, 
insignificant  in  amount,  may  be  the  cause  of  all  the  phenomena, 
and  yet  remain  too  slight  to  be  readily  recognized.  The  muscu- 
lar contraction  itself  is,  as  we  have  seen  (p.  85),  essentially  a 
translocation  of  molecules.     AVhatever  be  the  exact  way  in  which 

'  The  views  of  Du  Bois-Reymond  will  be  found  at  length  in  his  ear- 
lier publications,  Untersuch.  ii.  thierische  Electriciliit,  1848-60,  and  in 
the  later  articles  jjublished  in  Ge-;amrnelte  Abliandlungen  z.  allgemeinen 
]Muskel-  und  Xerven-Pliysik,  1875-77.  The  views  of  Hermann  will  be 
found  in  his  Untersucli.  zur  Physiol,  d.  JMuskeln  u.  Xerven,  1867-68, 
and  in  many  subsequent  papers  in  Pfliiger's  Archiv,  viz.,  vol.  iii  (1870), 
p.  15,  iv  (1871),  p.  149,  Electromotorische  Erscheinungen ;  v  (1872),  p. 
223,  vi  (1872),  p.  312,  Wirkung  galvanischer  Strome  ;  vi  (1872),  p.  560, 
Galvanische  Yerhalten  wiihrend  der  Erregnng;  vii  (1873),  p.  323,  Ge- 
setz  der  Erregungsleitnng ;  viii  (1874),  p.  258,  Electrotonus  ;  x  (1875), 
p.  215,  Polarisation  und  Erregnng;  xii  (1876),  p.  151,  Querstand  widi- 
rend  Erregung;  xv  (1877),  p.  233,  Fall-Rheotom ;  xvi  (1878),  p.  191, 
p.  410,  Actionsstroni  der  Muskeln  ;  xix  (1878),  p.  574,  Actionsstrome  des 
Nerven.  A  resume  of  Hermann's  views  is  given  by  himself  in  a  small 
pamphlet,  entitled  Die  Ergebnisse  neuerer  Unters.  a.  d.  Gebiet  d.  thier- 
isch.  Eleetricitat,  1878,  and  by  Dr.  Burdon-Sandei'son  in  Journ.  Physiol., 
i  (1878),  p.  196. 


THE  ENERGY  OF  A  MUSCULAR  CONTRACTION.   147 


this  translocation  is  eftectecl,it  is  fundamentally  the  result  of  a 
chemical  chansze,  of  what  we  have  already  seen  to  be  an  explo- 
sive decomposition  of  certain  parts  of  the  muscle-substance.  The 
energ}'  which  is  expended  in  the  mechanical  work  done  by  the 
muscle  has  its  source  in  the  latent  energy  of  the  muscle-substance 
set  free  by  that  explosion.  Concerning  the  nature  of  that  explo- 
sion we  only  know  at  present  that  it  results  in  the  production  of 
carbonic  and  lactic  acids,  and  that  heat^  is  set  free  as  well  as  the 
specific  muscular  energy.  There  is  a  general  parallelism  between 
the  amount  of  decomposition  (the  quantity  of  carbonic  (and  lactic) 
acids  produced)  and  the  amount  of  energy  set  free.  The  greater 
the  development  of  carbonic  acid  the  larger  is  the  contraction, 
and  the  higher  the  temperature. 

It  has  not  been  possil3le  hitherto  to  draw  up  a  complete  equa- 
tion between  the  latent  energy  of  the  material  and  the  two  forms 
of  actual  energy  set  free.  By  an  approximate  calculation  Helm- 
holtz  has  arrived  at  the  conclusion  that  in  the  human  body  one- 
lifth  of  the  energy  of  the  material  goes  out  as  mechanical  work, 
thus  contrasting  fa vorabh^  with  the  steam-engine,  in  which  it 
hardly  ever  amounts  to  more  than  one-tenth.  Fick-  has  come  to 
the  conclusion  that  the  proportion  of  energy  given  out  as  heat  to 
that  taking  on  the  form  of  work,  varies  according  to  the  resist- 
ance whicii  the  muscle  has  to  overcome  ;  the  greater  the  resist- 
ance the  larger  is  the  portion  of  the  total  energy  set  free  which 
goes  to  the  work.  The  muscle,  in  fact,  when  working  against 
resistance  does  its  work  with  increased  economy.  Under  the 
most  favoral^le  conditions,  e.  gf.,  when  contracting  against  great 
resistance,  the  energy  of  the  work  may  (in  the  case  of  frogs' 
muscles  deprived  of'blood-supph')  amount  to  one-fourth  that  of 
the  heat  given  out ;  but  Fick  believes  that  in  ordinar}^  circum- 
stances the  proportion  is  very  much  less,  as  low  even  as  a  twent}'- 
fifth.  The  muscle,  in  fact,  is  by  no  means  more  economical  than 
a  steam-engine  in  respect  to  trie  conversion  of  the  energy  of  chemi- 
cal action  into  mechanical  work. 

Xor  can  we  at  present  say  that  it  has  been  experimentally 
verified  in  any  given  contraction  that  the  mechanical  work  is  done 
at  the  expense  of  the  heat  which  would  be  otherwise  given  out. 
Thus  if  of  two  muscles  A  and  B,  A  be  not  loaded  and  B  loaded 
before  a  contraction  and  unloaded  at  the  height  of  contraction, 
it  is  obvious  that  A  does  no  external  work, "for  the  muscle  re- 
turns to  its  previous  condition,  while  B  does  work,  the  more  so 
the  heavier  the  load  and  the  more  frequently  it  is  raised.  If  now 
both  A  and  B  are  excited  by  the  same  stimulus  to  equal  con- 
tractions, the  temperature  of  A  ought  to  rise  more  than  5,  be- 
cause of  the  same  energy  set  free  in  each,  some  goes  out  as  work 
in  £,  but  in  A  none  goes  out  as  work,  and  all  escapes  as  heat. 

^  Tlie  heat  gis'en  out  by  muscles  will  be  further  discussed  in  Book  II 
in  connection  with  the  general  subject  of  Animal  Heat. 
^  Piiiigers  Arcliiv,  xvi  (1877),  p.  58. 


148  THE    CONTRACTILE    TISSUES. 


ExiKTinu'iit  shows,  on  the  conlrarv.  that  7>  is  the  warmer  of  the 
two,  the  reason  l)eini;  that  the  tension  caused  by  the  load  in- 
creases all  the  chemical  chani^es  in  the  muscle  (as  shown  by  tlie 
increased  i)roduction  of  carbonic  acid),  and  thus  increases  the 
total  eneruy  set  free.  If  A  and  i>  be  ecpially  loaded,  and  while 
A  does  no  work,  the  load  remaininiiail  the  time,  the  load  of  J>  is 
removed  at  the  heii:;ht  of  contraction,  it  is  then  found  that  A  ha- 
comes  the  warmer  of  the  two.  This  experiment  is  not  without 
objection  ;  for  ^1  is  (innnediately  after  the  contraction)  stretched 
by  its  load,  and  so  its  chemical  chanjjjes  still  increased,  whereas 
B  is  not  ;  and  Ileidenhain  has  shown  that  this  is  sufficient  to  ac- 
count for  A  being  the  warmer. 

Of  the  exact  nature  of  the  chemical  changes  we  know  nothing. 
As  has  been  already  stated  (p.  101),  there  is  no  evidence  of  nitro- 
genous products  being  given  oti"as  waste  ;  such  nitrogenous  crys- 
talline bodies  as  are  present  in  muscle,  kreatin,  etc.,  may  be 
regarded  as  the  wear  and  tear  of  the  machine,  and  not  as  prod- 
ucts of  the  material  consumed  in  the  work.  Yet  it  is  hardly 
consonant  with  what  we  know  elsewhere,  to  suppose  that  the 
contraction  of  a  muscular  fibre  has  for  its  essence  the  decompo- 
sition of  a  non-nitrogenous  substance  ;  and  we  may  suppose  that 
the  explosion  does  involve  some  nitrogenous  products,  which, 
however,  are  retained  within  the  tissue  and  used  up  again.  Her- 
mann, in.sisling  on  the  analogy  between  nuiscular  contraction 
and  rigor  mortis,  has  suggested  the  existence  of  a  hypothetical 
?7KK/CH,  which  during  a  contraction  splits  up  into  carbonic  acid, 
lactic  acid,  and  a  nitrogenous  bod}-.  He  further  supposes  the  ni- 
trogenous body  to  be  myosin,  w^hich,  however,  while  still  in  the 
form  of  a  gelatinous  clot,  is  redissolved  and  reconverted  into 
inogen.  But  the  fact  that  myosin  has  probably  antecedents  like 
those  of  fibrin,  and  is  not  formed  directly  as  a  product  of  the  de- 
composition of  a  more  complex  body,  and  especially  the  fact  that 
wdiile  in  rigor  mortis  extensibility  is  diminished,  in  a  contraction 
it  is  increased,  seem  insuperable  objections  to  this  view.  It  may 
be  worth  while  to  point  out  that  during  even  the  most  complete 
repose  muscle  is  undergoing  chemical  changes,  wdiich,  as  we 
know,  are  the  same  in  kind,  and  only  difier  in  degree  trom  those 
characteristic  of  a  contraction.  Thus  carbonic  acid  is  constantly 
being  produced,  and  probably  lactic  acid,  both  being  got  rid  of  as 
they  form,  just  as  they  are  got  rid  of  in  larger  quantities  during 
the  repose  which  follows  contraction.  Supposing  the  existence 
of  a  substance  which  splits  up  into  these  various  products,  and 
which  we  may  speak  of  as  the  true  contractile  material,  it  is  evi- 
dent that  this  material  being  thus  constantly  used  up,  must  be 
as  constantl}^  repaired.  Thus  a  stream  of  chemical  substances 
may  be  conceived  of  as  flowing  through  muscle,  the  raw  material 
brought  by  the  blood  ^  being  gradually  converted  into  true  con- 

^  Together  with  certain  nitrogenous  elements  still  remaining  in  the 
muscle,  according  to  the  view  explained  above. 


UNSTRIATED    MUSCULAR    TISSUE.  149 


tractile  stuff,  the  breaking  down  again  of  which  is  gentle  and 
gradual  so  long  as  the  muscle  is  at  rest ;  when  a  contraction 
takes  place,  the  decomposition  is  excessive  and  violent.  When 
rigor  mortis  sets  in,  the  whole  remaining  contractile  material  is 
de'composed.  It  has  been  already  stated  that  according  to  Her- 
mann the  total  quantity  of  carbonic  and  probably  of  lactic  acid 
produced  after  removal  from  the  body  is  the  same  whether  con- 
traction takes  place  or  not,  the  material  for  the  contraction  being 
apparently  taken  away  from  that  destined  for  rigor  mortis.  This 
means  that  the  manufacture  of  true  contractile  material  is  sud- 
denl}'  arrested  immediately  on  the  cessation  of  the  blood-current, 
no  more  being  afterwards  formed.  Such  a  state  of  things  is  quite 
contrar}^  to  our  general  physiological  experience,  and  there  are 
other  facts  which  render  it  doubtful.  Lastl}^  it  may  be  men- 
tioned that  no  satisfactory  explanation  can  be  given  of  the  con- 
nection between  the  microscopic  structure  of  a  striated  muscular 
fibre  and  its  contraction.  Striation  is  characteristic  of  muscles 
whose  contraction  is  rapid,  but  the  exact  purpose  of  the  strice 
remains  as  yet  unknown. 

It  was  Haller^  who  laid  the  foundations  of  our  knowledge  of 
the  Physiology  of  Muscle  and  Xerve  by  establishing  the  doctrine 
of  muscular  and  nervous  irritabilit}-.  The  most  important 
results  since  that  time  have  been  those  gained  by  the  investiga- 
tions of  Weber  ^  on  the  physical  changes  which  attend  a  muscular 
contraction,  of  Du  Bois-Eeymond  ^  on  the  electrical  phenomena 
of  muscle  and  nerve,  of  Helmholtz  *  on  the  velocitj^  of  nervous 
impulses,  and  on  the  relative  duration  of  the  several  phases  of 
a  contraction,  of  Ptlager  ^  on  electrotonus,  of  Kiihne  ^  on  the 
chemistry  of  muscle,  and  of  Hermann''  on  the  respiration  of  mus- 
cle and  on  the  electrical  plienomena  of  muscle  and  nerve.  The 
researches  of  other  and  more  recent  authors  are  quoted  in  the 
previous  text. 

Sec.  7.   Uxstriated  Muscular  Tissue. 

[Physiological  Anatomy  of  the  Unsfriated  lluscles. 

The  nnstriated  muscles  consist  of  flattened  bands  or 
layers,  which  are  made  up  of  bundles  of  fibres.  These  fibres 
are  composed  of  elongated,  fusiform,  protoplasmic  cells, 
containing  an  elongated  nucleus  or  nuclei,  which  is  usually 
surrounded  by  a  small  amount  of  granular  protoplasm. 
(Figs.  34  and  35.) 

^  De  Part.  Corp.  Hum.  sentientibus  et  irritabilibus,  1753. 
2  Muskelbeweguna:,  Wagner's  Handworterbuch.  ^  Op.  cit. 

*  Miiller's  ArchivVlSoO.     Berichte  Berlin.  Acad.,  1854,  1864. 
^  Untersuch.  it.  d.  Physiologie  des  Electrotonus,  1859. 
^  Protoplasma,  1864.  '  "^  Op.  cit. 

13 


loO 


THE    CONTRACTILE    TISSUES. 


Tliov  (U)  not  possess  a  sheath,  or  sarcok^nina  like  tlic 
skeletal  lihres,  and  wlien  ruptured  have  somewhat  irregu- 
larly squnred  ends. 

The  unstriated  muscles  are  almost  entirely  distributed  to 


Fig.  35. 


Fig.  34.— Three  unstriped  muscular  fibre  cells  from  human  arteries,  a  and  b  show 
cells  with  nuclei ;  />  is  a  cell  treated  with  acetic  acid,  making  nuclei  more  distinct. 

Fig.  35. — Muscular  fibre  cells  from  the  bladder,  a  shows  them  in  a  normal  condi- 
tion ;  6,  treated  with  acetic  acid,  which  dissolves  the  granular  contents,  leaving  the 
nuclei. 

the  viscera,  and  are  disposed  as  flattened  bands  or  la^'ers, 
which  cross  each  other  at  various  angles.  Generally  tiiey 
appear  as  two  layers  :  a  superficial  or  longitudinal,  and  a 
deep  or  circular  layer. 

This  form  of  muscular  fibre  is  found  in  the  skin,  where  the 
fibres  are  seen  to  have  an  oblique"  course,  running  from  the 
superficial  la3'ers  of  the  corium  to  the  hair-follicles,  where 
they  are  inserted.  (Fig.  36  )  Unstriped  muscular  tissue  is 
also  abundant  in  the  superficial  layers  of  the  corium,  at  the 
bases  of  the  papillae.  When  these  fibres  contract  they  cause 
numerous  papillaiy  elevations  to  appear  on  the  surface  of  the 
skin,  which  give  the  skin  the  appearance  of  what  is  com- 
monlv  termed  '•  goose-skin." 


UNSTRIATED    MUSCULAR    TISSUE. 


151 


The  unstriated  muscles  appear  to  be  more  intimately  con- 
nected with  the  sympathetic  nervous  system,  and  controlled 
chiefly  by  them,  vvliile  the  skeletal  muscles  are  animated  l)y 
tiie  cerel)ro-spinal  system.  According  to  some  observers  the 
fibres  of  the  intestines  are  almost  exclusive!}'  supplied  by  tlie 


Fig.  36. 


Perpendicular   Section  through   the  Scalp,  with  two  Hair-sacs,    a,  epidermis;   h, 
cutis;  c,  muscles  of  the  hair-follicles.— After  Kolliker. 


sympathetic  nerves.  In  the  former  class  of  fibres,  from  the 
fact  of  tlieir  being  genei'ally  uninfluenced  by  the  will,  and 
of  their  principal  distribution  being  to  the  organs  of  nutri- 
tion and  growth,  they  have  been  termed  the  muscles  of 
organic  life.  In  the  latter  class,  because  of  their  lieing  pre- 
sided over  b}^  the  cerebro-spinal  system,  their  more  intimate 
connection  with  the  animal  functions,  and  their  volitional 
character,  are  termed  the  muscles  of  animal  life.] 

Our  knowledge  of  the  phenomena  of  these  structures  is 
very  imperfect,  since  (in  vertebrates)  they  do  not  exist  in 
isolated  masses,  like  the  striated  muscles,  butoccur  as  con- 
stituents of  complex,  organs,  such  as  the  intestine,  ureter, 
uterus,  etc.  They  undergo  rigor  mortis;  and  what  little 
information  we  do  possess  concerning  their  chemical  and 
physical  features  leads  us  to  believe  that  the  processes  which 
take  place  in  them  are  fundamentally  identical  with  those 
occurring  in  striated  muscle,  the  two  ditfering  in  degree 
rather  than  in  kind.  When  stimulated,  they  contract.  If 
a  stimulus,  mechanical  or  elec-trical,  be  applied  to  tiie  intes- 
tine or  ureter  of  a  mammal,  a  circular  contraction  is  seen  to 
take  place  at  the  spot  stimulated.  The  contraction,  which 
is  preceded  bj^  a  very  long  latent  period,  lasts  a  very  con- 


152  THE    CONTRACTILE    TISSUES. 

siderable  time,  in  fact  several  seconds,  after  which  relaxa- 
tion slowly  takes  place.  That  is  to  say,  over  the  circulaily 
dispersed  fibres  of  tlie  intestine  (or  ureter)  at  the  spot  in 
question  there  has  passed  a  contraction-wave  remarkable  for 
its  long  latent  period  and  for  the  slowness  of  its  develop- 
ment. From  the  spot  so  directl>'  stimulated,  the  contraction 
may  pass  as  a  wave  (with  a  length  of  1  cm.  and  a  velocity 
of  iVom  20  to  80  millimeters  a  second  in  tiie  ureter^),  along 
the  circidar  coat  both  upwards  and  downwards.  The  longi- 
tudinal fibres  at  the  spot  stimulated  are  also  thrown  into 
contractions  of  altogether  similar  charactei',  and  a  wave  of 
contraction  may  also  travel  longitudinally  along  tiie  longi- 
tudinal coat  botli  upwards  and  downwaids.  It  is  evident, 
however,  that  the  wave  of  contraction,  of  which  we  are  now 
speaking,  is  in  one  respect  different  from  the  wave  of  con- 
traction treated  of  in  dealing  with  striated  muscle.  In  the 
latter  case  the  contraction-wave  was  one  propagated  along 
the  individual  fibre  ;  in  the  case  of  the  intestine  or  ureter  the 
wave  is  one  which  is  propagated  from  fibre  to  fibre,  both  in 
the  direction  of  the  fibres,  as  when  the  whole  circumference 
of  the  intestine  is  engaged  in  the  contraction,  or  when  tiie 
wave  travels  longitudinally  along  the  longitudinal  coat,  and 
also  in  a  direction  at  right  angles  to  the  axes  of  the  fibres, 
as  when  tlie  contraction-wave  travels  lengthways  along  the 
circular  coat  of  the  intestine,  or  when  it  passes  across  a 
breadtii  of  tiie  longitudinal  coat.  In  addition  to  this  differ- 
ence, however,  it  is  obvious  tliat  a  contraction-wave  passing 
along  even  a  single  nnstriated  fil)re  also  differs  from  that 
passing  along  a  striated  fil)re,  in  the  very  great  length  both 
of  its  latent  period  and  of  the  duration  of  its  contraction. 

If  the  stimulus  be  severe  when  mechanical,  or  if  the  inter- 
rupted current  be  used  as  a  stimulus,  the  duration  of  contraction 
may  be  still  further  prolonged  ;  but  there  is  no  evidence  that  a 
series  of  contractions  are  fused  into  a  tetanus,  as  is  the  case  in 
the  striated  muscles. 

Like  the  skeletal  muscles,  whose  nervous  elements  have  been 
rendered  functionally  incapable  (p.  115),  unstriated  muscles  are 
much  more  sensitive  to  the  making  and  breaking  of  a  constant 
current  than  to  induction-shock-. 

The  unstriated  muscles  seem  to  be  remarkably  susceptible  to 
the  influences  of  temperature.     Thus  according  to  Horvath'  the 

'  Enirehnann,  Pfliisjer's  Archiv,  ii  (1869),  243. 
2  Pfliiger's  Archiv,  xiii  (1876),  508. 


CARDIAC    MUSCLES.  153 


unstriated  muscles  of  the  trachea  will  not  contract  at  a  temper- 
ature below  12^  0.,  and  are  most  active  at  a  temperature  above 
21"^  C.  So  also  the  movements  of  the  intestine  cease  at  a  tem- 
perature below  19^  C. 

Waves  of  contraction  thus  passing  along  the  circular  and 
longitudinal  coats  of  the  intestine  give  rise  to  what  is  called 
peristaltic  acti(jn. 

In  striking  contradistinction  to  what  takes  place  in  the 
striated  muscles,  automatic  movements  are  exceedingl}' com- 
mon in  structures  built  up  of  non-striated  muscles  ;  these 
moreover  exliibit  a  great  tendency  to  rhythmic  action. 
Thus  the  peristaltic  action  of  the  intestine  and  ureters,  and 
the  corresponding  movements  of  the  uterus,  are  at  once 
rhythmic,  and  largely  automatic.  How  far  the  automatism 
and  the  rhythm  are  due  to  nervous  elements  is  uncertain. 

According  to  Engelmann'  the  middle  and  part  of  the  upper 
third  of  the  ureter  in  the  rabbit-  contains  no  discoverable  ner- 
vous ganglia,  yet  this  portion  exhibits  aut(miatic  rhythmic  con- 
tractions. We  may  suppose  that,  in  the  absence  of  an  adequate 
nervous  arrangement,  the  propagation  of  the  contraction-wave 
is,  in  this  part  of  the  ureter,  carried  on  by  the  simple  contact  of 
the  adjacaut  surface  of  the  fibres  (which,  as  is  known,  possess  no 
sarcolemma).  Tlie  fibres,  by  their  complete  contact,  may  be 
spoken  of  as  being  physioloylcalh/  continuous  with  each  other. 
[The  muscles  are  variously  affected  by  different  poisons.  Nar- 
cotics generally,  nitrite  of  amyl,  nitrite  of  potassium,  apomor- 
phine,  hydrocyanic  acid,  and  numerous  other  drugs  depress  or 
paralyze  them.  Physostigma  and  caftein  stimulate  them  if 
directl}^  applied.  Yeratria  first  stimulates  and  afterwards  par- 
alyzes them.  Ergot  seems  to  possess  a  remarkable  power  in 
causing  contraction  of  the  nmscles  of  the  uterus,  and  its  chief 
therapeutic  use  is  for  this  purpose.  When  they  are  placed  in 
certain  gases,  such  as  carlionic  acid,  carbonic  oxide,  hydrogen, 
etc.,  they  soon  lose  their  irritability.  In  an  atmosphere  of  oxy- 
gen they  will  remain  irritable  for  a  ver}^  long  period.  | 

Sec.  8.   Cardiac  Muscles. 

The  most  important  features  of  this  form  of  contractile 
tissue  will  be  studied  when  we  come  to  deal  with  the  heart. 
It  will  1)6  seen  that  they  are  intermediate  between  ordinary 
skeletal  and  non-striated  muscles. 

^  Op  cit. 

2  This  does  not  seem  to  hold  good  for  other  animals.  Cf.  Dogiel, 
Arch.  f.  micros.  Anat.,  xiv  (1878),  p.  64. 


151  THE    CONTRACTILE    TISSUES. 


Sec.  9.    Cilta. 

Ciliary  niovcMuont  (•<  nsists  in  the  rai)i(l  flexion  (into  a 
sickle  or  liook  form)  of  tlie  ciliinn  and  its  less  rapid  i-etnrn 
to  its  previous  strais^ht  form.  The  (rnniiiished  velocity  of 
the  return  leads  to  the  force  of  the  ciliary  action  being  ex- 
ertfd  in  the  same  direction  as  the  flexion.  The  cause  of 
the  flexion  seems  to  be  the  contraction  of  the  cilium,  and 
that  of  the  return  an  elastic  reaction. 

Various  attempts  to  explain  the  movement  by  the  presence  of 
special  nu'chanisms  at  the  base  of  the  cilia  have  hitherto  failed. 
Some  autiiors  have  attrilmted  the  movement  to  a  protoplasmic 
contraction  of  the  cell  itself,  the  cilium  acting  merely  as  a  mi- 
nute elastic  rod  ;  and  some  such  view  as  this  is  supported  by  the 
fact  that  no  movement  has  ever  been  observed  in  an  isolated 
cilium.  It  is  dithcult  however  to  understand  how  the  peculiar 
sickle-like  flexion  of  the  cilium  can  be  brought  about  unless  the 
contractile  material  is  continued  up  into  the  cilium  itself,' 

Ciliary  movement  appears  therefore  to  differ  from  ordi- 
nary muscidar  contraction  chiefly  in  the  size  of  the  appa- 
ratus concerned.  The  movement  is  exceedingly  rapid  ;  thus 
Engelmanu'^  has  estimated  that  in  the  frog  the  flexions  are 
repeated  at  least  twelve  times  in  a  second.  The  movement 
in  fact  is  too  rapid  to  be  visible;  it  can  only  be  seen  at  a 
time  when  exhaustion  and  coming  death  liave  begun  to  re- 
tard the  action  ;  thus  Engelmann  found  tliat  he  was  first 
able  to  count  them  when  their  rapidity  declined  to  eight  in 
a  second.  The  tail  of  a  spermatozoon  is  practically  a  single 
cilium. 

In  the  vertebrate  animal,  cilia  are,  as  far  as  we  know, 
wholly  independent  of  the  nervous  system,  and  their  move- 
ment is  probably  ceaseless.  In  such  animals,  however,  as 
Infusoria,  Hydrozoa,  etc.,  a  ciliary  tract  may  often  be  seen 
to  stop  and  go  on  again,  to  move  fast  or  slow,  according  to 
the  needs  of  the  economy,  and,  as  it  almost  seems,  according 
to  the  will  of  the  animal  Observations  with  galvanic  cur- 
rents, constant  and  interrupted,  have  not  led  to  an}'  satis- 
factory results,  and,  as  far  as  we  know  at  present,  ciliary 
action    is    must    affected   by  changes   of  temperature    and 

'  Cf.  Xu>shaiim,  Archiv  f.  micros.  Anat.,  xiv,  1877,  p.  390. 
-  Ueber  die  Flimmerbewegiing,  p.  22  (1868). 


MIGRATING    CELLS.  155 

chemical  media.  Moderate  heat  quickens  the  movements, 
but  a  rise  of  temperature  beyond  a  certain  limit  (about  40^  C. 
in  the  case  of  the  phar3'ngeal  membrane  of  the  frog^)  be- 
comes injurious;  cold  retards.  Very  dilute  alkalies  are 
favorable,  acids  are  injurious.  An  excess  of  carbonic  acid 
or  an  absence  of  oxygen  diminishes  or  arrests  the  move- 
ments, either  temporarily  or  permanently,  according  to  the 
length  of  the  exposure.  Chloroform  or  ether  in  slight  doses 
diminishes  or  suspends  the  action  temporaril}',  in  excess 
kills  and  disorganizes  the  cells. 

Sec.  10.  Migrating  Cells. 

We  have  already  (p.  61)  urged  the  view  that  an  amoeboid 
movement  of  a  white  corpuscle  is  essentialh'  a  form  of  con- 
traction. 

All  the  circumstances  which  affect  muscular  contraction, 
heat,  absence  or  presence  of  ox3'gen  and  carl)onic  acid,  etc., 
also  affect  protoplasmic  movements.  The  white  corpuscles, 
like  muscular  fibres,  suffer  rigor  mortis,  in  which  state  they 
become  spherical. 

The  complete  analogy  between  muscular  fibre  and  white  cor- 
puscle is  rendered  difficult  by  the  fact  that  complete  rest  of  the 
corpuscle  and  universal  contraction  of  the  corpuscle  both  result 
in  the  maintenance  of  the  same  spherical  form.  The  movement 
of  a  white  corpuscle  is  dependent  on  a  contraction  of  some  part. 
If  the  whole  corpuscle  suffers  the  change  which  occurring  in  any 
part  would  lead  to  a  movement  in  that  part,  no  outward  visible 
change  takes  place,  just  as  a  set  of  carefully  balanced  muscles 
would  remain  as  motionless  during  contraction  as  during  rest. 


^  Engelmann,  Onderzoek.  Ttrecht.  Phvsiol.  Lab.,  o'^^  Keeks,  v  (1878), 
p.  44. 


loG 


PROPERTIES    OF    NERVOUS    TISSUES. 


CHAPTER    III. 

THE  FUNDAMENTAL  PROPERTIES  OF  NERVOUS 
TISSUES. 

In  its  sim[)lest,  and  pi'ol)al)Iy  earliest  form,  a  nerve  is 
nothing  moie  than  a  thin  strand  of  irritable  protoplasm, 
forming  the  means  of  vital  eommnnication  between  a  sensi- 
tive ectodermie   cell  exposed  to  extrinsic   accidents,  and  a 

Fi<i.   37. 


re 


Diagram  to  Illustrate  the  Simplest  Forms  of  a  Nervous  System. 

A.  An  ectoderm  cell  e.c,  with  its  muscular  process  m.p.,  as  in  Hydra. 

B.  The  ectoderm  cell  e.c.  is  connected  with  the  muscle  cell  m.c.  by  means  of  the 
primary  motor  nerve  in.?i. 

C.  The  differentiated  sensitive  cell  s.c.  is  conoectf  d  by  means  of  the  sensory  nerve 
s.n.  with  the  central  cell  e.c,  which  is  again  connected  by  means  of  the  motor  nerve 
m.n.  with  the  muscle  cell  m.c. 


ranscular.  highly  contractile  cell   for  a  muscular  process  of 
the  same  cellj  buried  at  some  distance  from  the  surface  of 


SENSORY    AND    MOTOR    NERVES.  157 

the  body,  and  thus  less  suseeptihle  to  external  influences. 
(Fig.  37,  A,B.)  If  in  Hydra,  we  imagine  the  junction  of  the 
ectodermic  muscular  process  with  tiie  body  of  its  cell  to  be 
drawn  out  into  a  thin  thread  (as  is  said  to  be  the  case  in 
i-ome  other  Hydrozoa),  we  should  have  just  such  a  primary 
nerve.  Since  there  would  be  no  need  for  such  a  means  of 
communication  to  be  contractile  and  capable  of  itself  chang- 
ing in  form,  but  on  the  other  hand  an  advantage  in  its  re- 
maining immobile,  and  in  its  dimensions  being  reduced  as 
much  as  possible  consistent  with  the  maintenance  of  irrita- 
bility, the  primary  nerve  would  in  the  process  of  develop- 
ment lose  the  property  of  contractility  in  proportion  as  it 
became  moi'C  irritable,  i.e..  more  apt  in  the  propagation  of 
the  waves  of  disturbance  arising  in  the  ectodermic  cell. 

We  have  already  seen  that  automatism,  ?'.  e.,  the  power  of 
initiating  disturbances  or  vital  impulses,  independent  of  any 
immediate  disturbing  event  or  stimulus  from  without,  is  one 
of  tlie  fundamental  properties  of  protoplasm.  In  simpler, 
but  less  exact  language,  such  a  mass  of  protoplasm  as  an 
amoeba,  though  susceptible  in  the  highest  degree  to  influ- 
ences from  without,  *"  has  a  will  of  its  own  ;''  it  executes 
movements  which  cannot  be  explained  by  reference  to  any 
cljanges  in  surrounding  circumstances  at  the  time  being.  A 
hydra  has  also  a  will  of  its  own  ;  and  seeing  that  all  the 
constituent  cells  (beyond  the  distinction  into  ectoderm  and 
endoderm)  are  alike,  we  have  no  reason  for  thinking  that 
the  will  resides  in  one  cell  more  than  in  another,  but  are  led 
to  infer  that  the  protoplasm  of  each  of  the  cells  (of  the  ec- 
toderm at  least)  is  automatic,  the  will  of  the  individual 
lieing  the  co-ordinated  wills  of  the  component  cells.  In 
both  Hydra  and  Ama^ba  the  processes  concerned  in  auto- 
matic or  spontaneous  impulses,  though  in  origin  independent 
of,  are  subject  to  and  largely  modified  by  influences  pro- 
ceeding from  without.  Indeed,  the  great  value  of  automatic 
processes  in  a  living  body  depends  on  the  automatism  being 
affected  by  external  influences,  and  on  the  simple  effects  of 
stimulation  being  profoundly-  modified  by  automatic  action. 

The  next  step  of  development  beyond  Plydra  is  evidently 
to  differentiate  the  single  (ectodermic)  cell  into  two  cells,  of 
which  one,  b}^  division  of  labor,  confines  itself  chiefly  to  the 
simple  development  of  impulses  as  the  result  of  stimulation, 
leaving  to  the  other  the  task  of  automatic  action,  and  the 
more  complex  transformation  of  the  impulses  genei-ated  in 
itself.     The  latter,  which  we  may  call  the  eminentl}^  auto- 

U 


108  PROPERTIES    OF    NERVOUS    TISSUES. 

iiiatic  cell  (though  much  of  the  work  which  it  has  to  do  is 
of  the  kind  we  shall  i)i'esently  speak  of  as  reflex  action), 
will  naturally  be  withdrawn  from  the  surface  of  the  body, 
while  the  other,  which  we  may  call  the  eminently  sensitive 
cell,  will  still  retain  its  superficial  i)osition,  so  that  it  may 
most  readily  be  affected  l)y  all  changes  in  the  world  without. 
Fig.  .'n.  C  And  just  as  a  primary  motor  nerve  arises  as  a 
retained  thread  of  communication  between  a  sensitive  cell 
and  its  muscular  process,  so  a  primary  sennori/  nerve  may 
be  conceived  of  as  arising  as  a  thi'ead  of  communication 
between  an  eminently  sensitive  cell  and  its  twiu,  tiie  emi- 
nently automatic  or  central  cell  By  this  arrangement  the 
sensitive  cell,  relieved  of  the  heavy  burden  of  si)ontaueous 
action,  is  enabled  to  devote  itself  with  greater  vigor  to  the 
reception  of  external  influences;  while  the  automatic  cell, 
no  longer  hampered  by  the  physical  necessities  of  being 
which  are  imposed  on  the  superficial  cell,  exposed  as  this  is 
to  every  wind  and  wave,  but  secure  in  its  internal  retreat,  is 
able  with  similar  increased  energy  to  devote  itself  either 
to  the  production  of  spontaneous  impulses,  or  to  profoundly 
modifying  the  impulses  which  it  receives  from  the  sensitive 
cell.  Naturally  the  muscular  process  or  muscular  fibre 
would,  on  the  splitting  of  tiie  original  single  cell,  remain  in 
connection  with  the  more  eminently  automatic.  We  thus 
arrive  at  that  triple  fundamental  arrangement  of  a  nervous 
system  in  its  simplest  form,  viz.,  a  sensitive  cell  on  the  sur- 
face of  the  body  connected  by  means  of  a  sensory  nerve 
with  the  internal  automatic  central  nervous  cell,  which  in 
turn  is  connected  b}"  means  of  a  motor  nerve  with  the  mus- 
cular fibre-cell. 

We  have  alread}'  seen  that  the  ph3'siology  of  the  motor 
nerve  cannot,  without  inconvenience,  be  separated  from  that 
of  the  muscular  fibre.  In  the  same  way  the  physiology  of 
the  sensory  nerve  cannot  well  be  separated  from  those  modi- 
fications of  superficial  sensitive  cells  which  constitute  the 
organs  of  sense.  We  may  add  that  the  special  physiology 
of  the  central  nervous  cells  can  only  profitably  he  studied 
in  connection  with  the  sensory  organs.  In  the  present 
chapter,  therefore,  we  purpose  to  confine  ourselves  to  the 
consideration  of  the  simplest  and  most  general  proj^erties  of 
the  central  nervous  cells. 

These  are  arranged  in  the  vertebrate  body  in  two  great 
systems :  the  cerebro-spinal  axis  and  the  various  ganglia 
scattered  over  the  body ;  we  shall  deal  with  such  properties 


SENSORY    AND    MOTOR    NERVES.  159 

only  as  are  more  or  less  common  to  the  two  s^'steras.  We 
may  premise  that  as  far  as  our  kuowled^je  at  present  goes, 
the  processes  whicli  are  concerned  in  the  propag:ation  of 
nervous  impulses  along  a  sensory  nerve-trunk  are  identical 
witli  those  which  take  place  in  a  motor  nerve-trunk.  The 
phenomena  of  the  natural  nerve-current  of  the  negative 
variation  during  the  passage  of  an  impulse,  and  of  elec- 
trotonus  (and  these  facts  mark  out,  as  we  have  seen,  the 
limits  of  our  information  on  this  matter),  are  exactly  the 
same,  whether  the  piece  of  nerve-trunk  experimented  on  be 
a  mixed  nerve  trunk,  or  an  almost  purely  motor,  or  an  almost 
purely  sensory  nerve-trunk,  or  an  anterior  or  posterior  nerve- 
root,  or  the  special  sensory  nerve  of  a  particular  sense,  such 
as  the  optic  nerve.  In  both  sensory  and  motor  nerves  the 
changes  accompanying  a  nervous  impulse  are  transmitted 
equall}'  well  in  both  directions. 

We  seem  justified  in  concluding  tiiat  the  events  which 
occur  in  a  sensory  nerve  when  it  is  an  instrument  of  sensa- 
tion, differ  from  tliose  which  take  place  in  a  motor  nerve 
when  that  is  an  instrument  of  movement,  only  so  far  as  the 
sensory  imi)ulses  are  generated  by  particular  processes  which 
bear  the  stamp  of  the  sensory  cell  in  which  they  originated, 
while  the  motor  impulses  are  generated  by  particular  pro- 
cesses which  bear  the  stamp  of  the  central  nervous  cells  in 
which  they  in  turn  originated.  All  sensory  impulses  appear 
to  be  tetanic  in  nature,  i.  e.^  to  be  composed  of  a  series  of 
constituent  simple  impulses  ;  and  it  is  probable  that  while 
the  motor  impulses  which  proceed  from  the  central  nervous 
system  to  the  muscles  are  composed  of  simple  impulses  re- 
peated with  the  same  rapidity,  and  thus  giving  rise  to  the 
same  muscular  note  (p.  80), the  sensory  impulses  which  pro- 
ceed from  the  i)eripheral  sense  organs  to  the  central  nervous 
system  vary  exceedingly  as  to  the  way  in  which  their  con- 
stituent simple  impu-lses  are  combined.  It  is  indeed  possi- 
ble that  the  complex  sensory  impulses  which  give  rise,  for 
instance,  to  sight  and  touch  respectively,  ma}'  differ  only  in 
the  wave-length,  so  to  speak,  of  their  constituent  simple 
impulses,  much  in  the  same  way  as  red  light  differs  from 
blue  light. 

In  the  scheme  sketclied  out  above,  the  same  central  ner- 
vous cell  is  supposed  to  be  engaged  at  once,  both  in  origi- 
nating automatic  actions  and  in  modifying  sensory  impulses 
(/.  e.^  impulses  proceeding  from  the  superficial  sensitive  cells) 
previous  to  these  being  passed  on  to  the  muscular  fibre.     It 


160  PROPERTIES    OF    NERVOUS    TISSUES. 


is  evident  lli.it,  where  two  or  more  central  nervous  cells 
occur  together,  a  further  ditferenliation  would  he  of  advan- 
tage :  a  dirterentiation  into  cells  which,  tiiough  still  suscep- 
tible of  being  intlnenced  from  without,  siiould  he  more 
especially  restricted  to  automatic  action,  and  into  cells 
which  shouhl  forego  their  automatism  for  the  sake  of  l)eing 
more  efUcient  in  modifying  sensory  impulses,  with  a  view  of 
transmuting  them  into  motor  impulses,  and  so  of  giving  rise 
to  apjjropriate  movements.  We  thus  gain  the  fundamental 
and  })rimary  dilferentiation  of  the  work  of  a  central  nervous 
system  into  automatic  and  into  reflex  oi)erations.  These 
are  very  clearly  manifested  by  the  brain  and  spinal  cord, 
and  [probably  also,  though  this  is  less  certain,  by  the  spo- 
radic ganglia. 

Automatic  Actions. — In  the  vertebrate  animal  the  highest 
form  of  aiitomati.^m,  individual  volition,  with  which  con- 
scious intelligence  is  associated,  is  a  function  of  certain 
jmrts  of  the  brain.  There  are  evidences  of  the  existence 
in  the  brain  of  other  forms  of  automatism.  All  these  will 
be  considered  in  detail  hereafter. 

in  the  s|)inal  cord  separated  from  the  brain  by  section  of 
the  medulla  oblongata,  it  becomes  ditlicult  to  diaw  a  line 
between  purely  automatic  and  reflex  actions.  Thus,  when 
we  come  to  deal  with  respiration,  we  shall  see  tl»at  while 
there  can  be  no  doubt  that  the  muscular  respiratory  appa- 
ratus is  kept  at  work  by  impulses  proceeding,  in  a  rhythmic 
manner,  from  a  group  of  nerve-cells,  or  respiratory  nervous 
centre,  in  the  medulla  oblongata,  it  is  an  open  question 
whether  those  impulses,  whose  generation  is  certainly  mod- 
ified by  centripetal  impulses  passing  to  the  centre  along 
various  nerves,  are  absolutely  automatic,  i.  e  ,  whether  they 
can  continue  to  make  their  appearance  when  no  influences 
whatever  from  without  are  brought  to  bear  upon  the  centre. 
Similar  doid)ts  hover  round  other  automatic  functions  of  the 
si)inal  cord.  We  shall  see  hereafter  reasons  for  speaking  of 
the  existence  in  the  medulla  oblongata  of  a  vaso  motor  cen- 
tre, that  is  of  a  group  of  nerve-cells,  whence  impulses  ha- 
bitually })roceed  along  the  so-called  vaso-motor  nerves  to  the 
muscular  coats  of  the  small  arteries,  and  keep  these  vessels 
in  a  state  of  semi-contraction  or  tone.  Here  too  it  is  doubt- 
ful whether  these  motor  or  efi'ereut  impulses  can  be  generated 
in  the  al)sence  of  all  sensory  or  afferent  impulses.  The 
posterior  lymphatic  hearts  of  the  frog  are  connected  by  the 


AUTOMATIC    ACTIONS.  161 

small  tenth  pair  of  spinal  nerves  with  the  gray  matter  of 
the  termination  of  tiie  spinal  cord,  in  such  a  manner  that 
destruction  of  that  part  of  the  spinal  cord  or  section  of  the 
tenth  nerves  apparently  puts  an  end  to  the  riiythmic  pulsa- 
tions of  the  lympliatic  hearts.  Here  it  would  seem  as  if 
rhythmic  impulses  were  automatically  generated  in  the  lower 
end  of  the  cord,  and  proceeded  along  the  efferent  nerves  to 
the  hearts,  thus  determining  their  rhythmic  pulsations. 
But  if  it  be  true,  as  assorted,  that  the  rhytiimic  pulsations, 
though  arrested  for  a  time  hy  severance  of  tiie  nerves,  or 
destruction  of  the  lower  end  of  the  cord,  are  after  awhile 
resumed,  then  these,  too,  can  he  no  longer  counted  among 
the  automatic  plienomena  of  the  cord.  And  so  in  other 
instances  which  we  shall  meet  with  in  the  course  of  tiiis 
book.  The  existence  of  automatism,  then,  even  of  this 
comparatively  simple  character,  is  at  least  doubtful.  That 
all  higher  automatism  comparable  at  least  to  that  of  the 
cerebral  hemispheres  is  absent,  may  be  regarded  as  certain. 

In  the  sporadic  ganglia  the  evidence  of  automatic  action 
seems  more  clear,  and  yet  is  by  no  means  absolutely  deci- 
sive. The  beat  of  the  heart  is  a  typical  automatic  action  ; 
and,  since  the  heart  will  continue  to  beat  for  some  time 
when  isolated  from  the  rest  of  the  body  (that  of  a  cold- 
blooded animal  continuing  to  beat  for  hours,  or  even  days), 
its  automatism  must  lie  in  its  own  structures.  Wlien.  how- 
ever, we  come  to  discus^?  the  beat  of  the  heart  in  detail,  we 
shall  find  that  it  is  still  an  open  question  whether  the  au- 
tomatism is  confined  to  the  ganglia  (either  of  the  sinus  ve- 
nosus,  auricles,  or  auriculo-ventricular  boundary),  or  shared 
in  by  the  muscular  tissue  :  whether,  in  fact,  the  automatism 
is  a  nuiscular  automatism  like  tiiat  of  a  ciliated  cell,  or  the 
automatism  of  a  differentiated  nerve-cell.  And  yet  the 
heart  is  the  case  where  the  automatism  of  the  ganglia  seems 
clearest. 

The  peristaltic  contractions  of  the  alimentary  canal  are 
automatic  movements  ;  we  cannot  speak  of  them  as  being 
simply  excited  by  the  presence  of  food  in  the  canal,  any 
more  than  we  can  say  that  the  beat  of  the  heart  is  caused 
by  the  presence  of  blood  in  its  cavities.  When  absent  they 
may  be  set  agoing,  and  when  present  may  be  stopped  witii- 
out  any  change  in  the  contents  of  the  canal.  They  may.  of 
course,  be  influenced  by  the  contents,  just  as  the  l)eat  of  the 
heart  is  influenced  by  the  quantity  of  blood  in  its  cavities. 
Throughout  the   intestines   are   found  the  nerve  plexus  of 


1G2  PROPERTIES    OF    NERVOUS    TISSUES. 

Aucrbach  and  that  of  Meissiier  ;  to  each  or  both  of  tliesc 
the  automatism  of  the  peristaltic  movements  has  been  re- 
ferred. Yet  in  the  nreter,  whose  peristaltic  waves  of  con- • 
traction  closely  resemble  that  of  the  intestine,  antomatism 
is  evident  in  the  mid(]le  third  of  its  lentrth  even  when  com- 
pletely isolated  ;  in  which  region  (in  the  rabbit  at  least), 
according  to  Engelinann,^  ganglia,  and  indeed  nerve-cells, 
are  entirely  absent. 

Thus,  while  in  the  spinal  cord  there  is  doubt  whether 
pui'ely  automatic,  as  stringently  distinguished  from  reflex, 
actions  take  place,  in  the  case  of  the  sporadic  ganglia  the 
uncertainty  is  whether  the  clearly  automatic  movements  of 
the  organs  with  which  the  ganglia  are  associated  are  due  to 
the  nerve  cells  of  the  ganglia  or  to  the  muscular  tissue  itself. 

Keflex  Actions. — The  si)inal  cord  offers  the  best  and  most 
numerous  examples  of  reflex  action.  In  fact,  reflex  action 
may  be  said  to  be,  j)ar  excellence^  the  function  of  the  spinal 
cord  ;  and  the  gray  matter  of  the  spinal  cord  may  be  broadly 
considered  as  a  multitude  of  reflex  centres.  *We  have  here 
to  consider  the  cord  merely  in  its  general  aspects,  and  must 
postpone  the  special  consideration  of  the  particular  forms 
of  reflex  action  which  it  exhibits,  as  they  come  before  us  in 
various  connections,  or  until  we  have  to  deal  with  it  as  part 
of  the  great  central  nervous  machinery. 

In  its  simplest  form  a  reflex  action  is  as  follows:  All  the 
machinery  it  demands  is  (a)  a  sentient  surface  (external  or 
internal),  connected  by  (/;),  or,  to  adopt  the  more  general 
and  better  term,  atferent  nerve,  with  (c)  a  central  nerve  cell 
or  group  of  connected  nerve  cells,  which  is  in  relation  by 
means  of  (<;/)  a  motor,  or  eflferent,  nerve  or  nerves,  with  (e) 
a  muscle  or  muscles,  or  some  other  irritable  tissue  elements, 


[Fig.  38. 


iZ!- 


Ditigram  illustrating  simplest  form  of  reflex  apparatus  ] 

capable  of  responding,  by  some  change  in  their  condition, 
to  the  advent  of  efferent  impulses.  The  afferent  impulses 
started  in  a,  passing  along  6,  reach  the  centre  r,  are  there 
transmuted  into  efferent  impulses,  which,  passing  along  c/, 

'  Pfliiger's  Archiv  (1869),  ii,  243. 


KEFLEX    ACTIONS.  163 

finally  reach  e,  and  there  produce  a  cognizable  effect.  The 
essence  of  a  reflex  action  consists  in  the  transmutation,  by 
means  of  the  irritable  protoplasm  of  a  nerve-cell,  of  afferent 
into  efferent  impulses.  As  an  approach  to  a  knowledge  of 
the  nature  of  that  transmutation  we  may  lay  down  the  fol- 
lowing propositions: 

The  number^  inteni<ilii^  character,  and  disfribufion  of  the 
efferent  impuhea  is  determined  chieffy  by  the  events  which, 
take  place  in  the  protoplasm  of  the  reflex  centre.  It  is  not 
that  the  afferent  impulse  is  simply  reflected  in  the  nerve-cell, 
and  so  becomes  with  but  little  change  an  efferent  impulse. 
On  the  contrary,  an  afferent  impulse  passing  along  a  single 
sensory  fibre  may  give  rise  to  efferent  impulses  passing  along 
many  motor  nerves,  and  call  foith  the  most  complex  move- 
ments. An  instance  of  this  disproportion  of  the  afferent 
and  efferent  impidses  is  seen  in  the  case  where  the  contact 
with  the  glottis  of  a  foreign  body  so  insignificant  as  a  hair 
causes  a  violent  fit  of  coughing.  Under  such  circumstances 
a  slight  contact  with  the  mucous  membi-ane,  such  as  could 
not  possibly  give  rise  to  anything  more  than  few  and  feeble 
impulses,  may  cause  the  discharge  of  so  many  efferent  impulses 
along  so  many  motor  nerves,  that  not  only  all  tlie  respiratory 
muscles,  but  almost  all  the  muscles  of  the  body,  are  hi-ought 
into  action.  Similar  though  less  striking  instances  of  how 
incommensurate  are  afferent  and  efferent  impulses  may  l»e 
seen  in  reflex  actions.  In  fact  the  afferent  impulse,  when  it 
reaches  the  protoplasm  of  tlie  nerve,  produces  there  a  series 
of  changes,  of  explosive  disturbances,  which,  except  that 
the  nerve-cell  does  not  in  any  way  change  its  form,  may  be 
likened  to  the  explosive  clianges  in  a  muscle  on  tlie  arrival 
of  an  impulse  along  its  motor  nerve.^  The  changes  in  a 
nerve-cell  during  reflex  action,  we  might  say  during  its  ac- 
tivit}',  far  more  closely  resemble  the  changes  during  a  mus- 
cular contraction  tiiau  those  which  accompany  the  passage 
along  a  nerve  of  either  an  afferent  or  efferent  impulse.  The 
simple  passage  along  a  nerve  is  accompanied  by  little  ex- 
penditure of  energy;  it  neither  gains  nor  loses  force  to  any 
great  extent  as  it  progresses.  The  transmutation  in  a  nei've- 
cell  is  most  probably  (though  the  direct  proofs  are,  perha[)s, 
>vanting)  accom})anied  b}'  a  large  expenditure  of  energ}-,  and 

^  The  question  as  to  how  far  these  processes  in  the  central  cells  are 
connected  with  the  development  of  consciousness  is  here  purposely  passed 


ItU  PROPERTIES    OF    NERVOUS    TISSUES. 

a  simple  nervous  impulse  iu  suftei'ini^  this  transmutation  in 
a  central  nervous  origan  may  accumulate  in  intensit>'  to  a 
very  remarkable  extent,  as  in  the  case  of  strychnia  poisoning. 

The  )wture  of  the  I'fj'erent  impuheH  is^  however^  determined 
aho  by  the  nature  of  the  afferent  impulses.  The  nerve-centre 
remainino^  in  the  same  condition,  the  stronirer  or  more  nu- 
merous impulses  will  aive  rise  to  the  more  forcible  or  more 
comprehensive  movements.  Thus  if  the  flank  of  a  brainless 
froir  be  very  liohtly  touched,  tiie  only  reflex  movement  whicii 
is  visible  is  a  slioht  twitchins:  of  the  muscles  lying  immedi- 
ately underneath  the  spot  of  skin  stimulated.  If  tiie  stimulus 
be  increased,  the  movements  will  spread  to  tiie  hind-leg  of 
the  same  side,  which  frequently  will  execute  a  movement 
calculated  to  push  or  wij)e  away  the  stimulus.  By  forcibly 
pinching  the  same  si)0t  of  skin,  or  otherwise  increasing  the 
stimulus,  the  resulting  mf)vements  ma}^  be  led  to  embrace 
the  fore-leg  of  the  same  side,  then  the  opposite  side,  and 
finally,  almost  all  the  muscles  of  the  body.  In  other  words, 
the  disturbance  set  going  in  the  central  nerve-cells,  confined 
when  the  stimulus  is  slight  to  a  few  nerve-cells  and  to  a  few 
nerve-flbres,  overflown^  so  to  speak,  when  the  stimulus  is 
increased,  on  to  a  number  of  adjoining  (and  we  must  con- 
clude) connected  cells,  and  thus  tiirows  imi)ulses  into  a  large 
and  larger  numi»er  of  efferent  nerves. 

Certain  relations  may  tm  observed  between  the  .sentient  i^pot 
stimu'ated  and  the  resulting  movement.  In  tlie  simplest  cases 
of  i-eflex  action  this  relation  is  merely  that  the  muscles 
tiirown  into  action  are  those  governed  by  a  motor  nerve, 
which  is  the  fellow  of  the  sensory  nerve,  the  stimulation  of 
which  calls  forth  the  movement.  In  the  more  cojnj)lex  reflex 
action-i  of  tlie  brainless  frog,  and  in  other  cases,  the  relation 
is  of  such  a  kind  that  the  resulting  movement  bears  an  adnp- 
tati.on  to  the  stimulus;  the  foot  is  withdrawn  from  the  stim- 
ulus, or  the  movement  is  calculated  to  push  or  wipe  away 
the  stimulus.  In  other  words,  a  certain  jiurpoae  is  evident 
in  the  reflex  action. 

Thus  in  all  cases,  except  perhaps  the  very  simplest,  the 
movements  called  forth  by  a  reflex  action  are  exceedingly 
complex,  compared  with  those  which  result  from  the  direct 
stimulation  of  a  motor  trunk.  When  the  peripheral  stump 
of  a  divided  sciatic  nerve  is  stimulated  with  the  interrupted 
current,  the  muscles  of  the  leg  are  at  once  thrown  into 
tetanus,  continue  in  the  same  rigid  condition  during  the 
passage  of  the  current,  and  relax  immediately  on  the  current 


ACTIONS    OF    SPORADIC    GANGLIA.  165 

being  shut  oft'.  When  tlie  same  current  is  npplierl  for  a 
second  only,  to  the  skin  of  the  flank  of  a  brainless  frog,  the 
leg  is  drawn  up  and  the  foot  rnpidlv'  swept  over  the  spot 
irritated,  as  if  to  w  ipe  away  the  irritation  ;  but  this  move- 
ment is  a  complex  one,  requiring  the  contraction  of  partic- 
ular muscles  in  a  definite  sequence,  with  a  carefully  adjusted 
proportion  between  the  amounts  of  contraction  of  the  indi- 
vidual muscles.  And  this  complex  movement,  this  balanced 
and  arranged  series  of  contractions,  may  be  repeated  more 
than  once  as  the  result  of  a  single  stimulation  of  the  skin. 
When  a  deep  breath  is  caused  by  a  dash  of  cold  water,  the 
same  co-ordinated  and  carefully  arranged  series  of  contrac- 
tions is  also  seen  to  result,  as  part  of  a  reflex  action,  from 
a  simple  stimulus.  And  man}-  more  examples  might  be 
given. 

In  such  cases  as  these,  part  of  the  complexity  may  be  due 
to  the  fact  that  the  stimulus  is  applied  to  terminal  sensory 
organs  and  not  directly  to  a  nerve-trunk.  As  we  shall  see 
in  speaking  of  the  senses,  the  impulses  which  are  generated 
by  the  application  of  a  stimulus  to  a  sensory  organ  are 
more  complex  than  those  which  result  from  the  direct  stim- 
ulation of  a  sensory  nerve-trunk.  Nevertheless,  reflex  ac- 
tions of  great  if  not  of  equal  complexity  may  be  induced 
by  stimuli  applied  dii'ectly  to  a  nerve-trunk.  AYe  are  there- 
fore obliged  to  conclude  that  in  a  reflex  action,  the  processes 
which  are  originated  in  the  central  nerve  cells  by  the  arrival 
of  simple  impulses  along  afferent  nerves  may  be  highly 
complex;  and  that  it  is  the  constitution  and  condition  of 
the  nerve-cells  which  determine  the  complexity  and  charac- 
ter of  the  movements  which  are  effected.  In  other  words, 
the  central  nerve-cells  concerned  in  reflex  actions  are  to  be 
regarded  as  constituting  a  sort  of  molecular  machinery, 
the  character  of  the  resulting  movements  being^  determined 
by  the  nature  of  the  raachiuerj-  set  going  and  its  condition 
at  the  tiuie  being,  the  character  and  amount  of  the  afferent 
impulses  determining  exactly  what  parts  of  and  how  far  the 
central  machinerv  is  thrown  into  action. 

Actions  of  Sporadic  Ganglia. — Seeing  that  in  the  spinal 
cord,  the  nerve  cells  »ind()ui)tedly  are  the  central  structures 
concerned  in  the  production  of  reflex  action,  it  is  only  nat- 
ural to  infer  that  the  nerve-cells  of  the  sporadic  ganglia 
possess  similar  functions.  Yet  the  evidence  of  this  is  at 
present  of  very  limited  extent.     With  regard  to  the  ganglia 


166  PROPERTIES    OF    NERVOUS    TISSUES. 

on  tlic  posterior  roots  of  tlie  spinal  nerves,  all  the  evidence 
goes  to  show  that  these  possess  no  power  whatever  of  reflex 
action.  Of  the  larger  ganglia  visible  to  the  naked  eye,sncli 
as  the  ciliary,  otic,  etc.,  we  have  indications  of  reflex  action 
in  one  only,  viz.,  the  snbmaxillary,  and  these  indications 
are,  as  we  sliall  see  in  treating  of  the  salivary-  glands,  dis- 
pnted.  We  have  no  exact  proof  that  the  ganglia  of  the 
sympathetic  chain,  or  of  the  larger  symi)athetic  plexnses, 
are  cai)al)le  of  executing  reflex  actions. 

In  fact,  in  searching  for  reflex  actions  in  ganglia,  we  are 
reduced  to  the  small  microscopic  groups  of  cells  buried  in 
the  midst  of  the  tissues  to  which  they  belong,  such  as  the 
ganglia  of  the  heart,  of  the  intestine,  the  bladder,  etc. 
When  a  quiescent  frog's  heart  is  stimulated  by  touching  its 
surface,  a  beat  takes  place.  This  beat  is,  as  we  shall  see,  a 
complex,  co-ordinated  movement,  very  similar  to  a  reflex 
action  brought  about  b}'  means  of  the  sj)inal  cord  :  and  in 
its  production  it  is  probable  that  the  cardiac  ganglia  are  in 
some  wa}'  concerned.  W  hen  a  quiescent  intestine  is  touched 
or  otherwise  stimulated,  peristaltic  action  is  set  up.  Here 
again  the  ganglia  present  in  the  intestinal  walls  may  he 
supposed  to  play  a  part;  but  this  movement  is  much  more 
simple  than  the  beat  of  the  heart,  and  as  regards  it,  and 
more  especially  as  regards  the  similar  peristaltic  action  of 
the  ureter,  it  becomes  difficult  to  distinguish  between  a 
movement  governed  by  ganglia,  and  one  produced  by  direct 
stimulation  of  the  muscular  fliires.  We  have  seen  that  the 
great  distinction  between  a  reflex  action  and  a  movement 
caused  by  direct  stimulation  of  a  nerve  or  of  a  muscle  lies 
in  the  greater  complexity  of  the  former  ;  and  we  may  readily 
imagine,  that  by  continued  simplification  of  the  central  ner- 
vous machinery,  the  two  might  in  the  end  become  so  much 
alike  as  to  be  almost  indistinguishable. 

In  the  vertelMate  animal  then  the  chief  seat  of  reflex  ac- 
tion is  the  spinal  cord  and  biain.  We  say  '"and  brain  " 
because,  as  we  sliall  see  later  on,  the  brain,  in  addition  to 
its  automatism,  is  as  busy  a  fleld  of  reflex  action  as  the 
spinal  cord. 

Inhibition. — In  speaking  of  reflex  action,  we  took  it  for 
granted  that  the  spinal  cord  was,  at  the  moment  of  the 
arrival  of  the  afferent  impulses  at  tlie  central  nerve-cells,  in 
a  quiescent  state ;  that  the  nerve-cells  themselves  were  not 
engaged  in    any  automatic   action.     We  were  justified   in 


INHIBITION.  167 

doing  so,  because  as  far  as  the  muscles  general!}'  of  the 
l)ody  are  concerned,  the  spinal  cord  is  in  a  brainless  frog 
perfectly  quiescent  ;  an  afterent  impulse  reaching  an  ordi- 
nary nerve-cell  of  the  spinal  cord  does  not  find  it  preoccu- 
pied in  any  other  business.  But  what  happens  when  afferent 
impulses  reach  a  nerve-cell  or  a  group  of  nerve-cells  already 
engaged  in  automatic  action  ? 

We  have  already  referred  to  an  automatic  respiratory 
centre  in  the  medulla  oblongata.  AVe  may  here  premise, 
what  we  shall  show  more  in  detail  hereafter,  that  the  pneu- 
mogastric  nerve  is  peculiarly  associated  as  an  afferent  nerve 
with  tliis  respiratory  centre.  Xow  if  the  central  end  of  the 
divided  pneumogastric  be  stimulated  at  the  time  wlien  the 
respiratory  centre  is  engaged  in  its  accustomed  rhythmic 
action,  sending  out  complex  co-ordinated  impulses  of  inspi- 
ration (and  of  expiration)  at  regular  intervals,  one  of  two 
things  ma}'  happen,  the  choice  of  events  being  determined 
by  circumstances  which  need  not  be  considered  here. 

Tlie  most  striking  event,  and  the  one  whicli  interests  us 
now,  is  that  the  resi)iratory  rhythm  is  slowed  or  stopped  alto- 
gelJier.  That  is  to  say,  that  afferent  impulses  which,  under 
ordinary  conditions  would,  on  reaching  a  quiescent  nervous 
centre,  give  rise  to  movement,  may,  under  certain  condi- 
tions, when  brought  to  bear  on  an  already  active  automatic 
nervous  centre,  check  or  stop  movement  by  interfering  with 
the  production  of  efferent  impulses  in  that  centre.  This 
stopping  or  checking  an  already  present  action  is  spoken  of 
as  an  '•  inhibition  ;"  and  the  etfect  of  the  pneumogastric  in 
this  way  on  the  resi)iratory  centre  is  spoken  of  as  "the 
inhibitory  action  of  the  pneumogastric  on  the  respiratory 
centre." 

The  other  event  is  that  the  respiratory  rhythm  is  acceler- 
ated. We  shall  hereafter  discuss  the  explanation  of  the 
two  events.  We  may^  however,  premise  that  according  to 
one  view  the  pneumogastric  contains  among  its  afferent 
fibres  two  sets,  which  are  either  of  a  diff"ereni  nature  from 
each  other,  or  are  so  diff'erently  connected  with  the  respira- 
tory centre,  that  impulses  arriving  along  one  stop,  while 
those  arriving  along  the  other  quicken,  the  action  of  that 
centre.  Hence  the  one  set  are  called  "  inhibitory,"  the 
other  "accelerating"  or  "augmenting"  fibres.  But  we 
are  concerned  at  present  only  with  the  fact  that  the  stimu- 
lation of  a  nerve  may  produce  inhibitory  or  augmentative 
effects. 


168  PROPERTIES    OF    NERVOUS    TISSUES. 

Similarly  the  vaso-motor  (entre  in  tlie  medulla  may,  by 
impulses  arrivino;  along  various  afferent  tracts,  be  inliihited, 
duiinu'  whicii  the  museular  walls  of  various  arteries  are  re- 
laxed or  augmented,  whereby  the  tonic  contraction  of  various 
arteries  is  increased. 

The  most  striking  instance  of  inhibition  is  offered  by  the 
heart.  If,  wlien  tlie  heavt  is  beating  well  and  i-egulaily,  the 
pneumogastric  be  divided,  and  tlie  peri|)heral  portion  be 
stimulate*]  even  for  a  very  short  time  witli  an  interrupted 
current,  the  heart  is  imme<liately  brought  to  a  standstill. 
Its  beats  are  arrested,  it  lies  perfectly  flaccid  and  motionless, 
and  it  is  not  till  after  some  little  time  that  it  recommences 
its  beat.  Heie  again  it  is  usually  said  that  the  pneumo- 
gastric  contains  efferent  cardio-inliibitory  fibres,  impulses 
l)assing  along  which,  from  the  medulla,  stop  the  automatic 
actions  of  the  cardiac  ganglia  ;  the  respiratory  inhibitory 
fibres  of  the  same  nerve  ai-e  afferent,  i.  c  ,  impulses  pass 
along  them  up  to  the  medulla. 

Though  inhiltition  is  most  clearly  seen  in  the  case  of  au- 
tomatic actions,  other  actions  may  be  similarly  inhibited. 
Tlius,  as  we  shall  see  later  on,  the  reflex  actions  of  the  spinal 
cord  may,  l\v  apj)ropriate  means,  be  inhibited. 

To  sum  up,  then,  the  most  fundamental  properties  of 
nervous  tissues. 

Nerve-fibres  are  concerned  in  the  propagation  only,  not  in 
the  origination  or  transformation  of  nervous  impulses.  As 
far  as  is  at  present  known,  impulses  are  proi)agated  in  the 
same  manner  along  botii  sensory  and  motor  nerves.  Sensory 
impulses  differ  from  motor  impulses  inasmuch  as  the  former 
are  generated  in  sensory  organs  and  jjass  up  to  tiic  central 
nervous  cells,  vvliile  the  latter  pass  from  the  central  nervous 
cells  to  tlie  muscles  or  to  some  otiier  peripheral  organs. 

The  opeiaiions  of  the  nerve-cells  are  either  automatic  or 
reflex.  Jn  both  an  automatic  and  a  reflex  action,  the  di- 
versity and  the  co-ordination  of  the  impulses  is  determined 
by  the  conditi(»n  of  the  nerve  cells.  During  tiie  passage  of 
impulse  along  a  nerve-fibre  there  is  no  augmentation  of 
energy  ;  in  passing  through  a  nerve-cell  tiie  augmentation 
may  be,  and  generally  is,  most  considerable. 

When  afferent  impulses  reach  a  centre  already  in  action, 
tiie  activity  of  that  centre  may,  according  to  circumstances, 
be  either  depressed  or  exalted,  may  be  '"  inhibited "  or 
'•  augmented." 


THE    VASCULAR    MECHANISM.  169 


The  sketch  of  the  evokition  of  a  nervous  S3'stera  given  at  the 
hegmnjng  of  this  chapter  is  based  on  the  observations  of  Klein- 
enberg^  and  the  subsequent  results  of  Eimer,^  O.  and  R.  Hert- 
"vvig,^  and  Romanes.^  The  view  expressed  as  to  the  original 
continuity  of  muscle  and  nerve  is  supported  by  the  now  well- 
recognized  fact  that  in  skeletal  muscles  the  axis-cylinder  of  the 
motor  nerve  not  only  pierces  the  sarcolemma,  but  comes  into  close 
contact  with  the  contractile  substance  ;  and  this  truth  we  owe 
largely  to  Kiihne.^ 


CHAPTER  lY. 
THE  YASCULAIi  MECHAXISM. 

In  order  that  tiie  blood  may  be  a  satisfactory  medium  of 
communication  between  all  the  tissues  of  the  body,  two 
things  are  necessary.  In  the  first  place,  there  must  be 
through  all  parts  of  the  body  a  flow  of  blood,  of  a  certain 
rapidit}^  and  general  constanc}'.     In  the  second  place,  this 

^   Hydra,  Leipzig,  1872. 

^  Zoologisclie  Untersuch.,  1874.  Arcliiv  f.  micro.  Anat.,  xiv  (1877), 
p.  394. 

^  Das  Nerven-Svstem  und  die  Sinnes-Organe  der  Medusen,  1878. 

4  Phil.  Trans.,  iS76,  p.  209,  1877,  p.  659. 

^  Archiv  f.  xVnat.  und  Phys.,  1859,  p.  564.  Ueber  d.  peripherischen 
Endorgane  der  motorischen  Nerven,  1862,  and  subsequent  papers  in 
A^irchow's  Archiv,  Bde.*24,  27,  28,  and  29.  Doyere  undoubtedly  had 
previously  (1840)  seen  the  continuity  of  the  motor  nerve-tibre  with  the 
sarcolemma-less  muscular  fibre  in  invertebrates  (tardigrades),  and  Wag- 
ner (1847)  had  expressed  a  belief  that  in  vertebrates  also  the  motor 
nerve-fibre  ends  in  the  muscular  fibre.  Yet  we  owe  to  Kiihne  the  first 
definite  proof  that  both  in  vertebrates  and  in  invertebrates,  the  muscular 
fibres  of  which  possess  a  sarcolemma,  the  axis-cylinder  pierces  the  sar- 
colemma. We  are  indebted  to  him  also  for  the  discovery  of  tlie  mode 
of  termination  of  the  axis-cylinder  in  the  muscular  fibres  of  amphibia, 
as  well  as  for  a  correct  appreciation  of  the  structure  and  position  within 
the  sarcolemma  of  the  end-plate  or  essential  part  of  the  nerve-eminence 
(nerven-hiigel)  discovered  in  other  vertebrates  by  Eouget,  Krause,  and 
Engelmann. 


170  THE    VASCULAR    MECHANISM. 

flow  must  be  susceptible  of  botli  general  and  local  mod  id- 
eations. In  order  that  any  tissue  or  organ  may  readily 
adapt  itself  fo  changes  of  circumstances  (action,  repose, 
etc.),  it  is  of  advantnge  that  the  quantity  of  blood  passing 
to  it  should  he  not  absolutely  constant,  but  capable  of  va- 
riation. In  order  that  the  material  equilibrium  of  the  body 
may  be  maintained  as  exactly  as  possible,  it  is  desirable 
tliat  the  loading  of  the  blood  with  substances  proceeding 
from  the  unwonted  activity  of  any  one  tissue  should  be  ac- 
companied by  a  greater  flow  of  blood  through  some  excre- 
tory or  metabolic  tissue  b}'  which  these  substances  may  be 
removed.  Similarly  it  is  of  advantage  to  tlie  body  that  the 
general  flow  of  blood  should  in  some  circumstances  be  more 
energetic,  and  in  others  less  so,  than  normal. 

The  first  of  these  conditions  is  dependent  on  the  mechani- 
cal and  i)iiysical  properties  of  the  vascular  mechanism  ;  and 
the  })rohlems  connected  with  it  are  almost  exclusively  me- 
chanical or  physical  problems.  Tiie  second  of  these  con- 
ditions depends  on  the  intervention  of  the  nervous  system; 
and  the  problems  connected  with  it  are  essentially  physi- 
ological problems. 

I.  The  Physical  Phenomena  of  the  Circulation. 

Tlie  Apparatus  concerned  in  tiie  Maintenance  of  the  Nor- 
mal Flow  is  as  follows  : 

1.  The  heart,  beating  rhythmicall}"  by  virtue  of  its  con- 
tractility and  intrinsic  mechanisms,  and  at  each  beat  dis- 
charging a  certain  quantity  of  blood  into  the  aorta.  For 
simplicity's  sake  we  omit  for  the  present  the  pulmonar}'  circu- 
lation. [For  the  physiological  anatomy  of  tlie  heart  see  p. 
197.] 

2.jJThe  arteries,  higlily  elastic  throughout,  with  a  circular 
muscular  element  increasing  in  relative  importance  as  the 
arteries  diminish  in  size.  It  must  not  be  forgotten  that  the 
muscular  element  is  also  elastic. 

The  walls  of  the  arteries  consist  of  three  coats,  called  re- 
spectively the  internal,  middle,  and  external.  The  inner  or 
serous  coat  consists  of  an  internal  layer  of  ovoid  or  fusi- 
form, nucleated  epithelial  cells,  resting  upon  a  longitudinal 
la3'er  of  elastic  fibres,  which  on  account  of  its  reticulated  ap- 
pearance is  termed  the  fenedrated  membrane.  In  the  middle- 
sized  arteries  the  inner  coat  is  increased   in  thickness  by 


PHYSICAL    PHENOMENA    OF    THE    CIRCULATION.       171 

the  addition  of  connective  tissue  and  elastic  fibres  between 
the  epithelium  layer  and  the  fenestrated  membrane. 

The  middle  or  muscular  coat  varies  both  in  diaracter  and 
thickness  according  to  the  size  of  th-e  vessel.  In  the  smallest 
arteries  this  coat  may  be  altogether  absent,  or  merely  exist 
as  a  delicate  muscular  layer.  In  larger  arteries  there  may  be 
three  or  four  muscular  layers.  In  still  larger  vessels,  like 
the  femoral,  numerous  alternate  layers  of  elastic  and  mus- 
cular tissues  are  i)resent.  In  the  great  vessels  of  the  heart 
the  elastic  tissue  much  predominates,  the  muscular  element 
being  proportionately  less.  The  general  arrangement  of  the 
fibres  of  the  middle  coat  is  in  a  transverse  direction. 

The  external  coat  or  tunica  aduentitia  is  composed  prin- 
cipally of  connective  tissue,  having  intermingled  with  it  a 
greater  or  less  proportion  of  elastic  fibres.  In  arteries  of 
medium  size  the  external  coat  is  composed  of  two  layers,  an 
internal  elastic  and  a  superimposed  connective  tissue.  In 
smaller  arteries  the  elastic  tissue  entirely  disappears,  and 
the  connective  tissue  alone  forms  the  coat. 

The  arteries  are  generally  inclosed  in  a  fibro-areolar  en- 
velope, which  is  termed  a  sheath.  The  sheath  is  generally  a 
prolongation  or  continuation  of  the  fascia  of  the  particular 
part  through  which  the  vessel  runs  or  is  distributed. 

After  an  artery  is  ligated,  if  the  ligature  be  severed  and 
the  vessel  opened  it  will  be  seen  that  tiie  internal  and  middle 
coats  have  been  ruptured,  and  that  the  external  coat  alone 
remains  intact,  by  reason  of  its  comparative  toughness. 

The  principal  interest  to  the  physiologist  in  tlie  anatomy 
of  the  arteries  lies  in  the  middle  coat,  which,  on  account  of 
its  muscular  and  elastic  element,  plays  a  very  important 
part  in  the  pulse,  and  in  the  passage  of  the  current  of  blood 
through  the  body  to  the  capillaries.] 

When  an  artery  divides,  the  united  sectional  area  of  the 
branches  is,  as  a  rule,  larger  than  the  sectional  area  of  the 
stem.  Thus  the  collective  capacity  of  the  arteries  is  con- 
tinually (and  rapidly)  increasing  from  the  heart  towards  the 
capillaries.  If  all  the  arterial  branches  were  fused  together, 
they  would  form  a  funnel,  with  its  apex  at  the  aorta.  The 
united  sectional  area  of  the  capillaries  has  been  calculated 
by  Yierordt  to  amount  to  several  (eight?;  hundred  times 
that  of  the  aorta. 

3.  The  capillaries,  channels  of  exceedingly  small  but  va- 
riable size.    [They  average  about  the  ,-^  of  a  mm.  in  diam- 


I  rZ  THE    VASCULAR    MECHANISM. 

eter;  tlu'V  pervade  nearly  all  poitioiis  and  tissnes  of  the 
body,  and  ioim  a  e()ni))lex  inlerlacenient  of  anastomoses 
which  are  fonnd  between  the  terminal  ends  of  the  arterioles 
and  the  beginnings  of  the  veins.   (Fig.  30.) 


IG,  39. 


Web  of  a  Frog's  Foot.  Showing  arterioles  (2, 2, 2),  beginnings  of  veins  (1, 1, 1) ;  with 
intermediate  capillaries  with  their  anastomoses.  Arrows  indicate  the  direction  of 
the  blood-current. 


In  structure,  the  minutest  capillaries  are  composed  of  a 
simple  wall  of  ovoid,  fusiform  or  irregularly  shaped  nucleated 
epithelial  cells.  (Fig.  40.)  In  larger  ca[)illaries  they  have 
also  a  delicate,  transparent,  structureless  basement-mem- 
brane. The  lines  of  juncture  of  these  epithelium  cells  ctin 
be  brought  out  in  a  microscopical  preparation  with  silver 
nitrate,  wdiich  stains  them  black. 

The  form  and  intricacy  of  the  capillary  plexuses  in  the  dif- 
ferent tissues  depend  principally  upon  the  functional  rela- 
tion whicii  the  blood  bears  to  the  part,  and  to  the  molecidar 
arrangement  of  the  cells  composing  the  organ  or  tissue. 
Thus,  where  respiratory  changes  in  the  blood  are  most  ac- 
tive, the  plexuses  are  relatively  more  intricate.  This  is  also 
tiie  case  in  the  glands,  where  the  blood  supply  is  necessarily 
very  great.  Where  the  vessels  merely  convey  blood  for  nutri- 
tive purposes  the  plexuses  are  much  simplified.    Four  of  the 


PHYSICAL    PHENOMENA    OF    THE    CIRCULATION.       173 


dlfl'erent  forms  of  capillary  meshes,  which  are  dependent 
principalh'  upon  peculiarities  in  the  molecular  arrangement 
of  the  tissue  elements,    are  shown   in   the   accompanying 

Fig.   40. 


A,  Fine  capillaries  from  the  mesentery,  n,  capillariesof  larger  size  and  with  thicker 
-walls,  from  the  pcctcii  of  the  eye  of  a  bird. 

Figs.,  41,  42,  43,  44.     Thus,  in  muscles,  the  capillar}^  meshes 
are  very  much  elongated  ;  in  adipose  tissue  they  are  more 


Fig.  41. 


Fig.  42. 


1 -^M<^^^M 


Fig.  41.— Iiistritiutiui)  ol'  ( 'a].illaries  on  the  Surface  of  tho  Skin  of  the  Finger. 
Fig.  42. — Distribntion  of  Capillaries  aronnd  Follicles  of  Mucous  Membrane. 

or  less  rounded,  etc.]  Their  walls  are  elastic  (as  shown  by 
their  behavior  during  the  passage  of  blood-corpuscles  through 
them ),  exceedingly  thin,  and  permeable.  They  are  permea- 
ble both  in  the  sense  of  allowing  fluids  to  pass  through  them 
by  osmosis,  and  also  in  the  sense  of  allowing  white  and  red 
corpuscles  to  traverse  them.     The  small  arteries  and  veins, 

15 


174 


THE     V^ASCULAR    MECHANISM. 


whicli  ^radnall_\-  i):iss  into  niid  IVom  the  capillaries  properly 
so  called,  are  similarly  permeable,  the  more  so  the  smaller 
they  are. 

Vui.  4:?.  Fl(i.  44. 


I)i>triliiiti()ii  of  (ai'illaii  s  in  Mtisil 


Capillary  Network  around  Kat-colls. 


[4.  The  Vein.s. — The  coats  of  the  veins  are  three  in  number, 
similar  to  those  of  the  arteries,  the  princii)al  difference  to 
the  physiologist  being  in  the  component  parts  of  the  middle 


Fig.  40. 


V'l<..  45.— Vein  with  valve.'^  opon.— Alter  b.U.fo.s. 

Fig.  46.— Vein  with  valves  closed  ;  stream  of  blood  passing  off  by  lateral  chan- 
nel.—After  Dai.toN^. 

coat.  This  coat  in  the  veins  contains  a  larger  proportion 
of  connective  tissue,  with  a  smaller  proportion  of  muscu- 
lar and  elastic  fibres.  An  artery  when  empty  retains  its 
rounded  form ;  a  vein  immediately  collai)ses.  This  is  due 
to  the  abundance  or  deficiency  of  the  yellow  elastic  tissue 
element,  as  the  case  may  be. 


THE    CAPILLARY    CIRCULATION.  175 

The  arteries  are  active  agents  in  the  circulation  of  the  blood; 
the  veins  are  passive,  and  serve  as  channels  to  convey  the 
blood  from  the  capillaries  to  the  internal  organs. 

At  intervals  on  the  internal  surface  of  most  of  the  veins, 
projecting  semicircular  pouches  are  seen,  arranged  in  pairs, 
opposite  each  other.  These  pouches  are  the  valves  (Figs. 
45,  46)  of  the  veins,  and  are  formed  b}-  reduplications  of  the 
internal  and  middle  coats.  Their  function  is  to  prevent  a 
reflux  of  blood.  The  veins  form  numerous  anastomoses  ;  if, 
therefore,  a  vessel  becomes  filled,  and  the  current  stagnated, 
the  blood  will  take  a  different  channel,  as  is  shown  in  the 
above  figure.  (Fig.  46.)  These  bloodvessels  are  all  lined 
with  pavement  epithelium. 

The  walls  of  the  arteries  and  veins  are  supplied  with 
nourishment  by  small  vessels,  which  are  termed  the  I'asa 
vasorum.  These  vessels  form  capillary  plexuses  in  the 
middle  and  external  coats.  The  portion  of  the  inner  coat 
upon  which  the  epithelial  lining  rests,  as  well  as  the  epithe- 
lium, probably  receives  its  nourishment  from  the  blood  which 
courses  the  vessel.  The  arteries  are  supplied  with  nerves 
from  both  the  sympathetic  and  cerebro-spinal  systems  ;  prin- 
cipals from  the  former.  As  a  general  rule,  nerves  have  not 
been  found  in  the  venous  walls.] 

The  veins  are  less  elastic  than  the  arteries  and  with  a  ver}' 
variable  muscular  element.  The  united  sectional  area  of 
the  veins  diminishes  from  the  capillaries  to  the  heart,  thus 
resembling  the  arteries  ;  but  the  united  sectional  area  of  the 
venae  cav?e  at  their  embouchment  into  the  right  auricle  is 
greater  than  that  of  the  aorta  at  its  origin.  (The  proportion 
is  nearl}'  two  to  one.)  The  total  capacit}'  of  the  veins  is 
similarly  much  greater  than  that  of  the  arteries.  The  veins 
alone  can  hold  the  total  mass  of  blood  wiiich  in  life  is  dis- 
tributed over  both  arteries  and  veins.  Indeed  nearl}'  the 
whole  blood  is  capable  of  being  received  b\'  what  is  merejy 
a  part  of  the  veiious  system,  viz.,  the  vena  portffi  and  its 
branches.  Such  veins  as  are  for  various  reasons  liable  to  a 
reflux  of  blood  from  the  heart  towards  the  capillaries,  are 
provided  with  valves. 

Sec.  1.  Maix  General  Facts  of  the  Circulation. 

1.    TJie  Capillary  Circulation. 

If  th.e  web  of  a  frog's  foot  be  examined  with  a  microscope, 
the  blood,  as  judged  of  by  tlie  movements  of  the  corpuscles, 
is  seen  to  be  p;\ssing  in  a  continuous  stream  from  the  small 


176 


THE    VASCULAR    MECHANISM. 


arteries  through  the  capillaries  to  the  veins.  (Fig.  47.)  The 
velocity  is  greater  in  the  arteries  than  in  the  veins,  and  greater 
in  both  than  in  the  capillaries.  In  the  arteries  taint  j^ulsa- 
tions,  synchronous  with  the  heart's  beat,  are  occasionally 
visible;  and  not  unfrecinenlly  variations  in  velocity  and  in 
the  distribution  of  the  l)lood,  due  to  causes  which  will  be 
bereai'ter  discussed,  are  witnessed  from  time  to  time. 

[Fig.  47. 


Capillary  Plexus  in  a  portion  of  the  Web  of  a  Frog's  Foot,  magnified  llOdianietei^. 
1,  trunk  of  vein  ;  2,  2,  2,  its  brautbes  ari,>ing  from  the  arterial  capillaries;  .3,  3,  pig- 
ment-cells.] 

The  flow  through  the  smaller  capillaries  is  very  variable. 
Sometimes  the  coipuscles  are  seen  i)assing  through  the 
channel  (which  when  collapsed  may  have  a  diameter  smaller 
than  the  short  axis  of  a  red  corpuscle)  in  single  file  with 
great  regidarity  at  a  velocity  of  about  .57  mm.  in  a  second. 
(In  the  human  retina  the  velocity  is  .75  mm.  per  second 
according  to  Yierordt.)  At  other  times,  the  corpuscles 
which  pass  along  a  given  cap'llary  may  be  few  and  far  be- 
tween. Sometimes  the  corpuscle  may  remain  stationary  at 
the  entrance  into  a  capillary,  the  channel  itself  being  for 
some  little  distance  entirely  free  from  corpuscles.     An}' one 


THE    CAPILLARY    CIRCULATION.  177 

of  these  conditions  readih'  passes  into  another,  and,  espe- 
eiall}'  with  a  somewhat  feeble  circulation,  instances  of  all  of 
them  may  l)e  seen  in  the  same  field  of  the  microscope.  It 
is  only  in  the  case  of  a  A'ery  full  circnlation  that  all  the 
capillaries  can  be  seen  eqnally  filled  with  corpuscles.  The 
long  oval  red  corpuscle  moves  with  its  long  axis  parallel  to 
the  stream,  frequently  rotating  on  its  long  axis  and  some- 
times on  its  short  axis.  The  Hexibility  and  elasticity  of  a 
corpuscle  are  well  seen  when  it  is  being  driven  into  a  capil- 
lary narrower  than  itself,  or  when  it  becomes  temporarily 
lodged  at  the  angle  between  two  diverging  channels.  The 
small  mammalian  corpuscles  rotate  largely  as  they  are  driven 
along. 

In  the  larger  capillaries,  and  especially  in  the  small  arte- 
ries and  veins  which  peimit  the  passage  of  several  corpuscles 
abreast,  it  is  observed  that  the  red  corpuscles  run  in  the 
middle  of  the  channel,  forming  a  colored  core,  between 
which  and  the  sides  of  the  vessel  all  round  is  a  layer,  con- 
taining no  red  corpuscles.  In  this  layer,  the  so-called 
"  inert  layer,''  especially  in  that  of  the  veins,  are  frequently 
seen  white  corpuscles,  sometimes  clinging  to  the  sides  of 
the  vessel,  sometimes  rolling  slowly  along,  and  in  general 
moving  irregular!}',  and  often  in  jerks.  This  division  into 
an  inert  layer  and  an  axial  stream  is  due  to  the  fact  that  in 
any  stream  passing  through  a  closed  channel  the  friction  is 
greatest  at  the  immediate  sides,  and  diminishes  towards  the 
axis.  The  corpuscles  pass  where  the  friction  is  least,  in  the 
axis.  A  quite  similar  axial  core  is  seen  when  any  fine  par- 
ticles are  driven  in  a  stream  of  fluid  through  a  narrow  tube. 
The  phenomena  cease  with  the  flow  of  the  fluid.  The  pres- 
ence of  the  white  corpuscles  in  the  inert  layer  is  said  to  be 
flue  to  their  being  specifically  lighter  than  the  red  corpus- 
cles. When  fine  particles  of  two  kinds,  one  lighter  than 
the  other,  are  driven  through  a  narrow  tube,  the  heavier 
particles  flow  in  the  axis  and  the  lighter  in  the  more  periph- 
eral portions  of  the  stream.  The  white  corpuscles  how- 
ever are  distinctly  more  adhesive  than  the  red,  as  is  seen 
by  the  manner  in  which  they  become  fixed  to  the  glass  slide 
and  cover-slip  when  a  drop  of  blood  is  mounted  for  micro- 
scopical examination  ;  and  by  reason  of  this  adhesiveness 
they  may  become  tempora-ily  attached  to  the  walls  of  the 
vessel,  and  consequenth'  appear  in  the  inert  layer.  The 
resistance  to  the  flow  of  blood  thus  caused  by  the  friction 
generated  in  so  many  minute  passages,  is  one  of  the  most 
important  physical  facts  in  tiie  capillary  circulation.     In  the 


178 


THE    VASCULAR    MECHANISM. 


Fig.  48. 


j:.l.^ 


Apparatus  for  Inv  st'gating  Blood-pressure. 


THE    FLOW    IN    THE    ARTERIES.  179 


At  the  upper  right-hand  corner  is  seen,  on  an  enlarged  scale,  the  carotid  arterj', 
clamped  hy  the  forceps  bd,  with  the  vagus  nerve  v  lying  by  its  side.  The  artery  has 
been  ligatured  at  /'  and  the  glass  canula  c  has  been  introduced  into  the  artery  be- 
tween the  ligature  Z' and  the  forceps  bd,  imd  secured  in  position  by  the  ligature/. 
The  shrunken  artery  on  the  distal  side  of  the  canula  is  seen  at  ca'. 

p.  h.  is  a  box  containing  a  bottle  holding  a  saturated  solution  of  sodium  carbonate, 
and  capable  of  being  raised  or  lowered  at  pleasure.  The  solution  of  sodium  car- 
bonate flows  by  the  tube/),  t.  regulated  by  the  clamp  c"  into  the  tube  t.  The  tube  t 
is  connected  with  the  leaden  tube  t,  and  the  stopcock  c  with  the  manometer,  of 
which  TO  is  the  descending  and  m'  the  ascending  limb,  and  s  the  support.  The  mer- 
cury in  the  ascending  limb  bears  on  its  surface  the  float  fl.  a  long  rod  attached  to 
which  is  fitted  with  the  pen/)  writing  on  the  recording  surface  r.  The  clamp  cl.  at 
the  end  of  the  tube  t  has  an  arrangement  shown  on  a  larger  scale  at  the  right-hand 
upper  corner. 

The  descending  tube  m  of  the  manometer,  and  the  tube  /being  completely  filled 
along  its  whole  length  with  fluid  to  the  exclusion  of  all  air,  the  canula  c  is  filh^d 
with  fluid,  slipped  into  the  open  end  of  the  thick-walled  india-rubber  tube  /,  until 
it  meets  the  tube  t  (whose  position  within  the  india-rubber  tube  is  shown  by  the 
dotted  lines),  and  is  then  securely  fixed  in  this  position  by  the  clamp  cl. 

The  stopcocks  c  and  c"  are  now  opened,  and  the  pressure-bottle  raised  until  the 
i\iercury  in  the  manometer  is  raised  to  the  required  height.  The  clamp  c"  is  then 
closed,  and  the  forceps  6rf  removed  from  the  artery.  The  pressure  of  the  blood  in 
the  carotid  ca  is  in  consequence  biought  to  bear  through  t  upon  tlie  mercury  in  the 
inanometer. 

large  arteries  the  friction  is  small ;  it  increases  as  the}' 
divide,  and  receives  a  very  great  addition  in  the  minute 
arteries  and  capillaries.  It  need  perhaps  hardly  be  said 
that  this  peripheral  friction  not  only  opposes  the  flow  of 
blood  through  the  capillaries  themselves,  but,  working  back- 
wards along  the  whole  arterial  system,  has  to  be  met  by  the 
heart  at  each  systole  of  the  ventricle. 

2.    Tlte  Floiv  in  the  Arteries. 

When  an  artery  is  severed,  the  flow  from  the  proximal 
section  is  not  equable,  but  comes  in  jets,  wliich  correspond 
to  the  heart-beats,  though  the  flow  does  not  cease  between 
the  jets.  The  blood  is  ejected  with  considerable  force ; 
thus,  in  Dr.  Stephen  Hale's^  experiments,  when  the  crural 
artery  of  a  mare  was  severed,  the  jet,  even  after  much  loss 
of  lilood,  rose  to  the  heio-lit  of  two  feet.  The  larger  the 
artery  and  the  nearer  to  the  heart,  the  greater  the  force  with 
which  the  blood  issues,  and  the  more  marked  the  intermit- 
tence  of  the  flow.  The  flow  from  the  distal  section  may  be 
very  slight,  or  may  take  place  with  considerable  force  and 

'  Statistical  Essays,  vol.  ii,  p.  2  (1732). 


180  THE    VASCULAR    MECHANISM. 

marked  iiitcnnittence,  according  to  the  amount  of  collateral 
communication. 

Arterial  Pressure. — If,  while  the  blood  is  flowing  normally 
along  a  large  artery,  e.  g  ,  the  carotid,  a  mercury  (or  other) 
manometer  (Fig.  48)  be  connected  with  a  hole  in  the  side  of 
the  arter}',  so  that  there  is  free  communication  between  the 
interior  of  the  artery  and  the  proximal  (descending)  limb 
of  the  manometer,  the  following  facts  are  observed: 

Immediately  that  communication  is  established  between 
the  interior  of  the  artery  and  the  manometer,  blood  rushes 
from  the  former  into  the  latter,  driving  some  of  the  mer- 
cury from  the  descending  limb  into  the  ascending  limb,  and 
thus  causing  the  level  of  the  mercury  in  the  ascending  limb 
to  rise  rapidly.  This  rise  is  marked  by  jerks,  corresponding 
with  the  heart-beats.  Having  reached  a  certain  level,  the 
mercury  ceases  to  rise  any  more.  It  does  not,  however,  re- 
main ai)solutely  at  rest,  but  undergoes  oscillations  ;  it  keeps 
rising  and  falling.  Each  rise,  which  is  very  slight  compared 
with  the  total  height  to  which  the  mercury  has  risen,  has 
the  same  rhythm  as  the  systole  of  the  ventricle.  Similarly, 
each  fall  coriesponds  with  the  diastole. 

If  a  float,  swimming  on  the  top  of  the  mercury  in  the  as- 
cending limb  of  the  manometer,  and  bearing  a  brush  or 
other  marker,  be  brought  to  bear  on  a  travelling  surface, 
some  such  tracing  as  that  represented  in   Fig.  49  will  be 

Fig.  49. 


Tracing  of  Arterial  Pressure  with  a  ]\tercury  Manometer. 

The  smaller  curves  ;>,  p  are  the  pulse-curves.  The  space  from  r  to  r  embraces  a  respi- 
ratory undulation. 

described.  Each  of  the  smaller  curves  {p.  p)  corresponds 
to  a  heart-beat,  the  rise  corresponding  to  the  systole  and 
the  fall  to  the  diastole  of  the  ventricle.  The  larger  undu- 
lations {r,r)  in  the  tracing,  which  are  respirator}^  in  origin, 
will  be  discussed  hereafter.     This  observation   teaches  us 


ARTERIAL    PRESSURE.  181 

tliat  the  blood,  as  it  is  i)assing  along  the  carotid  avterv,is  ca- 
pable of  supporting  a  column  of  mercury  of  a  certain  height 
(measured  by  the  difference  of  level  between  the  mercury  in 
the  descending  limb,  and  that  in  the  ascending  limb  of  the 
manometer),  when  the  mercury  is  placed  in  direct  communi- 
cation with  the  side  of  the  stream  of  blood.  In  other  words, 
the  blood,  as  it  passes  through  the  artery,  exerts  a  lateral 
pressure  on  the  sides  of  tlie  artery  equal  to  so  many  millime- 
ters of  mercury.  In  this  lateral  pressure  we  have  further 
to  distinguish  between  the  slighter  oscillations  correspond- 
ing with  the  heart-beats,  and  a  mean  pressure  above  and 
below  which  the  oscillations  range.  A  similar  mean  pres- 
sure witli  similar  oscillations  is  found  when  any  artery  of 
the  body  is  examined  in  tlie  same  w^ay.  In  all  arteries  the 
blood  exerts  a  certain  pressure  on  the  walls  of  the  vessels 
which  contain  it.  This  is  generally  spoken  of  as  arterial 
pressure,  and  the  pressure  in  the  aorta  of  an}-  animal  is 
usuall}'  spoken  of  as  its  blood-pressure. 

Description  of  "Plxp'^riment — The  carotii,  or  other  vessel,  is 
laid  bare,  clam]ied  in  two  places  and  divided  between  the  clamps. 
Into  the  cut  ends  is  inserted  a  hoUov/  T  piece  of  the  same  bore  as 
the  artery,  the  cross  portion  forming  the  continuation  of  the 
artery.  The  vertical  portion  is  connected  by  means  of  a  non- 
elastic  flexible  tube  with  the  descending  limb  of  the  manometer. 
In  order  to  avoid  loss  of  blood  fluid  is  injected  into  the  flexible 
tube  until  the  mercury  in  the  manometer  stands  a  very  little  be- 
low what  may  be  beforehand  guessed  at  as  the  probable  mean 
pressure.  The  fluid  chosen  is  a  saturated  solution  of  sodium  car- 
bonate, with  a  view  to  hinder  the  coagulation  of  the  blood  in  the 
tube.  When  the  clamps  are  removed  from  the  artery  the  blood 
rushes  through  the  cross  of  th3  1—  piece.  Some  passes  into  the  side 
limb  of  the  H  piece,  and  continues  to  do  so  until  the  mean  pres- 
sure is  quite  reached.  Thenceforward  there  is  no  more  escape  ; 
but  the  pressure  continues  in  the  interior  of  the  cross  of  the  H 
piece,  is  transmitted  along  the  connecting  tube  to  the  manometer, 
and  the  mercury  continues  to  stand  at  a  height  indicative  of  the 
mean  pressure  with  oscillations  corresponding  to  the  heart's  beats. 
Practically  the  use  of  the  H  piece  is  found  inconvenient.  Ac- 
cordingly the  general  custom  is  to  ligature  the  artery,  to  place  a 
clamp  on  the  vessel  on  the  proximal  side  of  the  ligature,  and  to 
introduce  a  straight  canula,  Fi^;.  48,  connected  with  the  manom- 
eter, between  the  ligature  and  the  clamp.  In  this  case,  on  loosing 
the  clamp,  the  whole  column  of  l-)lood  in  the  artery  is  brought  to 
bear  on  the'  manometer,  and  the  tracings  taken  illustrate  the 
lateral  pressure,  not  of  the  artery,  but  of  the  vessel  (aorta,  etc., 
as  the  case  may  be),  of  which  it  is  itself  a  branch. 

16 


182 


THE    VASCULAR     MECHANISM. 


TiM('in<::s  of  the  inovomcnts  of  tlie  coluiiin  of  mercury  in  the 
niauonictiT  inaylK'  taken  either  on  a  smoked  surface  of  a  revolv- 


Fk;    50. 


Diagram  Illustrating  Pick's  Spring  :Mai)omotor. 

This  consists  essentially  of  a  hollow  Hattened  German  silver  tube  n,  curved  in  the 
form  of  an  incomplete  circle.  The  lower  open  end  h,  lirinly  fastened  to  the  stand  s, 
is  connected  with  a  tube  c,  bearing  a  stopcock.  To  the  upper  closed  end  is  attached 
a  light  upright  nnl  d  connected  with  the  writing  lever  /. 

Through  the  tube  c  the  hollow  curved  spring  is  filled  with  alcohol,  and  the  stop, 
cock  closed.  The  tulie  c  is  then  connectc  d  with  the  artery  by  means  of  a  non-elastic 
flexible  (leaden)  tube  filled  with  sodium  carbonate  solution.  On  opening  the  stop- 
cock the  vaiiations  of  pressure  of  the  blood  in  the  artery  are  communicated  to  the 
fluid  in  the  hollow  curved  spring:  at  each  increase  of  pressure  the  spring  expands, 
and  the  movement-^  of  the  free  end  are  transferred  by  d  to  the  writing  lever  I.  The 
instrument  as  generally  sent  out  also  bears  an  arrangement  (not  shown  in  the  dia- 
grajn)  by  which  the  point  of  the  lever  describes  a  straight  instead  of  a  curved  line. 
The  spring  manometer  is  exceedingly  useful  where  it  is  desirable  to  investigate 
closely  the  variations  in  the  form  of  the  pressure-curve.  In  order  to  measure  the 
amount  of  variation  the  insirument  must  be  experimentally  graduated. 

ing  cylinder  (Fig.  12),  or  by  means  of  a  brush  and  ink  on  a  con- 
tinuous roll  of  paper,  as  in  the  more  complex  kymograph  (Fig.  52). 


THE    VELOCITY    OF    THE    FLOW. 


18; 


In  such  a  mereiiry  manometer,  the  inertia  of  the  mercury  ob- 
scures many  of  the  features  of  the  minor  curves  caused  by  the  heart- 
beats. When,  therefore,  these,  rather  than  variations  in  the  mean 
pressure,  are  being  studied,  it  is  advisable  to  have  recourse  to  the 
spring  manometer  (Fig.  50),  introduced  by  Fick.  In  using  this 
instrument,  the  tube  t,  Fig.  48,  is  connected  -with  the  tube  c, 
Fiij.  50.  [A  tracing  obtained  by  Fick's  manometer  is  shown  in 
Fig.  51.] 

The  average  pressure  of  the  blood  in  the  same  bod}'  is 
greatest  in  the  largest  arteries,  and  diminishes  as  the  arteries 
get  less  ;  but  the  fall  is  a  very  gradual  one  until  the  smallest 
arteries  are  reached,  in  which  it  becomes  very  rapid.  In  the 
cnrotid  of  the  horse  the  mean  arterial  i)ressure  varies  from 
150  to  200  mm.  of  mercury;  of  tiie  dog  from  100  to  175:  of 
tlie  rabbit  from  50  to  90.  In  the  carotid  of  man  it  probal»ly 
amounts  to  150  or  200. 

Since  in  all  arteries  the  blood  is  pressing  on  the  arterial 
walls  with  some  considerable  foice,  all  the  arteries  must  be 
in  a  state  of  permanent  distension  so  long  as  blood  is  flow- 
ing through  them  from  the  heart.  When  tlie  blood-eui-rent 
is  cut  of}',  as  by  a  ligatui'e,  this  expansion  or  distension  dis- 
appears. 

Xot  only  is  there  a  permanent  expansion  corresponding 
to  the  mean  pressure,  but  just  as  the  mercury  in  the  man- 
ometer rises  above  the  level  of 
mean  pressure  at  each  systole  of 
tlie  heart,  and  falls  below  it  at 
each  diastole,  so  at  any  spot  in 
the  artery  there  is  for  each  heart- 
beat a  temporary  expansion,  suc- 
ceeded by  a  temporary  contrac- 
tion, the  diameter  of  the  artery 
in  its  temporary  expansions  and 
contractions  oscillating,  in  cor- 
respondence with  the  oscillations 
of  the    manometer,   beyond   and 

within  the  diameter  of  permanent  expansion.  These  tempo- 
rary expansions  constitute  what  is  called  the  pulse,  and  will 
be  discussed  more  fullv  hereafter. 


Fk 


Norma]  arterial  tracing  olitnined 
•with  the  i?pring  Manometer  ;  dog 
under  curara.l 


The  Velocity  of  the  Flow. — When  even  a  small  artery  is 
severed  a  considerable  quantity  of  blood  escapes  from  the 
proximal  cut  end  in  a  veiy  short  space  of  time.  That  is  to 
say,  the  blood  moves  in  the  arteries  from  the  heart  to  the 
capillaries  with   a  very  considerable  velocity.     By   various 


184 


THE    VASCULAR    MECHANISM 


methods,  this  vclocily  of  the  hlooil  current  lias  been  nieasiired 
at  (lilterent  parts  of  the  arterial  system  ;  the  results,  owing 
to  imperfections  in  the  methods  employed,  cannot  be  re- 
irarded  as  satisfactorily  exact,  but  may  be  accepted  as  ap- 
proxiniatively  true.     The  velocity  of  the  arterial  stream  is 


Lar;4e  Kymograph  with  conliuuous  roll  of  paper. 

The  clock-work  machinery,  some  of  the  details  of  which  are  seen,  unrolls  the 
paper  from  ihe  roll  C,  carries  it  smoothly  over  the  cylinder  B,  and  then  winds  it  up 
into  the  roll  A. 

Two  electroinagne^c  markers  are  seen  in  the  position  in  which  they  record  their 
movements  on  the  paper  as  it  travels  over  B.  The  manometer,  or  any  other  record- 
ing instrument  used,  can  be  fixed  either  in  the  notch  immediately  in  front  of  B,  or 
in  any  other  position  that  may  be  desired. 

greatest  in  the  largest  arteries,  and  diminishes  from  the  heart 
to  the  capillaries,  pari  passu,  with  the  increase,  so  to  speak, 
of  the  width  of  the  bed,  i.  6.,  with  the  increase  of  the  united 
sectional  area. 


Methods.— The  Hfemadromometer  of  Yolkmann  (Fig.  53).  An 
artery,  e.  q.^  a  carotid  is  clamped  in  two  places,  and  divided  be- 
tween the"clamps.  Two  canula3,  of  a  bore  as  nearly  equal  as  pos- 
sible to  that  of  the  artery,  or  of  a  know^n  bore,  are  inserted  in  the 
two  ends.  The  two  canuke  are  connected  by  means  of  two  stop- 
cocks, which  work  together,  with  the  two  ends  of  a  long  glass 


THE    VELOCITY    OF    THE    FLOW. 


tube,  bent  in  the  shape  of  U.  find  filled  with  water  or  with  a  colored 
innocuous  tluid.  The  clamps  on  the  artery  beinu-  released,  a  turn 
of  the  stopcocks  permits  the  blood  to  enter  the  proximal  end  of 
the  long  (j  tube,  alone:  which  it  courses,  driving  the  tluid  out  into 
the  artery  through  the  distal  end.  Attached  to  the  tube  is  a 
graduated  scale,  by  means  of  which  the  velocity  with  which  the 
blood  tlows  along  the  tube  may  be  read  off.  Even  supposmg  the 
canulfe  to  be  of  the  same  bore  as  the  artery,  it  is  evidentthat 
the  conditions  of  the  flow  through  the  tube  are  such  as  will  onl}'- 
admit  of  the  result  thus  gained  being  considered  as  an  approxi- 
mative estimation  of  the  real  velocity  in  the  artery  itself. 


[Kl<i.    or. 


m 


^^m<^-^^m^^^ 


^ 


Volkraann's  Iliemndromometer. 

The  conical  portions  of  the  instrunient  are  inserted  in  the  cut  ends  of  a  vein  or 

artery.    By  a  simple  arrangement  of  a  double  stopcock  ilie  blood-current  can  be 

made  to  pass  immediately  through  the  transverse  arm  as  in  A,  or  to  j)ass  through 

the  graduated  U-shaped  tube  as  in  B  ] 


The  Eheometer  (Stromuhr)  of  Ludwig.  This  consists  of  two 
glass  bulbs  ^1  and  B  (Fig.  5-1),  communicating  above  with  each 
other,  and  with  the  common  tube  C  by  which  Uiey  can  be  filled. 


186 


THE    VASCULAR    MECHANISM, 


Tlu'ir  lower  ends  arc  tixi-d  in  the  metal  disk  D,  which  can  he  made 
to  rotate  throii,i:;h  two  rii^dit  angles,  round  the  lower  disk  E.  In 
the  upper  disk  are  two  holes  a  and  h,  continuous  witli  A  and  B 
respectively,  and  in  the  lower  disk  are  two 
similar  holes  a'  and  h\  similarly  continuous 
with  the  tuhes  II  and  G.  Hence,  in  the 
position  of  the  disks  shown  in  the  ligure, 
the  tuhe  G  is  continuous  through  the  two 
disks  with  the  bull)  A  and  the  tuhe  H  with 

ff  \f     \     \k     the  bulb  7i.     On  turning  the  disk  i>  through 

(     B      il  )       two  right  angles  the  tube  G  becomes  con- 

tinuous with  B  instead  of  A^  and  the  tube 
7/ with  A  instead  of  B.  There  is  a  further 
arrangement,  omitted  from  the  figure  for 
the  sake  of  simplicity,  by  which,  when  tlie 
disk  D  is  turned  through  one  instead  of  two 
right  angles  from  either  of  the  above  posi- 
tions, G  becomes  directly  continuous  with 
jF/,  both  being  completely  shut  olf  from  the 
bull)S. 

The  ends  of  the  tubes  H  and  G  are  made 
to  tit  exactly  into  tw^o  canuhe  inserted  into 
the  two  cut  ends  of  the  artery  about  to  be 
and  having  a  bore  as  nearly  equal  as  pos- 


Dia^'raruinatic  Repre- 
sentation of  Ludwig'd 
Stronuihr. 


experimented  upon, 
sible  to  that  of  the  artery 

The  method  of  experimenting  is  as  follows.  The  disk  D,  being 
placud  in  the  intermediate  position,  so  that  a  and  h  are  l)Oth  cut 
otf  from  a'  and  h\  the  bulb  A  is  tilled  with  pure  olive  oil  up  to 
the  mark  x,  and  the  bulb  B^  the  rest  of  ^i,  and  the  Junction  C 
with  deJibrinated  blood  ;  and  C  is  then  clamped.  Tlie  tubes  H 
and  G  are  also  tilled  with  detlbrinated  blood,  and  G  is  inserted 
into  the  canula  of  the  central,  JI  into  that  of  the  peripheral, 
end  of  the  artery.  On  removing  the  clami)s  from  the  artery  the 
blood  tlows  through  G  to  i/,  and  so  back  into  the  artery.  The 
observation  now  begins  by  turning  the  disk  D  into  the  position 
shown  in  the  ligure  ;  the  blood  then  tloAvs  into  ^4,  driving  the  oil 
there  contained  out  before  it  into  the  bulb  7J,  in  the  direction  of 
the  arroAV,  the  detibrinated  blood  previously  present  in  B  passing 
by  H  into  the  artery,  and  so  into  the  system.  At  the  moment 
that  the  blood  is  seen  to  rise  to  the  mark  x,  the  disk  D  is  with 
all  possible  rapidity  turned  through  two  right  angles  ;  and  thus 
the  bulb  I>,  now  largely  tilled  with  oil,  placed  in  communication 
with  G.  The  blood-stream  now  drives  the  oil  back  into  A^  and 
the  new  blood  in  A  through  J7into  the  artery.  As  soon  as  the 
oil  has  wholly  returned  to  its  original  position,  the  disk  is  again 
turned  round,  and  A  once  more  placed  in  communication  with 
G,  and  the  oil  once  more  driven  from  A  to  B.  And  this  is  re- 
peated several  times  ;  indeed  generally  until  the  clotting  of  the 
blood  or  the  admixture  of  the  oil  with  the  blood  puts  an  end  to 
the  experiment.  Thus  the  flow  of  blood  is  used  to  till  alternately 
with  blood  or  oil  the  space  of  the  bulb  A,  whose  cavity  as  far  as 


THE    VELOCITY    OF    THE    FLOW.  187 


the  mark  x  has  been  exacth'  measured  :  hence  if  the  number  of 
times  in  any  given  time  the  disk  D  has  to  be  turned  round  be 
known,  the  number  of  times  A  has  been  tilled  is  also  known,  and 
thus  the  quantity  of  blood  whiclvhas  passed  in  that  time  through 
the  canula  connected  with  the  tube  G  is  directly  measured.  For 
instance,  supposing  that  the  quantity  held  by  the  bulb  A  when 
filled  up  to  the  mark  x  is  5  cc,  and  sui)posing  that  from  the  mo- 
ment of  allowing  the  first  5  cc.  of  blood  to  begin  to  enter  the 
tube  to  the  moment  when  the  escape  of  the  last  5  cc.  from  the 
arter}'  into  the  tube  was  complete,  100  seconds  had  elapsed, 
during  which  time  5  cc.  had  been  received  10  times  into  the  tube 
from  the  artery  (all  but  the  last  o  cc.  being  returned  into  the 
distal  portion  of  the  artery),  obviously  .5  cc.  of  blood  had  flowed 
from  the  proximal  section  of  the  arter}'  in  one  second.  Hence 
supposing  that  the  diameter  of  the  canula  (and  of  the  artery, 
they  being  the  same)  were  2  mm.,  with  a  sectional  area,  there- 
fore, of  3.14  square  mm.,  an  outflow  through  the  section  of  .5 
cc.  or  500  cmm.  in  a  second  would  give  (5."  5)5  ^  velocity  of 
about  159  mm.  in  a  second. 

The  H{ematochometerofVierordt(Fig.  55)  is  constructed  on  the 
principle  of  measuring  the  velocity  of 
the  current  b}'  observing  the  amount  of 
deviation  undergone  by  a  pendulum, 
the  free  end  of  which  hangs  loosely 
in  the  stream.  A  square  or  rectan- 
gular chamber,  one  side  of  which 
is  of  glass  and  marked  with  a  grad- 
uated scale  in  the  form  of  an  arc  of  a  '^ 
circle,  is  connected  by  means  of  tw  > 

short   tubes  with    the    two   cut   ends  of      Ha-.natochu.ue.er  of  Vicrordt. 

an    artery ;    the    blood    consequently 

flows  from  the  proximal  (central)  por-  «  a»^i  'a  mouthpiece.] 

tion  of  the  artery  through  the  chamber 

into  the  distal  portion'of  the  artery.  Within  the  chamber  and 
suspended  from  its  roof  is  a  short  pendulum,  which  when  the 
blood-stream  is  cut  oft'  from  the  chamber  hangs  motionless  in  a 
vertical  position,  lint  when  the  blood  is  allowed  to  flow  through 
the  chamber,  is  driven  by  the  force  of  the  current  out  of  its  posi- 
tion of  rest.  The  pendulum  is  so  placed  that  a  marker  attached 
to  its  free  end  travels  close  to  the  inner  surface  of  the  glass  side 
along  the  arc  of  the  graduated  side.  Hence  the  amount  of  devi- 
ation from  a  vertical  position  may  easily  be  read  ott'  on  the  scale 
from  the  outside.  The  graduation  of  the  scale  having  been  carried 
out  by  experimenting  with  streams  of  known  velocity,  the  veloc- 
ity can  at  once  be  calculated  from  the  amount  of  deviation. 

An  instrument  based  on  the  same  principle  has  been  invented 
by  Chauveau  and  improved  by  Lortet.  In  this  the  part  which 
corresponds  to  the  pendulum  inVierordt's  instrument  is  prolonged 
outside  the  chamber,  and  thus  the  portion  within  the  chamber  is 
made  to  form  the  short  arm  of  a  lever,  the  fulcrum  of  which  is  at 


188  THE    VASCULAR    MECHANISM. 


the  point  whore  tlie  wall  of  the  chaiii])cr  is  traversed  and  the  loni; 
arm  of  which  projects  outside.  (Fiji;.  oG.)  A  somewhat  wide 
tuhe,  the  wall  of  which  is  at  one  point  composed  of  an  india- 
ruhher  memhrane,  is  introduced,  hetween  the  two  cut  ends  of  an 
artery.     A  long  light  lever  pierces  the  india-ruhher  mendjrane. 

[Via.  5G. 


M.  Lortet's  lustrunient. 

a,  tube  open  fit  both  ends;  b,  square  opening  closed    by  india-rubber  membrane, 

which  is  pierced  by  the  lever,  the  thick  end  of  which  projects  into  the  vessel.] 

The  short  expanded  arm  of  this  lever  projecting. within  the  tuhe 
is  moved  on  its  fulcrum  in  the  india-ruljher  ring  hy  the  current 
of  blood  passing  through  the  tube,  the  greater  the  velocity  of  the 
current  the  larger  being  the  excursion  of  the  lever.  The  move- 
ments of  the  short  arm  give  rise  to  corresponding  movements  in 
the  opposite  direction  of  the  long  arm  outside  the  tube,  and  these, 
by  means  of  a  marker  attached  to  the  end  of  the  long  arm,  may 
be  directly  inscribed  on  a  recording  surface.  This  instrument  is 
ver}'  well  adapted  for  observing  changes  in  the  velocity  of  the 
flow.  In  determining  actual  velocities,  for  which  purpose  it  has 
to  be  experimentally  graduated,  it  is  not  so  useful. 

In  the  horse,  Yolkniann  found  the  velocity  of  the  stream 
to  1)6  in  the  carotid  artery  al»out  300  mm.,  in  the  maxillary 
artery  165  mm.,  and  in  the  metatarsal  artery  5()  mm.  in  the 
second.  (Fig.  50.)  Chauveau  detei'mined  the  velocity  in  the 
carotid  of  the  hoise  to  vary  from  520  to  150  mm.  per  sec.  at 
each  beat  of  the  heart,  flowing  at  the  former  rate  during  the 
heigiit  of  each  pnlse-exjiansion.  and  at  the  latter  in  the  in- 
terval between  each  two  beats.  Ijudwig  and  Dogiel  found  the 
velocity  in  the  dog  and  in  the  rabbit  to  vary  witliin  very  wide 
limits,  not  only  in  diflerent  arteries,  but  in  the  same  artery 
under  different  circumstances.  Thus  while  in  the  carotid  of 
the  rabbit  it  may  lie  said  to  vary  from  100  to  200  mm.  per 
sec,  and  in  the  carotid  of  the  dog  from  200  to  500  mm.  per 
see.,  both  these  limits  were  frequentl}' passed. 


THE    FLOW    IN    THE    VEINS.  189 


3.    The  FIoiv  in  the  Veins. 

When  a  vein  is  severed  the  flow  from  the  distal  cut  end 
(i  e.,  the  end  nearest  the  capillaries)  is  continuous,  the 
blood  is  ejected  with  comparatively  little  force,  and  with 
slight  velocity. 

When  a  vein  is  connected  with  a  manometer,  the  lateral 
pressure  is  found  to  be  very  small ;  it  is  greater  in  the  veins 
farther  from  the  heart  than  in  those  nearer  the  heart  In 
the  immediate  neighborhood  of  the  heart  the  pressure  ma}^ 
(during  the  inspiratory  movement)  become  negative,  i.  e., 
when  the  manometer  is  brought  into  connection  with  the 
interior  of  the  vein,  the  mercury  in  the  distal  limb  falls,  in- 
stead of,  as  in  the  case  of  the  artery,  rising. 

In  the  brachial  vein  of  the  sheep  Jacobson  found  the  mean  pres- 
sure to  be  4  mm.  of  mercury,  in  a  branch  of  the  same  9  mm.  In 
the  crural  it  was  11.4  mm.  In  the  subclavian  the  mean  pressure 
■was  negative,  viz.,  — .1  mm.,  becoming ^ — 1  mm.  during  inspira- 
tion, — 3  mm.  or  — 5  mm.  during  a  strong  inspiration,  and 
changing  to  positive  during  expiralion. 

The  level  of  mercury  in  the  manometer,  except  in  the  case 
of  certain  veins,  subject  to  influences  which  will  be  dis- 
cussed hereafter,  remains  constant.  The  pulse-oscillations, 
so  striking  in  the  arteries,  are  absent  in  the  veins.  In  the 
small  veins  the  velocity  of  the  current,  measured  in  the 
same  way  as  the  arteries,  is  ver}^  slight.  It  increases  in  the 
larger  veins,  corresponding  to  the  diminution  of  the  area  of 
''the  bed  j"  it  is  about  200  mm.  per  sec.  in  the  jugular  vein 
of  the  dog. 

Tims  the  flow  in  the  veins  presents  strong  contrasts  with 
that  in  the  arteries.  In  tlie  arteries,  even  in  the  smallest 
branches,  there  is  a  considerable  mean  pressure.  In  the 
veins,  even  in  the  small  veins  where  it  is  largest,  the  mean 
pressure  is  very  slight.  In  other  words,  there  is  always  a 
dilference  of  pressure  tending  to  make  the  blood  flow  con- 
tinuously from  the  arteries  into  the  veins.  A  pulse  is  i)res- 
ent  in  the  arteries,  but,  with  certain  exceptions,  absent  in 
the  veins.  The  velocity  of  the  stream  of  blood  in  the  arte- 
ries is  considerable  ;  in  the  small  veins  it  is  much  less,  but 
it  increases  in  the  larger  trunks  ;  for  in  both  arteries  and 
veins  it  corresponds  with  the  area  of  the  bed,  diminishing 
in  the  former  from  the  heart  to  the  capillaries,  and  increasing 
in  the  latter  from  the  capillaries  to  the  heart. 


190  THK    VASCULAR    MECHANISM. 

Jli/drdiilic  Prinriph'.^  of  llic  Cirfulaliou. 

All  tlio  iihovo  pIu'iK^iiHMKi  ni\'  llie  siini)le  rosiilts  C)f  an  iii- 
tennittent  Ibrct;  (like  tliat  of  the  systole  of  tlie  ventrk-le) 
woiUiiitj:  in  a  closed  circuit  of  hraiichiiio-  elastic  lnl)es,  s* 
an-ansj:e(l  that  while  the  individual  tubes  lirst  diminish  (from 
tlie  heart  to  the  capillaries)  and  then  increase  (Ir  >rn  the  cap- 
illaries to  the  heart),  the  area  of  the  bed  first  increases  and 
then  diminishes,  the  tubes  together  thus  forming  two  cones 
placed  l>ase  to  base  at  the  capillaries,  with  their  apices  con- 
veroing  to  the  heart.  To  this  it  must  be  added  that  the 
friction  in  the  small  arteries  or  cai)illaries,  at  the  junction 
of  the  bases  of  the  cones,  offers  a  very  great  resistance  to 
the  flow  of  the  blood  through  them.  It  is  this  peri|)heral 
resistance  (in  the  minute  arteries  and  capillaries,  for  the 
resistance  offered  by  the  friction  in  the  larger  vessels  may, 
when  compared  with  this,  be  practically  neglected),  reacting 
through  the  elastic  walls  of  the  arteries  upon  the  intermit- 
tent tbrce  of  the  henrt,  which  gives  the  circulation  of  the 
blood  its  peculiar  features. 

Circumstances  determining  the  Character  of  the  Flow. — 
"When  fluid  is  driven  by  an  inter  uittent  force,  as  by  a  pump, 
through  a  perfectly  rigid  tube  (or  system  of  tubes)  at  each 
stroke  of  the  pump  there  escapes  from  the  distal  end  of  the 
system  just  as  much  fluid  as  enters  it  at  the  proximal  end. 
The  esca|)e,  moreover,  takes  place  at  the  same  time  as  the 
entrance,  since  the  time  taken  up  by  the  transuiission  of  the 
shock  is  so  small  that  it  may  be  neglected.  This  result  re- 
mains the  same  when  any  ivsistance  to  the  flow  is  introduced 
into  the  system.  The  force  of  the  pump  remaining  the  same 
the  inti-oduction  of  the  resistance  undoubtedly  Icsslmis  the 
quantity  issuing  at  the  distal  end  of  each  stroke,  but  it  does 
so  simply  by  le.->sening  the  quantity  entering  at  the  proxi- 
mal end  ;  the  income  and  outgo  remain  e(pial  to  each  other, 
and  occur  at  almost  the  snnu  time.  And  what  is  true  of 
the  two  ends  is  also  true  of  any  )jart  of  the  course  of  the 
system,  so  far,  at  all  events,  as  the  following  proposition  is 
concerned,  that  in  a  system  of  rigid  tul>es,  either  with  or 
without  an  intercalated  resistance,  the  flow  caused  by  an 
intermittent  force  is,  in  every  pirt  of  the  tubes,  intermit- 
tent synchronously  with  that  force. 

In  a  systT^m  of  elastic  tubes  in  which  there  is  little  resist- 
ance  to  the   progress  of  the   fluid,  the  flow  caused   by  an 


INTERMITTENT    FLOW.  191 

intermittent  force  is  also  intermittent.  The  out^ro  being 
nearly  as  the  income,  tiie  elasticity  of  the  walls  of  the  tubes 
is  scarcely  at  all  called  into  play.  These  behave  practically 
like  rigid  tubes.  When,  however,  sufficient  resistance  is  in- 
troduced into  any  i)art  of  the  course,  the  fluid,  being  unable 
to  pass  by  the  resistance  as  rapidly  as  it  enters  the  system 
'from  the  pump,  tends  to  accumulate  on  the  pi'oximal  side  of 
the  resistance.  This  it  is  able  to  do  by  expanding  the  elastic 
walN  of  the  tubes.  At  each  stroke  of  the  pump  a  certain 
quantity  of  fluid  enters  the  system  at  the  proximal  end.  Of 
this  only  a  fraction  can  pass  through  the  resistance  during 
the  stroke.  At  the  moment  when  the  stroke  ceases  the  rest 
still  remains  on  the  proximal  side  of  the  resistance,  the 
elastic  tubes  having  expanded  to  receive  it.  During  the 
interval  Itetween  this  and  the  next  stroke,  the  distended 
elastic  tubes,  sti'iving  to  return  to  their  natural  undistended 
condition,  pre^s  on  this  extra  quantity  of  fluid  which  they 
contain  and  tend  to  drive  it  past  the  resistance.  Thus  in 
the  rigid  system  (and  in  the  elastic  system  without  resist- 
ance) there  issues,  from  the  distal  end  of  tlie  system,  at  each 
stroke  just  as  niuch  fluid  as  enters  it  at  the  proximal  end, 
while  between  the  strokes  there  is  perficL  quiet.  In  the 
elastic  system  with  resistance,  on  the  contrary,  the  quantity 
which  passes  the  resistance  is  only  a  fraction  of  that  wiiich 
enters  the  system  from  the  i)ump.  the  remainder  or  a 
portion  of  the  remainder  continuing  to  pass  during  the  in- 
terval between  the  strokes.  In  the  former  case  the  system 
is  no  fuller  at  the  end  of  the  stroke  than  at  the  l)eginning. 
In  the  latter  case  there  is  an  accumulation  of  fluid  between 
the  pump  and  the  resistance,  and  a  corresponding  distension 
of  that  part  of  the  system,  at  the  close  of  eacli  stroke — an 
accumulation  and  distension,  however,  which  go  on  dimin- 
ishing until  the  next  stroke  comes.  The  amount  of  fluid 
thus  remaining  after  the  stroke  will  depend  on  the  amount 
of  resistance  in  relation  to  the  force  of  the  stroke,  and  on 
the  distensibiiity  of  the  tubes  :  and  the  amount  which  passes 
the  i-esistaiice  befoi-e  the  next  stroke  will  depend  on  tlie  de- 
gree of  elastic  reaction  of  which  the  tubes  are  cai)able. 
Thus,  if  the  resistance  be  very  considerable  in  relation  to 
the  force  of  the  stroke,  and  the  tubes  very  distensible,  only  a 
small  portion  of  the  fluid  will  pa^-s  the  resistance,  the  greater 
part  remaining  lodged  between  the  pump  and  tlie  resistance. 
If  the  elastic  reactions  be  great,  the  lai'ge  [X'rtion  of  this  will 
be  passed  on  through  the  resistance  before  the  next  stroke 


192  THE    VASCULAR    MECHANISM. 

comes.  In  otlier  woids,  the  irreatcr  the  lesistance  (in  rela- 
tion to  the  force  of  tlie  stroke',  and  the  j^reater  the  elastic 
force  hroiiujht  into  play,  the  less  intermittent,  the  more 
nearly  conti.inous,  will  he  the  Ihnv  on  tiie  far  side  of  the 
resistance. 

If  the  first  stroke  he  succeeded  by  a  second  stroke  l)efore 
its  quantity  of  fluid  has  all  passed  l>y  the  resistance,  there 
will  he  an  additional  accumulation  of  fluid  on  the  near  side 
of  the  resistance,  an  additional  distension  of  the  tubes,  an 
additional  strain  on  their  elastic  powers,  and,  in  consequence, 
the  flow  between  this  second  stroke  and  tiie  third  will  be 
even  more  marked  than  that  between  the  first  and  tiie  second, 
thouuh  all  three  strokes  were  of  the  same  force,  the  addition 
being  due  to  the  extra  amount  of  elastic  force  called  into 
play.  In  fact,  it  is  evident  that,  if  there  be  a  sutlicient  store 
of  elastic  power  to  fall  back  upon,  by  continually  repeating 
the  strokes  a  state  of  things  will  be  at  last  arrived  at,  in 
which  tlie  elastic  force,  called  into  play  by  the  continually 
increasing  distension  of  the  tubes  on  the  near  side  of  the 
resistance,  will  be  sutlicient  to  drive  tiirough  the  lesistance, 
in  the  interval  between  each  two  strokes,  just  as  much  fluid 
as  enters  the  near  end  of  the  system  at  each  stroke.  Jn 
other  words,  the  elastic  reaction  of  the  walls  of  the  tubes 
\\\\\  have  converted  the  intermittent  into  a  continuous  flow. 
The  flow  on  the  far  side  of  the  resistance  is  in  this  case  not 
tlie  direct  result  of  the  strokes  of  the  pump.  All  the  force 
of  the  pum[)  is  spent,  fiist  in  getting  up,  and  afterwards  in 
keeping  up.  the  overdistension  of  the  tubes  on  the  near  side 
of  the  resistance;  it  is  the  overdistended  tubes  whieh  are 
the  cause  of  the  continuous  flow,  by  emptying  themselves 
into  the  far  side  of  the  resistance,  at  such  a  rate,  that  tliey 
discharge  through  the  resistance  during  a  stroke  and  in  the 
succeeding  interval  just  as  mucii  as  they  receive  from  the 
pump  by  the  stroke  itself. 

This  is  exactly  what  takes  place  in  tlie  vascular  system. 
The  friction  in  tiie  minute  ai'teries  and  capillaries  presents 
a  considerable  resistance  to  the  flow  of  blood  through  them 
into  the  small  veins.  In  consequence  of  this  resistance,  the 
force  of  the  heart's  beat  is  spent  in  maintaining  tlie  whole 
of  the  arterial  system  in  a  state  of  overdistensicm,  as  indi- 
cated by  the  arterial  pressure.  The  overdistended  arterial 
system  is,  by  the  agency  of  its  elastic  walls,  continually 
emptying  itself  by  overflowing  through  the  capillaries  into 
the  venous  system,  overflowing  at  such  a  rate,  that  just  as 


OVERFULL    ARTERIES.  1^'^ 

mucli  blood  passes  from  the  arteries  to  the  veins  during;  each 
systole  and  its  succeeding  diastole  as  enters  the  aorta  at 
each  systole. 

It  cannot  he  too  much  insisted  upon  that  the  whole  arte- 
rial system  is  overfull.  This  is  what  is  meant  by  the  hiiih 
arterial  pressure.  On  the  other  hand,  the  veins  are  much 
less  full.  Tins  is  shown  by  the  low  venous  pressure.  The 
overfull  arteries  are  continually  striving  to  pass  their  surplus 
in  a  continuous  stream  through  the  cai)illaries  into  the  veins, 
so  as  to  bring  Ijoth  venous  and  arterial  pressure  to  the  same 
level.  As  continually  the  heart  by  its  beat  is  keeping  the 
arteries  overfull,  and  thus  maintaining  the  difference  be- 
tween the  arterial  and  venous  pre>^sure,  and  thus  preserv- 
ing the  steady  cai)i!lary  stream.  When  the  heart  ceases  to 
l)eat,  the  arteries  do  succeed  in  emptying  their  surplus  into 
the  veins,  and  wiien  the  pressure  on  both  sides  of  the  cap- 
illaries is  thus  equalized,  the  flow  through  the  capillaries 
ceases. 

In  the  facts  just  discussed,  it  makes  no  essential  difference 
whether  the  outflow  on  the  far  side  of  the  resistance  be  an 
open  one,  or  whether,  as  is  the  case  in  the  vascular  system, 
the  fluid  be  returned  to  the  pump,  provided  onl3'  that  the 
resistance  offered  to  that  return  be  sufficiently  small.  We 
shall  see,  in  speaking  of  the  heart,  that,  so  far  from  there 
being  an}-  resistance  to  the  flow  of  blood  from  the  great 
veins  into  the  auricle,  the  flow  is  favored  by  a  variety  of 
circumstances.  We  have  seen  moreover  that,  besides  the 
very  sudden  decrease  in  tiie  immediate  neighborhood  of  the 
capillaries,  there  is  in  passing  along  the  whole  vascular  sys- 
tem from  the  aorta  to  the  ven?e  cavje  a  gradual  fall  of  pres- 
sure. A  little  consideration  shows  that  this  must  be  the 
case.  After  what  has  been  said  it  is  obvious  that  tiie  move- 
ment of  the  blood  may  be  compared  to  that  of  a  body  of 
fluid,  driven  by  pressure  from  the  ventricle  through  the 
vessels  to  its  outflow  in  the  auricle.  Were  the  pressure  a 
continuous  one,  and  were  there  no  capillary  resistance, 
there  would  be  a  gradual  fall  of  pressure,  from  the  part 
farthest  from  the  outfall,  viz.,  the  aorta,  to  the  part  nearest 
the  outfall,  viz  ,  the  ven}^  cavtB.  The  introduction  of  the 
capillary  resistance  and  its  attendant  phenomena  gives  rise 
to  the  feature  of  a  very  sudden  and  marked  fall  in  the  capil- 
lary region,  Itut  leaves  untouched  the  gradual  character  of 
the   fall   iu   the   rest  of  the  course,  from   the  aorta  to  the 


194  THE    VASCULAR    MECHANISiVI. 

ininuto   arteries,  and    fioin    the   ininule  veins   to  the   vena3 
cavjb. 

To  recnpitnlatc  :  Tiiere  are  three  eliief  factois  in  the  nie- 
chanies  (»1"  the  eircnhition,  ( 1)  tlie  I'oice  and  tVequeney  of 
the  heart-beat,  (2)  the  peripheral  resistanee,  (8)  theehistieity 
of  the  arterial  walls.  These  three  factors,  in  order  to  pro- 
dnee  a  normal  eircnlation,  innst  be  in  a  certain  relation  to 
each  other.  A  ilistnrbance  of  these  relations  brinj^s  abont 
abnormal  conditions.  Tims,  if  the  capillary  resistance  be 
rednced  beyond  certain  limits,  while  the  force  and  frequency 
of  the  heart  remain  the  same,  so  much  blood  passes  through 
the  capillaries  at  each  stroke  of  the  heart  that  there  is  not 
suflicient  left  behind  to  distend  the  arteries,  and  britig  their 
elasticity  into  play-  In  tliis  case  tiie  intei'mittence  of  the 
arterial  flow  is  continued  on  into  the  veins.  An  instanceof 
this  is  seen  in  the  experiments  on  the  sul)maxillary  gland, 
whei-e  sonietimes  the  capillai-y  resistance  in  the  gland  is  so 
much  lowered  that  the  blood  in  the  veins  of  the  gland  pul- 
sates.' A  like  result  occurs  when,  the  ca))iliary  resistance 
remaining  the  sauie,  the  force  or  frequency  of  the  heart's 
beat  is  lowered.  Thus  the  beats  may  be  so  feeble  that  at 
each  stroke  no  more  blood,  or  but  little  more,  enters  the 
arterial  system  than  can  pass  through  the  cai)illaries  befoie 
the  next  stroke  ;  or  so  infrequent  that  the  whole  quantity 
sent  on  by  a  stroke  has  time  to  escai)e  before  the  next  stroke 
comes,  if,  while  the  heart's  beat  and  the  resistance  remain 
the  same,  the  elasticity  of  the  arterial  walls  be  leduced,  the 
arteiies  will  be  unable  to  expand  sutHciently  to  retain  the 
surplus  of  each  stroke  or  to  exert  suHicient  elastic  reaction 
to  cariT  forward  the  stream  between  the  strokes;  and  in 
conse(i[uence  more  or  less  intermittence  will  become  mani- 
fest. 

^lare}'^  states  that  when  fluid  is  driven  through  tw^o  tubes  of 
equal  calibre,  one  elastic  and  the  other  rigid,  with  equal  force  and 
like  intermittence,  the  outflow  through  the  elastic  tube  is  greater 
than  through  the  rigid  tube.  This  he  attributes  to  the  fact  that 
in  the  rigid  tube  all  the  friction  flills  in  the  period  of  the  stroke, 
when  the  velocity  of  the  stream  is  greatest,  and  is  therefore 
greater  than  in  the  elastic  tube  where  it  is  distributed  as  w^ell  over 
the  interval  between  the  strokes.  Under  this  view,  the  arrange- 
ments of  the  vascular  system  are  useful,  not  only  in  causing  the 

'  See  Book  1,  cap.  i,  sec.  2,  on  the  vSecretion  of  the  Digestive  Juices. 
2  Ann.  d.  Sci.  Kat.  (iv),  viii,  p.  329. 


VARIATIONS    IN    VELOCITY.  195 


flow  throiioli  tlie  caiiillaries  to  be  continuous,  and  therefore  best 
adapted  for  carrying  on  the  interchange  between  the  tissues  and 
the  blood,  but  also  in  providing  that  the  flow  should  be  as  large 
as  possible. 


Circumstances  determining"  the  Velocity  of  the  Flow. — We 
have  seen  that  the  velocity  of  the  Idood-stream  diminishes 
from  the  aorta  to  tlie  ca[)illaries,  and  increases  from  the 
capilhii'ies  to  the  great  veins.  Thus  in  the  dog-  tlie  velocity 
in  the  great  arteries  may  be  stated  at  from  ::^00  to  500  mm., 
in  the  capillaries  at  less  than  1  mm.  (.5  to  .75  mm.),  and  in 
the  large  veins  at  about  200  mm.  in  a  second,  in  fact,  the 
greater  part  of  the  time  of  the  circuit  is  taken  up  in  the 
capillary  region.  An  iron  salt,  injected  into  the  jugular 
vein  of  one  side  of  the  neck  of  a  horse,  makes  its  appearance 
in  tlie  blood  of  the  jugular  vein  of  the  other  side  in  about 
thirty  seconds. 

Ilering's  mean  result  in  the  horse  was  27.6  seconds.  In  the 
dog  Yierordt  found  it  to  be  15.2  seconds  ;  in  the  rabbit  7  seconds. 

Without  laying  too  much  stress  on  this  ex[)eriment,  it 
may  be  taken  as  a  fair  indication  of  the  time  in  which  the 
whole  circuit  may  be  completed.  It  takes  about  the  same 
time  (see  p.  176)  to  pass  tiirough  abcait  20  mm.  of  capilla- 
ries. Hence,  if  any  corpuscle  had  in  its  circuit  to  pass 
through  10  mm.  of  ca[)inaries,  half  the  whole  time  of  its 
journey  would  be  spent  in  the  narrow  channels  of  the  capil- 
laries. Since,  however,  the  average  length  of  a  capillary  is 
about  .5  mm.,  about  one  second  is  spent  in  the  capillaries. 
Jnasmnch  as  the  purposes  served  by  the  blood  are  chietly 
carried  out  in  the  capdlaries,  it  is  obviously  of  advantage 
that  its  stay  in  them  should  be  prolonged. 

The  permanent  variations  in  the  velocity  of  the  stream  are 
directly  dependent  oi;  the  area  of  '•  the  bed."  When  a  fluid 
is  driven  by  a  uniform  pressure  through  a  narrow  tube  with 
an  enlargement  in  the  middle,  the  velocity  of  the  stream 
diminishes  in  the  enlargement,  but  increases  again  when  the 
tube  once  more  narrows.  So  a  river  slackens  speed  in  a 
broad,  but  rushes  on  rapidly  again  when  the  banks  close  in. 
Exactly  in  the  same  way  the  velocity  of  the  blood-stream 
slackens  from  the  aorta  to  the  capillaries  corresponding  with 
the  increased  total  bed,  but  hurries  on  again  as  the  nu- 
merous veins  are  gathered  into  the  smaller  bed  of  the  ven.ne 
cavse.     The  loss  of  velocity'  in  the  capillaries,  as  compared 


196  THE    VASCULAR    MECHANISM. 


\\\{\\  the  arteries,  is  not  due  to  there  beinj^  so  miicli  more 
friction  in  the  narrow  ciiannels  ot"  the  former  tlian  in  the 
wide  canals  of  the  latter.  For  the  peripheral  resistance 
cansed  by  the  friction  in  tiie  capillaries  and  small  arteries 
is  an  obstacle  not  only  to  the  flow  of  blood  throu*^h  tiiese 
sinall  vessels  where  the  resistance  is  actually  f^enerated,  bnt 
also  to  the  escape  of  the  blood  from  the  large  into  the  small 
arteries,  and  indeed  from  the  heart  into  the  large  arteries. 
It  exerts  its  influence  along  the  whole  arterial  tract.  And 
it  is  obvious  that  if  it  were  this  peripheral  r^'sistance  which 
checked  the  How  in  the  capillaries,  thei*e  could  be  no  re- 
covery of  velocity  along  the  venous  tract.  The  rapidity  of 
the  flow  in  arteries,  capillaiies,  and  veins,  is  in  each  case 
d«'termined  by  the  total  sectional  area  of  the  channels. 
There  is,  however,  a  loss  of  velocity  on  the  whole  course. 
At  each  stroke  as  much  blood  enters  the  right  auricle  as 
Issues  from  the  left  ventricle;  but  the  sectional  area  of  the 
ven?e  cavj^i  is  greater  tiian  that  of  the  aorta,  so  that  even  if 
tlie  auricle  were  filled  in  exactly  the  same  time  as  the  ven- 
tricle is  emptied,  the  blood  must  pass  more  rapidly  through 
the  narrow  aorta  than  through  the  broad  venae  cavai,  in 
order  that  the  same  quantity  of  blood  should  pass  each  in 
the  same  time.  The  diastole  of  the  auricle,  however,  is  dis- 
tinctly longer  than  the  systole  of  the  ventricle  ;  the  time 
during  which  the  auricle  is  being  filled  is  greater  than  that 
during  which  the  ventricle  is  being  emptied,  and  hence  the 
velocity  of  the  venous  flow  into  the  auricle  must  be  still  less 
than  that  of  tlie  arterial  blood  in  the  commencing  aorta. 

The  temporary  variations  of  the  velocity  of  tiie  stream  in 
any  given  channel,  and  these  wq  have  already  (p.  190)  seen 
to  be  very  considerable  in  the  case  of  the  arteries  at  least, 
are  dependent  on  a  variety  of  circumstances.  In  a  tube  of 
constant  calibi'e,  the  velocitv  with  which  fluid  flows  from 
one  point  to  another,  for  instance  from  the  point  a  to  the 
l)oint  6,  will  be  in  main  dependent  on  the  difference  between 
the  pressure,  existing  at  a  and  b.  The  lower  the  pressure  at 
h  as  comi)ared  with  a  the  greater  the  rapidity  with  which 
the  fluid  flows  from  a  to  h.  And  temporary  variations  of 
pressures  form  undoubtedly  the  main  cause  of  the  tempo- 
rar3-  variations  observable  in  the  velocity  of  the  arterial  flow.  • 
Thus  with  each  systole  of  the  ventricle  there  is  an  increase 
of  velocity  in  tlie  whole  arterial  flow  followed  by  a  diminu- 
tion during  the  diastole.  So  also  if  the  peripheral  resist- 
ance in  the  minute  arteries  into  which  a  larger  artery  divides 


ANATOMY  OF  THE  HEART.  197 

be  suddenly  lowered  (by  the  action  of  vaso-motor  nerves,  in 
a  manner  which  we  shall  presently  discuss),  ivithout^  the 
calibre  of  the  largej-  artei-y  itself  being  chomged^  the  pres- 
sure on  tlie  distal  (peripheral)  side  of  the  artery  ma}'  be 
much  diminished,  wliile  the  pressure  on  the  proximal  (car- 
diac) side  remains  at  first  unaltered  ;  and  this  would  neces- 
sarily cause  an  increase  in  the  rapidity  of  the  stream  through 
that  artery.  But,  as  we  shall  see  later  on,  from  the  compli- 
cations of  the  vascular  macliinery  such  prolilems  as  these 
become  very  intricate  ;  and  the  results  of  observations  on 
variations  in  arterial  velocity  are  not  altogether  intelligible. 
It  has  been  suggested  that  varying  conditions  of  the  blood, 
by  affecting  the  amount  of  adhesion  between  the  blood  and 
tlie  walls  of  the  vessels,  may  be  an  important  factor  in  de- 
termining the  variations  in  the  velocity  of  the  stream/ 

Sec.  2.— The  Heart. 
[  The  Fhys^iological  Anatomy  of  the  Heart. 

The  heart  is  a  hollow,  muscular  organ,  having  a  shape  simi- 
lar to  that  of  a  flattened  cone.  It  is  situated  obliquely  within 
the  chest,  immediately  posterior  to  the  sternum;  resting 
upon  the  diaphragm  ;  supported  in  position  by  the  bloodves- 
sels ;  and  covered  by  the  pericardium.  Roughly  sketched, 
the  position  of  the  base  of  the  cone  corresponds  to  a  line 
drawn  a  little  to  the  right  of  the  sternum,  from  the  second 
intercostal  space  to  the  sternal  articulation  of  the  sixth  and 
seventh  cartilages  of  the  right  side.  The  apex  corresponds 
to  a  point  in  the  left  fifth  intercostal  space,  a  little  interior 
to  a  vertical  line  drawn  across  the  nipple. 

The  muscular  fibi'es  composing  the  heart  are  peculiar  in 
character  to  the  organ  itself.  The}^  are  striated,  but  differ 
from  the  ordinary  skeletal  muscles.  In  the  skeletal  mu.scles 
the  fibres  are  entirely  distinct  and  separable,  possessing  dis- 
tinct longitudinal  and  transverse  lines  of  cleavage.  But  in 
the  fibres  of  the  heart,  as  seen  in  Fig.  57,  the  lines  of  cleav- 
age are  partially  lost  and  apj)arent  anastomoses  formed. 
The  fibres  of  the  heart  rarel}'  have  a  sarcolemmatous  cov- 
ering. These  fibres  ma}^  conveniently  be  divided  into  two 
layers,  the  superficial  and  deep.  The  superficial  layer  of  the 
fii)res  of  the  ventricles  consists  of  several  laminae,  which  have 

^  Ludwig  and  Dogiel,  Ludwia:'s  Arbeiten,  1867.  Cf.  also  Ewald, 
Archiv  f.  Anat.  u.  Phys.,  1877,  p.'208. 

17 


15)8 


THE    VASCULAR    MECHANISM. 


a  ])cciiliar  spiral  anangcinent  iiiiiuiiig  from  right  to  left, 
siimiUitiiig  a  rigiire  8.  This  peuiiliar  arrangement  is  of 
physiological  importance  in  explaining  several  of  the  phe- 


Fk;.  57 


Anastomosing  muscular  fibres  oT  tlie  heart  seen  in  longitudinal  section.  On  the 
right  tlie  limits  of  the  separate  cells  with  their  nuclei  are  exhibited  somewhat  dia- 
grammaticaUy. 

nomena  observed  in  the  cardiac  beat,  as  will  be  pointed  out 
liereafter.     The  deep  layer  is  circular. 

The  heart  can  with  great  propriet}'  be  considered  as  a  double 
organ — a  right,  or  pulmonar}^ ;  a  left,  or  systemic  heart; 
each  containing  two  cavities,  called  respectively  an  auricle 
and  ventricle.  The  right  and  left  cavities  of  the  heart  are 
separated  by  a  muscular  })artilion  called  the  inter-auriculo- 
ventricular  septum.  Tiie  position  of  this  septum  is  marked 
on  the  external  surface  of  tiie  heart  by  two  grooves. 

The  walls  of  the  left  heart  are  much  thicker  than  those  of 
the  right.  This  is  due  to  the  fact  of  the  greater  propulsive 
ffM'ce  necessary  to  overcome  the  resistance  of  the  systemic, 
than  is  necessary  to  overcome  that  of  the  pulmonic  vessels. 

The  auricles  are  separated  from  the  ventricles  by  peculiar 
valvelike  pendulous  curtains,  so  arranged  as  to  freely  allow 
of  the  passage  of  blood  from  the  auricles  into  the  ventricles, 
and,  by  a  peculiar  valvelike  mechanism,  prevent  a  reflux 
current  by  becoming  closed. 

There  are  two  distinct  sets  of  valves  in  the  heart,  the 
auriculo-ventricular  and  the  semilunar.     The  auriculo-ven- 


ANATOMY  OF  THE  HEART. 


199 


tricular  valves  are  two  in  number,  the  right  and  left  (Fio:s.  58, 
59,60).  The  right  is  called  the  tricuspid,  and  consists  of  three 

Fig.  58. 


The  right  auricle  and  veutricle  op°neil,  and  a  part  of  their  right  and  anterior 
■walls  removed,  so  as  to  show  iheir  interior  — \^  1,  superior  vena  cava;  2,  inferior 
vena  cava;  2'.  hepatic  vein^cut  short;  3,  right  auricle;  3',  placed  in  the  fossa  ovalis, 
below  which  ia  the  Eustachian  valve;  o",  is  placed  close  to  the  aperture  of  the 
coronary  vein ;  -j-  +,  placed  in  the  auriculo-ventricular  groove,  where  a  narrow 
portion  of  the  adjacent  walls  of  the  auricle  and  ventricle  has  been  preserved;  4,  4, 
cavity  of  the  right  ventricle,  also  showing  inter-ventricular  septum:  the  ui>per 
figure  is  immediately  below  the  semihiuar  valves ;  4',  large  columna  carnea  or  mu9- 
culus  papillaris  ;  5.  5',  .5",  tricuspid  valve ;  6,  placed  in  the  interior  of  the  pulmonary 
artery,  a  part  of  the  anterior  wall  of  that  vessel  having  been  removed,  and  a  nar- 
row portion  of  it  preserved  at  its  commencement  where  the  semilunar  valves  are 
attached  ;  7,  concavity  of  the  aortic  arch  close  to  the  cord  of  the  ductus  arteriosus ; 
8.  ascending  part  or  sinus  of  the  arch  covered  at  its  commencement  by  the  auricular 
appendix  and  pulmonary  artery;  9,  placed  between  the  innominate  and  left  carotid 
arteries;  10,  appendix  of  the  left  auricle;  11,  11,  the  outside  of  ihe  left  ventricle, 
the  lower  figure  near  the  apex  —From  Quoin's  Anatomy. 


200 


THE    VASCULAR    MECEIANISM. 


cusps  or  leaflets   (Figs.  58,  00).     The  left,  or  mitral  valve, 
consists  of  two  leaflets  only  (Figs.  59,  CtOj,  and   is  ph^.sio- 


Fl<i.  o9. 


Tlie  left  auricle  and  ventricle  opened,  and  a  part  of  their  anterior  and  left  walls 
removed,  so  as  to  show  their  interior — 3,^.  The  pulmonary  artery  has  been  divided 
at  its  commencement  so  as  to  show  the  aorta;  the  opening  into  the  left  ventricle 
has  been  carried  a  short  distance  into  the  aorta,  between  two  of  the  segments  of  the 
semilunar  valves;  the  left  part  of  the  auricle  with  its  appendix  has  been  removed. 
The  right  auricle  has  been  thrown  out  of  view.  1,  the  two  right  puiuonary  veins 
cut  short;  their  openings  are  seen  within  the  auricle;  1',  placed  within  the  cavity 
of  the  auricle  on  the  left  side  of  the  septuin  and  on  the  part  which  forms  the  re- 
mains of  the  valve  of  the  foramen  ovale,  of  which  tlie  crescentic  fold  is  seen  towards 
the  left  hand  of  1' ;  2,  a  narrow  portion  of  the  wall  of  the  auricle  and  ventricle  pre- 
served round  the  auriculo-veutricular  orifice;  3,  .3',  the  cut  surface  of  the  walls  of 


ANATOMY  OF  THE  HEART.  201 


the  ventricle,  seen  to  become  very  much  tliinner  towards  3"  at  the  apex  ;  4.  a  small 
part  of  the  anterior  wall  of  the  left  ventricle,  which  has  been  preserved  with  the 
principal  anterior  columna  carnea  or  musculus  papillaris  attached  to  it;  5,  5,  raus- 
culi  papillares;  5',  the  left  side  of  the  septum,  between  the  two  ventricles,  within 
the  cavity  of  the  left  ventricle;  6,  6',  the  mitral  valve;  7,  placed  in  the  interior  of 
the  aorta,  near  its  commencement  and  above  the  three  segments  of  its  semilunar 
valve,  which  are  han^iuo;  loosely  together;  7',  the  exterior  of  the  great  aortic  sinus; 
8,  the  root  of  the  pulmonary  artery  and  its  semilunar  valves ;  8',  the  separated  por- 
tion of  the  pulmonary  artery  remaining  attached  to  the  aorta  by  9,  tlie  cord  of  the 
ductus  arteriosus  ;  10,  the  arteries  rising  from  the  summit  of  the  aortic  arch. — From 
Qua  ill's  Anatomy. 

logically  the  stronger  of  the  two.  The  aurieulo-ventricular 
valves  are  formed  by  reduplications  of  the  endocardium, 
and  strengthened  by  fibrous  tissue.  They  are  attached  by 
their  bases  to  the  auriculo-ventricular  orifices;  the  portions 
of  their  sides  nearest  the  bases  are  attached  to  each  other, 
thus  forming  a  continuous  circular  membrane.  To  the  free 
margin  and  ventricular  surfaces  of  these  valves  are  attached 
numerous  tendinous  cords,  which  connect  the  valves  with 
the  muHculi  papillarei^.  They  are  called  the  chordat^  tendineae. 
On  the  intra-ventricular  surface  of  the  heart  numerous  mus- 
cular bands  are  seen,  which  are  called  the  column  at  carueae. 
These  bands  are  of  three  kinds:  those  attached  by  one  of 
their  sides  and  by  both  extremities  to  the  ventricles  ;  those 
attached  by  both  extremities;  and  those  attached  by  one 
extremity  alone,  the  other  extremity  connecting  with  the 
auriculo-ventricular  valves  by  means  of  the  intervening 
chordte  tendinenp.  These  \?ii\.QY  column ae  carneae  are  distin- 
guished by  the  name  of  musculi  papillarei^  (I^'igs-  58,  59). 

There  are  also  two  sets  of  semilunar  valves,  the  aortic 
and  pulmonary  (Figs.  58,  5^,  (;0).  Each  of  these  sets  of 
valves  consists  of  three  semilunar  segments-  The  pulmonary 
is  situated  at  the  junction  of  tiie  pulraonai-y  artery  with  the 
right  ventricle.  The  aortic  is  situated  at  the  junction  of 
the  aorta  with  the  left  ventricle.  On  the  middle  of  each  of 
the  free  edges  of  Miese  valves  is  a  small  nodule,  called  the 
corpus  Arantii\,  which,  when  the  valves  become  closed,  come 
together  and  are  disposed  in  a  spiral  form.  The}'  thus  close 
up  an  opening  which  would  obvious!}'  be  present  were  they 
absent. 

Behind  each  of  the  semilunar  valves  is  a  pouch-like  expan- 
sion ;  these  are  termed  the  sinuses  of  Valsalca.  In  the 
aortic  walls,  at  about  the  free  margin  of  the  right  and  left 
semilunar  valves,  the  orifices  of  the  coronary  arteries  which 
supply  the  heart  with  blood  are  seen. 

The  semilunar  valves  are  formed  by  reduplications  of  the 
lining  membrane,  and  strengthened   bv  fibrous  tissue. 


202 


THE    VASCULAR     MECUANlSxM. 


The  passage  of  blood  lliroiigli  the  heart,  can  thus  he  briefly 
stated:  coTnini^  from  the  system  througli  the  veiiie  cav{«  it 
eniers  the  right  auricle  ;  iVom  tiie  right  auricle,  it  passes  to 
the  right  ventricle  ;  thence  to  the  lungs  through  the  pulmon- 
ary artery.  After  passing  through  tiie  lungs  it  again  enters 
the  heart  through  tiie  pulmonary  veins  into  the  left  auricle; 
from  the  left  auricle  it  i)asses  into  the  left  ventricle,  and  from 
thence  through  the  aorta  into  the  general  system  (Fig.  61)]. 

[Fio.  60. 


View  of  the  base  of  the  ventriciihir  part  of  the  lieart,  showing  the  relative  position 
of  the  arterial  and  auriculo-ventricular  orifice  —%.  The  muscular  fibres  of  the 
ventricles  are  exposed  by  the  removal  of  the  pericardium,  fat,  blo(xl vessels,  etc. ;  the 
pulmonary  artery  and  aorta  have  been  removed  by  a  section  made  immediately  be- 
yond the  attachment  of  the  semilunar  valves,  and  the  auricles  have  been  removed 
immediately. aVjove  the  auriculo-ventricular  orifices.  The  semilunar,  and  auriculo- 
ventricular  valves  are  in  the  ntaily  closed  condition.  1, 1,  the  base  of  the  right  ven- 
tricle ;  r,  the  conus  arteriosus,  which  is  a  conical  expansion  of  the  right  ventriclp, 
immediately  at  the  point  where  the  pulmonary  artery  arises;  2,  2,  the  ba-^e  of  the 
left  ventricle;  3,  .3,  the  divided  wall  of  the  right  auricle;  4,  that  of  the  left;  5,  5'  rt'\ 
the  tricuspid  valve;  6,  6',  the  mitral  valve.  In  the  angles  between  these  segments 
are  seen  the  smaller  fringes  frequently  observed;  7,  the  anterior  part  of  the  pul- 
monary artery;  8,  placed  upon  the  posterior  part  of  the  root  of  the  aorta;  9,  the 
right,  9',  the  left  coronary  artery.— From  QuaiiVs  Anatomy.] 

The  heart  is  a  pump,  the  motive  power  of  which  is  sup- 
plied by  the  contraction  of  its  muscular  fibres.  Its  action, 
consequently,  presents  problems  whicii  are  partly  meciian- 
ical  and  partly  vital.  Regarded  as  a  pump,  its  effects  are 
determined  by  the  frequency  of  the  beats,  by  the  force  of 
each  beat,  by  the  character  of  each  beat,— whether,  for  in- 


PHENOMENA    OF    THE    NORMAL    BEAT. 


m 


stance,  slow  and  lingering,  or  sudden  and  sliarp, — and  b}' 
the  quantity  of  fluid  ejected  at  each  beat.  Hence,  with  a 
given  frequency,  force,  and  character  of  beat,  and  a  given 
quantity  ejected  at  each  beat,  the  problems  which  have  to 
be  dealt  with  are  for  the  most  part  mechanical.  The  vital 
problems  are  chiefly  connected  with  the  causes  which  deter- 

[Fi(f.  61. 


Diagram  of  the  Circulation  through  the  Heart,  a,  a,  Vena  cava,  superior  and  infe- 
rior, b,  Right  ventricle,  c.  Pulmonary  artery,  d.  Pulmonary  vein,  e,  Left  ven- 
tricle.   /,  Aorta.— After  Daltox.] 

mine  the  frequenc}^,  force,  and  character  of  the  beat.  The 
quantity  ejected  at  each  beat  is  governed  more  by  the  state 
of  the  rest  of  the  body  than  by  that  of  the  heart  itself. 


The  Phenomena  of  the  Normal  Beat. 

The  Visible  Movements. — When  the  chest  of  a  mammal  is 
opened  and  artificial  respiration  kept  up,  a  complete  beat  of 
the  whole  heart,  or  cardiac  cycle,  may  be  observed  to  take 
place  as  follows  : 

The  great  veins,  inferior  and  superior  venae  cavje  and  pul- 
monaiy  veins  are  seen,  while  full  of  blood,  to  contract  in  the 


204  THE    VASCULAR    MECHANISM. 

neighborhood  of  tlie  licart;  the  contraction  iini.s  in  a  peri- 
staltic wave  towards  the  aiuicies,  increasing  in  intensity  as  it 
goes.  Arrived  at  the  anricles,  which  are  then  fnll  of  i)lood, 
the  wave  suddenly  spreads,  at  a  rate  too  rapid  to  i)e  fairly 
jndged  l\v  the  eye,  over  the  whole  of  those  organs,  which 
accordingly  contract  witli  a  sndden  sharp  systole.  In  the 
systole  tiie  walls  of  the  auricles  press  towards  the  auriculo- 
ventriciilar  oritices,  an.d  the  auricular  ap|)endages  are  drawn 
inwards,  becoming  smaller  and  paler.  During  the  auricular 
systole  the  ventricles  may  be  seen  to  become  more  and 
more  turgid.  Then  follows,  as  it  were  immediately,  the  ven- 
tricular systole,  during  which  the  ventricles  become  shorter 
and  thicker.  Held  between  the  fingers  they  are  felt  to  be- 
come tense  and  hard.  As  the  systole  pi'ogresses  the  aorta 
and  pulmonary  arteries  are  seen  to  expand  and  elongate, 
and  the  heart  to  twist  slightly  on  its  long  axis,  so  that  while 
tiie  base  is  fixed  by  the  great  arteries,  the  apex  moves  from 
the  left  and  behind  towards  the  front  and  right ;  hence  more 
of  the  left  ventricle  becomes  displayed.  [This  peculiar 
twisting  movement  of  the  apex  during  systole  is  due  to  the 
peculiar  whorl-like  arrangement  of  the  si)iral  layer  of  mus- 
cles around  the  apex.]  As  the  systole  gives  way  to  the  suc- 
ceeding pause  or  diastole,  the  ventricles  flatten  and  elongate, 
the  aorta  and  pulmonary  artery  contract  and  shorten,  the 
heart  turns  back  towards  the  left,  and  thus  the  cycle  is 
completed. 

More  exact  observation  shows,  as  regards  the  change  of 
form  of  the  v^entricular  portion,  that  this,  during  diastole, 
has  somewhat  the  shape  of  a  flattened  cone,  with  an  elli[)se, 
having  its  long  diameter  from  right  to  left,  as  a  base,  i)ut 
during  the  systole  becomes  a  shorter,  more  regular  cone, 
with  a  circle  for  its  base,  having  lessened  chiefl}'  in  its  lon- 
gitudinal and  riglit-to-left  diameters,  and  slightly  only  in  its 
antero-posterior  diameter.  According  to  Kiirschner,'  the 
circumference  of  the  base  of  the  ventricle  is  absolutely 
increased  during  the  systole;  a  tape  placed  around  the  base 
becomes  tense  at  the  commencement  of  the  systole,  while 
the  cavity  is  still  full  of  blood. 

When  the  chest  is  opened,  the  heart  is  deprived  of  its 
natural  supports;  and  consequently,  under  such  circum- 
stances, its  change  of  position  during  the  systole  cannot  be 
properly  studied.  For  it  must  be  remembered  that  the 
heart,  closely  covered  by  the  pericardium,  lies  immediately 

^  Wagner's  Handworterbuch,  Art.  Hertzthatigkeit. 


CARDIAC    IMPULSE.  205 

under  the  sternum  ami  ribs,  there  beino-  between  tliem 
nothing  more  than  a  small  amount  of  mediastinal  connec- 
tive tissue,  and  rests  on  the  slope  of  tlie  diaphragm  below, 
with  the  bmgs  on  eitlier  side.  If,  in  tiie  unopened  cliest  of 
a  rabbit  or  dog,  tliree  needles  be  inserted  through  the  chest- 
wall  so  that  their  points  are  plunged  into  the  substance  of 
the  ventricle,  one  (B)  at  the  base,  close  to  the  auricles,  an- 
other (A)  through  the  apex,  and  a  third  (M)  at  about  the 
middle  of  the  ventricle,  all  three  needles  will  be  observed  to 
move  at  each  beat  of  the  heart.  The  head  of  B  will  move 
suddeidy  upwards,  showing  that  the  point  of  the  needle 
plunged  in  the  ventricle  moves  downwards,  whereas  A  will 
only  quiver,  and  move  neither  distinctly  upwards  nor  down- 
wards. ]\l  will  move  upwards  (and  therefore  its  point  down- 
wards), but  not  to  the  same  extent  as  B.  The  nearer  to  B 
M  is,  the  more  it  moves  ;  the  nearer  to  A,  the  less.  Thus, 
while  during  the  beat,  the  base  (B ;  moves  downwards  as 
the  result  of  the  contraction  (and  longitudinal  shortening) 
of  the  ventricle,  the  apex  (A)  does  not  ciiange  its  place,  the 
shortening  of  the  ventricle  itself  being  compensated  b}'  the 
lenothenino-  of  the  oreat  arteries.     The  middle  of  the  ven- 

rp  o  J^ 

tricle  moves  downwards  more  than  the  apex,  but  less  than 
the  extreme  base.  After  the  death  of  the  animal  the 
needles,  if  properly  inserted  at  first,  perpendicularly  to  the 
chest,  will  be  found  with  all  their  heads  directed  down- 
wards, indicating  that  the  whole  venti-icle  has  been  drawn 
up  by  the  contraction  of  the  empty  aorta  and  pulmonary 
artery. 

Cardiac  Impulse. — If  the  hand  be  placed  on  the  chest,  a 
shock  or  impulse  will  be  %lt  at  each  beat,  and  on  examina- 
tion this  impulse,  ''cardiac  impulse,"  will  be  found  to  be 
synchronous  with  the  systole  of  the  ventricle.  In  man,  the 
cardiac  impulse  maybe  most  distinctly  felt  in  the  fifth  costal 
interspace,  about  a'n  inch  below  and  a  little  to  the  median 
side  of  the  left  nip})le.  The  same  impulse  may  be  felt  in  an 
animal  by  making  an  incision  through  the  diaphragm  from 
the  alxlomen,  and  placing  the  finger  between  the  chest-wall 
and  the  apex.  It  then  can  be  distinctly  recognized  as  the 
result  of  the  hardening  of  the  ventricle  ibiring  the  systole. 
And  the  impulse  which  is  felt  on  the  outside  of  the  chest  is 
the  same  hardening  of  the  stationary  portion  of  the  ventricle 
in  contact  v»'ith  the  chest-wall,  transmitted  through  the  chest- 
wall  to  the  finger.     In  its  flaccid  state,  during  diastole,  the 

LS 


20(5  TIID    VASCULAR    MECHANISM. 

ajicx  is  (in  a  staii(lin<2;  i)osition  at  least)  liore  in  contact  with 
the  chest-wail,  lying  between  it  and  the  tolerably  resistant 
(lia[)liragin.  During  the  systole,  while  occnj)ying.  as  we 
have  rfeen,  the  same  position,  it  suddenly  grows  tense  and 
hard.  The  ventricles,  in  executing  their  systole,  have  to 
contract  against  resistance.  Tiiey  have  to  produce  within 
their  cavities,  tensions  greater  than  tliose  in  the  aorta  and 
I)ulinonary  arteries,  resi)ectively.  This  is,  in  fact,  the  object 
of  the  systole.  Hence,  during  the  swift  s\  stole,  the  ventric- 
ular portion  of  the  heart  becomes  suddenly-  tense,  just  as  a 
bladder  full  of  fluid  would  become  tense  and  hard  when 
forcibly  squeezed.  The  sudden  onset  of  this  hardness  gives 
an  impulse  or  sliock  both  to  the  cliest-wall  and  to  the  dia- 
piiragm,  wdiich  may  be  felt  readily  both  on  the  chest-wall, 
and  also  through  the  diaphragm  when  the  abdomen  is  opened, 
and  the  finger  inserted.  [Tlie  twisting  of  tlie  apex  throws 
it  against  the  chest-wall,  and  is  therefore  another  factor  in 
the  formation  of  tlie  cardiac  imi)ulse.  The  recoil  of  the 
heart  (which  may  be  compared  to '^  the  kicking  of  a  gun 
Avhen  it  is  fired  off")  is  also  a  factor  in  causing  the  im- 
pulse.] If  the  modification  of  the  si)hygm()graph  (see 
section  on  Pulse  ^,  called  the  cardiograph,  be  [)laced  on  the 
spot  where  the  impulse  is  felt  most  strongly,  the  lever  is  seen 
to  be  raised  during  the  systole  of  the  ventricles,  and  to  fall 
again  as  the  systole  passes  away,  very  much  as  if  it  were 
placed  on  the  heart  directly.  A  tracing  may  thus  be  ob- 
tained (Fig.  62),  of  which  we  shall  have  to  speak  more  full}' 
immediately.  If  the  button  of  the  lever  be  placed,  not  on 
the  exact  spot  of  the  impulse,  but  at  a  little  distance  from 
it,  the  lever  will  be  depret^^ed  during  the  systole.  While  at 
the  spot  of  imi^ulse  itself  the  contact  of  the  ventricle  is 
increased  during  systole,  away  from  the  spot  the  ventricle 
retires  from  the  chest-wall  (by  the  diminution  of  its  right- 
to-left  diameter),  and  hence,  by  the  mediastinal  attachments 
of  the  pericardium,  draws  the  chest-w^all  after  it. 

Endocardiac  Pressure. — In  order  to  study  moi'e  fully  the 
changes  going  on  in  the  heart  during  the  cardiac  cycle,  it 
becomes  necessary  to  know  something  of  what  is  taking 
place  in  the  interior  of  the  cavities  of  the  heart.  Chauveau 
and  Mare}',^  by  introducing  into  the  right  auricle  and  ven- 
tricle respectively  of  the  horse,  througli  the  jugular   vein, 

Marev,  T'lronlation  dii  Sano-. 


ENDOCARDIAC    PRESSURE. 


:07 


small  elastic  bags,  each  communicating  with  a  recording 
tambour,  were  enabled  to  take  simultaneous  tracings  of  all 
the  changes  of  pressure  occurring  in  the  two  cavities.  These 
results  are  embodied  in  Fig.  G2,  of  which  the  upper  curve 


Fig.  62. 


Tracing  of  the  Varialions  of  Pressure  in  theRight  Auriileand  VeiitiiLle,  and  of  the 
Cardiac  Impulse,  in  the  Horse. — After  Marey.  To  be  read  from  left  to  riglit.« 
The  upper  curve  represents  the  variation  of  pressure  within  the  auricle,  the  mid- 
dle curve  the  variations  of  pressure  within  the  ventricle  ;  these  two  therefore  illus- 
trate changes  taking  place  in  the  interior  of  the  heart.  The  lower  curve  rejtreseiits 
the  variations  of  pressure  t.^ansmitted  to  a  lever  outside  the  chest  and  constituting 
the  cardiac  impulse.  A  complete  cardiac  cycle,  beginning  at  the  close  of  the  ven- 
tricular systole,  is  comprised  between  the  thick  vertical  lines  land  II.  The  thin 
vertical  lines  represent  tenths  of  a  second,  a,  The  gradual  tilling  of  the  auricle  and 
ventricle  ;  b,  the  auricular  systcjle  ;  c,  the  veiiti  itulai  systole  ;  d,  oscillations  of  pres- 
sure, interpreted  by  Matey  as  caused  by  vibrations  of  the  auriculu-ventricular 
valves;  e  probably  marks  the  closing  of  the  semilunar  valvts. 

represents  the  changes  of  pressure  in  the  auricle,  the  middle 
curve  the  changes  of  pressure  in  the  ventricle, and  the  lower 


'  It  imist  be  remembered  that  the  curves  in  the  diagram  are  intended 
merely  to  ilhistrate  the  variations  of  pressure  occurring  at  difleien?' 
times  in  th(e  same  ciiamber,  or  to  show  what  changes  in  tlie  one  chamber 
are  coincident  in  point  of  time  with  changes  in  the  other.  They  in  no 
way  indicate  the  amount  of  pressure  in  the  auricle  as  compared  with 
that  in  the  ventricle. 


208 


THE    VASCULAR     MECHANISM. 


curve  the  cnr(lio<Trn])liic  1vnein<>;  of  tlie  rai'(1iac  impnlso. 
All  these  curves  were  taken  siimiltaueoiisly  on  the  same 
recording  surface. 

Method. — A  tube  of  appropriate  curvature  is  furnished  with 
two  small  elastic  liags,  one  at  the  extreme  end  and  the  other  at 
such  a  distance  that  when  the  former  is  within  the  cavity  of  the 
ventricle  the  latter  is  in  the  cavity  of  the  auricle.     Each  bag 


Marey's  Tambour,  with  Cardiac  Sound. 

A.  A  simple  cardiac  sound  sucli  as  may  be  used  for  the  exploration  of  the  left 
ventriel'.  The  portion  a  of  the  ampulla  at  the  end  is  of  thin  india-rubber,  stretched 
over  au  open  framework,  with  metallic  supports  above  and  b;  low.  The  lung  tube  b 
serves  to  introduce  it  into  the  cavity  which  it  is  desired  to  explore. 

B.  The  Tambour.  The  metal  chamber  m  is  covered  in  an  air-tight  manner  with 
the  india-rubber  c,  bearing  a  tliin  metal  plate  ??i' to  which  is  altaclud  the  leverZ 
moving  on  the  hinge  //.  The  whole  tambour  can  be  placed  by  means  of  the  clamp 
c/  at  any  height  on  the  upright  s'.  The  india-rubber  tube  <  serves  to  connect  the 
interior  of  the  tambour  titlier  with  the  cavity  of  the  ampulla  of  A  or  with  any 
other  cavity.  Supposing  that  t ho  tube  <  were  connected  with  6,  any  pressure  ex- 
erted on  a  would  cause  the  roof  of  the  tambour  to  lise  and  the  point  of  the  lever 
would  be  proportionately  raised. 


(Fig.  63,  A)  communicates  b}^  a  separate  air-tight  tube  with  an 
air-tight  taml)()ur  (Fig.  03  B),  on  which  a  lever  rests  so  that  any 
pressure  on  either  bag  is  communicated  to  the  cavity  of  its  re- 
spective tambour,  the  lever  of  which  is  raised  in   proportion. 


ENDOCARDIAC    PRESSURE.  209 


The  writing-points  of  all  three  levers  are  brought  to  bear  on  the 
snnae  recording  surfiice  exactly  nnderneath  each  other.  The 
tube  is  careful!}"  introduced  through  the  right  jugular  vein  into 
the  right  side  of  the  heart  until  the  lower  (ventricular)  bag  is 
fairly  in  the  cavity  of  the  right  ventricle,  and  consequently  the 
upper  (auricular)  bag  in  the  cavity  of  the  right  auricle.  Changes 
of  pressure  in  either  cavity  then  cause  movements  of  the  corre- 
sponding lever.  When  the  pressure  is  increased,  for  instance  in 
the  auricle,  the  auricular  lever  is  raised  and  describes  on  the  re- 
cording surface  an  ascending  curve  ;  when  the  pressure  is  taken 


A  complete  cardiac  cycle  is  comprised  between  the  verti- 
cal lines  I  and  II,  Fig.  02.  The  recording  surface  was 
travelling  at  such  a  rate  that  the  intervals  between  any  two 
of  tiie  thin  vertical  lines  corresponds  to  one-tentli  of  a 
second.  Hence  in  this  case  the  whole  cardiac  cycle  occu- 
pied about  i^ths  of  a  second.  Any  point  in  the  cycle  might, 
of  course,  be  taken  as  its  commencement.  In  the  tigure 
the  cycle  is  supposed  to  begin  shortly  after  the  end  of  tiie 
ventricular  systole,  and  the  beginning  of  the  diastole. 

On  examining  the  three  curves  we  see,  at  a^  a  steady  rise 
of  the  auricular,  accompanied  b}-  similar  gradual  ascents  of 
the  ventricular,  and  also  of  the  cardiograph  lever.  These 
may  be  interpreted  as  indicating  that  the  blood  is  pouring 
from  the  great  veins  into  the  auricle,  increasing  the  pressure 
there,  and  at  the  same  time  passing  on  into  the  ventricle, 
increasing  also  the  internal  pressure  there,  a' ^  and  also,  by 
distending  the  ventricle,  causing  it  to  pi-ess  somewhat  on 
the  chest-wall  and  thus  to  raise  the  cardiograph  lever,  a'\ 
This  continues  for  about  y%ths  of  a  second,  and  is  then 
followed  by  the  sudden  rise  of  auricular  pressure  h  due  to 
the  auricular  systole,  followed  by  a  sudden  fall  as  the  blood 
escapes  into  the  ventricle.  The  sudden  entrance  of  blood 
into  the  ventricle  causes  a  sudden  increase  of  the  pressure 
in  the  ventricle  as  indicated  by  the  ventricular  lever  6',  and 
a  sudden  increase*  in  the  pressure  on  the  chest-wall  h'^. 
The  auricular  systole  is  followed  immediately  by  the  sudden 
strong  venti'icular  systole  c\  the  pressure  rising  ver}'  ab- 
ruptly. Owing-  to  the  presence  of  the  tricuspid  valves,  this 
increase  of  pressure  is  kept  off  the  auricle  altogether;  but 
the  chest-wall,  as  shown  by  the  tracing  at  c" ,  feels  the  sud- 
den increase  of  the  pressure  of  the  ventricle  against  it. 
The  ventricular  pressure  lasts  for  some  time,  gradually  de- 
clining, and  then  suddenly  falls.  This  may  be  interpreted 
as  indicating  that  the  systole  rapidly  reaches  a  maximum, 


210 


THE    VASCULAR    MECHANISM. 


maintains  that  niaxininni  wit  h  a  sliglit  decline  only  for  some 
little  time,  and  then  snddenly  ceases.  The  oscillations 
durin<r  tiie  maximnm,  as  seen  at  ^/',  and  also  manifest  in  the 
anricnlar  cnrve,  and  in  the  im[)ulse  cnrve  at  d'\  are  inter- 
preted by  Marey  as  due  to  vibrations  of  the  tricuspid  valves, 
but  their  causation  is  at  i)rcsent  by  no  means  clear.  At  the 
end  of  the  ventricular  systole,  the  descent  of  the  lever  is 
broken  by  a  sli<!:ht  rise  at  e' ^  visible  also  in  the  auricle  at  t^, 
and  even  in  the  impulse  curve  at  e".  This  is  interpreted 
by  Marey  as  indicatinjx  the  closure  of  the  semilunar  valves. 
After  this  sliiriit  rise,  the  ventricular  curve  and  the  impulse 
curve  fall  to  their  lowest  points,  while  the  auricle  is  already 
beiz:innino:  to  fill;  and  the  cardiac  cycle  begins  anew. 

Thus  of  the  whole  period  of  a  beat,  the  largest  fraction 
is  that  of  the  diastole,  or  "  passive  interval,"  i.  e.,  of  the 
interval  between  the  end  of  the  ventricular  and  the  com- 
mencement of  the  auricular  systole.  The  next  largest  is 
that  of  the  ventricular  systole,  and  the  smallest  that  of  the 
auricular  systole.  The  duration  of  the  diastole  is  usually 
given  as  |-  of  the  whole  period,  that  of  the  whole  systole 
being  g,  of  which  far  the  greatest  part  is  taken  up  by  the 
ventricle  ;  but  in  these  measurements  the  systole  is  supposed 
to  end  with  the  cessation  of  the  ventricle's  contraction,  and 
not  to  include  its  relaxation.  Dcmders  found  the  ventricu- 
lar systole,  as  determined  by  the  time  elapsing  between  the 
commencement  of  the  first  and  of  the  second  sounds,  and, 
therefore,  including  the  relaxation,  as  well  as  the  contrac- 
tion of  the  ventricular  fibres,  to  occupy  on  the  average  .301 
to  .327  sec,  or  40  to  46  per  cent,  of  the  whole  period. 
Landois'  gives  the  following  measurements,  the  whole  cycle 
lasting  1.130  sec. 

Mean  duration  of  auricular  systole 

to  l)egiuning of  veniritular  sys- 
tole  '   .  .177  sec.     1 

Mean  duration  of  ventricular  con- 

traclion, 192    " 

Mean  duration  of  niaintenance  of 

contraction,        .        .        .        .  .082    " 
Mean  duration  from  b^'ginning  of 

relaxation  to  closure  of  seuii-  j 

lunar  valves, 072    "   J  1 

Mean  duration  of  closure  of  valves  | 

to  bt^ginning  of  pause.      .        ..200     "        )■      Xu 
Mean   duration   of   remainder    of  | 

cycle 407    "       J 


.451  sec.  =  systole  of  the  heart  as 
nsuallv  understood. 


.346 


systole  of  ventricle  as 
measured  by  Donders. 


diastole  of  the  heart 
usually  understood. 


1.130 


''  Cbt.  med.  Wiss.,  1806,  p.  179. 


ENDOCARDIAC  PRESSURE.  211 

Tlie  proportions,  however,  are  not  tixecl,  l>ut  vary  some- 
what. Practically  speaking,  there  is  no  interval  between 
the  auricular  and  ventricular  systole,  the  latter  being  sepa- 
rated from  the  former  bv  a  fraction  of  time  which  is  almost 
inapprecialile. 

Although  the  instrument  of  Chauveau  and  Marey  may  be 
experimentally  graduated  and  thus  used  to  measure  the 
amount  of  pressure  in  the  several  cavities  of  the  heart,  more 
exact  results  may  be  gained  by  passing  through  tlie  jugular 
vein  into  the  right  auricle  and  thence  into  the  right  ven- 
tricle, or  through  the  carotid  artery  into  the  left  ventricle, 
a  tube  open  at  the  end  introduced  into  the  heart  and  con- 
nected at  the  other  end  with  a  manometer.  Variations  of 
pressure  in  tlie  cardiac  cavities  are  thus  transmitted  directly 
to  the  mercury  col-imn  of  the  manometer  in  the  same  way 
as  tiiose  of  an  artery  when  arterial  pressure  is  measured. 
Further,  by  usirig  maximum  and  minimum  manometers,  the 
maximum  and  minimum  pressures  of  the  several  cavities 
may  be  determined.  In  this  way  in  the  dog  a  maximum 
pressure  has  been  observed  in  the  left  ventricle  of  about 
140  mm.  (mercury),  in  the  right  ventricle  of  about  ()0  ram., 
and  in  the  right  auricle  of  about  20  mm.  During  the  dias- 
tole, or  rather  immediately  after  the  systole,  the  pressure  in 
the  two  ventricles  and  even  in  the  auricle  may  become  nega- 
tive, i.  e.,  sink  below  the  pressure  of  the  atmosphere.  In 
the  left  ventricle  (of  the  dog)  a  minimum  pressure  varying 
from  — 52  to  — 20  mm.  may  be  reached,  the  minimum  of  the 
right  ventricle  being  from  — 1  7  to  — 16  mm.,  and  of  the  right 
auricle  from  — 12  to  — T  mm.^  Part  of  this  diminution  of 
pressure  in  the  cardiac  cavities  may  be  due,  as  will  be  ex- 
plained in  a  later  pait  of  this  work,  to  the  aspiration  of  the 
thorax  in  the  res[jiratory  movements.  But  even  when  the 
thorax  is  opened  and  artificial  respiration  kept  up,  under 
which  circumstances  no  such  as|)i ration  takes  place,  the 
pressure  in  the  left  ventricle  may  sink  as  low  as  — 24  mm 
The  occurrence  of  so  marked  a  negative  pressure  in  the  ven- 
tricular cavities  shows  that  these  cavities,  but  especially  the 
left,  exert  a  considerable  suction  power  during  diastole. 
The  heart,  in  fact,  appears  to  act  not  only  as  a  force-pump, 
but  also  as  a  suction-pump,  thereby  aiding  to  refill  itself 
with  blood  at  each  stroke  ;  tlie  suction  of  the  left  ventricle 
besides  greatly  assisting  the  circulation  through  the  lungs. 

'  These  nnrabers  are  to  be  considered  merely  as  instances  which  have 
been  observed,  and  not  as  averages  drawn  from  a  large  number  of  cases. 


212 


THE    VASCULAR    MECHANISM. 


The  results  iDjiven  above  are  those  of  Goltz  and  GauleJ  The 
priiK-iplc  of  thoir  niaxiimiin  niaiionictcr,  Fii^.  (54,  consists  in  the 
inlnxhu-tion  into  the  twhi^  leading  from  tlui  licart  to  Uw  mercury 
colunni  of  a  (modilieil  cup  and  l)air)  valvo,  oiK-nin^,  like  the  aortic 
semihmar  valves,  easily  from  the  lu-art,  l)ut  closini;  tirmly  when 
lluid  attempts  to  return  to  the  heart.  ]>y  reversini:;  the  direction 
of  the  valve,  the  manometer  is  converted  from  a  maxinuun  into 


Fig   G4. 


Tlie  Maximum  MaiiomLtor  of  Goltz  and  Gaiile. 

At  e  a  connection  is  made  with  the  tiilie  Ifading  to  the  Ik  art.  When  the  screw 
clamp  k  is  closed,  the  valve  v  comes  into  action,  and  the  instiument,  in  the  position 
of  the  valve  shown"  in  tlie  tigure,  is  a  maximum  manometer.  By  rever.sin<j  the  direc- 
tion of  r  it  is  converted  into  a  minimum  manometer.  When  ^•  is  opened,  the  varia- 
tions of  pressure  are  conveyed  along  o,  and  the  in.strument  then  acts  like  an  ordi- 
nary manometer. 

a  minimum.  When  an  ordinary  manometer  is  connected  with  a 
ventricular  cavity,  the  movements  of  the  mercury  do  not  follow 
exactl}'  the  rapid  variations  of  i)ressure  of  the  cavity,  and  the 
height  of  the  column  fails  to  indicate  both  the  highest  and  the 
lowest  pressures.  Hence,  as  Fick^  observed,  especially  with 
rapidly  beating  hearts,  the  pressure  in  the  ventricle  may  ajjpear 


1  Pfliiger's  Archiv,  xvii  (1878),  p.  100. 

^  Arbeiterf  a.  d.  phvsiolog.  Laborator.  d.  "Wiirzburger  Hochschule, 
Lief,  ii  (1873),  p.  183.  ' 


ENDOCARDIAC    PRESSURE. 


213 


to  he  less  than  that  in  the  aorta.  Thus  in  Ficr.  05,  when  the  tube  is 
slipped  at  b  from  the  aorta  into  the  left  ventricle,  and  the  manom- 
eter at  the  same  time  converted  from  a  maximum  into  an  ordi- 
nary manometer,  the  curve  of  the  ventricular  pressure  falls  below 
that  of  the  aorta.  As  soon,  however,  as  the  manometer  is  con- 
verted, as  at  c,  into  a  maximum  manometer,  it  becomes  evident 
that  the  maximum  pressure  in  the  left  ventricle  is  as  high  (in  the 

Fig.  65. 


Curve  of  Pressure  in  Aorta  and  Left  Ventricle  of  the  Dog,  taken  with  the  Manom- 
eter of  Goliz  and  Gaule.    (To  be  read  from  left  to  right.) 

Before  a,  the  manometer  is  working  as  an  ordinarj' manometer  connected  with  the 
aorta,  and  the  curve  shows  both  the  heart-heats  and  the  respiratory  curves,  the^ 
latter  strongly  marked.  At  n  the  luauometer  is  made  maximum  by  clamping  k 
(Fig.  64),  and  the  curve  then  sliows  the  straight  line  of  the  maximum  aortic  pres- 
sure. At  b  the  tube  of  the  manometer  is  slipped  down  into  the  left  ventricle,  and  at 
the  same  time  converted  into  an  ordinary  manometer  by  opening  /:;  the  heart- 
beats, marked  on  the  respiratory  curves,  are  seen  at  a  level  lower  than  that  of  the 
aortic  pressure.  But;  when  at  c  the  manometer  is  changed  back  again  into  a  maxi- 
mum manometer,  the  pressure  rl.ses  at  each  heart-beat  until  a  maximum  is  readied, 
which  is  as  higli,  and  in  this  case,  probably  on  account  of  the  heart  beating  more 
strongly,  very  distluctly  higher  than  the  aortic  maximum. 

figure  slightly  higher)  as  that  in  the  aorta.  Goltz  and  Gaule  re- 
gard the  negative  pressure  of  diastole  as  due  to  the  elasticity  of 
the  ventricular  walls,  by  virtue  of  which  these  structures,  pressed 
closely  in  contact  during  the  latter  part  of  the  systole,  spring 
asunder  with  considerable  energy  when  the  relaxation  of  the 
muscular  fibres  begins  :  Br" eke,  however,  has  given  another  ex- 
planation of  the  dilation  of  the  ventricular  cavities,  see  p.  216. 
Marey'  had  previously,  by  a  graduation  of  the  instrument  de- 


Op,  cit. 


214  TIIK    VASCULAR    MECHANISM. 


scribed  above,  (letonniiied  the  pressure  in  the  horse  to  be  in  the 
left  ventricle  about  iJOO  nun.,  in  the  rii^ht  ventricle  only  about  2') 
nun.,  while  that  of  the  riijlit  auricle  Ik;  estimated  at  not  more 
than  '2  or  ."{  nun.  He  too  believed  the  pressure  in  both  ventricles 
to  become  neiijative  after  systole,  especially  in  the  case  of  the  left 
side.  Fick'  had  also  by  introducing;  a  tube  in  the  several  cavities 
of  the  heart  and  making  use  of  liis  spring  manometer  (see  Fig. 
50,  p.  lS-2)  arrived  at  results  which  agree  with  those  of  Goltz  and 
Gaule  in  so  far  as  the  ventricular  cavities  are  concerned.  lie 
found  in  the  dog  the  pressure  to  be  in  the  right  ventricle  from  20 
to  40  nun.,  in  the  left  ventricle  about  140  mm.  According  to 
liim,  however,  the  ])ressure  in  the  right  auricle  is  nearly  constant, 
varying  not  more  than  2  mm.  from  the  base  Ynw,  of  atmosi)heric 
pressure,  and  remaining  for  the  most  ])art  slightly  below.  This 
Fick  gives  as  a  support  to  the  view  held  by  him,  that  the  proper 
function  of  the  auricles  is  to  equalize  and  keep  constant  the 
pressure  at  the  entrance  of  the  great  veins  into  the  heart. 

The'  3[echanism  of  (he  Valves. 

The  auriculo-ventricular  valves  present  no  ditiiculty.     As 
the  blood  is  being  driven   bj-  the  auricular  systole  into  the 

[Fig.  6i;. 


Diagniin  of  valves  of  the  heart. — After  Dalton.] 

ventricle,  a  reflux  current  is  set  up.  by  which  the  blood, 
passing  aloug  the  sides  of  the  ventricle,  gets  between  them 

^  Op.  cit. 


THE  VALVES  OF  THE  HEART.         215 

and  the  flaps  of  tlie  valve  (whether  tricuspid  or  mitral).  As 
the  pressure  of  the  auricular  systole  diminishes,  the  same 
reflux  currents  floats  the  flaps  up,  until  at  the  extreme  end 
of  the  systole  they  meet,  and  thus  the  orifice  is  at  once  and 
firmlv  closed,  at  the  very  bei^inning  of  the  ventricular  beat. 
(Figs.  66  and  67  )  The  increasing  intra- ventricular  pressure 
serves  onlv  to  render  the  valve  more  and  more  tense,  and 
in  consequence  more  secure,  the  cliordiB  tendine.e  and  the 
contraction  of   the   papillary   muscles   (simultaneous    with 

[Fig.  67. 


Diagram  of  valves  of  the  heart. — After  Dalton.] 

that  of  the  rest  of  the  ventricular  walls)  preventing  the 
valve  from  being  inverted  into  the  auricle,  and,  indeed, 
keeping  the  valvular  sheet  convex  to  the  ventricular  cavity, 
by  which  means  the  complete  emptying  of  the  ventricle  is 
more  fully  effected.  Since  the  same  papillary  muscle  is  in 
many  cases  connected  by  ciiordce  with  the  adjacent  edges 
of  two  flaps,  its  contraction  also  serves  to  keep  these  flaps 
in  more  complete  apposition.  Moreover,  the  extreme  bor- 
ders of  the  valves,  outside  the  attachments  of  the  chords, 
are  excessively  thin,  so  that  when  the  valve  is  closed,  these 
thin  portions  are  pressed  flat  together  back  to  back ;  hence 


21G  THE    VASCULAR    MECHANISM. 


wliile  till'  loiiirlicr  ccnti-al  pints  of  the  valves  hear  the  force 
of  the  veiitrieiilar  systole,  the  opposed  Ihiii  niemhranous 
edges,  pressed  toirelher  !))•  the  blood,  more  com})letely  secure 
the  closure  of  the  orifice. 

The  semilunar  valves  are,  duriii<Tj  the  ventiicular  systole, 
pressed  outwards  towards  the  arterial  walls,  and  thus  offer  no 
obstacle  to  the  escape  of  blood  from  the  cavities  of  the  ventri- 
cles. As  the  ventriculai"  syst(  le  diminishes,  a  reflux  current 
j)artially  fills  the  pockets,  and  tends  to  carry  their  free  mar- 
gins towards  the  middle  of  the  tube.  Upon  the  sudden 
close  of  the  systole,  the  elastic  rebound  of  the  arterial  vvalls 
causes  a  sudden  current  backwards,  which,  filling  and  dis- 
tending the  pockets,  causes  their  free  margins  to  come  into 
complete  and  firm  contact,  and  thus  entirely  blocks  the  way. 
The  cor[)ora  Arantii  meet  in  the  centre,  and  the  thin  mem- 
branous festoons  or  lunuhe  are  brought  into  exact  apposi- 
tion. As  in  the  tricuspid  valves,  so  here,  while  the  pressure 
of  the  blood  is  borne  by  the  tougher  bodies  of  the  several 
valves,  each  two  thin  adjacent  Innida?,  pressed  together  l)y 
the  blood  acting  on  both  sides  of  them,  are  kept  in  complete 
contact,  without  any  strain  being  put  upon  them  ;  in  this 
way  the  orifice  is  closed  in  a  most  eflicient  manner. 

An  ingenious  view  has  been  put  forward  by  Br'.icke'  concerning 
the  action  of  the  semilunar  valves.  He  maintains  that  during 
the  ventricular  systole,  the  flaps  are  pressed  back  flat  against  the 
arterial  walls,  and  in  the  case  of  the  aorta  completely  cover  up 
the  orifices  of  the  coronary  arteries  ;  hence  the  flow  of  blood 
from  the  aorta  into  the  coronary  arteries  can  take  place  only  dur- 
ing the  ventricular  diastole,  or  at  the  very  beginning  of  the  sys- 
tole, and  not  at  all  during  the  systole  itself.  The  object  of  this, 
he  argues,  is  tw^ofold.  In  the  first  place,  the  muscular  tissue  of 
the  ventricle  is  not  1)urdened  with  blood  at  the  moment  that  it  is 
undergoing  contraction,  but  receives  its  nutritive  supply  during 
the  phase  of  relaxation  ;  hence  the  whole  force  of  the  contraction 
of  the  ventricular  fibres  is  spent  on  the  contents  of  the  cavity, 
and  none  is  \vasted  in  compression  of  the  intra-muscular  bhxjd- 
vessels.  In  the  second  place,  the  efiect  of  the  flow,  at  the  close 
of  the  systole,  into  the  previously  emptied  coronary  arteries,  is 
to  unfold,  so  to  speak,  the  collapsed  cavities  of  the  ventricles  very 
much  in  the  same  way  as  the  collapsed  cavity  of  a  doul)l(;-walled 
ball  may  be  reinstated  by  the  forcible  injection  of  fluid  into  the 
space  between  the  two  walls.    Through  this  particular  behavior 

1  Wien.  Sitz.-Berichte,  1854 ;  and  Der  Verschluss  d.  Kranzschlaga- 
dern. 


THE  VALVES  OF  THE  HEART.         217 


of  the  valves,  in  fact,  the  heart,  as  an  after-eftect  of  the  systole, 
dilates  its  own  ventricles  ;  hence  the  mechanism  has  been  cilled 
b\'  Br'iicke  a  "self-regulating  mechanism." 

Brucke's  view  has,  however,  been  much  disputed.  In  the  first 
place,  we  know  that  the  flow  of  blood  from  an  ordinary  skeletal 
muscle,  though  it  may  sufier  a  brief  initial  check  (probably  from 
compression  of  the  larger  veins),  is  increased  and  not  diminished 
by  a  tetanic  contraction  of  the  muscle,  the  increase  being  visible 
while  the  contraction  is  still  at  its  height.^  Corresponding  to 
this  lasting  increased  flow  from  the  veins  there  must  be  an  in- 
creased flow  into  the  arteries.  And  in  certain  dispositions  of  the 
bloodvessels  and  muscular  fibres  (as  when  a  vessel  is  surrounded 
by  fibres  running  lengthways  parallel  to  itself),  the  increased 
thickening  of  the  fibres  will  tend  not  to  compress  but  to  dilate 
the  vessel.  The  advantage  to  the  muscular  tissue,  therefore,  of 
the  closure  of  the  coronary  arteries  seems  at  least  doubtful.  In 
the  second  place,  it  has  been  urged  that,  in  point  of  fact,  the 
coronary  arteries  are  not  covered  by  the  valves.  Brlicke  replies 
that  they  may  appear  uncovered  during  dissection  after  death, 
but  are  actually  covered  during  life.  He  moreover  brings  forward 
an  experiment  on  a  pig's  heart  removed  from  the  body,  in  which 
a  stream  of  water  sent  through  the  pulmonary  veins  and  auricle 
into  the  left  ventricle  issues  through  the  open  aorta,  without  a 
drop  of  it  appearing  at  the  cut  end  of  an  open  coronary  artery, 
if  the  aorta  be  maintained  in  a  proper  position,  and  all  vibration 
and  jar  be  avoided  ;  and  argues  that  it  is  the  closure  of  the  ori- 
fices by  the  valves  which  prevents  the  flow,  because  any  shake 
sufficient  to  develop  a  backward  current  in  the  aorta  and  thus  to 
lift  up  the  valves,  at  once  gives  rise  to  a  flow.  If,  however,  as 
has  been  stated,  the  experiment  wifi  succeed  equally  well  in  the 
absence  of  the  valves,  and  will  not  succeed  if  the  free  exit  of 
fluid  from  the  end  of  the  aorta  be  hindered  though  the  valves  be 
intact,  the  absence  of  a  flow  through  the  coronary  artery  must 
be  due  to  a  deficiency  of  pressure  in  the  aorta  and  not  to  an}-  ac- 
tion of  the  valves.  The  undoubted  fact  that  blood  fiows  from  a 
■wounded  coronary  artery  in  jerks  corresponding  to  the  systole 
and  not  to  the  diastole,  Brlicke  meets  with  the  observation  that 
the  coronary  arteries  must  share  just  previous  to  the  closure  of 
the  valves  in  that  increased  pressure  in  the  aorta  which  is  the 
cause  of  the  closure  of  the  valves,  and  thtit  the  higher  pressure 
thus  gained  at  the  beginning  of  the  systole  is  maintained  during 
the  systole  by  the  obstruction  to  the  outward  flow  arising  from 
the  contracting  fibres  compressing  the  small  vessels;  while  the 
empty  condition  of  the  small  branches  of  the  coronar}-  arteries 
and  of  the  veins  at  the  commencement  of  the  diastole,  must  di- 
minish the  pressure  in  the  main  coronary  arteries  themselves 
during  diastole,  and  so  prevent  a  diastolic  spurt  from  a  wound  in 

^  Gaskell,  Ludwig's  Arbeiten,  1876 ;  and  Journ.  Anat.  and  Phvs.,  xi, 
360. 


218  TnE    VASCULAR    MECHANISM. 

thoiii.  This,  however,  is  liardly  satisfa(ttory,  since  as  regards 
the  systole,  as  lias  l)een  urged  above,  an  obstruction  of  the  tlow 
from  compression  by  the  muscular  libres  is  at  least  doubtful,  and 
as  regards  the  diastole  the  sui)i)osed  empty  condition  of  the  coro- 
nary vessels  can  produce  an  ellect  only  at  the  very  beginning  of 
the  diastole.  On  the  other  hand,  Ceradini,'  who  observed  the 
condition  of  the  valves  in  an  excised  heart  by  looking  down 
through  a  wide  glass  tube  inserted  into  the  aorta,  is  of  "oi)inion 
that  during  the  systole  the  valves  are  not  applied  close  to  the 
arterial  wall,  but  tioat  in  an  intermediate  position  of  equilil^rium, 
maintained  by  rellux  currents,  their  orilice  taking  on  the  form  of 
an  equilateral  triangle  with  curved  sides.  The  same  retlux  cur- 
rents gradually  (but  of  course  rapidly)  close  the  oritice  as  the 
force  of  the  systole  diminishes,  and  the  effect  of  the  elastic  re- 
bound is  simply  to  render  the  closure  tense  and  firm.  Thus, 
argues  Ceradini,  no  regurgitation  of  fluid  from  the  aorta  into  the 
ventricle  at  the  end  of  the  systole  and  the  beginning  of  the  dias- 
tole is  possible,  and  a  hurtful  waste,  which  on  Brlicke's  hypoth- 
esis seems  unavoidable,  is  averted. 

The  passage  of  the  blood  through  the  heart  takes  place  as 
follows  :  The  righL  auricle  during  its  diastole,  by  the  relax- 
ation of  its  muscular  fibres,  and  by  the  fact  that  all  pressure 
from  the  ventricle  is  removed  by  the  tension  of  the  tricuspid 
valves,  offers  but  little  resistance  to  the  ingress  of  blood 
from  the  veins.  On  the  other  hand,  the  blood  in  the  trunks, 
both  superior  and  inferior  vena  cava,  is  under  a  certain 
though  low  pressure,  augmented  in  the  case  of  the  superior 
vena  cava  by  gravity,  and  in  consequence  flows  into  the 
empty  auricle.  At  each  inspiration,  this  flow  is  favored  by 
the  negative  pressure  in  the  heart  and  great  vessels  caused 
by  the  respiratory  movements.  Before  this  has  gone  on 
very  long,  the  diastole  of  the  ventricle  begins,  its  cavity 
suddenly  dilates,  the  pressure  in  that  cavity  becomes  nega- 
tive, drawing  the  blood  into  it,  the  flaps  of  the  tricuspid 
valve  fall  back,  and  blood  for  some  little  time  flows  in  an 
unbroken  stream  from  the  ven.ne  cavse  into  the  ventricle.  In 
a  short  time,  however,  before  much  blood  has  had  time  to 
enter  the  ventricle,  the  auricle  is  full,  and  forthwith  its  shaip 
sudden  systole  takes  place.  Partly  by  reason  of  the  onwaid 
pressure  in  the  veins,  which  ir.creases  rapidly  from  the  heart 
towards  the  capillaries,  partly  from  the  presence  of  valves 
in  the  venous  trunks  and  at  the  mouth  of  the  inferior  vena 


^  Der  Mechanismus  der  halbmondformigen  Herzklappen.     Leipzig, 
1872. 


THE  VALVES  OF  THE  HEART.         219 

cava,  but  still  more  from  the  fact  that  the  systole  begins  at 
the  great  veins  themselves  and  spreads  thence  over  the  auri- 
cle, the  force  of  the  auricular  contraction  is  spent  in  driving 
the  blood,  not  back  into  the  veins,  but  into  the  ventricle  where 
the  pressure  is  still  exceedingly  low. 

Whether  there  is  any  backward  flow  at  all  into  the  veins,  or 
even  an  interruption  to  the  forward  tlow%  or  wdiether  by  the  pro- 
gressive character  of  the  systole  the  flow  of  blood  continues,  so 
to  speak,  to  follow  up  the  systole  without  break  so  that  the 
stream  from  the  veins  into  the  auricle  is  really  continuous,  is  at 
present  doubtful  ;  though  a  shght  positive  w^ave  of  pressure 
synchronous  with  the  auricular  systole,  travelling  backward 
along  the  veins,  has  been  observed  at  least  in  cases  wdiere  the 
heart  is  beating  vigorously.  The  question  of  a  negative  venous 
pulse,  i.  e.,  the"  transmission  backwards  of  the  negative  pressure 
of  the  right  cardiac  cavities,  will  be  considered  later  on. 

The  ventricle  thus  being  filled,  the  play  of  the  tricuspid 
valves  described  above  comes  into  action,  the  auricular  sys- 
tole is  followed  by  that  of  the  ventricle,  and  the  pressure 
within  the  ventricle,  cut  off  from  the  auricle  by  the  tricuspid 
valves,  is  brought  to  bear  entirely  on  the  conus  arteriosus 
and  the  pulmonary  semilunar  valves.  As  soon  as  by  the 
rapidly  increasing  force  of  the  ventricular  contraction,  the 
pressure  within  the  ventricle  becomes  greater  than  that  in 
the  pulmonary  arter}'.  the  semilunar  valves  open,  and  the 
still  increasing  systole  discharges  the  contents  of  the  ven- 
tricle into  that  vessel.  But  as  the  systole  passes  off,  the 
pressure  in  the  artery  becomes  greater  than  that  in  the 
cavity  of  the  ventricle,  and  a  rebound  of  the  blood  takes 
place.  The  first  act  of  this  rebound  however  is,  as  w^e  have 
seen,  firmly  to  close  the  semilunar  valves,  and  thus  to  shut 
off'  the  overdistended  artery  from  the  now  empty,  or  nearly 
empt}',  ventricle. 

During  the  whole. of  this  time  the  left  side  has  witii  still 
greater  energy  been  executing  the  same  manoeuvre.  At  the 
same  time  that  the  veniB  cavi«  are  filling  the  right  auricle, 
the  pulmonary  veins  are  filling  the  left  auricle.  At  the  same 
time  that  the  right  auricle  is  contracting,  the  left  auricle  is 
contracting  too.  The  systole  of  the  left  ventricle  is  syn- 
chronous with  that  of  the  right  ventricle,  but  executed  with 
greater  force  ;  and  the  flow  of  blood  is  guided  on  the  left 
side  by  the  mitral  and  aortic  valves  in  the  same  way  that  it 
is  on  the  right  by  the  tricuspid  valves  and  those  of  the  pul- 
monary artery. 


220 


THE    VASCULAR    MECHANISM, 


The  SouuiU  of  (lie  Heart. 

AVIrmi  tlie  ear  is  applied  to  tlie  eliest,  either  direetly  or 
by  means  of  a  stetlioseope,  two  sounds  are  heard,  the  first 
a  eomparatively  long  didl  boomino;  sound,  tiie  second  a  short 
sliaip  sudden  one.  Between  tlie  first  and  second  sounds, 
the  interval  of  time  is  very  short,  too  short  to  be  measurable, 
but  between  the  second  and  the  succeeding  first  sound  there 
is  a  distinct  pause.  The  sounds  have  been  likened  to  the 
pronunciation  of  the  syllables,  Ifibb,  dup,  so  that  the  cardiac 

Fig.  68. 


Diagrammatic  Represc  ntation  of  the  Movements  and  Sounds  of  the  Heart  during  a 
Cardiac  I'eriud.— After  Dr.  Sharpey. 

The  ventricular  systole,  whith  is  here  used  to  denote  the  action  of  the  ventri- 
cle up  to  the  closure  of  the  semihiiiar  valvi  s,  is  represented  as  occujjying  about 
45  per  cent.,  and  the  two  sounds  together  as  rather  more  tlian  half,  of  the  wh<de 
period;  but  the  diagram  is  intended  to  show  merely  the  general  relations  of  tiie 
various  events,  and  not  to  serve  as  a  means  of  nitasuremeut. 


cycle,  as  far  as  the  sounds  are  concerned,  might  be  repre- 
sented by:  lubb,  dup,  pause.  The  relative  duration  of  the 
sounds,  and  of  the  pause,  as  well  as  their  relations  in  point 
of  time  to  the  changes  taking  place  in  the  heart,  are  shown 
in  the  above  diagram,  Fig.  G8. 

The  second  short  shar()  sound  presents  no  difliculties.     It 
is  coincident  in  point  of  time  with  the  closure  (;f  the  semi- 


THE    SOUNDS    OF    THE    HEART.  221 

lunar  valves,  and  is  heard  to  the  best  advantage  over  the 
second  right  costal  cartilage  close  to  its  junction  with  the 
sternum,  i.  <?.,  at  the  point  where  the  aortic  arch  comes  near- 
est to  the  surfiice.  Its  characters  are  such  as  would  Itelong 
to  a  sound  generated  by  the  sudden  tension  of  valves  like 
tiie  semilunar  valves.  It  is  obscured  and  altered,  replaced 
b3'  '"murmurs"  when  the  semilunar  valves  are  affected  by 
disease,  the  alteration  licing  most  manifest  to  the  ear  at  the 
above-mentioned  spot  when  the  aortic  valves  are  affected. 
When  the  aortic  valves  are  hooked  up  l»y  means  of  a  wire 
Intioduced  down  the  arteries,  the  second  sound  is  obliterated 
and  replaced  by  a  murmur.  These  facts  prove  that  the 
second  sound  is  due  to  the  sudden  tension  of  the  aortic 
(and  pulmonary)  semilunar  valves. 

The  first  sound,  longer,  duller,  and  of  a  more  "  booming  " 
character  than  the  second,  heard  with  greatest  distinctness 
at  the  spot  where  the  cardiac  impulse  is  felt,  presents  many 
dirtlculties  in  the  way  of  a  complete  explanation.  It  is 
heard  distinctly  when  the  chest-walls  are  removed.  The 
cardiac  impulse  therefore  can  have  little  or  nothing  to  do 
with  it.  In  point  of  time,  and  in  the  position  in  which  it 
may  be  heard  to  the  greatest  advantage  (at  the  spot  of  the 
cardiac  in  pulse  where  the  ventricles  come  nearest  to  the 
surface),  it  corresponds  to  the  closure  of  the  auriculo-ven- 
tricular  valves.  In  point  of  character  it  is  not  such  a  sound 
as  one  would  expect  from  the  vibration  of  membranous 
structures,  but  has,  on  the  contrary,  many  of  the  characters 
of  a  muscular  sound.  In  favor  of  its  being  a  valvular  sound, 
may  be  urged  the  fact  that  it  is  obscured,  altered,  replaced 
by  murmurs,  when  the  tricuspid  or  mitral  valves  are  diseased  ; 
and  Halford^  found  that  clamping  the  great  veins  stopped 
the  sound  though  the  beat  continued.  On  the  other  hand, 
Ludwig  and  DogieP  heard  the  sound  distinctly  in  a  blood- 
less dog's  heart,  in  w-hich  there  was  no  fluid  to  render  the 
valves  tense  and  set-tliem  vibrating.  But  there  is  a  great 
difficulty  in  regarding  it  as  a  muscular  sound,  for  a  muscular 
sound  is  the  result  of  a  tetanic  contraction,  the  height  of 
the  note  produced  varying  with  the  number  per  second  of 
the  simple  contractions  which  go  to  make  up  the  tetanus. 
A  simple  contraction  or  spasm  cannot  possibly  produce  a 
musical  sound,  such  as  is  the  cardiac  sound.     The  beat  of 

^  Action  and  Sounds  of  the  Heart.     London,  1860. 
^  Lndwig's  Arbeiten,  .Jahrg.,  1868. 


222  THE     VASCULAR    MECHANISM. 

the  heart  is  a  comparatively  slow  long  continued  single 
s|)asin,  and  not  a  tetanic  contraction.  In  its  long  latent 
period,  and  in  all  its  characters,  the  heart's  beat  bears  the 
stani})  oC  being  a  single  spasm.  If  so  itcannotgive  rise  to 
a  note  :  and  ihe  attempt  to  solve  the  ditlicuity  by  suj)posing 
that,  though  the  contraction  of  each  cardiac  fibre  is  simple, 
there  is  a  sequence  of  these  simple  contractions  over  the 
whole  heart  in  conse(iuence  of  the  several  fibres  not  con- 
tracting at  the  same  time,  and  that  this  sequence  generates 
the  sound,  does  not  appear  ver}'  satisfactory. 

"When  the  nerve  of  the  rlieoscoi)ic  muscle-nerve  preparation 
(p.  91)  is  placed  over  the  heart,  each  beat  of  the  heart  (ventricle 
or  auricle)  is  followed  by  a  single  spasm,  not  by  tetanus,  of  the 
rheoscopic  mus(;le.  By  properly  disposing  the  nerve  of  the  prep- 
aration a  contraction  corresponding  to  the  systole  of  the  auricle 
followed  rapidly  by  a  second  corresponding  to  the  systole  of  the 
ventricle  may  be  obtained,  but  in  each  case  the  contraction  in 
the  leg  is  simple  and  not  tetanic.  This  result  is  consistent  with 
the  view  that  the  systole  is  a  simple  spasm,  but  cannot  be  re- 
garded as  a  proof  that  it  is  such.  For  it  is  not  every  tetanus  in 
a  muscle  which  will  give  a  secondary  tetanus  in  the  rheoscopic 
muscle.  When  the  "tetanus  in  a  muscle  is  induced  by  the  ordi- 
nary interrupted  current  applied  directly  to  the  nerve  of  the 
muscle,  the  tetanus  in  the  rheoscopic  nmscle  appears  \vithout 
difticulty  ;  but  where  the  tetanus  is  produced  by  a  constant  cur- 
rent, the  so-called  breaking  or  making  tetanus  (p.  106),  the  rheo- 
scopic muscle  responds  by  a  single  (initial)  spasm  instead  of  a 
tetanus.  The  pronounced  tetanus  of  strychnia  similarly  gives 
rise  to  a  simple  initial  spasm  and  not  to  a  tetanus  of  the  rheo- 
scopic muscle,  and  the  same  feature  is  characteristic  of  the 
natural  respiratory  contractions  of  the  diaphragm,  and  probably 
of  all  voluntary  contractions.* 

Moreover,  in  cases  of  hypertrophy,  where  the  muscular 
element  and  action  is  increased,  the  sound,  so  far  from  being 
iiicreased,  is  impaired.  Hence,  the  first  sound  whether  it, 
be  regaided  as  the  result  of  the  vibration  of  the  auriculo- 
ventricular  valves,  acted  upon  by,  and  in  turn  acting  on 
columns  of  blood,  or  as  a  muscular  sound,  presents  great 
difficulties.  No  other  cause,  in  the  least  satisfactory,  has 
been  suggested  ;  and  the  difficulties  are  rather  incieased 
tiian  met  by  supposing  that  the  sound  is  at  once  both  val- 
vular and  muscular  in  orio:in. 


Hering  u.  Friedrich,  Wien.  iSitzungs-Berichte,  Ixxii  (1875). 


THE    WORK    DONE    BY    THE    HEART.  223 


The  Work  Dune. 

We  can  measure  with  exactness  the  intra- ventricular  pres- 
sure, the  lengtli  of  each  systole,  and  the  number  of  times 
the  systole  is  repeated  in  a  given  period,  but  perhaps  the 
most  important  factor  of  all  in  the  determination  of  the 
work  of  the  vascular  mechanism,  the  quantity  ejected  from 
the  ventricle  into  tiie  aorta  at  each  SNstole,  cannot  be  accu- 
rately determined ;  we  are  obliged  to  fall  back  on  calcula- 
tions having  i^nan}'  sources  of  error.  The  mean  result  of 
these  calculations  gives  about  180  grams  (6  ounces)  as  the 
quantity  of  blood  which  is  driven  from  each  ventricle  at  eacli 
systole  in  a  full-grown  man  of  average  size  and  weight.  It 
is  evident  that  exactly  the  same  quantit}'  must  issue  at  a 
beat  from  eacii  ventricle;  for  if  the  right  ventricle  at  each 
beat  gave  out  ratiiei-  less  than  the  left,  after  a  certain  num- 
ber of  beats  the  whole  of  the  blood  would  be  gathered  in  the 
systemic  circulation.  Similarly,  if  the  left  ventricle  gave 
out  less  than  the  right,  all  the  blood  would  soon  be  crowded 
into  the  lungs.  The  fact  that  the  pressure  in  the  right  ven- 
tricle is  so  much  less  than  in  the  left  (30  or  40  mm.  as  com- 
pared with  200  mm.  of  mercury),  is  due,  not  to  ditferences 
in  the  quantity  of  blood  in  the  cavities,  but  to  the  fact  that 
the  peripheral  resistance  which  lias  to  be  overcome  in  the 
lungs  is  so  much  less  than  that  in  the  rest  of  the  body. 

Various  methods  have  been  adopted  for  calculating  the  aver- 
age amount  of  blood  ejected  at  each  ventricular  systole.  It  has 
been  calculated  from  the  capacity  of  the  recently  removed  and  as 
yet  not  rigid  ventricle,  filled  with  blood  under  a  pressure  equal  to 
the  calculated  average  pressure  in  the  ventricle-  This  method 
of  course  presupposes  that  the  wdiole  contents  of  the  ventricle  are 
ejected  at  each  systole.  Volkmann'  measured  the  secti(»nal  area 
of  the  aorta,  and  taking  an  average  velocity  of  the  blood  in  the 
aorta  (a  very  uncertain  datum),  calculated  the  quantity  of  blood 
which  must  pass  through  the  sectional  area  in  a  given  time. 
The  number  of  beats  in  that  time  then  gave  him  the  quantity 
flowing  through  the  area  and  consequently  ejected  from  the  heart 
at  eacii  beat.  The  mean  of  many  experiments  on  difterent  ani- 
mals came  out  .0025  per  cent,  of  the  body  weight,  which  in  a  mnn 
of  75  kilos  would  be  187.5  grams.  Vierordt  measured  the  mean 
velocity  and  the  sectional  area  in  the  carotid,  and  thence,  from 
a  measurement  of  the  sectional  area  of  the  aorta,  and  from  a  cal- 
culation of  the  blood's  mean  velocity  in  it,  based  on  the  supposi- 

'   Hiimodynamik,  p.  206. 


224  THE    VASCULAR    MECHANISM. 


tion  that  the  mean  velocity  in  an  artery  was  inversely  as  its  sec- 
tional area,  arrived  at  the  quantity  tlowinij:  throuuh  the  aortic 
sectional  area  in  a  <iiven  time,  and  thus  at  the  quantity  ])assing 
at  each  heat.  Both  these  calculations  are  vitiated  hy  the  fact 
that  the  variations  of  velocity  in  the  aorta  are  so  great  that  any 
mean  has  really  hut  little  positive  value. 

Fick'  hy  means  of  calculations  hased  partly  on  the  data  gained 
hy  ohserving  the  increase  of  tlie  volume  of  the  whole  si)*m  at 
each  cardiac  systole,  arrived  at  results  much  less  than  either  of 
the  ahove.  In  one  case  he  estitnated  the  quantity  ejected  from 
the  heart  at  each  beat  at  53  grm.,  and  in  a  second  case  aj,  77 
grm. 

It  must  be  remembered  that  though  it  is  of  advantage  to 
speak  of  an  average  quantity  ejected  at  ench  stroke,  it  is 
more  than  probable  that  that  quantity  may  vary  within 
very  wide  limits.  Takiug,  however,  180  grms.  as  tlie  quan- 
tit}',  in  man,  ejected  at  each  stroke  at  a  pleasure  of  250  mm.^ 
of  mercury,  whicli  is  equivalent  to  3.21  meters  of  blood, 
this  means  that  the  left  ventricle  is  capable  at  its  systole  of 
lifting  180  gims.  3.21  m.  high,  i.  e.^  it  does  578  grammeters 
of  work  at  each  beat.  Supposing  tlie  heart  to  beat  72  times 
a  minute,  this  would  give  for  the  day's  work  of  the  left 
ventricle,  nearly  00,000  kilogrammeters  ;  calculating  the 
work  of  tlie  right  ventricde  at  one-fourth  that  of  the  left, 
the  work  of  the  whole  heart  would  amount  to  75,000  kilo- 
grammeters. A  calculation  of  more  practical  value  is  the 
following.  Taking  the  quantity  of  blood  as  j'g  of  the  body 
weight,  the  blood  of  a  man  weighing  75  kilos  would  be  about 
5760  grms.  If  180  grms.  left  the  ventricle  at  each  beat,  a 
quantity  equivalent  to  the  whole  blood  would  pass  through 
the  heart  in  32  beats,  ?'  e..  in  less  than  half  a  minute. 


Variations  in  the  HearV^  Beat. 

These  are  for  the  most  part  in  reality  vital  phenomena, 
i.  e..  brou:.dit  about  by  events  depending  on  changes  in  the 
vital  properties  of  some  or  other  of  the  tissues  of  tlie  body. 
It  will  be  convenient,  liowever,  briefly  to  review  them  here, 
though  the  discussion  of  their  causation  must  be  deferied 
to  its  appropriate  place. 

^  Untei-such,  physiol.  Lab.  Zurich.  Hochschule,  Hft.  1,  p.  51,  1869. 
2  A  high  estimate  is  purposely  taken  here. 


225 


The  frequency  of  tlie  heart,  i.  e.,  the  nuniher  of  beats  in 
any  iiiven  time,  may  vary.  The  average  rate  of  the  human 
pulse  or  lieart-heat  is  72  a  minute.  It  is  quicker  in  children 
than  in  adults,  hut  quickens  aijain  a  little  in  advanced  age. 
It  is  quicker  in  tiie  adult  female  than  in  the  adult  male,  in 
l)ersons  of  short  stature  than  in  tall  people.  It  is  increased 
by  exertion,  and  thus  is  quicker  in  a  standing  than  in  a  sit- 
ting, and  in  a  sitting  than  in  a  lying  posture.  It  is  quickened 
by  meals,  and  while  varying  thus  from  time  to  time  during 
the  day,  is  on  the  whole  quicker  in  the  evening  than  in  eaily 
morning.  It  is  said  to  be  on  the  whole  quicker  in  summer 
than  in  winter.  Even  independently  of  muscular  exertion 
it  seems  to  be  quickened  i)y  great  altitudes.  Its  rate  is 
profoundly  influenced  by  mental  conditions. 

The  length  of  the  systole  may  vary,  though  as  a  general 
and  broad  rule  it  may  be  stated  that  a  frequent  ditfers  from 
an  infrequent  pulse  chiefly  by  the  length  of  the  diastole. 

Bonders  found  the  length  of  the  systole  as  measured  by  the 
interval  betvreen  the  first  and  second  sounds  to  be  lor  ordinary 
pulses  remarkably  constant  in  different  persons,  varying  not 
more  than  from  .327  to  .301  sec,  and  being  therefore  relatively 
to  the  whole  cardiac  period  less  in  slow  than  in  quick  pulses. 

The  force  of  the  beat  may  vary  ;  tlie  ventricular  systole 
ma}'  be  weak  or  strong. 

When  the  rate  of  beat  is  suddenly  increased  there  is  a  tendency 
for  the  individual  beats  to  be  diminished  in  force,  and  on  the 
other  hand  to  be  increased  in  force  when  the  rate  is  diminished. 
But  there  is  no  necessary  connection  between  rate  and  strength  ; 
both  a  frequent  and  an  infrequent  pulse  may  be  either  weak  or 
strong. 

The  character  of  the  beat  may  vary  ;  the  systole  may  be 
sudden  and  sharp,  rapidly  reaching  a  maximum  and  rapidly 
declining,  or  slow  and  lengthened,  reaching  its  mnximum 
only  after  some  time  and  declining  very  gradually  ;  the 
latter  being  th6  slow  pulse  {puUu^  tardan)  as  distinguished 
from  the  infre(iuent  pulse  { puhus  rarus).  Tlie  pulse  is 
also  sometimes  spoken  of  as  being  slapping,  and  sometimes 
as  heaving. 

The  rhythm  may  be  inferinitU'nt  or  irrrguhir.  Thus  in 
an  intermittent  pulse,  a  beat  may  be   so  to  speak  dropped: 


\'l^ 


THE    VASCULAR    MKCUaNISM. 


the  hiatus  ot'CMii-iinii'  either  reL):uhuly  or  irregularly.     In   an 
irregular   rhythm   succeeding   Ijeats   may    dirter   in   length, 


force,  or  character. 


Sec.  3.  The  Pulse. 


"When  the  finger  is  placed  on  an  artery,  such  as  the  radial, 
an  intermittent  pressure  on  the  finger,  coming  and  going 
with  the  beat  of  the  heart,  is  felt.  When  a  light  lever  sucii 
as  that  of  the  sphygmograpli  (Fig.  69)  is  placed  on  the  ar- 
tery, the  lever  is  raised  at  each  beat,  falling  between.     The 

\\'IG.  G'J. 


Marey's  Sphygmograph. 

B,  B,  is  where  the  sphygmograph  is  applied  to  the  arm  ;  R,  spring  which  rests 
upon  radial  artery;  V,  screw  for  adjusting  markiui;  lever  L;  H,  clock-work  ;  P. 
smoked  paper  upon  which  tracing  is  made;  r,  small  spring  for  causing  descent  of 
lever  after  raising.] 

pressure  on  the  finger,  and  the  raising  of  the  lever,  are  expres- 
sions of  the  expansion  of  the  elastic  artery,  of  the  temporary 
additional  distension  which  the  artery  undergoes  at  each 
systole  of  the  ventricle.  This  intermittent  expansion  is 
called  the  pulse  ;  it  corresponds  exactly  to  the  intermittent 
outflow  of  blood  from  a  severed  artery,  being  present  in  the 
arteries  only,  and  except  under  particular  circumstances, 
absent  from  the  veins  and  capillaries.  The  expansion  is 
frequently  visible  to  the  e^e,  and   in  some  cases,  as  where 


THE    PULSE. 


227 


an  artery  bas  a  ])eiKl,  may  cause  a  certain  amount  of  loco- 
motion of  the  vessel. 

All  the  more  important  phenomena  of  the  pulse  may  be 
witnessed  on  an  artificial  scheme  (Fig.  TO). 

If  two  levers  be  placed  on  the  arterial  tubes  of  an  arti- 
ficial' sclieme.  one  near  to  the  pump,  and  the  other  near  to 
the  peripheral  resistance,  with  a  considerable  length  of 
tubing  between  them,  and  i)oth  levers  be  made  to  write  on 
a  recording  surface,  one  immediately  below  the  other,  so 
that  their  curves  can  be  more  easily  compared,  the  following- 
facts  may  be  observed,  when  the  pump  is  set  to  work  regu- 
larly : 

[Fig.  70. 


Appiratus  of  Marev  for  showiug  Mode  in  which  Pulse  is  Propagated  in  the  Arte- 
ries. ^  is  a  rubber  pump,  with  valve  attachment,  to  prevent  a  regurgitant  current ; 
I,  I',  I",  are  levers  resting  on  a  gum  tube,  at  intervals  of  20  cm.  of  tuLing;  C,  drum 
upon  which  tracing  is  made  ;  H,  clock-work  to  revolve  drum.] 

1.  With  each  stroke  of  the  pump  each  lever  fFig.  71,1 
and  II)  rises  to  a  maximum,  la,  2a,  and  then  fallsagain, 
thus  describing  a  curve — the  pulse-curve.'^  This  shows'that 
tiie  expansion  of  the  tul)ing  passes  the  point  on  which  the 
lever  rests  in  the  form  of  a  wave.  At  one  moment  the  lever 
is  quiet:    the  tube  beneath   it  is  simply  distended  to  the 

'  By  this  is  simply  meant  a  system  of  tubes,  along  which  fluid  can  be 
driven  by  a  pump  worked  at  regular  intervals.  In  the  course  of  the 
tubes  a  (variable)  resistance  is  introduced  in  imitation  of  the  capillary 
resistance.'  The  tubes  on  the  proximal  side  of  the  resistance  conse- 
quently represent  arteries  ;  those  on  tiie  distal  side,  veins. 

'  Cf.  Marey,  Trav.  d.  Lab.,  i  (1875),  p.  100. 


228 


THE    VASCULAR    MECHANISM. 


Fig.  71. 


oacK 


I     I      I 

Pulse-curves  descriWed  by  a  series  of  sphyfjiiiogritphic  levers  placed  at  intervals  of 
20  ciu.  from  each  other  aloii'?  an  elastic  tuV)e  into  which  fluid  ii  forced  by  the  sudden 
stroke  of  a  pump.  The  pulse-wave  is  travelling  from  left  to  right,  as  indicated  hy 
the  arrows  over  the  primary  (a)  and  secondary  (b,  c)  pulse-waves.  Tiie  dotted  ver- 
tical lines  drawn  from  the  summit  of  the  several  primary  waves  to  the  tuning-fork 
curve  below,  each  complete  vibration  of  which  occupies  -go  sec,  allow  the  time  to  be 
m  asured  which  is  taken  up  by  the  wave  in  pa'^sing  along  '20  cm.  of  the  tubing. 
The  waves  a'  are  waves  reflcited  from  the  closed  distal  end  of  thn  tubing  ;  this  is  indi- 
cated hy  the  direction  of  the  arrows.  It  will  be  ohserved  that  in  the  more  distant 
lever,  VI,  the  reflected  wave,  having  but  a  slight  distance  to  travel,  becomes  fused 
with  the  primary  wave. — After  Marey. 


THE    PULSE.  229 

normal  permanent  amount  indicative  of  tiie  mean  arterial 
pressure;  at  the  next  moment  tlie  pulse  expansion  reaches 
the  lever,  and  the  lever  begins  to  rise,  and  continues  to  do 
so  until  the  top  of  the  wave  reaches  it,  after  which  it  falls 
again  until  it  is  once  more  at  rest,  the  wave  having  com- 
pletel}'  passed  by. 

The  rise  of  each  lever  is  somewhat  sudden,  but  the  fall  is 
more  gradual,  and  is  generally  marked  with  some  irregular- 
ities. The  suddenness  of  the  rise  is  due  to  the  suddenness 
with  which  the  sliarp  stroke  of  the  pump  expands  the  tube; 
the  fall  is  more  gradual  because  the  elastic  reaction  of  the 
walls,  whereby  the  tube  returns  to  its  former  condition  after 
the  expanding  power  of  the  pump  has  ceased,  is  gradual  in 
its  action. 

2.  The  size  and  form  of  each  curve  depends  in  part  on 
the  amount  of  pressure  exerted  by  the  levers  on  the  tube. 
If  the  levers  only  just  touch  the  tube  in  its  expanded  state, 
the  rise  in  each  will  be  insigtiificant.  If,  on  the  other  hand, 
they  be  pressed  down  too  firmly,  the  tube  beneath  will  not 
be  able  to  expand  as  it  otherwise  would,  and  the  rise  of  the 
levers  will  be  proportionately  diminished.  There  is  a  cer- 
tain pressure,  depending  on  the  expansive  power  of  the 
tubing,  at  which  tiie  tracings  are  best  marked. 

3.  If  the  points  of  the  two  levers  be  placed  exactly  one 
under  the  other  on  the  recording  surface,  it  is  obvious 
that,  the  levers  being  alike  except  for  their  position  on  the 
tube,  any  ditlerence  in  time  between  the  movements  of  the 
two  levers  will  be  shown  by  an  interval  ])etween  the  begin- 
nings of  the  curves  they  describe,  if  the  recording  surface 
be  made  to  travel  sufficiently  rapidly. 

If  the  movements  of  the  two  levers  be  thus  compared,  it 
will  be  seen  that  the  far  lever  (Fig.  71.11)  commences  later 
than  the  near  one  (Fig.  71,  I);  the  farther  apart  the  two 
levers  are  the  greater  is  the  interval  in  time  between  their 
curves.  Compare  the  series  I  to  VI  (Fig.  71).  This  means 
that  the  wave  of  expansion,  the  pulse-wave,  takes  some  time 
to  travel  along  the  tube.  By  exact  measurement  it  would 
similarl}'  be  found  that  the  rise  of  the  near  lever  began 
some  fraction  of  a  second  after  the  stroke  of  the  pump. 

This  travelling  of  the  expansion-wave,  or  pulse- wave,  must 
be  carefully  distinguished  from  the  propagation  of  the  shock 
given  by  the  stroke  of  the  pump.     Wlien  a  long  glass  (or 

20 


230  THE    VASCULAR    MECHANISM. 

otlier  rigifl)  tube  filled  with  water  is  smartly  tapped  at  one 
end.  the  lilow  is  immediately  felt  as  a  siioek  at  the  other  end. 
The  transmission  of  this  shock,  if  cnrefnlly  measured,  would 
he  found  to  he  exceed inj^ly  raj)id  ;  compared  with  the  pulse- 
wave  now  under  consideration  it  would  he  practically  in- 
stantaneous. When  fluid  is  driven  by  the  strokes  of  a  pump 
along  a  rigid  tube  a  similar  shock,  travelling  equally  rapidly, 
may  be  readily  felt,  and  might  be  registered  with  a  lever. 
When,  however,  the  tube  alojig  which  the  fluid  is  being 
pumped  is  elastic,  the  force  of  the  pump  is  so  much  taken 
up  in  exjjanding  the  tube  that  the  shock  is  reduced  to  very 
small  dimensions.  It  becomes  so  slight  that  it  makes  no 
imi)ression  on  such  levers  as  are  used  to  register  the  expan- 
sion-wave. 

The  velocit}'  with  whicii  the  pulse-wave  travels  depends 
chiefly  on  the  amount  of  rigidity  possessed  by  the  tubing. 
The  more  extensible  (with  corresponding  elastic  reaction) 
the  tnbe,  the  slower  is  the  wave  ;  the  more  rigid  the  tube 
becomes,  the  faster  the  wave  travels.  According  to  Donders 
the  size  of  the  tube  has  no  marked  influence;  but  Moens^ 
finds  it  to  be  less  in  the  wider  tubes.  According  to  Marey 
the  initial  velocity,  the  steepness  of  the  wave,  has  an  influ- 
ence on  its  rate  of  progress.  In  the  human  body  the  wave 
has  been  estimated  to  travel  at  a  rate  of  9  to  10  meters 
(Weber,  9.240;  Garrod,  9-10.8;  or,  Recording  to  Landois, 
5  to  6  meters)  a  second.  It  probably  varies  very  consider- 
ably. According  to  all  observers  the  velocity  of  the  wave 
in  passing  from  the  groin  to  the  foot  is  greater  than  that  in 
passing  from  the  axilla  to  the  wrist  ((j743  mm.  against  577  2). 
This  is  i)robably  due  to  the  fact  that  the  femoral  arter}^  with 
its  branches  is  more  rigid  than  the  axillary. 

Since  with  increase  of  mean  tension  the  arteries  become  more 
and  more  rigid,  it  would  be  expected  that  the  velocity  would 
increase  with  the  mean  tension  ;  and  Moens,^  in  opposition  to 
Weber's  earlier  results,  fluds  that  it  docs. 

4.  Wiien  two  curves  taken  at  diflferent  distances  from  the 
pump  arecom[)ared  with  each  other,  the  far  curve  will  be  found 
to  be  shallower,  with  a  less  sudden  rise,  and  with  a  nK)re 
rounded  summit  than  the  near  curve  ;  compare  5a  with  la, Fig. 
71.    In  other  words,  the  pulse-wave,  as  it  travels  onward,  be- 

1  Die  Pulscurve,  Leiden,  1878.  '  Op.  cit. 


THE    PULSE.  231 

comes  dimiiiislied  and  flattened  out.  If  a  series  of  levers, 
otherwise  alike,  were  })laccd  at  intervals  on  a  piece  of  tubing 
sufficiently  long  to  convert  tlie  intermittent  stream  into  a 
continuous  flow,  the  pulse-wave  might  be  observed  to  grad- 
ually flatten  out  and  grow  less  until  it  ceased  to  be  visible. 

Care  must  be  taken  not  to  confound  the  progression  of 
the  pulse-wave  with  the  progression  of  the  fluid  itself.  The 
pulse-wave  travels  over  the  moving  blood  somewhat  as  a 
rapidl}'  moving  natural  wave  ti'avels  along  a  sluogjshly  flow- 
ing river,  the  velocity  of  the  pulse-wave  being  9  meters  per 
second,  while  that  of  the  current  of  blood  is  not  more  than 
.5  meter  per  second  even  in  the  large  arteries,  and  dimin- 
ishes rapidly  in  the  smaller  ones. 

Taking  the  duration  of  the  systole  of  the  ventricle  as  j^q 
of  a  second,  it  is  evident  that  the  pulse  wave  started  b}'  any 
one  systole,  if  it  travels  at  9  m.  per  second,  will  before  the 
end  of  the  .<ystole  have  reached  a  point  j\  of  9  m.  =  3.6  m. 
distant  from  the  ventricle.  In  other  wortls,  the  wave-length 
of  the  pulse-wave  is  much  longer  than  the  wdiole  of  the 
arterial  system,  so  that  the  beginning  of  each  wave  has 
become  lost  in  the  small  arteries  and  capillaries  some  time 
before  the  end  of  it  has  finally  left  the  ventricle. 

The  general  causation  of  the  pulse  may  then  be  summed 
up  somewhat  as  follows:  The  systole  of  the  ventricle  drives 
a  quantity  of  fluid  into  the  already  full  aorta.  The  portion 
of  the  aorta  next  to  the  heart  expands  to  receive  it,  thus 
giving  rise  to  the  sudden  up-stroke  of  the  pulse-curve.  The 
systole  over,  the  aortic  walls,  by  virtue  of  their  elasticitv, 
tend  to  return  to  their  former  calibre,  and  the  aortic  valves 
being  closed,  this  elnstic  force  is  spent  in  driving  the  blood 
onward.  The  elastic  recoil  being  slower  than  the  initial 
expansion,  the  down-stroke  of  the  pulse-curve  is  more  grad- 
ual than  the  upstroke.  Of  this  portion  of  the  aorta,  which 
actually  receives  the  blood  ejected  from  the  heart,  the  part 
immediately  adjacent  to  the  semilunar  valves  begins  to  ex- 
pand first,  and  the  expansion  travels  thence  on  to  the  end 
of  this  portion.  In  the  same  wa\^  it  travels  on  from  this 
portion  through  all  the  succeeding  portions  of  the  arterial 
system.  For  the  total  expansion  required  to  make  room 
for  the  new  quantit}'  of  blood  cannot  be  provided  l\v  that 
portion  alone  of  the  aorta  into  which  the  blood  is  actually 
received  ;  it  is  supplied  by  the  whole  arterial  system  ;  the 
old  quantity  of  blood  which  is  replaced  by  the  new  in  this 
portion  has  to  find  room  for  itself  in  the  rest  of  the  arterial 


232  THE    VASCULAR    MECHANISM 

space.  As  the  expniision  travels  onward,  liowever.  the  in- 
crtoxr.  of  pressure  which  each  portion  transmits  to  tlie  snc- 
ceedinsr  portion  will  Ite  less  tluui  that  which  it  received  from 
ti»e  precedin^i;  portion,  for  tlie  whole  inciease  of  pressure 
due  to  t!ie  systole  of  the  ventricle  has  to  he  distrihuted  over 
tiie  whole  of  the  arterial  system  ;  and  a  fraction  of  it  must, 
therefore,  he  left  behind  at  eacii  stage  of  its  progress;  that 
is  to  say,  tiie  expansion  is  continually  growing  less  as  the 
pulse  travels  from  tiie  heart  to  the  capillaries;  hence  the 
diminished  iieight  of  the  pulse-curve  in  the  more  distant 
arteries,  and  its  disapj^earance  in  the  capillaries. 

Secondary  Waves. — In  the  natural  pulse-curve  the  funda- 
mental wave  is  seen  to  be  marked  by  two  or  more  Sf'condari/ 
waves  imposed  upon  it.  These  secondary  waves  vary  much 
according  to  circumstances,  and  are  consequently  of  inter- 
est, as  throwing  light  on  the  condition  of  the  vascular 
system. 

In  an  artificial  scheme,  two  kinds  of  secondary  waves  are 
seen. 

1.  Waves  of  oscillation.  When  a  moderate  quantity  of 
fluid  is  injected  into  the  tube  at  each  stroke,  one,  two,  or 
more  secondary  waves  are  seen  to  follow  the  primary  one. 
They  are  the  more  marked,  the  more  sudden  the  stroke,  the 
more  extensible  (and  elastic)  the  tubing,  and  the  less  the 
pressure  in  it.  When  the  pump  is  a  pump  without  valves, 
they  form  a  regular  decreasing  series,  succeeding  the  pri- 
mary wave,  and  travelling  at  the  same  velocity  as  it  (Fig. 
71,1,  II,  III,  6,  c),  but  becoming  sooner  obliterated. 

These  waves  are  due  to  the  inertia  of  the  elastic  walls, 
and  of  the  contained  tluid,  and  so  correspond  to  the  sec- 
ondary oscillations  of  the  mercury  in  a  manometer.  If  the 
tube  be  filled  with  air  instead  of  water,  they  are  almost 
entirely  absent.  If  mercury  be  employed  instead  of  water, 
they  become  very  conspicuous. 

When  the  quantity  of  fluid  injected  is  large  compared 
with  the  calibre  of  the  tubing,  the  secondary  waves  may  be 
seen  on  the  descending  line  of  the  primar}'  wave. 

2.  Reflected  waves.  When  tlie  tube  of  the  artificial 
scheme  bearing  two  levers  is  blocked  just  beyond  the  far 
lever,  the  primary  wave  is  seen  to  be  accompanied  by  a 
second   wave,  which   at  the   far  lever  is  seen  close  to,  and 


THE    PULSE.  233 

often  fused  into,  the  primary  wave  (Fig.  71,  VI,  a')^  but  at 
the  near  lever  is  at  some  distance  from  it  (Fig.  71,1,  a'), 
being  the  farther  from  it,  the  longer  the  interval  between 
the  lever  and  the  block  in  the  tube.  This  second  wave  is 
evidently  the  primary  wave  reflected  at  the  block  and  trav- 
elling l)ackwards  towards  the  pump.  It  thus  of  course 
passes  the  far  lever  before  the  near  one.  The  secondary 
waves  of  oscillation  raa}^  be  similarly'  reflected. 

Of  the  secondary  waves  on  the  natural  pulse-curve,  two 
deserve  special  notice. 

The  first  and  most  important  is  the  dicrotic  ivai:e^  occur- 
ring towanls  the  end  of  the  descent.  This  is  always  more 
or  less  marked  in  every  pulse  ;  it  raa}^  be  witnessed  in  the 
aorta  as  well  as  in  other  arteries  (Fig.  72, a  to  e,  C).  Some- 
times it  is  so  slight  as  to  be  hardly  discernible.  Sometimes 
it  is  so  marked  as  to  give  rise  to  the  appearance  of  a  double 
pulse,  hence  the  name  (Fig.  34,/,  gr,  C). 

It  is  more  pointed  in  the  aorta,  and  in  the  larger  arteries  near 
to  the  heart,  than  in  the  more  distant  and  smaller  ones  ;  its  sum- 
mit indeed  rounds  oft'  more  rapidly  than  does  that  of  the  primary 
one.  The  interval  between  the  primary  and  dicrotic  rises  of  the 
pulse-curve  is  longer  in  the  more  distant  arteries.'  and  longer 
even  in  the  more  distant  parts  of  the  same  artery.^  It  dimin- 
ishes as  the  mean  tension  increases.'^ 


YiG.l-lb. 


a.  Sphygraograpli  Tracing- from  the  Ascending  Aorta  (Aneurisnial  Dilation).  Am- 
plified 40  times. 

In  this  and  the  succeeding  pulse-curves,  B  indicates  the  predicrotic  wave,  C  the 
dicrotic  wave.^ 

N.  B. — These  curves  arc  introduced  to  show  the  general  features  of  the  pulse-curve 
in  various  arteries.  Not  being  on  the  same  scale  or  taken  under  the  same  circum- 
stances, they  are  not  intended  for  careful  comparison. 

b.  From  Carotid  Artery  of  a  Healthy  Man  (tet.  26),  amplified  30  times. 

^  Landois,  op.  cit.  ^  Moens,  op.  cit.  ^  Moens,  op.  cit. 

*  For  this  imd  the  succeeding  pulse-curves  I  am  indebted  to  the  great 
kindness  of  Dr.  Galabin. 


234 


Tllb:    VASCULAR     MECHANISM. 


Fui.l2c. 


Vui.l2d. 


c.  From  tlic  liuilial  Artery  of  the  same  person  as  72  b.    Pressure,  4  oz.    Amplifii'd 
90  times,  as  are  also  tlie  siicceedin^j curves. 
(Where  not  otherwise  indicated  this  i:*  the  amplification  of  all  the  pulse-curves.) 
(/.  From  Uadial  Artery  of  a  Healthy  Man  L-ss  athletic  than  72  c.     Pressure,  '.i  oz. 


Fig.  72  e. 


1 
e.  From  the  Dorsalis  Pedis  of  the  same  person  as  b  and  c.    Pressure,  3  oz. 

Fig.  72/.  Fio.  72fir. 


/.  Tracing  of  Pulse  fully  Dicrotic:  Predicrotie  Wave  also  shown.  Pressure,  3  oz. 
(?  Typhoid    fever.) 

g.  Pulse  fully  Dicrotic,  and  Dicrotic  Wave  very  large.  Pressure,  1  oz.  (Typhoid 
Fever.) 


Fir;.  72  /:. 


//.  Pulse  with  very  large  Predicrotie  Wave.  Pressure,  4  ounces.  (Acute  alhiimi- 
nuria.) 

/;.  Hyperdicrotie  Pulse,  the  Dicrotic  Wave  becoming  lost  on  the  succeeding  beat. 
Pressure,  14  ounce.    After  hajmorrhage  in  typhoid  lever. 

The  conditions  wliicli  favor  the  prominence  of  the  dicrotic 
wave  are  cliiefly :  (1)  A  sadden  strong  ventricular  systole. 
(2)  Low  tension.  Hence  dicrotism.  not  previously  well 
marked,  may  he  hronoht  on  at  once  hy  diminution  of  the 
peripheral  resistance  by  section  of  the  vasomotor  nerves. 


THE    PULSE.  235 

(See  Section  5.)  (3)  Extensibility  (with  elastic  reaction)  of 
the  arterial  walls.  Hence  dicrotism  is  not  well  seen  in  arte- 
ries rigid  from  disease.  It  may  lie  well  marked  in  one 
artery  and  yet  very  slight  in  another. 

Can  we  explain  the  dicrotic  wave  b\'  showing  that  it  is 
either  a  wave  of  oscillation  or  a  reflected  wave?  That  the 
dicrotic  wave  is  not  one  reflected  from  the  periphery  is 
clearly  shown  by  the  fact  that  its  distance  from  the  summit 
of  the  primary  curve  is  either  greater  or  at  least  is  not  reg- 
ularly less  at  points  of  the  arteries  nearer  the  capillaries 
than  at  points  farther  from  them.  This  feature,  indeed, 
shows  that  the  dicrotic  wave  cannot  be  in  any  w^ay  a  retro- 
grade wave.  Again  the  more  the  primary  wave  is  obliter- 
ated b}-  the  elastic  action  of  the  arterial  walls,  the  less 
should  be  the  reflected  wave.  Hence  dicrotism  should 
diminish  with  increased  extensibility  and  elastic  reaction 
of  the  walls.  The  reverse  is  the  case.  Besides,  the  multi- 
tudinous peripheral  division  of  the  arterial  system  would 
render  one  large  peiipherally  reflected  wave  impossible. 

On  the  other  hand,  all  the  conditions  which  favor  dicrot- 
ism also  favor  the  occurrence  of  waves  of  oscillation.  If 
Fig.  71  I  be  comp:\red  with  Fig.  72  c,  the  similarity  between 
the  wave  of  oscillation  b  in  the  one  case  and  the  dicrotic 
wave  C  in  the  other  is  very  striking.  And  we  shall  prob- 
ably not  go  far  wrong  if  we  regard  the  dicrotic  wave  as 
in  the  main  a  wave  of  oscillation.  There  is,  however,  evidence 
that  it  is  not  a  simple  wave  of  oscillation  but  one  of  mixed  char- 
acter, the  movement  of  oscillation  being  reinforced  by  a  wave 
of  expansion  arising  from  the  closure  of  the  aortic  valves. 

It  has  been  questioned  whether  waves  of  oscillation,  so  mani- 
fest in  an  artificial  scheme,  do  occur  to  any  extent  in  the  arteries 
of  the  body,  surrounded  as  these  are  ])y  tissues  which  it  is  argued 
must  tend  to  act  as  dampers  towards  any  oscillations  due  to 
inertia.  But  there  is  no  positive  evidence  of  the  existence  of  any 
such  marked  damping  action,  and  the  remarkable  similarity  be- 
tween the  tracings  obtained  by  means  of  exposed  tubes  and  those 
given  by  arteries  in  situ  is  sufficient  evidence  that  in  this  respect 
the  two  behave  alike. 

That,  however,  the  dicrotic  wave  is  not  simply  due  to  the  inertia 
of  the  vessels  but  mixed  in  character,  is  shown  b}-  its  peculiar 
features.  In  simple  waves  of  oscillation,  such  as  those  shown  in 
Fig.  71  I,  the  first  wave  of  oscillation  is  the  largest,  the  succeed- 
ing ones  diminishing  in  size.  Now  the  dicrotic  wave,  though 
undoubtedly  the  most  prominent  and  in  man}- cases  the  only  ob- 
servable secondary  wave,  is  not  the  first  secondary  wave.     It  is 


2oQ  THE    VASCULAR    MECUANISM. 


frequently  pivcedod  l>y  the  so-called  "  i)redierotie  "  wave,  which 
sometimes  (Fi.u:.  72  h),  of  considerable  size,  is  probably  also  a 
wave  of  oscillation.  If  both  thesis  are  waves  of  oscillation,  there 
must  be  causes  at  work  tending  to  diminish  the  lirst(predicrotic) 
or  to  exairijerate  the  second  (dicrotic).  And  there  is  an  event 
which  readily  sujiirests  itself  as  likely  to  reinforce  the  later  occur- 
ring wave  of  oscillation,  viz.,  the  closure  of  the  aortic  valves. 
At  the  close  of  the  ventricular  systole  the  pressure  in  the  aorta 
becomes  hio;her  than  that  in  the  ventricle  itself,  and  the  blood  in 
consequence  tends  to  How  back  towards  the  ventricle.  Thus  the 
pressure  of  the  aorta  having  reached  its  maximum  begins 
to  fall  by  reason  of  the  backward  as  well  as  of  the  forward  How 
of  the  blood.  But  the  closure  of  the  semilunar  valves  gives 
a  check  to  this  fall.  A  new  wave  of  expansion  starting  from 
the  valves  is  propagated  along  the  aorta  and  great  arteries  in 
sequence  to  the  main  primary  wave.  If  we  suppose  this  wave, 
due  to  the  closure  of  the  aortic  valves,  to  coincide  with  a  wave  of 
oscillation,  the  prominence  of  the  latter  as  the  dicrotic  wave  be- 
comes intelligible.  This  view  is  supported  by  the  fact  that 
insutliciency  in  the  working  of  the  semilunar  valves,  the  so-called 
aortic  regurgitation,  materially  interferes  with  the  develoj^nent 
of  the  dicrotic  wave.  That  the  wave  in  question  should  wholly 
disappear  under  these  circumstances  is  not  to  be  expected,  seeing 
on  the  one  hand  that  it  is  partly  a  wave  of  oscillation,  and  on  the 
other  that  the  valves  need  not  be  perfectly  closed  in  order  that  a 
secondary  wave  of  expansion  may  l)e  started  at  the  end  of  the 
systole.  Such  a  wave  would  be  originated  by  any  obstacle  to 
the  return  of  blood  into  the  ventricle  ;  and  such  an  obstacle  must 
exist  with  even  the  most  imperfect  valves,  or  otherwise  the  cir- 
culation would  soon  come  to  an  end. 

Burdon-Sanderson  however  denies  that  the  aortic  valves  act  as 
above  explained  in  producing  the  dicrotic  wave,  basing  his  opin- 
ion on  the  grounds  :  1st.  That  not  only  may  the  dicrotic  wave  be 
produced,  but  that  a  tracing  presenting  all  the  graphical  charac- 
ters of  the  radial  pulse  tracing  may  be  obtained  on  an  artilicial 
scheme  in  the  absence  of  an}^  valves  corresponding  to  the  aortic 
valves  ;  2d.  That  the  form  of  a  tracing  taken  at  any  point  of  an 
artificial  scheme  may  be  modified  at  pleasure,  and  any  natural 
pulse  tracing  imitated  by  introducing  changes  into  the  distal  por- 
tion of  the  scheme  while  the  portion  corresponding  to  the  heart 
remains  absolutely  the  same.  The  view  he  takes  is  somewhat  as 
follows.  If  A  be  a  point  in  the  arterial  system  and  B  a  more 
distal  point,  the  maximum  expansion  of  B  will  take  place  some- 
what later  than  the  maximum  expansion  of  A;  when  B  is  at  its 
maximum  of  expansion,  A  will  be  already  declining.  As  the  elastic 
reaction  of  B  sets  in  it  exerts  a  pressure  not  only  forwards  but 
backwards,  so  that  the  decline  of  expansion  in  B  may  be  regarded 
as  giving  rise  to  a  wave  of  expansion  travelling  forwards,  and  to 
a  wave  of  expansion  travelling  backwards,  the  latter  reaching  A 
during  the  decline  of  expansion  at  that  point,  and  therefore 
giving  rise  in  ^  to  a  secondary  expansion.     This  secondary  ex- 


THE    PULSE.  237 


pansion  due  to  the  action  of  the  artery  at  the  single  point  B  is  of 
course  small ;  hut  what  is  true  of -B  is  also  true  of  all  the  points 
distal  to  A.  Consequentl}"  the  artery  at  the  point  A  is,  during 
the  decline  of  its  primary  expansion,  suhject  to  a  secondary  ex- 
pansion, caused  by  the  elastic  reaction  of  all  the  arteries  in  front 
of,  i.  e.,  more  distal  than  itself.  The  dicrotic  wave  at  any  given 
point  is,  in  fact,  a  secondary  expansion,  brought  about  by  the 
combined  elastic  reaction  of  the  more  distal  portions  of  the 
system. 

Moens^  compares  the  dicrotic  wave  to  the  waves  which  he  calls 
"waves  of  closure,"  seen  when  the  tiow  of  fluid  through  a  tube 
is  suddenly  checked,  and  looks  upon  it  as  simply  a  wave  gener- 
ated by  the  reflux  of  blood  against  the  closed  aortic  valves. 

Mosso,^  while  admitting  the  dicrotic  wave  to  be  a  wave  of  os- 
cillation, affirms,  in  opposition  to  most  other  observers,  that  it  is 
diminished  by  a  diminution  of  tension,  being  lessened,  or  even 
abolished  when  the  artery  dilates. 

The  other  secondary  wave  woi-thy  of  notice,  the  so  called 
predicrolic  wave,  Fig.  72  //,  B,  is  much  more  variable  than 
the  dicrotic.  Its  mode  of  origin  is  obscure,  but  it  is  proba- 
bl}'  a  wave  of  oscillation. 

Sometimes,  though  rarely,  the  dicrotic  wave  is  followed  by  still 
another  wave,  which  seems  to  be  simply  a  wave  of  oscillation. 
The  pulse  is  then  said  to  be  "tricrotic." 

In  some  instances  the  predicrotic  wave  appears  to  be  broken 
into  two,  and  it  becomes  often  very  difficult  to  distinguish  those 
secondary  waves  of  the  pulse-curve  which  are  really  due  to  events 
taking  place  in  the  artery  from  those  which  have  their  origin 
(through  inertia  in  the  spring,  etc.)  in  the  instrument  itself.^  It 
is  worthy  of  notice  that  the  summit  of  the  curve  of  intra-ven- 
tricular  pressure.  Fig,  62.  is  also  marked  by  one  or  more  secon- 
dary waves,  bearing  a  considerable  resemblance  to  the  predicrotic 
wave.  In  the  curves  obtained  by  Landois,"  by  allowing  the  blood 
from  the  end  of  a  divided  artery  to  spurt  out  on  to  a  recording 
surface,  there  is  no  trace  of  a  predicrotic  wave,  though  the  dicro- 
tic wave  is  exceedingly  well-marked. 

The  pulse  then  is  the  expression  of  two  sets  of  conditions  : 
one  pertaining  to  the  heart,  and  tlie  other  to  the  arterial 
system.  The  arterial  cc^nditions  remaining  tiie  same,  the 
characters  of  the  pulse  ma}^  be  modified  by  changes  taking 

^  Op.  cit.  2  Variazioni  Locali  del  Polso,  1878. 

3  Compare  Galabin,  -Journ.  of  Anat.  and  Phvs.,  vol.  viii,  p.  1 ;  also 
vol.  X,  p.  297. 

*  Pfluger's  Archiv,  ix  (1874),  71. 


2.'^S  THE    VASCULAR    MECHANISM. 

\)\i\vc  ill  tlic  beat  of  tlie  heart  ;  and  attain,  the  beat  of  the 
l)eart  remain inji;  tiie  same,  the  pulse  may  be  modified  by 
chan<2:es  takino;  place  in  the  arterial  walls.  Hence  the  diag- 
nostic value  of  the  pulse-characters.  It  must,  however,  be 
remembered  that  arterial  changes  may  be  accompanied  by 
compensating  cardiac  changes  to  such  an  exteiit  that  the 
same  features  of  the  j)ulse  may  obtain  under  totally  diverse 
conditions,  provided  that  these  conditions  att'ect  both  factors 
in  compensating  directions. 

Venous  Pulse. — Under  certain  circumstances  the  pulse  maybe 
carried  on  from  the  arteries  through  the  capillaries  into  the  veins. 
Thus,  when  the  salivar}'  gland  is  actively  secreting,  the  blood 
may  issue  from  the  gland  through  the  veins  in  a  rapid  pulsating 
stream.  This,  as  will  be  explained  hereafter,  is  due  to  a  dilation 
of  the  arteries.  Such  exceptional  cases  do  not  militate  against 
the  general  assertion  made  on  p.  22(3,  that  the  pulse  is  absent 
from  the  veins. 

If,  as  was  stated  on  p  211,  the  pressure  in  the  right  ventricle 
and  auricle  becomes  negative  at  the  beginning  of  the  diastole  of 
the  ventricle,  we  should  expect  to  find  that  a  wave  of  diminished 
pressure  travelled  backwards  from  the  heart,  along  the  great 
veins  ;  and  man}'  authors  have  insisted  on  the  existence  of  such 
a  ''  negative  pulse  "  even  in  health.  Thus  Mosso'  gives  tracings 
of  the^:)ressure  curves  of  the  jugular  and  other  veins  which  are 
marked  by  depressions  corresponding  to  the  elevations  of  the 
arterial  pressure  curves. 

Variations  of  pressure  in  the  great  veins  due  to  the  respiratory 
movements  are  sometimes  spoken  of  as  a  venous  pulse  ;  the  na- 
ture of  these  variations  will  be  explained  in  treating  of  respira- 
tion. 

II.    The  Yital  Phenomexa  of  the  Circulation. 

So  far  the  facts  with  which  we  have  had  to  deal,  with  the 
exception  of  the  heart's  beat  itself,  have  been  simply  physi- 
cal facts.  All  the  essential  phenomena  which  we  have 
studied  uja}'  be  reproduced  on  a  dead  model.  Such  an  un- 
varying mechanical  vascular  system  would,  however,  be 
useless  to  a  living  l)ody  whose  actions  were  at  all  compli- 
cated. The  prominent  feature  of  a  living  mechanism  is  the 
power  of  adapting  itself  to  changes  in  its  internal  and  ex- 
ternal circumstances.  In  such  a  system  as  we  have  sketched 
above,  there  would  be  but  scanty  power  of  adaptation.    The 

1  Archivio  p.  I.  Scien.  Med.,  ii  (1878),  p.  401. 


VITAL    PHENOxMENA    OF    THE    CIRCULATION.       239 

well  constructed  machine  might  work  with  beautiful  regu- 
larity ;  but  its  regularity  would  l)e  its  destruction.  The 
same  quantity  of  blood  would  always  flow  in  the  same  steady 
stream  through  each  and  every  tissue  and  organ,  irrespec- 
tive of  local  and  general  wants.  Tlie  brain  and  the  stom- 
ach, whether  at  work  and  needing  much,  or  at  rest  and 
needing  little,  would  receive  their  ration  of  blood  allotted 
with  a  pernicious  monotony.  Just  the  same  amount  of 
blood  would  pass  through  the  skin  on  the  hottest  as  on  the 
coldest  day.  The  canon  of  the  life  of  every  part  of  the 
whole  period  of  its  existence  would  be  furnished  by  the  in- 
born diameter  of  its  bloodvessels,  and  by  the  unvarying 
motive  power  of  the  heart. 

Such  a  rigid  system,  however,  does  not  exist  in  actual 
living  beings.  Tlie  vascular  mechanism  in  all  animals  which 
possess  one  is  capable  of  local  and  general  modifications, 
adapting  it  to  local  and  general  changes  of  circumstances. 
These  modifications  fall  into  two  great  classes: 

1.  Changes  in  the  heart's  beat.  These  being  central,  have, 
of  course,  a  general  effect. 

2.  Changes  in  the  peripheral  resistance,  due  to  variations 
in  the  calibre  of  the  minute  arteries,  brought  about  by  the 
agency  of  their  contractile  muscular  coats.  These  changes 
may  be  either  local  or  general. 

To  these  may  be  added  as  subsidiar}-  modifying  events: 

3.  Changes  in  the  peripheral  resistance  of  the  capillaries 
due  to  alterations  in  the  adhesiveness  of  the  capillary  walls 
or  to  other  influences  arising  out  of  the  as  yet  obscure  rela- 
tions existing  between  the  blood  within  and  the  tissue  without 
the  thin  peimeable  capillary  walls,  and  depending  on  the 
vital  conditions  of  the  one  or  of  tlie  other.  Such  changes 
causing  an  increase  of  peripheral  resistance  are  seen  to  a 
marked  degree  in  inflammation. 

4.  Changes  in  the  quantity  of  blood  in  circulation. 

The  two  first  and  chief  classes  of  events  (and  probably 
the  third)  are  directly  under  the  dominion  of  the  nervous 
system.  It  is  by  means  of  the  nervous  system  that  the 
heart's  beat  and  the  calibre  of  the  minute  arteries  are  brought 
into  relation  with  each  other,  and  with  almost  every  part  of 


210  THE    VASCULAR    MECHANISM. 

the  body.  It  is  by  means  of  tlio  nervous  system  aetiiJ^ 
either  on  tiie  heart,  or  on  the  small  arteries,  or  on  both,  that 
a  chano-e  of  cireunistanees  afl'eeting  eitlier  the  whole  or  a 
part  of  the  body  is  met  by  compensatinfr  or  legnlativo 
changes  in  the  flow  of  blood.  Jt  is  by  means  of  the  nervous 
system  that  an  organ  has  a  more  full  supply  of  blood  when 
at  work  than  when  at  rest,  that  the  stream  of  blood  through 
the  skin  rises  and  ebbs  with  the  rise  and  fall  of  the  temper- 
ature of  the  air,  that  the  work  of  the  heart  is  tempered  to 
meet  the  strain  of  overfull  arteries,  and  that  the  arterial 
gates  open  and  shut  as  the  force  of  the  central  pump  waxes 
and  wanes.  Each  of  these  vital  factors  of  the  circulation 
must  therefore  be  considered  in  connection  with  those 
parts  of  the  nervous  system  which  are  concerned  in  their 
action. 

Sec.  4.  Changes  in  the  Beat  of  the  Heart. 

We  have  already  discussed  the  more  purely  meciJanical 
phenomena  of  the  heart.  We  have  therefore  in  the  present 
section  only  to  inquire  into  the  nature  and  working  of  the 
mechanism  by  which  the  beat  of  the  heart  is  maintained, 
varied,  and  regulated. 

When  a  frog's  ventricle  which  has  ceased  to  beat  sponta- 
neously is  stimulated  by  touching  it  with  a  blunt  needle,  a 
beat  is  frequently  called  forth  ;  this  artilicial  beat  differs  in 
no  obvious  characters  from  a  natural  beat.  The  latent 
period  of  such  an  artificial  beat  is  remarkably  long,  the 
length  varying  within  very  wide  limits.  Thus  the  cardinc 
contraction  is  more  like  that  of  an  unstriated  than  of  a 
striated  muscle.  The  beat  is  in  fact  a  modified  or  peculiar 
form  of  i)eristaltic  contraction.  In  the  hearts  of  some  ani- 
mals, the  ventricle  forms  a  straight  tube  ;  and  in  these  the 
l)eristaltic  character  of  the  heat  is  obvious  ;  but  in  a  twisted 
tube  like  that  of  the  vertebrate  ventricle,  ordinary  peristaltic 
action  would  be  impotent  to  drive  the  blood  onward,  and  is 
accordingly  so  far  modified  that  the  peristaltic  character  of 
the  beat  is  recognized  only  v,hen  the  action  of  the  heart 
becomes  slow  and  feeble. 

The  cardiac,  like  the  skeletal  muscular  fi!)re,  after  a  con- 
traction returns  by  relaxation  to  its  previous  shape,  and  the 
whole  ventricle  (or  whole  heart)  regains  after  a  heat  the 
form  natural  to  its  quiescent  state.  This  diastolic  expan- 
sion, though  increased  by,  is  not  dependent  on,  the  influx  of 


THE    BEAT    OF    THE    HEART.  241 

fluid  into  the  cavities  of  the  lieart.  Thus  the  cavity  of  tlie 
empty  quiescent  mammalian  left  ventricle,  though  smaller 
than  when  it  is  distended  with  blood  as  in  its  normal  action, 
is  larger  than  when  it  is  in  systole  or  when  riijor  mortis  has 
set  in  ;  moreover  if  its  dimensions  be  artificially  lessened,  as 
when  it  is  squeezed  with  the  hand,  it  returns  by  an  elastic 
reaction  to  its  former  volume  when  the  pressure  is  removed. 
It  is  by  this  elastic  expansion  that  the  negative  pressure 
during  diastole  (p.  213j  is  probably  brought  about. 

One  great  feature  of  the  cardiac  beat  produced  by  artificial 
stimulation  is  seen  in  the  absence  of  any  relationship  between 
the  strength  of  the  stimulus  employed  to  produce  a  beat  and  the 
amount  of  contraction  evoked.  The  beat  with  which  a  heart 
responds  to  a  stimulus,  e  f/.,  a  single  induction-shock,  is,  if  there 
be  any  response  at  all,  equally  large  when  a  feeble  as  when  a 
strong  stimulus  is  used,  though  the  strength  of  the  beat  evoked 
either  by  a  strong  or  a  weak  stimulus  may  vary  considerably 
within  even  a  very  short  period  of  time. 

When  a  second  induction-shock  is  sent  in  at  a  certain  interval 
after  a  first,  the  beat  due  to  the  second  shock  is  often  larger  than 
the  first,  the  beneficial  efiects  of  a  contraction  (see  p.  127)  being 
even  still  more  manifest  in  the  heart  than  in  an  ordinary  skeletal 
muscle.  Frequently  by  successive  shocks  of  equal  intensity  a 
"  staircase  "  of  beats  of  successively  increasing  amplitude  may 
be  produced. 

When  a  secdud  induction-shock  follows  upon  the  first  too  rap- 
idly, it  is  apparently  without  effect  ;  no  second  beat  is  produced. 
So  also  when  a  series  of  rapidl}'-  repeated  induction-shocks  are 
sent  in,  a  certain  number  of  them  are  thus  "ineffectual ;  "  the 
application  of  the  ordinary  interrupted  current  gives  rise  not  to 
a  tetanus  but  to  a  rhythmic  series  of  beats.  The  "refractory 
period,"  which  is  so  brief  in  the  skeletal  muscle  (see  p.  117),  is 
very  prolonged  in  the  cardiac  muscle.  So  also  in  a  spontaneously 
beating  heart,  induction-shocks  sent  in  at  a  certain  phase  of  a 
cardiac  cycle,  e.  r/.,  the  commencement  of  the  systole,  are  ineffec- 
tual, though  they  produce  forced  beats  when  sent  in  at  the  other 
phases  of  the  cycle. ^ 

The  elasticity  of  the  cardiac  walls  is,  in  a  health}^  condition, 
like  that  of  a  skeletal  muscle,  very  perfect.  It  is  however  soon 
interfered  with  by  imperfect  nutrition;  and  a  "  contraction  re- 
mainder "  (p.  85)  under  certain  circumstances  is  readily  devel- 
oped. ^ 

Under  the  influences  of  certain  poisons,  veratrin,   digitalin, 

'  Cf.  Bowditch,  Ludwig's  Arbeiten,  1871,  and  Marev,  Travaux  du 
Laborat.,  ii'(1876^,  p.  63. 

'^  Koy,  Journ.  Physiol,  i  (1878),  p.  452. 


242  THE    VASCULAR    MECHANISM. 


etc.,  the  leiiirth  of  the  beat  is  enormously  ])roloniTe(l,  and  the 
ventricle  eventually  thrown  into  a  remarkably  contracted  condi- 
tion, the  exact  nature  of  which  is  ])erhai)s  not  thoroui;hly  under- 
stood, thouirh  it  is  believed  by  many  to  be  due  to  a  deticiency  of 
elastic  reaction/ 

I  The  force  of  the  cardiac  beat  is  extremely  modified  by  the 
action  of  certa'n  drun;s.  Hellebore,  chloroform,  hydrocysmic 
acid,  aconite,  jervia,  tartar  emetic,  nitrite  of  amyl,"  nitrite  of 
potassium,  all  reduce  the  force  by  a  direct  ])aralysant  action  on 
the  heart  muscle.  Alcohol,  ammonia,  and  quinine  have  the 
same  paralytic  effect  if  ,Li;iven  in  very  laroe  doses.  Calabar  bean, 
ether,  opium,  alcohol,  and  ammonia  increase  the  force  by  direct 
cardiac  action.  Yeratria  and  caltein  increase  the  force,  which 
is  soon  followed  by  a  diminution. 

Hellebore,  calabar  bean,  potassium  bromide,  aconite,  Jervia, 
and  quinine  (large  doses)  diminish  the  frequency  of  the  pulse ; 
and  ether  and  alcohol  (?)  increase  the  frequency  by  direct  action 
on  the  cardiac  muscle.  Many  of  the  above-named  drugs  act  also 
upon  the  cardiac  nerves  or  centres  (see  pp.  248  and  254)  which 
more  or  less  influence  or  modify  their  direct  cardiac  action. 
Quinine  in  large  doses  diminishes  blood  pressure  ;  calabar  bean 
causes  first  a  decrease,  then  a  rise,  followed  by  a  fall ;  and  digi- 
talis (also  stimulates  vaso-motor  centre,  and  ammonia  cause  an 
increase  by  direct  c  irdiac  action.] 

Nervous  Mechanism  of  the  Beat. — The  beat  of  tlie  heart 
is  an  automatic  action  ;  the  muscular  contractions  vviiicii 
constitute  the  beat  are  caused  by  impulses  wliich  arise  spon- 
taneously in  the  heart  itself. 

The  heart  of  a  frog  (or  of  a  turtle  or  fish,  etc.)  will  con- 
tinue to  heat  for  hours,  or  under  favorable  circumstances 
for  days,  after  removal  from  the  body.  The  beat  goes  on  even 
after  the  cavities  have  been  cleared  of  blood,  and  indeed 
when  they  are  almost  empty  of  all  (iiiid.  The  beats  are 
more  vigorous  and  last  longer  vvhen  the  heart  is  removed 
by  incisions  which  leave  the  sinus  venosus  still  attached  to 
the  auricles.  The  excised  heart  does,  however,  though  for 
a  shorter  time  and  not  so  readily,  continue  to  beat  sponta- 
neously when  removed  by  an  incision  carried  through  the 
auricles  so  that  a  portion  or  even  the  whole  of  the  auricles 
together  with  the  sinus  venosus  is  left  behind  in  the  body. 
In  this  case  the  parts  left  behind  are  seen  also  to  go  on 
beating  by  themselves. 

If  in  an  excised  heart  the  ventricle  be  divided  from  the 
auricles,  both  ventricle  and  auricle  will  go  on  beating.    Each 

^  Schmiedeberg,  Ludwig's  Festgabe  (1874),  p.  222. 


NERVOUS    MECHANISM    OF    THE    BEAT.  243 

moiety  has  then  an  independent  rhythm.  If  the  sponta- 
aeously  heating  auricle  be  bisected  longitudinally,  each 
lateral  half  will  go  on  beating  spontaneously.  Each  lateral 
half  may  be  still  further  divided,  and  yet  the  pieces  will, 
under  favorable  circumstances,  go  on  pulsating.  The  ven- 
tricle will  go  on  beating  wlien  bisected  longitudinally  :  but 
if  it  be  cut  across  transversely,  the  lower  half  remains  mo- 
tionless, while  the  upper  goes  on  pulsating.  The  power  of 
spontaneous  pulsation  is  limited  to  the  extreme  base,  for  if 
the  transverse  incision  be  carried  only  at  a  little  distance 
from  the  auriculo-ventricular  groove  all  power  of  sponta- 
neous pulsation  is  lost  in  the  lower  part.  When  these  sev- 
eral parts  of  the  heart  are  examined,  it  is  found  that  in  all 
of  those  which  iieat  spontaneously  ganglia  are  present,  while 
from  the  ventricle  except  at  the  extreme  base  ganglia  are 
absent.  There  are  ganglia  in  the  sinus,  ganglia  in  the 
auricular  septum  and  walls,  ganglia  in  the  auriculo-ven- 
tricular groove,  but  none  have  l)een  found  in  the  mass  of  the 
ventricle  itself  From  these  facts  the  conclusion  is  drawn 
that  the  spontaneous  pulsations  in  the  heart  are  in  some 
way  associated  with,  and  due  to  the  action  of,  the  ganglia 
scattered  in  its  substance.  Of  these  ganglia  those  in  the 
sinus  seem  more  potent  than  those  in  other  parts  of  the 
heart. 

The  exact  manner  in  which  these  ganglia  act  is  still  obscure. 
The  vigor  of  the  rhythmic  contractions,  and  the  time  they  con- 
tinue to  go  on  is  so  much  greater  in  the  case  of  the  heart  retain- 
ing the  sinus  venosus  than  in  that  from  which  it  has  been  re- 
moved, that  man}'  regard  the  beats  of  the  former  only  as  really 
automatic.  The}'  look  upon  the  beats  of  the  latter,  though  re- 
peated rln'thmically,  and  that  for  even  a  long  series,  to  be  the 
result  of  some  stimulation  or  other.  They  accordingly  speak  of 
the  sinus  ganglia  as  being  automatic,  and  of  the  rest  as  being  of 
reflex  or  other  function. 

Though  the  portion.comprising  the  lower  two-thirds  of  the  ven- 
tricle remains  after  separation  from  the  basal  third  permanently 
quiescent,  it  may  be  thrown  into  rhythmic  contractions,  indis- 
tinguishaijle  in  their  character  from  normal  beats,  by  the  appli- 
cation of  the  constant  current.  It  will  also  give  apparently 
spontaneous  rhythmic  beats,  when  supplied,  according  to  the 
Leipzig  method,  with  rabbit's  serum  or  dilute  rabbit's  blood. ^ 

1  Merunowicz,  Ludwig's  Arbeiten,  1875,  p.  132.  Compare,  however, 
Bernstein,  Ce'ntralbt.  f.  med.  Wiss.,  1876,  385,  435.  Bowditch,  Journ. 
Physiol.,  i  (1878),  p.  104. 


24:4 


THE    VASCULAR    MECHANISM. 


For  this  purpose,  a  tube,  completely  divided  by  a  lon.Gjitudinal 
])artitiou  into  two  canals,  is  introduced  into  the  cavity  of  the  ven- 
tricle, and  the  latter  securely  ligatured  round  the  tube  at  the 


[Fig.  73. 


Diagram  to  aid  in  understanding  the  Action  of  the  Nerves  upon  the  Heart.  The 
right  half  represents  the  course  of  the  inhibitory,  and  the  left  the  course  of  the  accel- 
erating nerves  of  the  heart;  the  arrows  showing  the  direction  in  which  impressions 
are  conveyed.  The  ellipse  at  the  upper  extremity  of  the  vagus  looking  like  the  sec- 
tion of  the  nerve  is  intended  to  represent  the  vagal  nucleus  or  centre. — After  Car- 
penter.] 

junction  of   the  upper  and   middle  thirds.      Fluid  introduced 
through  one  canal  at  a  low  pressure  distends  the  ventricle,  and 


INHIBITION    OF    THE    BEAT.  245 


when  a  beat  takes  place,  is  driven  out  througli  the  otlier  canal. 
Fed  in  this  way  with  rabbit's  (or  sheep's,  etc.)  serum  or  blood, 
almost  any  part  of  the  ventricle  may  be  made  after  a  period  of 
rest  to  execute  what  are  apparently  spontaneous  rhythmic  pul- 
sations. If  it  be  urged  that  the  serum  or  blood  is  a  stimulus 
which  provokes  contractions,  there  still  remains  the  difficulty, 
why  the  continued  stimulus  produces  not  a  continued  contrac- 
tion, but  a  rhythmic  pulsation.  Moreover,  in  the  case  of  the 
rhythmic  beats  evoked  by  the  constant  current,  the  current  cannot 
during  its  passage  be  regarded  as  a  stimulus  in  the  ordinary  sense 
of  the'word. 

The  beat  of  the  mammalian  heart  cannot  be  studied  in 
the  same  way  as  tliat  of  the  frog,  for  the  former  ceases  to 
beat  almost  immediately  after  removal  from  the  body  ;  but 
all  the  facts  which  have  hitherto  been  observed  go  to  prove 
that  the  heart  of  a  warm  blooded  animal  is  governed  by  a 
nervous  mechanism  similar  to  that  which  has  just  been  de- 
scribed. 

Just  as  the  two  auricles  of  the  frog's  lieart  beat  synchro- 
nously under  all  circumstances  (excepting  actual  separa- 
tion), so  also  the  two  ventricles  of  tlie  mammalian  heart  act 
completely  as  one.  A  want  of  synchronism  in  the  two  ven- 
tricles, though  it  has  been  called  in  to  exi:)lain  certain  patho- 
logical phenomena,  has  not  been  observed  experimentally. 

The  occurrence  of  two  cardiac  impulses  to  one  arterial  pulse, 
i.  e  ,  an  intermittence  of  the  arterial  pulse  unaccompanied  b\-  a 
cardiac  intermittence,  which  has  sometimes  suggested  the  idea  of 
a  want  of  synchronism  in  the  two  ventricles,  leading  to  a  double 
cardiac  impulse,  may  be  otherwise  explained.  In  such  a  case,  of 
the  two  contractions  of  the  ventricle  one  is  so  weak  that  it  fails 
to  throw  into  the  arterial  S3'Stem  enough  blood  to  give  rise  to  a 
pulse-wave . 

Inhibition  of  the  Beat. — The  beat  of  the  heart  may  be 
sto[)ped  or  checked,  i  e.,  may  be  inhibited  by  efferent  im- 
pulses descending  the  vagus  nerve  (Fig.  73). 

If  while  the  beats  of  the  heart  of  a  frog  or  rabbit  are  being 
carefully  registered  (Fig.  74)  an  interrupted  current  of 
moderate  strength  be  sent  through  one  of  the  vagi,  the  heart 
is  seen  to  stop  beating.  It  remains  for  a  time  in  diastole, 
perfect!}^  motionless  and  flaccid.  If  the  duration  of  tlie  cur- 
rent be  sliort  and  tlie  strength  of  the  current  great,  the 
standstill  may  continue  after  the  current  has  been  shut  off; 

21 


2i6 


THE    VASCULAR    MECHANISM. 


I  lie  boats  when  tliey  reaj^pear  are  ijenerally  at  first  feehle  and 
infrequent,  hut  soon  reach  or  even  go  l)eyon(l  their  previous 
vigor  and  frecpiency.  A  wholly  similar  inhibition  may  be 
seen  in  the  mammal;  and  indeed  in  man.  Czermak,  by 
l)ressing  his  vagus  against  a  small  osseous  tumor  in  his 
neck,  and  thus  meciianically  stimulating  the  nerve,  was 
able  to  stop  at  will  the  beating  of  his  own  heart ;  it  need 
hardly  be  added  that  such  an  experiment  is  a  dangerous 
one. 

The  effect  is  not  produced  instantaneously:  if  on  the  curve 
the  point  be  exactly-  marked  as  at  a  (Fig.  74),  where  the 


mMMMM^ 


lumm 


Inhibition  of  Frog's  Heart  by  Stimulation  of  the  Vagus. 

The  contractions  of  the  ventricle  are  registered  by  means  of  a  simple  lever,  so  that 
each  rise  of  the  lever  corresponds  to  a  beat.  The  interrupted  current  was  thrown  in 
at  «,  and  shut  off  at  6.  It  will  be  seen  that  one  heat  occuired  after  a,  and  tliat  the 
pause  continued  for  some  tiuie  after  b.    (To  be  read  from  right  to  left.) 


current  is  made,  it  will  frequently  be  found  that  one  beat  at 
least  occurs  after  the  current  has  passed  into  the  nerve.  In 
other  words,  the  inhil)itoiy  action  of  the  vagus  has  a  long 
latent  period  ;  this  has  been  estimated  by  Bonders  to  last 
in  the  rabbit  .10  second.  The  inhibitory  effect  is  at  a  maxi- 
mum soon  after  the  moment  of  application  of  the  current, 
and  diminishes  gradually  onward ;  so  much  so  is  this  the 
case  that,  when  the  current  is  applied  for  more  than  a  very 
short  time,  the  heart  recommences  beating  before  the  cur- 
rent is  removed.  The  eflect,  especiall}'  with  weak  currents, 
is  much  more  in  the  direction  of  prolonging  the  diastole 
than  of  diminishing  the  extent  of  the  systole.  Hence  with 
w  eak  currents  no  actual  stoppage  takes  place,  but  the  pauses 
between  the  beats  are  much  prolonged,  especially  at  the 
beginning  of  the  action  of  the  current,  and  the  pulse  thereby 


INHIBITION    OF    THE    BEAT.  247 

rondei'ed  slow.  During  the  standstill  direct  stimulation  of 
the  heart,  as  by  touehinii'  tiie  auricle  or  ventricle,  will  [)ro- 
diice  a  single  beat ;  though  spontaneous  pulsations  are  ab- 
sent, the  irritability  of  the  muscular  tibres  is  not  destroyed. 

The  stimulus  need  not  be  an  interrupted  current;  me- 
chanical and  ciiemical  stimulation  of  the  vagus  also  produces 
inhibition,  thongh  less  readily. 

After  atropiu,  even  in  a  minute  dose,  has  been  injected 
into  the  blood,  stimulation  of  the  vagus,  even  with  the  most 
powerful  currents.  [)roduces  no  inhibition  whatever.  The 
heart  continues  to  beat  as  if  nothing  were  happening; 
atropin,  in  some  way  or  other,  does  away  with  the  normal 
iuhil)itory  action  of  the  vagus. 

The  above  facts  show  that  the  events  which  are  at  the  bottom 
of  vagus  inhibition  are  complex.  The  following  considerations 
render  this  still  more  evident : 

A  single  induction-shock  rarely  produces  an  effect  which  can 
be  measured;  but  a  series  of  shocks,  repeated  at  intervals  (the 
interval  may  be  equal  to  or  even  greater  than  the  length  of  a 
whole  cardiac  C3'cle),  produces  very  marked  inhibition. 

If  one  application  of  the  current  be  rapidl}'  followed  b}'  a  second 
application  of  the  same  current,  the  etlects  are  very  markedly 
less.  This  seems  to  be  due  ]iartly  to  exhaustion  of  the  vagus 
tibres,  but  also  to  something  which  has  taken  place  in  the  heart 
itself;  for  a  stimulation  of  one  vagus,  immediatel}^  foUowinsj  a 
stimulation  of  the  other,  at  least  when  prolonged,  is  diminished 
in  effect,^ 

The  stimulus  may  be  applied  at  any  part  of  the  course  of  either 
vagus  (though  it  frequently  happens  in  the  frog  that  one  vagus 
is  more  efficient  than  the  other)  ;  but.  perhaps,  "the  most  marked 
effects  are  produced  when  the  electrodes  are  placed  on  the  bound- 
ary-line between  the  sinus  venosus  and  the  auricles. 

In  slight  urari  poisoning  the  inhibitor}-  action  of  the  vagus  is 
still  present ;  in  the  profounder  stages  it  disajipears,  but  even 
then  inhibition  may  be  obtained  by  applying  the  electrodes  to 
the  sinus. 

In  order  to  explain  this  result  it  has  been  supposed  that  the 
inhibitory  fibres  of  the  vagus  terminate  in  an  inhibitory  me- 
chanism (probably  ganglionic  in  nature),  seated  in  the  heart 
itself,  and  that  the  urari,  while  in  large  doses  it  ma}*  paralyze 
the  terminal  tibres  of  die  vagus,  leaves  this  inhibitory  mechanism 
intact  and  capable  of  being  thrown  into  activity  by  a  stimulus 
applied  directly  to  the  sinus.  After  atropin  has  been  given,  in- 
hibition cannot  be  brought  b}- stimulation  either  of  the  vagus  tibres 
or  of  the  sinus  ;  or,  indeed,  of  any  part  of  the  heart.     Hence  it 

^  Cf.  Gamgee  and  Priestley,  .Jonrn.  Phvsiol.,  i  (1878),  p.  39. 


248  THE    VASCULAR    MECHANISM. 


is  inferriMl  lliat  iitropin,  unlike  iirari,  p.anilyzes  this  intrinsic  in- 
hibitory nu'chanism  itsi'lf  (Fi.i;.  7)5). 

At'liT  the  application  of  niuscarin  or  jahorandi  the  lienrt  stops 
beatinu:,  and  remains  in  diastole  in  perfectt  standstill.  Its  ap- 
pearance is  then  exactly  that  of  a  heart  inhibited  by  ])rofoun(l 
and  lastini:;  vauus  stimulation.  This  ellect  is  not  hindered  by 
urari.  The  application,  however,  of  a  small  dose  of  atr()j)in  at 
once  restores  the  beat.  These  facts  are  inter])reted  as  meaninj^ 
that  muscarin  (or  jahorandi)  stimulates  or  excites  the  inhibitory 
apparatus  spoken  of  above,  which  atro])in  paralyzes  or  places 
hors  de  combat.  It  is  doubtful  whether  the  standstill  produced 
by  muscarin,  after  it  has  been  put  on  one  side  by  atropin,  can  be 
brought  back  again  by  further  doses  of  niuscarin.  In  the  case 
of  jahorandi  it  can.  When  jahorandi  is  carefully  applied  to  the 
ventricle  externally  the  ventricle  may  be  brought  to  a  standstill, 
while  the  auricles  continue  to  go  on  beating  as  usual.* 

Nicotin,  when  given,  tirst  slows  the  heart  even  to  a  stand- 
still ;  but  after  awhile  the  beats  recover  their  usual  rhythm. 
Stimulation  of  the  vagus  is  then  found  to  have  no  eflect ;  mus- 
carin, however,  at  once  produces  a  standstill,  which,  in  turn, 
may  be  removed  by  atropin.  The  initial  slowing  etfect  is  absent 
if  atroi)in  or  urari  be  previously  given.  These  facts  are  inter- 
preted as  showing  that  nicotin  lirst  excites  the  terminal  iibres  of 
the  vagus,  producing  inhibitory  etlects,  but  that  this  excitement 
ends  in  an  exhaustion  of  these  fibres.  The  action  of  the  drug, 
however,  is  limited  to  the  terminal  tibres  of  the  vagus,  and  does 
not  bear  on  the  intrinsic  inhibitory  apparatus  with  which  these 
fibres  are  connected  ;  hence  while,  after  nicotin  poisoning,  stimu- 
lation of  the  trunk  of  the  vagus  is  ineii'ectual,  a  small  dose  of 
muscarin,  which  acts  directly  on  the  apparatus  itself,  produces 
standstill. 

[Calabar  bean,  ergot,  hydrocyanic  acid,  and  veratria  stimulate 
the  vagi  nerves.  Digitalis  and  oi^ium  stimulate  both  the  vagi 
nerves  and  the  vagi"  or  "  cardio-inhibitory  "  centres  (p.  25(i). 
Strychnia  and  belladonna  paralyze  the  vagi  nerves.  Nitrite  of 
amyl  paralyzes  the  centres.  Opium,  veratroidia,  alcohol  (large 
doses)  primarily  stimulate,  then  paralyze  the  inhibitory  nerves. 
Chloroform,  veratria,  first  stimulate,  and  then  paralyze  the 
centres.  Digitalis  also  stimulates  the  intra-cardiac  inhibitory 
ganglia.  ] 

According  to  NueP  stimulation  of  the  vagus,  while  it  produces 
in  the  ventricle  simply  lengthening  of  the  diastole,  without 
change  in  the  force  of  the  systole,  has  a  marked  elfect  on  the 
force  of  the  systole  of  the  auricle.  Roy"*  finds  direct  stimulation 
of  the  auricle  to  bring  about,  according  to  the  spot  stimulated, 


'  Lmgley,  JoiiPi.  Anal.,  x  (1875),  b 
■^  Pdii^er's  Archiv,  ix  (1874),  p.  88. 
3  Jonrn.  Phy.-;iot.,  1  il878),  p.  4o2, 


REFLEX    INHIBITION.  249 


sometimes  slowing,  sometimes  quickening  of  the  beat,  with  in- 
crease or  with  decrease  of  force. 

If  a  Ugature  be  drawn  tightly  round  the  junction  of  the  sinus 
venosus  with  the  auricles,  or  if  the  auricles  be  separated  from 
the  sinus  by  an  incision  carried  along  the  boundary-line  between 
the  two,  a  standstill  is  produced  closely  resembling  a  very  pro- 
longed vagus  inhibition.  The  quiescence  thus  induced  may  last 
an  indetinite  time.  This  experiment  we  owe  to  Stannius.^  Dur- 
ing the  standstill,  a  pulsation  may  be  induced  by  a  stimulus 
applied  directly-  to  the  heart,  a  whole  series  of  beats  being  evoked 
v;hen  a  mechanical  stimulus,  such  as  the  prick  of  a  needle,  is  ap- 
plied over  the  seat  of  Bidder's  ganglia  at  the  junction  of  the 
auricles  with  the  ventricles,  or  tothe  ganglia  in  the  auricles  and 
in  the  bulbus  ; '  and  when  the  ventricle  is  separated  by  an  incis- 
ion from  the  auricles,  the  former  will  recommence  beating,  while 
the  latter  remain  as  quiescent  as  before.  A  rhythmic  beat  may 
also  be  induced  during  the  standstill  by  applying  the  constant 
current,  during  the  action  of  which  there  is  a  great  tendency  for 
the  ventricle  to  beat  before  the  auricles. 

Two  interpretations  have  been  offered  of  this  standstill.  It 
has  been  suggested  that  the  ligature  or  section  stimulates  the 
endings  of  the  vagus,  and  so  produces  inhibition.  This  is  dis- 
proved by  the  fact  that  the  standstill  appears  equally  well, 
whether  atropin  have  been  previously  given  or  not.  According 
to  the  other  view,  the  really  automatic  movements  of  the  heart 
depend  on  the  ganglia  in  the  sinus,  the  pulsations  which  appear 
in  the  isolated  ventricle  or  auricles  being  in  reality  retiex  pulsa- 
tions, or  pulsations  caused  by  some  stimulus  not  really  auto- 
matic, and  therefore  not  so  lasting  ;  or,  if  there  be  an  automatic 
apparatus  in  ventricle  or  auricle,  it  is  kept  in  check  by  the  action 
of  the  inhibitory  apparatus  spoken  of  above,  and  only  makes  its 
presence  felt  on  some  stimulus  being  applied.  This  view  again 
is  disproved  by  the  fact  that  if  the  sinus  be  gradually  separated 
from  the  auricles,  no  standstill  takes  place.  The  whole  subject 
needs  further  elucidation. 

Reflex  Inhibition. — This  inhibitory  action  of  the  vagus 
may  be  brought  about  by  retiex  action.  If  the  abdomen  of 
a  frog  be  laid  bare,  aiid  the  intestine  be  struck  sharply,  as 
with  tlie  handle  of  *a  scalpel,  tiie  heart  will  stand  still  in 
diastole  with  all  the  phenomena  of  vagus  inhibition.  If  the 
vervi  me>^enierici  or  the  connections  of  these  nerves  with 
the  sympathetic  chain  be  stimulated  with  the  interrupted 
current,  cardiac  inhibition  is  similarly  produced.     If  in  these 


^  MiiHer's  Archiv,  1852,  p.  85. 

-  Muuk,  Vferhandl.  Berl.  phvsiol.  Gesell.,  reported  in  Archiv.  f.  Anat. 
u.  Phys.,  1879,  p.  5G9. 


250  THE    VASCULAR    MECHANISM. 

two  experiments  both  vai^i  are  divided,  or  tlie  medulla 
ohlongata  destroyed,  inliiltition  is  not  produced,  liowever 
miR'h  either  tiie  intestine  or  tlie  mesenteric  nerves  be  stim- 
ulated. This  shows  that  tlie  phenomena  are  caused  i)y 
impulses  ascending  along  the  mesenteric  nerves  to  the 
medulla,  and  so  affecting  a  portion  of  that  organ  as  to  give 
rise  by  reflex  action  to  impulses  which  descend  the  vagi  as 
inhil)itory  impulses.  The  portion  of  the  medulla  thus  medi- 
ating between  the  afferent  and  efferent  impulses  may  be 
spoken  of  as  the  cardio-inhibitory  [or  vagal]  centre. 

If  the  peritoneal  surface  of  the  intestine  be  inflamed,  very 
gentle  stimulation  of  the  inflamed  surface  will  produce 
marked  inhil)ition  ;  and  in  general  the  alimentary  tract 
seems  in  closer  connection  with  the  cardio-inhibitory  centre 
than  other  parts  of  the  body  ;  but  apparently  stimuli  if 
sufliciently  powerful  will  through  reflex  action  })roduce  in- 
hilution  frotn  whatever  part  of  the  body  they  may  come. 
Tims  crushing  a  frog's  foot  will  stop  the  heart.  In  ourselves 
the  fainting  from  emotion  or  fi-om  severe  pain  is  the  result 
of  a  reflex  inhibition  of  the  heart,  the  afl^erent  impulses  in 
the  one  case  at  least,  and  probably  in  both  cases,  reaching 
the  medulla  from  the  brain. 

Direct  stimulation  of  the  centre  itself,  such  as  occurs 
during  the  destruction  of  or  results  from  injury  to  the  me- 
dulla, of  course  produces  inhil)ition  ;  and  inhibition  through 
one  vagus  may  be  brought  about  b}'  stimulation  of  the  cen- 
tral end  of  the  other. 

Thus  by  nervous  links,  the  regulative  action  of  the  inhib- 
itory mechanism  is  brought  into  more  or  less  close  com- 
munion with  all  parts  of  the  body. 

The  question  naturally  arises,  Has  this  cardio-inhibitory  cen- 
tre any  constant  automatic  action  V 

In  the  dog,  and  also,  though  to  a  far  less  extent,  in  the  rabbit, 
section  of  both  vagi  is  followed  by  a  quickening  of  the  heart's 
beat.  This  result  maj''  be  interpreted  as  showing  that  the  centre 
in  the  medulla  exercises  a  permanent  restraining  influence  on  the 
heart ;  that  organ  in  fact  being  habitually  curbed.  (The  argu- 
ment that  the  effects  of  an  artificial  stimulation  of  the  vagus 
soon  wear  off,  and  that  therefore  a  permanent  stimulation  of  the 
vagi,  lead  in  ;^  to  permanent  inhibitory  action,  would  be  impossi- 
ble, may  be  met  by  the  suggestion  that  the  effects  of  natui-al 
stimulation  need  not  necessarily  wear  off'.)  If,  however,  previous 
to  the  section  of  the  vagi,  afferent  impulses  to  the  centre  in  the 


ACCELERATOR    NERVES.  251 


medulla  are  cut  off  by  the  section  of  the  spinal  cord  below  the 
niudulla,  and  by  division  of  the  cervical  S3'mpathetic  chain,  no 
acceleration  follows  the  division  of  the  vaiji.  Tliis  would  show 
that  the  action  of  the  medulla  in  this  matter  is  purely  reflex  and 
not  automatic.  Such  an  experiment,  however,  introduces  many 
sources  of  error  ;  and,  perhaps,  the  question  itself  is  at  bottom  a 
barren  one.  Granting,  however,  the  existence  of  a  centre  in  the 
medulla,  which  either  automatically  or  otherwise  is  in  permanent 
action,  it  is  obviously  open  to  ns  to  speak  of  reflex  inhibition  as 
being  brought  about  by  influences  which  augment  the  action  of 
that  centre.  But  we  have  seen  that  active  nervous  centres  are 
subject,  not  only  to  augmentative,  but  also  to  inhibitory  influ- 
ences. Hence  the  cardio-inhibitor}'  centre  might  itself  be  inhib- 
ited by  impulses  reaching  it  from  various  quarters.  In  other 
words,  the  beat  of  the  heart  might  be  quickened  by  a  lessening 
of  the  normal  action  of  its  inhibitor}'  centre  in  the  medulla.  It 
is  in  fact  probable,  that  man}'  cases  of  quickening  of  the  heart's 
beat  are  produced  in  this  way,  though  the  matter  requires  fur- 
ther investigation. 

Accelerator  Nerves.— The  heart's  beat  may  in  the  mammal 
be  quickened,  even  after  division  of  both  vagi,  by  direct  stimula- 
tion of  the  cervical  spinal  cord.  The  eftects  produced,  however, 
are  very  complex,  and  led,  on  their  first  being  made  known,  to 
much  discussion,  one  outcome  of  which  was  the  discovery  of  cer- 
tain nerves  of  a  very  peculiar  character,  which  pass  from  the 
cervical  spinal  cord,  frequently  along  the  nerve  accompanying 
the  vertebral  artery,  and  reach  the  heart  through  the  last  cervical 
and  first  thoracic  ganglia ;  these  have  been  called  the  "accele- 
rator nerves  "  (Fig"  73).  Their  course  is  different  in  the  rabbit  and 
in  the  dog,  Figs.  tS  and  76,  and,  indeed,  varies  even  in  the  same 
kind  of  animal.  Stimulation  of  these  nerves  with  the  interrupted 
current  causes  a  quickening  of  the  heart's  beat,  in  which  what  is 
gained  in  rate  is  lost  in  force,  for  the  blood-pressure  is  not  neces- 
sarily increased,  but  may  remain  the  same,  or  even  be  diminished. 
Not  only  is  the  latent  period  of  the  action  of  these  nerves  con- 
siderable, but  it  moreover  takes  a  very  long  time,  as  much  as  10 
seconds,  even  with  maximal  stimulation,  before  the  maximum  of 
acceleration  is  reached  (the  acceleration  often  continuing  after 
the  stimulus  has  been  removed),  and  the  decline  back  to  the 
normal  pulse-rate  is  still  slower.  Stimulation  for  even  a  second 
may  thus  produce  an  acceleration  lasting  a  considerable  time. 
These  accelerator  nerves  seem'  to  be  unaffected  by  the  various 
poisons,  including  urari,  which  act  upon  the  vagus  and  other 
parts  of  the  nervous  system  of  the  heart,  and  are  effective  in  the 
midst  of  profound  asphyxia.  Their  influence  is  closely  dependent 
on  temperature  ;  at  low  temperatures  their  influence  is  slight,  and 
long  in  making  its  appearance  ;  as  the  temperature  rises  their 

^  Schmiedeberg,  Lndwig's  Arbeiten,  1871. 


THE    VASCULAR    MECHANISM. 


action  hc'conios  more  spct'dily  developed  and  more  powerful. 
They  are  not  to  he  considered  as  antai^onislic  to  the  va.iz;i;  for  ifdur- 
iuij;  maximum  stimulation  of  the  accelerator  nerves  the  vaj^us  he 


Fk;.  75. 


jT'nch  {     n.dep, 


n.rec. 


The  Last  Cervical  imd  First  Thoracic  (lan-lia  in  the  Kabhit.    (Leftside.)    (Some- 
what diagraniniatic,  juany  of  the  various  brandies  being  omitted.) 

Track.,  trachea.  Ca.,  carotid  artery,  .v?).,  siil)chivian  artery,  n.  Faj^.,  the  vagus 
trunk,  n.rfc,  the  recurrent  laryngeaL  .^ym  ,  the  cervical  .synipathelic  uerve  ending 
in  the  inferior  cervical  ganglion,  *//.  cerr.  inf.  Two  roots  of  the  ganglion  are  shown, 
rad  ,  the  lower  of  the  two  accompanying  the  vertebral  artery,  A.  vert.,  being  thw  one 
generally  pussessing  accelerator  properties,  gl.  thor.pr.,  the  first  thoracic  ganglion. 
Its  two  branches  communicating  with  the  c**rvical  ganglion  surround  the  subclavian 
artery  forming  the  annulus  of  Vieussens.  sym.  Ihor.,  the  thoracic  sympathetic  chain, 
n.  (f  17) ,  depressor  nerve.  This  is  JDintxl  iu  its  course  by  a  branch  from  the  lower 
cervical  ganglion,  there  being  a  small  ganglion  at  their  junction,  fron)  whicli  proceed 
nerves  to  form  a  plexus  over  the  arch  of  the  aorta.  It  is  this  branch  from  the  lower 
cervical  ganglion  which  possesses  accelerator  properties — hence  tlie  course  of  the 
accelerator  filjres  is  indicated  in  the  ligure  by  the  arrows. 

Stimulated,  even  with  minimum  currents,  inhibition  is  produced 
with  the  same  readiness  as  if  these  were  not  acting.^    The  period 


'  Baxt.,  Die  Stellung  des  N.  vagus  zuni  N.  accelerans,  Ludwig's  Ar- 
beiten,  1875. 


ACCELERATOR    NERVES. 


253 


of  inhibition,  ho^vever,  is  followed  by  a  period  of  acceleration 
similar  to  that  produced  by  the  action  of  the  accelerator  alone, 
the  vagus  action  appearing  simply  to  suspend,  during  its  con- 


FiCt.  7G, 


'v.s^/im, 


e-r^ 


The  Last  Ci-rvkal  and  First  Thoracic  Ganglia  in  the  Dog. 
The  cardiac  nerves  of  the  dog.  The  figure  is  largely  diagrammatic,  and  represcnta 
the  left  side, 
r.  sym.,  the  united  vagus  and  cervical  sympathetic  nerves,  gl.  cerv.  i.,  the  inferior 
cervical  ganglion,  n.  v.,  the  continuation  of  the  trunk  of  the  vagus,  aren.  V.,  the 
two  branches  forminsr  the  annulusof  Vif-ussens  round  the  subclavian  arters-,  «)7. 
suftc'.,  and  joining  gr^  ^A./»r.,  the  first  thoracic  or  stellate  ganglion  (the  branch  rvin- 
niug  in  front  of  the  artery  is  considered  by  Schmiedeberg  to  be  an  especial  charnel 
of  accelerator  fibres),  sym.  ihorac. ,  the  sympathetic  trvink  in  the  thorax,  r.  vert., 
communicating  branches  from  the  cervical  nerves  running  alongside  the  vertebral 
artery,  the  rami  vertebrales.  n.  rec  the  recurrent  laryngeal,  n.  c,  cardiac  branches 
from  the  lower  cervical  ganglion,  accelerator  nerves  of  Schmiedeberg.  n'.  c'.,  cardiac 
branches  from  the  first  thoracic  ganglion,  accelerator  nerves  of  Cyon.  n".c".,  car- 
diac branch  from  recurrent  nerve,  r.  rec,  branch  from  lower  cervical  ganglion  to 
the  recurrent  nerve,  often  containing  accelerator  fibres. 

tinuance,  the  manifestation  of  the  accelerator  action  but  not  to 
annul  it.  We  know  at  present  little  concerning  the  share  which 
these  nerves  take  in  the  natural  action  of  the  economy.  If,  as 
later  researches  of  Baxt^  would  seem  to  show,  their  accelerating 
effect  is  characterized,  not  only  by  a  diminution  of  the  diastole, 

1  Archiv  f.  Anat.  u.  Phys.,  1878,  p.  121. 

99 


254  THE    VASCULAR    MECHANISM 


but  also  by  ;in  acliial  sborlcninuj  of  Ibc  cainliac  systole,  it  is  ob- 
vious tbat  the  quickcniuLi;  of  llic  heart's  beat  proiluccd  by  their 
aetion  is  soniethin<:;  (juile  dillereut  from  the  (luiekeniujj;  indireetly 
brought  about  by  a  cliniiuution  of  the  aelivity  of  the  eardio- 
iuhibitory  centre.  Baxt  compares  their  action  to  that  of  lieat 
directly  iutluencinjj:  the  cardiac  tissues;  and  the  comparison  is 
certainly  a  suuuestive  one. 

^lany  observers  have  obtained  an  acceleration  of  the  heart's 
beats  upon  stinuilation,  under  certain  circumstances,  of  the  trunk 
of  the  vagus  (Fig.  7."]).  And  Schilf  maintains  that  the  accele- 
rator nerves  described  above  come  from  the  vagus  and  not  from 
the  spinal  cord. 

[Alcohol  (in  small  doses)  and  ammonia  stimulate  the  accele- 
rator nerves  ;  belladonna  stinudates  both  the  accelerator  nei'ves 
and  centres.  Apomorphia^  probably  stimulates  the  accelerator 
fibres  of  the  vagi  nerves.] 

The  beat  of  the  lieart  may  also  be  modified  by  influences 
bearing  directly  on  the  nutrition  of  the  heart.  The  tissues 
of  the  heart,  like  all  other  tissues,  need  an  adequate  supply 
of  blood  of  a  proper  quality  ;  if  the  blood  vary  in  quality 
or  quantity,  the  beat  of  the  heart  is  correspondingly  alfected. 
The  excised  frog's  heart,  as  we  have  seen,  continues  to  beajt 
for  some  considerable  time,  though  a})parently  empty  of 
blood.  After  awhile,  however,  the  beats  diminish  and  dis- 
ai)pear ;  and  theii"  disappearance  is  greatly  hastened  by 
washing  out  tlie  heart  with  a  normal  saline  solution 
which,  when  allowed  to  flow  through  the  cavities  of  the 
heart,  readily  permeates  the  tissues  on  account  of  the 
peculiar  construction  of  the  frog's  cardiac  walls.  If  such 
a  '•  washed  out  "  quiescent  heart  be  fed  in  the  manner  de- 
scribed at  p.  244,  with  diluted  blood  (of  the  rabbit,  sheep, 
etc.)  it  may  be  restored  to  functional  activity.  A  similar 
but  less  complete  restoration  may  be  witnessed  if  serum  be 
used  instead  of  blood ;  and  a  heart  fed  regularly  with  fresh 
supplies  of  blood,  or  even  of  serum,  may  be  kept  beating 
for  a  very  great  length  of  time. 

The  beneficial  action  seems  to  be  partly  due  to  the  alkaline 
serum  neutralizing  the  acids  continually  i)roduced  by  the  muscu- 
lar contractions  ;  for  dilute  alkaline  solutions,  ex.  (jr.^  a  solution 
of  sodium  hydrate  .005  per  cent,  in  the  normal  saline  solution, 
are  even  more  eflicient  than  serum.'     Gaule^  further  finds  that 

^  Ptliiger's  Archiv,  xviii  (1878),  p.  172.  See  also  many  previous 
papers  there  quoted. 

2  [Reichert,  Phvs.  Action  of  Apomorphise  Hvdrochloras ;  Phil.  Med. 
Times,  X,  Xos.  314,  315,  316.] 

^  Merunovicz,  Ludwig's  Arbeiten,  1875,  p.  132.  Gaule,  Arch.  f. 
Anat.  u.  Phvs.,  1S78,  p.  291.  *  Op.  cit. 


INFLUENCES    AFFECTING    THE    BEAT.  255 


the  beats  are  assisted,  especiall}'  as  regards  their  force,  hj^  adding 
to  the  alkaline  solution  a  trace  of  peptone. 

When  the  heart  is  fed  with  rabbit's  serum,  the  beats, 
whether  spontaneous  or  provoked  by  stimulation,  are  apt 
to  become  intermittent  and  to  arrange  themselves  into 
groups.  This  intermittence  is  due  to  the  chemical  action 
of  the  serum;  and  it  is  probable  that  cardiac  intermittences 
seen  during  life  have  often  a  similar  causation.  Various 
chemical  substances  in  the  blood,  natural  or  morbid,  may 
thus  affect  the  lieart's  beat  by  acting  on  its  muscular  fibres, 
its  reflex  or  automatic  ganglia,  or  its  intrinsic  inhibitory 
apparatus. 

The  physical  or  mechanical  circumstances  of  the  heart 
also  affect  its  beat ;  of  these  perhaps  the  most  important  is 
the  amount  of  the  distension  of  its  cavities.  The  con- 
tractions of  cardiac  muscle,  like  those  of  ordinar}-  muscle 
(see  p.  1 18),  are  increased  up  to  a  certain  limit  by  the  resist- 
ance which  the}'  have  to  overcome  ;  a  full  ventricle  will, 
other  things  being  equal,  contract  more  vigoroush'  than  one 
less  full ;  though,  as  in  muscle,  the  limit  at  which  resistance 
is  beneficial  may  be  passed,  and  an  overfull  ventricle  will 
cease  to  beat  at  all. 

The  influences  of  resistance  in  the  case  of  the  heart  are,  how- 
ever, more  complex  than  those  of  ordinary  muscle,  since  in  the 
former  we  have  to  deal  with  the  rate  as  well  as  the  vigor  of  the 
beat. 

Under  normal  conditions  the  ventricle  probably  empties 
itself  completely  at  each  systole.  Hence  an  increase  in  the 
quantity  of  blood  in  the  ventricle  would  augment  the  work 
clone  in  two  ways :  the  quantity  thrown  out  would  be 
greater,  and  the  increased  quantity  w^ould  be  ejected  with 
greater  force.  Further,  since  the  distension  of  the  ventricle 
is  (at  the  commencement  of  the  systole  at  all  events)  de- 
pendent on  the  auricular  s^'stole,  the  work  of  the  ventricle 
(and  tlierefore  of  the  heart  as  a  whole)  is  in  a  measure  gov- 
erned by  the  auricle.^ 

The  Relation  of  the  Heart's  Beat  to  Blood-pressure. — 

When  the   blood-pi-essure   is   high,  not  onl}-  is   the   resist- 
ance to  the  ventricular  systole  increased,  but  other  things 

^  Cf.  Roy,  Journ.  of  Pliys.,  i  (1878),  p.  452. 


25(3  THE    VASCULAR    MECHANISM. 

beinir  eciiitil,  more  1)1(K)(1  Adw.s  throuirh  the  coronary  artery. 
J5otli  these  events  would  ini-rense  the  work  of  the  heart,  and 
we  iiiiglit  expect  that  the  inciease  would  be  manifest  in  the 
rate  of  the  rhythm  as  well  as  in  the  force  of  the  individual 
heats.  As  a  matter  of  fact,  however,  we  do  not  find  this. 
On  the  contrary,  as  Marey  has  insisted,  the  relation  of 
heart-beat  to  pressure  may  be  put  almost  in  the  form  of  a 
law,  thai  '*  the  rate  of  the  beat  is  in  inverse  ratio  to  the 
arterial  pressure;"  a  rise  of  pressure  being  accompanied  by 
a  diminution,  and  fall  of  pressure  with  an  increase  of  the 
pulse-rate.  This,  however,  only  holds  good  if  the  vagi  be 
intact.  If  these  be  previously  divided,  then  in  whatever  way 
the  blood-pressure  be  raised — whether  by  injecting  blood  or 
clam[)ing  the  aorta,  or  increasing  the  periphernl  resistaiice, 
through  that  action  of  the  vaso-motor  nerves  which  we  shall 
have  to  describe  directly — or  in  whatever  way  it  be  lowered, 
no  very  clear  and  decided  relation  between  blood-pressure 
and  pulse-rate  is  observed.*  It  is  inferred,  therefore,  that 
increased  blood-pressure  causes  a  slowing  of  the  pulse,  when 
the  vagi  are  intact,  because  tlie  cardio-inhibitory  centre  in 
the  medulla  is  thereby  stimulated,  and  the  heart  in  conse- 
quence to  a  certain  extent  inhibited. 

When  the  blood-pressure,  after  section  of  the  vagi,  is  raised  by 
the  injection  of  additional  blood  or  by  clamping  the  aorta,  the 
heart's  beats  are  increased  in  strength,  as  shown  by  the  larger 
excursions  of  the  manometer  ;  the  fact  that  this  is  not  accompa- 
nied by  any  change  in  the  rate,  suggests  that  there  must  be  some 
compensating  agency  at  work.  Sometimes,  even  after  section  of 
the  vagi,  a  slight  slowing  is  observed  when  the  pressure  is  in- 
creased ;  this  iias  been  attri1)uted  to  the  action  of  the  increased 
arterial  pressure  on  the  endings  of  the  vagus  fibres  in  the  heart 
itself. 


The  Effects  on  the  Circulation  of  Changes  in  the  FlearVs 

Beat. 

Any  variation  in  the  heart's  beat  directly  affects  the  blood- 
pressure  unless  some  compensating  influence  be  at  work. 
The  most  extreme  case  is  that  of  complete  inhibition.  Thus, 
if  while  a  tracing  of  arterial  pressure  is  being  taken,  the 
beat  of  the  heart  be  suddenly  arrested,  some  such  curve  as 
that  represented  in  Fig.  77  will  be  obtained.     It  will  be  ob- 

'  Nawrocki,  Lud wig's  Festgabe,  p.  ccv. 


INHIBITION    AND    BLOOD  -  PR  ESSUR  E, 


257 


served  that  immediately  after  the  last  beat  there  is  a  sudden 
rapid  fall  of  the  blood-pressure,  the  curve  described  by  the 
float  more  or  less  closely  resembling  a  parabola.  At  the 
close  of  the  last  systole,  the  arterial  system  is  at  irs  maxi- 
mum of  distension  ;  forthwith  the  elastic  reaction  of  the  ar- 
terial walls  propels  the  blood  forward  into  the  veins,  and 
there  being  no  fresh  fluid  injected  from  the  heart,  the  fall 
of  the  mercury  is  unbroken,  being  rapid  at  first,  but  slower 
afterwards,  as  the  elastic  force  of  the  arterial  walls  is  more 


-X 


Tracing  showiug  the  Influence  of  Cardiac  Inhibition  on  Biood-prcssiire.    From  a 

Kabbit. 

The  current  was  thrown  into  the  vagus  at  a  and  shut  off  at  b.  It  will  be  observed 
that  one  beat  is  recorded  after  the  conimeneenient  of  the  stimulation.  Then  follows 
a  very  rapid  fall,  continuing  after  the  cessation  of  the  stimulus.  Witli  the  returning 
beats,  the  mercury  rises  by  leaps  until  the  noimal  pressure  is  regained. 


and  more  used  up.  With  the  returning  beats,  the  mercury 
correspondingly  rises  in  successive  leaps  until  the  noimnl 
pressure  is  regained.  The  size  of  these  returning  leaps  of 
the  mercury  may  se.em  extraordinary,  Fig.  78,  but  it  must 
be  remembered  that  b^^  far  the  greater  part  of  the  force  of 
the  first  few  strokes  of  the  heart  is  expended  in  distending 
the  arterial  system,  a  small  portion  only  of  the  blood  which 
is  ejected  into  the  arteries  passing  on  into  the  veins.  As 
the  arterial  pressure  rises,  more  and  more  blood  passes  at 
each  beat  through  the  capillaries,  tuid  the  rise  of  the  mer- 
cury at  each  beat  becomes  less  and  less,  until  at  last  the 
whole  contents  of  the  ventricle  pass  at  each  stroke  into  the 
veins,  and  the  mean  arterial  pressure  is  established.    To  this 


258 


THE    VASCULAR    MECHANISM, 


it  may  be  added  that  the  force  of  tlie  individual  beats  is 
somewhat  oreater  after  tlian  before  inhibition  ;  that  is  to  say, 
the  period  of  depression  is  followed  by  a  period  of  reaction, 


Fifi.  78. 


/f\f\f\ 


\     1     1 


111 


^     ^    1 


Blood -pressure  during  Cardiac  Inhibition.  From  a  Dog. 
(The  tracing  reads  from  right  to  left.) 
The  line  T  indicates  the  velocity  at  which  the  recording  surface  was  travelling, 
the  vertical  lines  marking  seconds.  The  line  S  indicates  the  application  of  the 
stimulus,  an  interrupted  current  being  thrown  into  the  vagus  during  the  break 
in  the  line.  It  will  be  noticed  that,  in  this  case,  the  stimulus  being  comparatively 
weak,  the  effect  is  rather  an  extreme  slowing  than  an  actual  cessation  of  the  beats. 
The  large  leaps  of  the  mercury,  b,  caused  partly  by  the  slowness  of  the  beats,  are 
very  conspicuous,  indeed  unusually  large. 


of  exaltation.     Besides,  the  inertia  of  tlie  mercury  tends  to 
magnify  the  effects  of  the  initial  beats. 

If  wiiile  the  force  of  the  individual  beats  remains  constant 


V  A  so -MOTOR    NERVES.  259 

the  freqiienc\v  is  increased  or  diminished — and  vice  versa^  if 
while  tlie  frequency  remains  the  same  the  force  is  increased 
or  diminished — the  pressure  is  proportionately  increased  or 
diminished.  This  clearly  must  be  the  case  ;  but  ol)viously 
it  is  quite  possible  that  the  beats  might,  while  more  frequent, 
so  lose  in  force,  or  while  less  frequent,  so  increase  in  force, 
that  no  difference  in  the  mean  pressure  should  result.  And 
this  indeed  is  not  unfrequently  the  case.  So  much  so,  that 
variations  in  the  heart-beat  must  always  be  looked  upon  as 
a  far  less  important  factor  of  blood  pressure  than  the  periph- 
eral resistance. 

Thus  wdien  the  heart's  beat  is  quickened  by  stimulation  of  the 
accelerator,  no  increase  in  the  blood-pressure  is  observed.  This, 
in  the  absence  of  an}^  peripheral  changes,  must  result  from  a  pro- 
portionate diminution  of  the  force  of  the  individual  strokes. 

An  increase  in  the  quantity  of  blood  ejected  at  each  beat 
must  necessarily  augment,  and  a  decrease  diminish,  the 
blood-pressure,  other  things  remaining  the  same.  But  the 
quantity  sent  out  at  each  beat,  on  the  supposition  that  the 
ventricle  always  empties  itself  at  each  systole,  will  de- 
pend on  the  quantity  entering  into  the  ventricle  during  each 
diastole,  and  that  will  be  determined  by  the  circumstances 
not  of  the  heart  itself,  but  of  some  other  part  or  jmrts  of  the 
bod3\ 

Sec.  5.    Changes  in  the  Calibre  of  the  Minute 
Arteries.     Yaso-Motor  Actions. 

The  middle  coat  of  all  arteries  contains  circularly  dis- 
posed plain  muscular  Hbres.  As  the  arteries  become  smaller 
the  muscular  element  becomes  more  and  more  prominent  as 
compared  with  the  elastic  element,  until,  in  the  minute  arte- 
ries,the  middle  coat  consists  entirely  of  a  series  of  plain  muscu- 
lar fibres  wrapped  round  the  elastic  internal  coat.  Nerve-fibres 
belonging  to  tlie  sympathetic  system  are  distributed  largely 
to  bloodvessels,  but  their  terminations  have  not  as  yet  been 
clearly  made  out.  By  galvanic,  or  still  better  by  mechanical, 
stimulation,  this  muscular  coat  may,  in  the  living  artery,  be 
made  to  contract.  During  this  contraction,  which  has  the 
slow  character  belonging  to  the  contractions  of  all  plain 
muscle,  the  calibre  of  tlie  vessel  is  diminished. 

If  the  web  of  a  froi^r's  foot  be  examined  under  the  micro- 


200  THE    VASCULAR     MECHANISM. 

scope  any  individual  small  nrtory  will  be  found  to  vary  in 
cnlilue,  being  sometimes  narrowed  nnd  sometimes  dilated. 
l)uiin<::  tile  narrowing;,  wliicii  is  obviously  due  to  a  contrac- 
tion of  the  muscular  coat  of  the  artery,  the  attached  cnj)!!- 
lary  area  with  the  corres])ondintr  veins  becomes  less  filled 
with  blood  and  paler.  During  the  stage  of  dilation,  which 
corresponds  to  the  relaxation  of  the  muscular  coat,  the  same 
l)arts  are  fuller  of  blood  and  redder.  It  is  obvious  that  ti»e 
pressure  at  the  entrance  into  any  given  artery  remaining 
the  same,  more  blood  will  enter  tiie  artery  when  relaxation 
takes  place,  and  consecpiently  the  resistance  offered  by  the 
artery  is  lessened,  and  less  when  contraction  occurs,  and 
the  resistance  is  consequently  incieased.  The  blood  always 
flows  in  the  direction  of  least  resistance. 

The  small  arteries  frequently  manifest  what  may  be  called 
spontaneous  variations  in  their  calibre,  and  these  variations  are 
very  apt  to  take  on  a  distinctly  rhythmical  character.  If  a  small 
artery  in  the  web  of  the  frog  be  carefully  watched,  it  will  be  seen 
from  time  to  time  to  vary  very  considerably  in  width,  without 
any  obvious  change  taking'place  in  the  heart's  beat,  or  any  events 
occurring  in  the  general  vaso-motor  system.  Similar  variations 
may  be  witnessed  in  the  ves.sels  of  the  mesentery  of  a  mannnal. 

The  most  striking  and  most  easily  observed  instance  of  rhyth- 
mical constriction  and  dilation  is  to  be  found  in  the  median  artery 
of  the  ear  of  the  rabbits  If  the  ear  be  held  up  before  the  light  it 
will  l)e  seen  that  at  one  moment  the  artery  appears  as  a  delicate, 
hardly  visible  pale  streak  ;  the  whole  ear  being  at  the  same  time 
pallid.  After  awdiile  the  artery  slowly  widens  out,  becomes  thick 
and  red.  the  whole  ear  blushing,  and  many  small  vessels  previ- 
ously invisible  cominp  into  view^  Again  the  artery  narrows  and 
the  blush  fades  awa}' ;  and  this  may  be  repeated  at  somewdiat 
irregular  intervals  several  times  a  minute.  The  extent  and  regu- 
larity of  the  rhythm  are  usually  markedly  increased  if  the  rabbit 
be  held  u])  b}-  the  ears  for  a  sliort  time  previous  to  the  observa- 
tion. If  the  sympathetic  be  severed,  these  rhythmic  movements 
cease  for  a  time;  but  in  the  course  of  a  few^lays  are  re-estab- 
lished, even  if  the  superior  cervical  ganglion  be  removed.  Thus 
though  normally  de[)endent  on  the  central  nervous  sjstem  (un- 
less Ave  suppose  that  the  mere  section  of  the  nerve  is  sufficient  to 
create  a  shock  lasting  days)  these  rhythmic  movements  can  make 
their  appearance  independently  of  that  system.  Some  local  me- 
chanism is,  therefore,  suggested  ;  and  3'et  no  ganglionic  cells  have 
been  discovered  which  would  serve  as  such  a  mechanism.  Similar 
rhythmic  variations  in  the  calibre  of  the  arteries  have  been  ob- 
served in  several  places,  ex.  cfr.^  in  the  saphena  artery  of  the  rab- 
bit, in  the  axillary  artery  of  the  tortoise,  and  in  the  small  arte- 
ries of  the  musfles  of  the  frog  ;  probably  they  are  widely  spread. 


VASO -MOTOR    NERVES.  261 


They  may  be  compared  with  the  rhythmic  movements  of  the 
veins  in  the  bat's  wing  and  of  the  caudal  vein  of  the  eel. 

The  extent  and  intensity  of  the  constriction  or  dilation 
are  found  to  vary  very  largely.  Irregular  variations  of 
slight  extent  occur  even  when  the  animal  is  apparently  sub- 
jected to  no  disturbing  causes  ;  while  as  the  result  of  experi- 
mental interference  the  arteries  may  become  either  con- 
stricted, in  some  cases  almost  to  obliteration,  or  dilated 
until  they  acquire  double  or  more  than  double  their  normal 
diameter.  This  constriction  or  dilation  may  he  brought 
about  not  only  by  treatment  applied  directly  to  the  web,  but 
also  by  changes  affecting  the  nerve  of  the  leg.  Thus  section 
of  the  sciatic  nerve  is  generally  followed  hy  a  very  marked 
dilation,  wiiile  stimulation  of  the  peripheral  stump  of  the 
divided  nerve  by  an  interrupted  current  of  moderate  in- 
tensity, is  followed  by  a  constriction,  often  so  great  as  almost 
to  obliterate  some  of  the  minute  arteries. 

The  facts  show  that  the  contractile  elements  of  the  minute 
arteries  of  the  web  of  the  frog's  foot  are  capable  by  contrac- 
tion or  relaxation  of  causing  constriction  or  dilation  of  the 
calibre  of  the  arteries;  and  that  this  condition  of  constric- 
tion or  dilation  may  be  brought  about  througii  the  agency 
of  nerves. 

These  effects  are  not  absolutely  constant.  Sometimes  the  dila- 
tion following  upon  section  is  preceded  by  a  passing  constriction, 
and  sometimes  the  section  is  followed  by  no  distinct  alteration 
in  the  calibre  of  the  vessels  of  the  web  beyond  perhaps  an  initial 
constriction.  Sometimes  the  constriction  consequent  on  stimu- 
lation is  followed  by  a  dilation,  which  may  or  may  not  be 
marked.  The  constriction  of  the  arteries  of  tlie  web  as  the  result 
of  nerve  stimulation,  is  more  certain  when  the  small  nerve  sup- 
plying the  foot  is  operated  on  than  when  the  main  trunk  of  the 
sciatic  is  stimulated  high  up.  We  shall,  later  on,  discuss  the 
nature  of  these  variations. 

Vaso-motor  Nerves. — In  warm  Vdooded  animals,  though 
we  cannot  readily,  as  in  the  frog,  watch  tlie  circulation  under 
the  microscope,  wo  have  abundant  evidence  of  the  influence 
of  the  nervous  system  on  the  calibre  of  the  arteries.  Thus 
in  the  mammal,  division  of  the  cervical  sympathetic  on  one 
side  of  the  neck  causes  a  dilation  of  the  minute  arteries  of 
the  head  on  the  same  side,  shown  by  an  increased  suj)ply  of 
blood  to  the  parts.  If  the  experiment  be  performed  on  a 
rabbit,  the  effect  on  the  circulation  in  the  ear  is  verv  strik- 


262  THE    VASCULAR    MECHANISM, 


iiiir.  The  whole  ear  of  the  side  operated  on  is  much  redder 
tiian  normal,  its  arteries  are  obviously  dilated,  its  veins  un- 
usually full,  innumerable  minute  vessels  before  invisible 
come  into  view,  and  the  temperature  may  be  more  than  a 
deiiree  hitrher  than  on  the  other  side. 

Division  of  the  sciatic  nerve  in  a  mammal  causes  a  similar 
dilation  of  the  small  arteries  of  the  foot  and  leo^.  Where 
the  condition  of  the  circulation  can  be  readily  examined,  as 
for  instance  in  the  hairless  balls  of  the  toes,  especially  when 
these  are  not  pigmented,  the  vessels  are  seen  to  be  dilated 
and  injected,  and  a  thermometer  placed  between  the  toes 
shows  a  rise  of  temperature  amounting,  it  may  be,  to  sev- 
eral degrees.  Division  of  the  brachial  plexus  produces  a 
similar  dilation  of  the  bloodvessels  of  the  front  limb. 
Division  of  the  splanchnic  nerve  produces  a  dilation  of  the 
bloodvessels  of  the  intestines  and  other  abdominal  viscera. 
Division  in  the  mammal  of  the  lingual  nerve  on  one  side  of 
the  head  causes  a  dilation  of  the  vessels  in  the  correspond- 
ino;  half  of  the  tono;ue.  A  similar  effect  follows  division  of 
the  hypoglossal ;  and  if  both  lingual  and  hypoglossal  be 
severed  the  effect  is  still  more  marked. 

Division  of  a  nerve  supplying  a  muscle  causes  a  large  and 
sudden  increase  in  the  venous  flow  from  the  muscle,  indi- 
cating that  the  muscular  arteries  have  become  dilated  ;  and 
in  the  frog  this  dilation,  consequent  on  section  of  the  nerve, 
may  be  actually  observed  by  placing  a  thin  muscle,  such  as 
the  mylo-hyoid,  under  the  microscope  and  watching  the 
calibre  of  the  small  arteries  and  the  circulation  of  the  blood 
through  them  while  the  nerve  is  being  cut. 

We  find,  in  fact,  that  in  almost  all  parts  of  the  body  cer- 
tain "vascular  areas  "  stand  in  such  a  relation  to  certain 
nerves  that  the  division  of  one  of  these  nerves  causes  a 
dilation  of  the  minute  arteries  in,  and  consequently  an  in- 
creased supply  of  blood  to,  a  corresponding  vascular  area. 
We  may  speak  of  these  nerves  as  "  vasomotor  "  nerves,  or 
more  correctly,  since  in  the  vast  majority  of  cases  the  nerves 
in  question  have  other  functions  than  that  of  governing 
arteries,  as  containing  vasomotor  fibres,  much  in  the  same 
way  as  an  ordinary  spinal  nerve  is  spoken  of  as  containing 
sensor}^  and  motor  fibres ;  and  from  what  has  been  said 
above  it  is  evident  that  these  vaso-motor  fibres  are  found 
sometimes  in  sympathetic,  sometimes  in  cerebro-spiual 
nerves. 

Since  division  of  a  vaso-motor  nerve,  or  nerve  containing 


VASO-MOTOR    NERVES.  263 

vaso-raotor  fibres,  leads  to  the  dilation  of  the  arteries  of  its 
appropriate  vascular  area,  it  is  obvious  that  previous  to  that 
division  these  arteries  were  in  a  state  of  permanent  con- 
striction, due  to  a  permanent  contraction  of  their  muscular 
coats.  This  permanent  constriction,  which  may  vary  con- 
siderably in  degree  (the  dilating  effects  of  section  of  the 
vaso-motor  nerve  correspondingly  varying  in  amount),  is 
spoken  of  as  ''tone,"  "arterial  tone."  Arteries  in  sucli  a 
state  of  permanent  constriction  as  under  ordinar\^  circum- 
stances is  normal  to  arteries  whose  vaso-motor  fibres  have 
not  been  divided  and  which  are  otherwise  in  a  normal 
condition,  are  said  to  ''  possess  tone."  When,  as  after 
division  of  the  vaso-motor  fibres,  the  constriction  gives 
place  to  dilation  the  arteries  are  said  to  have  "lost  tone," 
and  when,  under  various  circumstances  which  we  shall  study 
hereafter,  tlie  constriction  becomes  greater  than  normal, 
their  tone  is  said  to  be  iucreased. 

A  very  little  consideration  will  show  that  this  arterial  tone 
is  a  most  important  factor  in  the  circulation.  In  the  first 
place  the  whole  flow  of  blood  in  the  body  is  adapted  to  and 
governed  by  what  we  ma}^  call  the  general  tone  of  the  arteries 
of  the  body  at  laru^e.  In  a  normal  condition  of  the  body,  if 
not  all,  at  least  the  vast  majority  of  the  minute  arteries  of 
the  body  are  in  a  state  of  tonic,  i.  «.,  of  moderate,  constric- 
tion, and  it  is  the  narrowing  due  to  this  constriction  which 
forms  a  large  item  of  that  peripheral  resistance  which  we 
have  seen  (p.  191)  to  be  one  of  the  two  great  factors  of  blood- 
pressure.  The  normal  general  blood  pressure,  and  therefore 
the  normal  flow  of  blood,  is  in  fact  dependent  on  the  "  geueral 
tone  "  of  the  minute  arteries.  In  the  second  place,  changes 
in  local  tone,  i.  e.,  the  toneof  an}' particular  vascular  area,  have 
very  decided  effects  on  the  circulation.  These  effects  are  both 
local  and  general,  as  the  following  considerations  will  show. 

Let  us  suppose  that  the  artery  A  is  iu  a  condition  of  nor- 
mal tone,  is  midway  between  extreme  constriction  and 
dilation.  The  flow  through  A  is  determined  by  the  resist- 
ance in  A  and  in  the  vascular  tract  which  it  supplies,  in 
relation  to  the  mean  arterial  pressure,  which  again  is  depend- 
ent on  the  way  in  which  the  heart  is  beating  and  on  tiie 
peripheral  resistance  of  all  tlie  small  arteries  and  capillaries, 
A  included.  If,  while  the  heart  and  the  rest  of  the  arteries 
remain  unchanged,  A  be  constricted,  the  peripheral  resist- 
ance in  A  will  increase,  and  this  increase  of  resistance  will 
lead  to  an  increase  of  the  general  arterial  pressure.     This 


L>(j4  the  vascular  mechanism. 

incrense  of  pressure  will  tend  to  cause  the  Mood  in  the  body 
at  lariic  to  flow  more  rapidly  from  the  arteries  into  the  veins. 
The  constriction  of  A  however  will  i)revent  any  increase  of 
the  How  throutrh  it,  in  fact  will  make  the  How  through  it  less 
than  before.  Hence  the  whole  increase  of  discharge  from 
the  arterial  into  the  venous  system  must  take  place  through 
channels  other  than  A.  Thus  as  the  result  of  the  constric- 
tion of  any  artery  there  occur,  (I)  diminished  flow  through 
the  artery  itself,  (2)  increased  general  arterial  pressure, 
leading  to  (3)  increased  flow  through  the  other  arteries.  If, 
on  the  other  hand,  A  he  dilated,  while  the  heart  and  other 
arteiies  remain  unciianged,  the  i)eri[)heral  resistance  in  A  is 
diminished.  This  leads  to  a  lowering  of  the  general  arterial 
l)ressure,  which  in  turn  causes  the  blood  to  flow  less  rapidl}' 
from  the  arteries  into  the  veins  The  dilation  of  A  however 
permits,  even  with  the  lowered  pressure,  more  blood  to  pass 
through  it  than  before.  Hence  the  diminished  flow  tells  all 
the  more  on  the  rest  of  the  arteries.  Thus,  as  the  result  of 
the  dilation  of  any  artery,  there  occur  (1)  increased  flow  of 
blood  through  the  artery  itself.  (2)  diminished  general  pres- 
sure, and  (3)  diminished  flow  through  the  other  arteiies. 
Where  the  artery  thus  constricted  or  dilated  is  small,  the 
local  ertect,  the  diminution  or  increase  of  flowthrough  itself, 
is  much  more  marked  than  the  general  effects,  the  change 
in  blood-pressure  and  the  flow  through  other  arteries.  When, 
however,  the  area  the  arteries  of  which  are  affected  is  large, 
the  general  effects  are  very  striking.  Thus  if  while  a  trac- 
ing of  the  blood-pressure  is  being  taken  by  means  of  a 
manometer  connected  with  the  carcjtid  artery,  the  splanchnic 
nerves  be  divided,  a  conspicuous  but  steady  fall  of  pressure 
is  observed,  very  similar  to  that  which  is  seen  in  Fig.  79. 
The  section  of  the  splanchnic  nerves  causes  the  mesenteric 
and  other  abdominal  arteries  to  dilate,  and  these  being  very 
numerous,  a  large  amount  of  peripheral  resistance  is  taken 
away,  and  tlie  blood-i)ressure  falls  accordingly  ;  a  large  in- 
crease of  flow  into  the  portal  veins  takes  })lace,  and  the 
sup})ly  of  blood  to  the  face,  arms,  and  legs  is  proportionally 
diminished.  It  will  be  observed  that  the  dilation  of  the 
arteries  is  not  instantaneous  but  somewhat  gradual,  the 
pressure  sinking  not  abruptly  but  with  a  gentle  curve. 

Arterial  tone  then,  both  general  and  local,  is  a  powerful 
instrument  for  determining  the  flow  of  blood  to  the  various 
organs,  and  tissues  of  the  body,  and  thus  becomes  a  means 
of    indirectly    influencing   their   functional    activity.      We 


VASO -MOTOR    NERVES.  265 


should  accordiiigiv  expect  to  find  that  the  vaso-motor  nerves 
were  connected  with,  and  arterial  tone  reojulated  by,  the 
central  nervous  system,  in  order  that  the  calibre  of  the  arte- 
ries of,  and  the  supply  of  blood  sent  to,  this  or  that  vascular 
area  might  be  varied  according  to  the  varying  needs  of  the 
economy.     And  experiment  proves  this  to  he  the  case. 

We  stated  that  section  of  the  cervical  sympathetic  in  the 
neck  causes  dilation  or  loss  of  tone  in  the  bloodvessels  of 
the  head  and  face.  This  is  true  at  whatever  point  of  the 
course  of  the  nerve  from  the  upper  to  the  lower  cervical  gan- 
glion, both  included,  the  section  be  made.  Xo  such  dilation 
of  the  vessels  of  the  head  and  face  takes  place  when  tlie 
thoracic  sympathetic  chain  is  divided  anywhere  below  the 
upper  thoracic  ganglion;  but  dilation  does  occur  after  divi- 
sion of  certain  of  the  rami  cominunicante!<  connecting  the 
spinal  cord  with  the  cervical  sympathetic  through  the  lower 
cervical  or  upper  thoracic  ganglion.  Hence  it  is  clear  that 
the  normal  tone  of  the  arteries  of  the  head  and  face  is  main- 
tained by  influences  (whose  exact  nature  we  shall  study 
presently)  proceeding  from  the  central  nervous  system,  pass- 
ing through  certain  rami  communicantes  (the  exact  path 
being  somewhat  uncertain  or  possibly  not  constant)  into  the 
cervical  sympathetic,  and  ascending  to  the  head  and  face  by 
that  nerve.  In  other  words,  the  vaso-motor  fibres  of  the 
vessels  of  the  head  and  face  may  be  traced  down  the  sym- 
pathetic to  tiie  lower  cervical  ganglion,  and  thence  by  rami 
communicantes  into  the  spinal  cord. 

In  a  similar  manner  the  vaso-motor  fibres  of  the  splanch- 
nic nerves  governing  the  mesenteric  and  otiier  abdominal 
arteries  can  also  be  traced  into  the  spinal  cord,  as  may  also 
those  of  the  sciatic  governing  the  bloodvessels  of  the  hind 
limb  and  of  the  brachial  nerves  governing  those  of  the  fore 
limb.  In  fact  all  the  vasor-motor  fibres  (with  certain  special 
exceptions  wliich  will  be  discussed  presently)  may  thus  be 
traced  into  the  spinal  cord  :  they  are  all  connected  with  the 
central  nervous  system.  There  is  at  present  some  uncer- 
tainty in  certain  cases  as  to  the  exact  manner  in  which  the 
fibres  pass  fronj  the  spinal  cord  to  this  or  that  nerve,  as,  for 
instance,  along  which  nerve-roots  the  vaso-motor  fibres 
eventually  joining  the  sciatic  trunk  run,  whether  they  all 
pass  on  their  way  into  the  abdominal  sympathetic  or  not,  and 
the  like;  but  these  are  questions  which  need  not  delay  us 
now  ;  in  whichever  wa}^  they  may  be  settled,  they  do  not 
affect  the  important  fact  that  in  some  way  or  other  all  vaso- 


2tJG  TIIK     VASCULAR     MECHANISM. 

motor  lihivs  spriiiji^  from  tlu^  ceiitrnl  nervous  system,  nn<l 
that  (willi  (.'crtiiiM  special  exceptions)  what  we  have  called 
the  normal  tone  of  the  various  vascular  areas  is  maintained 
bv  influences  proceedin<>^  from  the  central  nervous  system. 

Far  njore  important,  however,  than  the  maintenance  of  a 
normal  tone  whicii,  indeed,  miijht  be  at  once  and  forever 
arranged  for  ])y  the  proper  natural  calibre  of  the  elastic 
bloodvessels,  is  the  power  which  the  central  nervous  system 
l)ossesses  of  var3ing  the  tone  of  this  or  that  artery  or 
jiroui)  of  arteries,  of  increasin<^  it  or  of  diminishing  it.  of 
jtroducing  constriction  or  dilation  in  those  arteries,  and  thus, 
as  we  have  seen  on  j).  204,  of  effecting  changes  in  general 
or  local  blood-pressure  or  in  both,  and  conse(piently  of  de- 
termining a  flow  of  blood  in  this  or  that  direction,  accord- 
ing to  the  needs  of  the  econoni3\  And  the  exercise  of  this 
carefully  arranged  manipidation  of  the  muscular  walls  of 
the  arteries  may  be  called  forth  in  either  direction,  in  the 
way  of  constriction  or  in  the  way  of  dilation  for  of  both  at 
the  same  time,  one  in  one  area,  and  the  other  in  others),  by 
means  of  nervous  impulses  eitliei"  originating  in  the  cential 
nervous  system  itself  or  started  by  afferent  impulses  pass- 
ing up  to  the  central  nervous  system  from  some  sentient 
surface. 

]jlushing  is  a  familiar  instance  of  vascular  dilation  brought 
about  by  the  action  of  the  central  nervous  system.  Nervous 
impulses  started  in  some  parts  of  the  brain  by  an  emotion 
l)roduce  certain  changes  in  the  central  nervous  system  (the 
exact  nature  and  localit}'  of  these  clianges  we  shall  discuss 
presently)  which  have  in  turn  an  effect  on  the  vaso-motor 
fibres  of  the  cervical  symi)athetic  almost  exactly  the  same 
as  that  produced  by  section  of  the  nerve.  In  consequence, 
the  muscular  walls  of  the  arteries  of  the  head  and  face  relax, 
the  arteries  dilate,  and  the  whole  region  becomes  suf!used. 
Sometimes  an  emotion  gives  rise,  not  to  blushing,  but  to 
the  opposite,  pallor.  In  a  great  number  of  cases  this  has 
quite  a  different  cause,  being  due  to  a  sudden  diminution, 
or  even  temporary  arrest  of  the  heart's  beats;  but  in  some 
cases  it  may  occur  without  any  change  in  the  beat  of  the 
heart,  and  is  then  due  to  a  condition  the  ver}'  converse  of 
that  of  blushing,  that  is,  to  an  increased  arterial  constriction  ; 
and  this  increased  constriction,  like  the  dilation  of  blushing, 
is  effected  through  the  agenc}'  of  the  central  nervous  system 
and  the  cervical  sympathetic.  These  are  familiar  examples, 
but  we  have  in  abundance  exact  experimental  evidence  of 


VASO-MOTOR    NERVES. 


267 


the  effect  of  afferent  impulses  in  inducing  tlirongh  the  cen- 
tral nervous  system  vaso-motor  changes  and  thus  bringing 
about  sometimes  constriction,  sometimes  dilation,  sometimes 
the  two  together.  The  action  of  the  so-called  depressor 
nerve  is  a  sti'iking  instance  of  reflex  dilation  as  it  may  be 
called. 

If,  while  the  pressure  in  an  artery  such  as  the  carotid  is 
being  registered,  the  depressor  nerve,  which  is  a  branch  of 
the  vagus  running  alongside  tlie  carotid  artery  and  S3'm- 
pathetic  nerve  (Fig.  75,  n.  dep.)^  be  divided,  and  its  central 
end  (i.  e.^  the  one  connected  with  the  brain)  be  stimnlated 
with  the  interrupted  current,  a  gradual  but  marked  fall  of 


Fig, 


W^N 


Tracing  showing  the  Effect  on  Blood-pressure  of  stimulating  the  central  end  of  the 
Depressor  Nerve  iu  the  Rabbit.  To  be  read  from  right  to  left. 
Vindicates  the  rate  at  which  the  recording  surface  was  travelling;  the  intervals 
marked  correspond  to  seconds.  Cthe  moment  at  which  the  current  was  thrown  into 
the  nerve.  O  the  moment  at  which  it  was  shut  off.  The  effect  is  some  time  in  de- 
veloping, and  lasts  after  the  current  has  been  taken  off.  The  larger  undulations  are 
the  respiratory  curves;  the  pulse-oscillations  are  very  s-mall. 

pressure  in  the  carotid  is  observed,  lasting,  where  the  period 
of  stimulation  is  short,  some  time  after  the  removal  of  the 
stimulus  (Fig.  -79).  Since  the  beat  of  the  heart  is  not 
markedly  changed,  the  fall  of  pressure  must  be  due  to  the 
diminution  of  peripheral  resistance  occasioned  by  the  dila- 
tion of  some  arteries.  And  there  is  evidence  that  the 
arteries  thus  dilated  are  chiefly  if  not  exclusively  those 
arteries  of  the  abdominal  viscera  which  are  govei'ned   by 


268  TllK    VASCULAR    MECHANISM. 


tlic  splniu'lmic  nerve.  For  if  l)otli  llie  splaiiclmic  nerves 
jire  divided  previous  to  tiu;  ex|)eiinient,  the  fjiil  of  pressure 
Mlieu  the  depressor  is  stimulated  is  very  small,  in  faet  al- 
most insio;ni(icant.  The  inference  from  this  is  clear ;  the 
allerent  impulses  passino-  along  the  depressor  have  so  affected 
some  part  of  the  central  nervous  system  that  the  influences 
which,  in  a  normal  condition  of  things,  passing  along  the 
splanchnic  nerves  keep  the  minute  arteries  of  the  abdominal 
viscera  in  a  state  of  moderate  tonic  constriction,  fail  alto- 
gether, and  those  aiteries  in  consequence  dilate  just  as  they 
do  when  the  splanchnic  nerves  are  divided,  the  effect  being 
j)ossibly  increased  by  the  similar  dilation  of  other  smaller 
vascular  areas. 

The  condition  of  the  splanchnic  or  other  vascular  areas 
mny  moreover  be  changed,  and  thus  tiie  general  blood-pres- 
sure modified,  by  afferent  impulses  passing  along  other 
nerves  than  the  depressor,  the  modification  taking  on  ac- 
cording to  circumstances  the  form  either  of  decrease  or  of 
increase. 

Thus,  if  in  an  animal  placed  under  the  influence  of  urari 
the  central  stump  of  the  divided  sciatic  nerve  be  stimulated, 
an  increase  of  blood-pressure,  almost  exactly  the  reverse  of 
the  decrease  brought  al)Out  by  stimulating  the  dei)ressor,  is 
observed.  The  curve  of  the  blood-pressure,  after  a  latent 
period  during  which  no  changes  are  visible,  rises  steadily 
without  any  corresponding  change  in  the  heart's  beat, 
reaches  a  maximum,  and  after  awhile  slowly  falls  again,  the 
fall  sometimes  beginning  to  ai)pear  before  the  stimulus  has 
been  removed.  There  can  be  no  doubt  that  the  rise  of  pres- 
sure is  due  to  the  constriction  of  certain  arteries  ;  the 
arteries  in  question  being  those  of  the  splanchnic  area  cer- 
tainly, and  possibly  of  other  vascular  areas  as  well.  The 
effect  is  not  confined  to  the  sciatic  ;  stimulation  of  any  nerve 
containing  afferent  fibres  will  produce  the  same  rise  of  pres- 
sure, and  so  constant  is  the  result  that  the  experiment  may 
be  made  use  of  as  a  method  for  determining  the  existence 
of  afferent  fil)res  in  any  given  nerve  and  even  the  paths  of 
centripetal  impulses  through  the  spinal  cord. 

If,  on  the  other  hand,  the  animal  be  under  not  urari  but 
chloral,  instead  of  a  rise  of  blood-pressure  a  fall,  quite  sim- 
ilar to  that  caused  by  stimulating  the  depressor,  is  observed 
when  an  afferent  nerve  is  stimulated.  The  condition  of  the 
central  nervous  system  seems  to  determine  whether  the  re- 
flex effect  on   the  vaso-motor  fibres   is   in  the  direction  of 


VASO-MOTOR    NERVES.  269 

constriction  leading  to  a  rise,  or  of  dilation  leading  to  a  fall 
of  blood-pressure. 

The  causes  of  the  ditference  between  chloral  and  urarl  are  not 
yet  clearl}'  worked  out.  Variations  in  respiration  will  not  ex- 
plain it.  Xor  can  the  solution  be  found  b}'  supposing  that  in 
urari  poisoning  cerebral  functions  are  active  while  in  chloral 
poisoning  they  are  in  abeyance.  If  the  brain  be  removed  with- 
out much  bleeding,  subsequent  stimulation  of  a  sensory  nerve 
under  urari  still  gives  a  rise  of  pressure.  If  there  be  much 
bleeding  hoAvever  a  fall  is  witnessed.  This  suggests  the  idea  that 
after  bleeding  and  under  chloral,  the  part  of  the  central  nervous 
sj'stem  concerned  in  the  action,  and  serving  a  nervous  centre,  is 
enfeebled  or  exhausted,  and  that  stimulation  of  the  enfeebled  or 
exhausted  centre  always  causes  depression.  This  view  is  sup- 
ported by  the  fact,  that  in  ordinary  stimulation  under  urari  the 
decline  of  the  rise  appears  sooner  the  more  often  the  stimulation 
is  repeated,  and  that  after  many  repetitions  the  decline  passes 
into  a  distinct  fall,  and  at  last  only  a  fall  is  observed. ' 

In  the  instances  just  quoted,  the  effect  of  the  stimulation 
of  the  atierent  nerve  may  be  spoken  of  as  a  general  one  ;  it 
is  the  general  blood-pressure  which  is  diminished  or  in- 
creased ;  though  in  the  case  of  the  depressor  at  all  events 
it  is  chiefly  in  the  splanchnic  area  that  the  constriction  or 
dilation  takes  place. 

There  are  however  some  remarkable  cases  where  a  local 
effect  can  be  readil}'  distinguished  from  the  general  effect, 
because  the  two  are  in  opposite  directions.  Thus  if  in  a 
rabbit,  under  urari,  the  central  stump  of  the  auricularis 
magnus  nerve  or  of  the  auricularis  posterior  be  stimulated, 
the  rise  of  general  pressure  which  is  caused  b}' the  stimula- 
tion of  this  as  of  an}'  other  afferent  nerve,  is  accompanied 
by  a  dilation  of  the  artery  of  the  ear.  That  is  to  say,  the 
afferent  impulses  passing  along  the  auricular  nerve  while 
affecting  the  central  nervous  system  in  an  ordinary  way,  so 
as  to  cause  constriction  of  many  of  the  arteries  of  the  body 
(but  chiefly  probably  the  splanchnic  vessels),  at  the  same 
lime  so  affect  some  particular  part  more  especially  connected 
with  the  vaso-motor  fibres  governing  the  arter}'  of  the  ear, 
as  to  lead  to  the  dilation  of  that  vessel. 

According  to  Loven,-  to  whom  we  are  indebted  for  this  obser- 
vation, the  local  dilation  in  the  ear  is  preceded  by  an  initial  con- 

^   Cf.  Latschenberger  and  Deahiia,  Pfl tiger's  Archiv,  xii  (1876),  p.  lo7. 
-  Liidwiar's  Arbeiten,  1866. 

23 


270  THE    VASCULAR    MECHANISM. 


striction.     A  similar  initial  constriction  has  been  witnessed  in 
other  cases  of  retiex  dilation. 

According  to  lleideuhain,'  this  experiment  illustrates  not  so 
much  the  contrast  between  local  and  i^^eneral  eflects  as  the  ditler- 
ence  of  behavior  between  vessels  supplying  the  skin  and  those 
distributed  to  other  tissues  ;  for  he  atiirms  that  reflex  vaso-motor 
action  in  respect  to  cutan(M)us  arteries  is  at  all  events  wlien 
caused  by  artilicial  stimulation  always  in  the  direction  of  dila- 
tion. 

So  also  in  the  same  animal  stimulation  of  branches  of  tiie 
tibial  nerve  causes  dilation  of  the  saphena  artery,  together 
with  constriction  of  other  arteries,  as  shown  by  the  con- 
comitant rise  of  pressure.  And  there  are  probably  innu- 
merable instances  of  the  same  kind  of  action  going  on  in 
the  body  during  life,  for  it  is  evident  that  the  increased  flow 
of  blood  to  the  organ  which  is  the  object  of  the  local  dila- 
tion, must  l)e  assisted  if  a  general  constriction  is  at  the  same 
time  taking  place  in  other  regions. 

The  general  effect  may  not  always  be  obvious,  may  per- 
ha[)S  be  often  absent,  so  that  the  h)cal  dilation  or  constric- 
tion, as  the  case  ma}'  be,  is  the  only  obvious  result  of  the 
vaso-motor  action.  When  the  ear  of  the  rabbit  is  gently 
tickled,  the  effect  that  is  seen  is  a  blushing  of  the  ear,  and 
though  this  maybe  in  part  dne,  as  we  shall  see.tothe  action 
of  a  local  mechanism,  the  case  we  have  just  cited  shows  that 
the  central  nervous  system  must  be  largely  engaged.  When 
the  right  hand  is  dipped  in  cold  water,  the  temperature  of 
the  left  hand  falls,  on  account  of  a  reflex  constriction  of  the 
vessels  of  the  skin  of  that  hand  caused  by  the  stimulus 
applied  to  the  other.  Many  more  instances  might  be  quoted, 
and  we  shall  again  and  again  come  upon  examples.  The 
numerous  jjathological  phenomena  classed  under  sympa- 
thetic action,  such  as  the  affection  of  one  eye  by  disease  in 
the  other,  are  probably  in  part  at  least  the  results  of  reflex 
vaso-motor  action. 

We  have  said  enough  to  sliow  that  the  caliln-e  of  the  small 
artei'ies,  which  by  determining  the  peripheral  resistance 
forms  one  important  factor  regidating  the  flow  of  blood,  is 
sul)ject  to  influences  proceeding  from  all  parts  of  the  body, 
the  influences  reaching  the  arteries  in  a  reflex  manner  by 
means  of  the  central  nervous  system,  the  afferent  impulses 
being  for  the  most  part  carried  by  ordinary  sensory  nerves, 

'  Cf.  O.stroumofi;  Pfl tiger's  Archiv,  xii  (1876),  p.  219. 


VASO-MOTOR    NERVES.  271 

^Yllile  the  efferent  impulses  pass  along  special  vaso-motor 
nerves,  which,  though  the  centre  of  the  reflex  action  lies  in 
the  cerebro-spinal  axis,  have  a  great  tendency  to  run  in 
sympathetic  tracts. 

The  afferent  impulses  of  course  need  not  start  from  the 
peripheral  nerve-endings.  They  may,  for  instance,  arise  in 
the  brain.  Thus,  as  we  have  seen,  an  emotion  originating 
in  tlie  cerebrum  mav,  b}^  vaso-motor  action,  give  rise  either 
to  blushing  or  to  pallor.  Xay  more,  changes  may  be  in- 
duced in  the  central  nervous  system  itself  without  the  need 
of  any  impulses  reaching  it  from  without.  When  we  come 
to  discuss  tiie  relations  of  respiration  to  the  circulation,  we 
shall  see  reason  to  think  that  the  vaso-motor  action  of  the 
central  nervous  system  may  be  directh*  affected  by  the  con- 
dition of  the  blood  passing  through  it,  so  that  if  the  quan- 
tity of  oxygen  in  the  blood  be  reduced,  a  general  arterial 
constriction  takes  place,  and  a  rise  of  blood  pressure  fol- 
lows ;  while  with  a  return  of  oxygen  to  the  blood,  the  ves- 
sels dilate  and  pressure  falls.  We  shall  return  to  these 
phenomena  later  on. 

It  is  more  than  probable  that  man}-  substances  introduced  into 
the  blood,  or  arising  in  the  blood  from  natural  or  morbid  changes, 
may  affect  blood-pressure  b}'  acting  directl}'  on  the  nervous  cen- 
tres. 

In  many  ways  then,  and  to  a  varying  degree  and  extent, 
the  central  nervous  system  can  bring  about  arterial  constric- 
tion or  dilation,  general  or  local.  We  have  now  to  study 
the  question.  What  is  more  exactly  the  nature  of  the  ner- 
vous influences  which  lead  to  constriction  and  dilation  re- 
spectively'?  How  do  those  which  cause  constriction  diflfer 
from  those  which  cause  dihation  ? 

In  the  fundamental  experiment  of  tlie  cervical  sympa- 
thetic, when  arterial  dilation  has  followed  upon  section  of 
the  nerve,  if  the  peripheral  stump  of  the  divided  nerve  be 
stimulated,  the  dilation  gives  place  to  constriction,  the 
blush  is  replaced  b}^  pallor.  If  the  stimulus  be  very 
strong  the  constriction  is  greater  than  normal,  but  by  care- 
fully adjusting  the  strength  of  the  stimulus,  tlie  circulation 
maybe  brought  to  quite  a  normal  condition,  the  '"loss  of 
tone  "  consequent  on  the  severance  of  the  vaso-motor  fibres 
from  the  central  nervous  system  may  be  replaced,  and  not 
more  than  replaced,  by  an  artificial  tone  generated  l>y  the 
action  of  the  stimulus  on  the  sympathetic  nerve.     The  most 


272  THE    VASCULAR    MECHANISM. 

natural  iiUerprt'tation,  tluTefore,  of  the  vasomotor  action 
in  tills  case  is  to  snppose  that  tlie  normal  tone  of  the  arteries 
of  the  fiice  is  maintained  l»y  ''  tonic"  constrictive  impnlscs 
of  a  certain  intensity  which  pass  from  the  central  nervons 
system  along  the  sympathetic,  and  that  the  dilation  of  the 
same  arteries  is  due  sim|)ly  to  a  diminution  or  absence  of 
these  constrictive  impulses,  an  increased  constriction  or 
pallor  being  similarly  due  to  an  increase  l)eyond  what  is 
normal  of  these  same  impulses.  Jn  other  words,  the  ner- 
vous influences  leading  to  arterial  dilation  and  constric- 
tion dilfer  in  degree  only,  not  in  kind,  and  may  be  consid- 
ered as  being  merely  phases  (of  decrease  or  of  increase  as 
the  case  ma}'  be)  of  tiie  same  action.  And  if  we  turn  to 
the  splanchnic  nerve  we  find  a  similar  interpretation  equally 
valid.  Stimulation  of  the  splanchnic  nerve  causes  constric- 
tion of  the  arteries  governed  by  that  nerve,  apparently  be- 
cause the  stimulation  supplies  artificially  the  constrictive 
impulses  which,  so  loiTg  as  the  nerve  is  intact,  pass  down 
it  from  the  central  nervous  system,  giving  the  requisite  tone 
to  its  vascular  area,  and  the  loss  of  which  by  division  of  the 
nerve  gives  rise  to  dilation.  So  that  were  we  to  stop  our 
inquiries  at  this  point,  our  explanation  of  vaso-motor  action 
would  be  very  simple.  AVe  might  speak  of  constrictive  im- 
pulses as  ptissing  from  the  central  nervous  system  to  the 
various  vascular  areas,  to  such  an  extent  as  to  constitute 
normal  tone,  but  as  being  susceptible  either  of  iidiibition, 
complete  or  }){jrtial,  thus  leading  to  greater  or  less  arterial 
dilation,  or  of  augmentation,  thus  leading  to  excessive  con- 
striction. 

But  this  simple  view  appears  insufficient  when  we  push 
our  studies  furtlier. 

In  the  fii'st  place  such  a  conception  does  not  cover  all 
the  facts  connected  even  with  the  two  nerves  just  mentioned. 
For  the  dilation  or  loss  of  tone  which  follows  upon  sec- 
tion of  the  cervical  sympathetic  (and  the  same  is  true  of  the 
splanchnic)  is  not  permanent;  after  awhile,  it  may  be  not 
until  after  several  days,  it  may  be  sooner,  the  dilation  dis- 
appears and  the  arteries  regain  their  usual  calil  re.  This 
recovery  is  not  due  to  any  regeneration  of  vaso-motor  fibres 
in  the  sympathetic,  for  it  may  be  observed  when  the  wMiole 
length  of  the  nerve  including  the  superior  cervical  ganglion 
is  rt-mov  ed.  When  recovery  of  tone  has  thus  tnken  place,  di- 
lation (.rincieased  constriction  may  be  occasioned  by  l(,cal 
treatment;  the  ear  may  be  made  to  blush  or  to  pale  by  the 


VASO-MOTOR    NERVES.  273 

application  of  heat  or  cold,  by  gentle  stroking  or  rough 
handling  and  tlie  like  ;  but  neither  the  one  nor  the  other 
condition  can  be  brought  about  b^'  the  intervention  of  the 
central  nervous  system.  From  this  it  is  clear  that  what  we 
have  spoken  of  as  the  tone  of  the  vessels  of  the  face,  though 
influenced  by  and  in  a  measure  dependent  on  the  central 
nervous  system,  is  not  simply  the  result  of  an  efltbrt  of  that 
system.  The  muscular  walls  of  the  arteries  are  not  mere  pas- 
sive instruments  worked  by  the  cerebro-spinal  axis  through 
the  cervical  sympatlietic  ;  obviously  the}'  have  an  intrinsic 
tone  of  their  own.  dependent  possibly  on  some  local  nervous 
mechanism,  though  in  the  ear  at  least  no  such  meciianism 
has  3'et  been  found  ;  and  it  seems  natural  to  suppose  that 
when  the  central  nervous  system  causes  dilation  or  constric- 
tion of  the  vessels  of  tlie  face,  it  makes  use,  in  so  doing,  of 
this  intrinsic  local  tone.  But  if  so,  then  the  simple  view 
entertained  above,  that  arterial  dilation  and  constriction 
are  simply  determined  by  the  decrease  or  increase  of  tonic 
constrictive  impulses  parsing  directly  from  the  central  ner- 
vous system  is  not  a  complete  representation  of  the  facts. 

In  the  second  place,  if  we  turn  fr(mi  the  sympathetic  or 
splanchnic  to  other  nerves  containing  vaso-raotor  fibres,  we 
meet  with  still  greater  dithculties.  To  take,  for  instance, 
a  nerve  snppl3ing  a  muscle,  such  as  that  going,  in  the  frog, 
to  the  mylo-hyoid  mus(tle.  Here,  as  in  the  cervical  sympa- 
thetic, section  of  the  nerve  produces  dilation,  but  that  dila- 
tion is  even  more  transient  tlian  in  the  case  of  tlie  sympa- 
thetic ;  the  vessels  speedily  return  to  their  former  calibre. 
And  then  it  is  found  that  stimulation  of  whatever  strength 
of  the  peripheral  jiortion  of  the  divided  nerve  brings  about 
not  constriction,  but  dilation.  A  similar  dilation  is  seen 
when  the  nerve  of  a  mammalian  muscle  is  stimulated,  and 
probably  occurs  in  the  case  of  all  muscular  nerves.^  So, 
also,  with  the  lingual,  section  of  which,  as  we  have  already 
stated,  produces  dilation  of  the  vessels  of  the  tongue  ; 
stimulation  of  the  peripheral  portion  of  the  divided  nerve 
gives  rise  to  dilation,  no  constriction  ever  making  its  ap- 
pearance. There  are,  therefore,  in  the  bod}'  nerves,  stimu- 
lation of  which,  as  well  as  mere  section,  always  brings  about 
arterial  dilation. 

Tiiere  are  other  nerves  in  the  body  of  a  mixed  character, 
intermediate  between  the  cervical  sympathetic  on   the  one 

^  Gai^kell,  .Journal  Physiol.,  i  (1878),  p.  202. 


27-i  THE    VASCULAR    MECHANISM. 

liaiul  and  tlu'  linirual  or  iiiiisciilnr  nerves  on  the  otiier, 
stimulation  produeinir  now  constriction,  now  dilation.  Such 
a  nerve  is  the  sciatic  of  a  mammal.  We  have  already  seen 
that  section  of  this  nerve  produces  dilation  of  the  vessels 
of  the  foot;  but  the  dilation  so  caused  after  a  few  days  dis- 
appears ;  the  foot  on  the  side  on  which  the  nerve  was  divided 
becomes  not  only  as  cool  and  pale,  but  frequently  cooler  and 
l)alerthan  thefooton  the  sound  side.  If  the  peripheral  portion 
of  the  divided  nerve  be  stimulated  with  an  interrupted  cur- 
rent, immediately  or  very  shortly  after  division,  the  dilation 
due  to  the  division  gives  place  to  constriction  ;  the  sciatic 
acts  then  quite  like  the  cervical  sympathetic,  except,  per- 
hai)s,  that  this  artificial  constriction  cannot  be  maintained 
for  so  long  a  time,  and  is  very  apt  to  be  followed  by  in- 
creased dilation.  If.  however,  the  stimulation  be  deferred 
for  some  days,  until  the  dilation  has  given  place  to  a  return- 
ing constriction,  the  etfect  is  not  constriction,  but  dilation  ; 
the  nerve  then  acts  like  a  muscular  nerve,  and  not  like  the 
cervical  symi)atlietic.  In  fact,  by  variations  in  the  attendant 
circumstances,  and  in  the  mode  of  stimulation,  into  the  de- 
tails of  which  we  cannot  enter  now.  stimulation  of  the  divided 
sciatic  may,  at  the  will  of  the  experimenter,  be  made  to  pro- 
duce either  arterial  dilation  or  arterial  constriction. 

In  all  the  al)ove  cases  section  of  the  nerve  produces  dila- 
tion, whether  the  subsequent  stimulation  causes  constriction 
or  dilation  ;  the  dilation  after  section  may  be  sometimes  not 
very  marked,  but  is  always  present  to  some  extent  or  other. 
I>ut  there  are  certain  nerves  section  of  which  produces  no 
marked  changes  in  the  vascular  areas  to  which  tliey  are  dis- 
tributed, and  yet  stimulation  of  which  brings  about  dila- 
tion often  of  an  extreme  character.  A  striking  example  of 
this  is  seen  in  the  so-called  nervi  erigentes.  The  erection 
of  the  penis  is,  putting  aside  the  subsidiary  action  of  mus- 
cular bands  in  restraining  the  outflow  through  the  veins, 
chiefly  due  to  the  dilation  of  branches  of  the  pudic  arteries, 
whereby  a  large  quantity  of  blood  is  discharged  into  the 
venous  sinuses.  Erection  may  in  the  dog  be  artificially  pro- 
duced l)y  stimulating  the  peripheral  ends  of  the  divided 
nervi  erigentes,  which  are  branches  from  the  first  and  sec- 
ond, and  sometimes  from  the  third,  sacral  nerve  passing 
across  the  pelvis.  On  applying  the  interrupted  current  to 
the  peripheral  ends  of  these  nerves  the  corpora  cavernosa 
at  once  become  turbid.  And  yet  simple  section  of  these 
nervi  erigentes  will  not  in  itself  give  rise  to  erection. 


VASO-MOTOR    NERVES.  275 


According  to  Loven^  and  Xicolski,^  section  of  the  pudic  nerves 
causes  a  partial  dilation  of  the  vessels  of  the  penis,  under  which 
circumstances  Nicolski  tinds  section  of  the  nervi  erigentes  to  pro- 
duce a  constriction,  which  also  appears  even  when  the  pudic 
nerves  have  not  previously  been  divided.  This  result  indicates 
the  existence  of  tonic  dilating  impulses  passing  normall}'  down 
the  nervi  erigentes,  and  normally  restrained  b}- antagonistic  con- 
strictive impulses  passing  along  the  pudic  nerves. 

A  similar  case  is  presented  by  the  submaxillary  gland. 
As  will  be  explained  more  in  detail  in  treating  of  secretion, 
this  gland  is  supplied  by  two  nerves,  by  branches  of  the 
chorda  tympani  reaching  it  along  its  duct,  and  by  branches 
of  the  cervical  sympathetic  reaching  it  along  its  arteries. 
Neither  section  of  the  chorda  tympani  nor  section  of  the 
cervical  s\'mpatlietic  produces  any  very  marked  effect  in  the 
circulation  of  the  gland.  Yet  stimulation  of  the  former  will 
bring  about  a  most  striking  dilation,  of  the  latter  a  no  less 
striking  constriction,  of  the  arteries  of  the  gland. 

How  can  we  construct  a  view  of  the  action  of  vaso-motor 
nerves  which  will  bo  consistent  with  all  these  various  facts  ? 

In  the  first  place,  we  must  admit  the  existence  of  a  local 
tone  in  the  several  vascular  areas,  independent  of  the  cen- 
tral nervous  system.  In  such  cases  as  the  corpora  cavernosa 
of  the  penis  and  the  submaxillar}-  gland  this  independence 
is  unmistakable  ;  in  otiier  regions  it  is  not  at  first  sight  so 
apparent,  but,  as  we  have  already  urged,  must  be  admitted 
even  for  these. 

In  the  second  place,  as  is  strikingly  shown  b}'  the  case  of 
the  submaxillary  gland,  there  are  nerves  which,  since  they 
always  cause  dilation,  ma^'be  called  vaso-dilaloi^  nerves,  and 
nerves  which,  since  they  always  cause  constriction,  may  be 
called  voiio  constrictor  nerves.  Examples  of  the  first  are 
seen  in  the  nervi  erigentes,  the  ciiorda  tympani,  the  nerves 
of  muscles,  etc. ;  of  the  second,  in  the  cervical  sj-mpathetic, 
the  splanchnic,  etc.  .  Or,  to  be  more  exact,  we  may  say  that 
the  vaso-raotor  fibres  of  the  former  are  vaso-dilator ;  of  the 
latter,  vaso-constrictor.  It  will  not  escape  notice  that  the 
vaso-dilator  fibres  run  chiefly  at  least  in  the  cerebro-spinal, 
vaso-constrictor  in  tlie  sympathetic  nerves. 

In  the  third  place,  the  cases  of  the  corpora  cavernosa  of 
the  penis  and  the  sui)maxillary  gland  suggest  the  idea  that 
dilation  is  the  result  of  the  complete  or  partial  loss  of  local 


'   Op.  cit.  ^  Hol'uiann  ii.  Seliwalbe,  Bericht.  vi  (1877),  p.  79. 


2lb  THE    VASCULAR    MECHANISM. 

loiu'.  IhiiL  in  fact  vaso-ilihitors  act  l)y  inhibiLiiiii;,  and  vaso- 
constrictors I)}'  aiigiuciiting,  the  activity  of  the  mechanism 
(whatever  it  be)  wliich  gives  rise  to  tiie  local  tone. 

The  erection  of  the  penis  which  follows  stimulation  of  the 
iiers'i  erigentes,  and  the  injection  of  the  snbniaxillary  gland 
which  follows  stimulation  of  the  chorda  tympani,  present  a 
very  close  analogy  to  the  inhibition  of  the  heart  by  stimu- 
lation of  the  vagus.  Just  as  tlie  rhythmic  contraction  of 
the  cardiac  fibre  is  stoi)i)ed  by  the  vagus,  so  the  tonic  con- 
traction of  the  arterial  libre  (and  this  tonic  contraction 
is  indeed  at  bottom  an  obscure  rhythmic  contraction)  is 
stopped  by  the  chorda  or  the  nervi  erigentes.  And  it  seems 
to  be  very  natural  to  draw  the  conclusion  that  dilation  is 
in  all  cases  mere  inhibition,  and  constriction  in  all  cases 
mere  augmentation,  of  local  tone.  But  tempting  as  this 
view  is,  and  usefid  perhaps  as  it  may  be  as  a  working  hy- 
pothesis, it  must  not  be  regarded  as  deflnitel}'  proved.  It 
is  cpiite  possible  tliat  dilation  may  be  brought  about  in  ditter- 
tnt  ways  in  different  cases;  ancl  so  also  with  constriction. 

The  "  inhibitory  "  explanation  of  dilation  must  of  necessity 
remain  unsatisfactory  until  our  information  concerning  the  na- 
ture of  the  local  mechanism  is  increased. 

Along  the  course  both  of  the  chorda  tympani  and  nervi  eri- 
gentes numerous  ganglion  cells  are  distributed,  and  their  pres- 
ence gives  additional  point  to  the  comparison  of  the  local  me- 
chanism with  the  intrinsic  nervous  mechanism  of  the  heart. 
Xicolski'  has  still  further  extended  the  analogy  of  the  nervi 
erigentes  with  the  inhibitory  fibres  of  the  pneumogastric,  by 
showing  that  atropin  paralyzes  the  dilating  tibres  of  the  nervi 
erigentes,  while  muscarin  produces  erection  apparently  by  stimu- 
lating the  local  dilator  mechanism.  Still,  atropin  does  not  par- 
alyze the  dilator  fibres  of  the  chorda. 

Further,  the  occurence  of  dilation  after  simple  section  of  a 
nerve  raises  an  interesting  question.  Do  the  arteries  in 
such  a  case  dilate  because  the  ver\' section  of  the  nerve  acts 
as  a  stimulus  to  vasodilator  fibres,  or  because  the  local  tone 
is  insufficient  to  keep  up  an  adequate  arterial  constriction 
unless  it  l)e  supplemented  by  additional  tonic  impulses 
reaching  the  local  mechanism  from  the  central  nervous  sys- 
tem, which  s;ipi)lement  is  lost  by  section  of  the  nerve  ?  Ob- 
viously, if  mere  section  is  a  stimulus  to  vasodilator  fit)res 
of  such  a  potency  as  to  give  rise  to  a  dilation  lasting  hours, 

^  Op.  cit. 


VASO-iMOTOR    NERVES.  277 

or  it  may  be  da^'s,  all  evidence  of  "  tonic  "  impulses  pro- 
ceeding from  the  central  nervous  system  is  done  away  with. 
We  can  then  only  speak  of  dilation  and  constriction  as  being 
the  result  of  the  action  of  vaso-dilator  and  vaso- con- 
strictor fibres  respectively,  both  worked  in  a  reflex  manner 
by  the  central  nervous  system.  Into  the  discussion  whether 
such  an  inter[)retation  of  tlie  effects  of  simple  section  is  jus- 
tified by  facts  or  not,  and  into  the  allied  controversy  con- 
cerning the  reason  why  the  A'aso-motor  effects  of  stimulating 
tile  afferent  fibres  of  the  sciatic  and  other  nerves  var}'  so 
much  under  different  circumstances,  we  cannot  enter  here. 
We  must  content  ourselves  with  tlie  general  conclusion  that 
though  local  tone  may  exist  independentl}'  of  the  central 
nervous  system,  the  condition  of  the  various  vascular  areas, 
in  the  living  bod3'  in  a  normal  condition,  is  arranged  and 
modified  to  meet  passing  or  permanent  needs,  by  the  cen- 
tral nervous  system  tlirough  the  agency  of  vaso- motor 
nerves,  and  that  these  vnso-motor  nerves  in  some  cases, 
since  they  are  used  to  give  rise  to  dilation  only,  may  be 
spoken  of  as  vaso-dilator  nerves,  or  as  containing  vaso- 
dilator fibres,  in  other  cases  may  similarly  be  called  vaso- 
constrictor, and  in  j'et  a  third  class  of  cases  be  regarded  as 
mixed  in  character,  since  according  to  circumstances  they 
give  rise  either  to  dilation  or  to  constriction. 

There  remains  the  important  question,  What  part  of  the 
central  nervous  system  is  it  which  intermediates  as  a  ner- 
vous vaso-motor  centre  or  centres  either  of  purel}^  reflex  or 
of  partly  reflex  and  partly  automatic  action,  between  various 
afferent  impulses  and  the  efferent  vaso-motor  impulses  lead- 
ing either  to  dilation  or  constriction  ? 

We  liave  seen  (p.  268)  that  stimulation  of  the  central 
stump  of  the  divided  sciatic  gives  rise,  in  an  animal  under 
urari,  to  an  increase  of  general  blood-pressure,  brought  about 
ciiiefly,  if  not  entirel}',  b}^  an  augmentation  of  constiictive 
impulses  passing  along  the  splanchnic  nerves.  This  in- 
crease of  blood-pressure  is  manifested,  with  (in  satisfactory 
experiments)  undiminished  intensity,  even  when  the  whole 
of  the  brain,  down  to  a  certain  limit  in  the  medulla  oblon- 
gata, has  been  removed.  But  if  the  removal  be  carried  be- 
yond this  limit,  or  if  a  small  area  of  the  medulla  oblongata 
lying  above  the  calamus  scriptorius  be  removed,  the  effect 
on  the  general  blood-pressure  of  stimulating  the  central 
stump  of  the  sciatic,  we  might  add,  of  any  other  afferent 

24 


278  THE    VASCULAR    MECHANISM. 

nerve,  is  comparatively  insisjnificant.  Obviously  this  small 
portion  of  tlie  medulla  oblonirata  aets  as  a  vaso-motor  cen- 
tre, by  the  action  of  wliicli  ordinary  alferent  impulses  coming 
from  the  sciatic  or  any  otlier  alferent  nerve,  are  trans- 
formed into  vaso-motor  impulses  of  constrictive  or,  as  in 
the  case  of  an  animal  under  chloral  (see  p.  2G1)),  of  dilating 
ertect,  and  so  discharned  along  the  si)lanchnic  nerves. 

The  vaso-motor  (ibres  of  the  cervical  sympathetic  and  of 
many  other  nerves  Tuay  similarly  be  traced  to  tiiis  same 
region  of  the  medulla  oblongata.  AVhetlier  all  vasomotor 
fibres  are  actually  in  connection  with  it  is  more  than  doubt- 
ful ;  but  at  all  events  the  fibres  passing  to  so  man}'  vascular 
areas,  and  those  of  such  magnitude  and  importance,  are  by 
means  of  it  brought  into  functional  relationship  witii  so 
many,  if  not  all,  of  the  afferent  nerves  of  the  body,  that  it 
may  fairly  be  spoken  of  as  the  general  vaso-motor  centre. 

Owsjannikow^  places  the  lower  limit  of  this  medullary  vaso- 
motor centre  in  the  rabbit  at  a  horizontal  line  drawn  about  4  or 
5  mm.  above  the  point  of  the  calamus  scriptorius,  and  the  upper 
limit  at  about  4  mm.  higher  up,  ?'.  c,  aljout  1  or  2  mm.  below  the 
corpora  quadrigemina.  When  in  carrying  transverse  sections  of 
the  brain  successively  lower  and  lower  down,  the  upper  limit  was 
first  reached,  the  first  efiects  in  the  way  of  diminishing  the  rise 
of  blood-pressure  resulting  from  stimulation  of  the  sciatic,  were 
observed.  On  carrying  the  sections  still  lower,  the  effects  of  the 
stimulation  of  the  sciatic  became  less  and  less,  until  when  the 
low^er  limit  was  reached  no  effects  at  all  were  observed.  The  cen- 
tre is,  according  to  him,  bilateral,  the  halves  being  placed,  not  in 
the  middle  line,  but  more  sideways  and  rather  nearer  the  anterior 
than  the  posterior  surface. 

Dittmar,^  while  confirming  in  general  Owsjannikow's  results, 
limits  the  nervous  area  thus  capable  of  acting  as  a  reffex  vaso- 
motor centre  to  a  small  prismatic  space  in  the  forward  prolonga- 
tion of  the  lateral  columns  after  they  have  given  off'  their  fibres 
to  the  decussating  pyramids.  This  space  is  largely  occupied  by 
a  mass  of  gray  matter,  called  by  Clarke  the  antero-lateral  nu- 
cleus, containing  large  multipolar  cells,  and  lying  close  to  the 
origin  of  the  facial.  Miescher '  had  previously  shown  that  the 
afferent  impulses  which  affect  the  vaso-motor  centre  run  in  the 
lateral  columns. 

TThether  this  me'duUary  vaso-motor  centre  has  any  dis- 
tinct automatic  action,  whether  it  may  be  regarded  as  con- 

1  Ludwig's  Arbeiten,  1871,  p.  21.  ^  n^ij.,  1873,  p.  103. 

3  Ibid.,  18G0,  p.  172. 


VASO-MOTOR    NERVES.  279 

tinually  generating  out  of  its  own  molecular  oscillations, 
and  discharging  along  the  vaso-motor  fibres,  impulses  where- 
by the  general  arterial  tone  is  maintained,  is  a  question 
which,  like  the  allied  question  mooted  on  p.  2T2,  need  not  be 
discussed  here.  Granting  even  the  existence  of  such  auto- 
matic functions,  tiiey  must  be  of  secondary  importance.  As 
we  have  already  urged,  the  great  use  of  the  whole  vaso- 
motor system  is  not  to  maintain  a  general  arterial  tone,  but 
to  modify,  according  to  the  needs  of  the  economy,  the  con- 
dition of  this  or  that  vascular  area. 

Besides  this  general  vaso-motor  centre  in  the  medulla, 
other  parts  of  the  spinal  cord  are  capable  of  acting  as  vaso- 
motor centres,  i.  e.,  of  transforming  afferent  impulses  into 
efferent  vasomotor  impulses  of  dilation  or  constriction. 
Thus,  when  in  the  dog  tiie  spinal  cord  is  divided  in  tiie  dor- 
sal region,  the  vascular  areas  of  the  hinder  part  of  the  body, 
after  a  temporary  dilation  (whicli  may  be  due  in  part  at 
least  to  their  severance  from  the  medullary  vaso-motor 
centre,  but  wliich  probably  is  rather  to  be  attributed  to  tlie 
shock  of  the  operation  on  the  lumbar  cord  and  the  nervous 
mechanisms  connected  with  it),  regain  their  tone  ;  and  then 
the  tone  of  one  or  other  of  these  areas  may  be  modified  in 
the  direction  certainly  of  dilation,  and  possibl}',  but  this  is 
by  no  means  so  certain,  of  constriction  b}'  afferent  impulses 
reaching  the  lumbar  cord.  Erection  of  the  penis  through  the 
nervi  erigentes  may  be  brought  about  by  suitable  stimula- 
tion of  sensory  surfaces,  and  dilation  of  various  vessels  of 
the  limbs  readily  produced  by  stimulation  of  the  central 
stump  of  one  or  anotlier  nerve. 

And  what  is  true  of  the  lumbar,  is  apparently  true  also 
of  the  dorsal  cord,  and,  indeed,  of  all  parts  of  the  spinal 
cord.  Interlaced  with  the  reflex  and  other  mechanisms  for 
the  contraction  of  the  skeletal  muscles,  with  which  the 
spinal  cord,  as  we  shall  hereafter  see,  is  crowded,  are  proba- 
bly vaso-motor  centres  or  mechanisms,  the  details  of  whose 
topography  and  functions  have  yet  to  be  worked  out.  Pnmii- 
nent  among  them,  whether  by  reason  solely  of  its  special 
coiinection  with  the  splanchnic  nerves,  and  thus  with  the 
capacious  vascular  area  of  the  abdominal  viscera,  or  whether 
because  in  addition  it  exercises  a  controlling  co-ordinating 
power  over  the  minor  centres  in  the  rest  of  the  cord,  is  the 
centre  or  mechanism  placed  in  the  particular  part  of  the 
medulla  oblongata  spoken  of  above.  Through  it  and  through 
them,  the  delicate  machinery  of  the  circulation,  which  de- 


280  TllK    VASCULAR    MECHANISM. 

terniiiios  the  blood-siipply,  and  so  llic  activity  of  oncli  tissue 
and  organ,  is  able  to  ivspoiid  by  narrowing  or  widening 
arteries  to  the  ever-varying  demands,  and  lo  meet  by  com- 
pensating changes  the  sliocks  and  strains  of  daily  life. 

Vaso-constrictor  and  Vaso-dilator  Nerves.— The  i)rc)l)li'ms 
connected  "with  this  topic  may  prulitahly  be  studied  under  three 
lieads  : 

1.  Is  dilation  merely  the  consequence  of  the  diminution,  partial 
or  complete,  of  what'we  may  call  central  tonicity,  i.  c,  of  con- 
strictive impulses  ])roceeding  from  the  central  nervous  system,  or 
may  it  occur  as  the  direct  result  of  the  stimulation  of  dilator 
til)res '? 

There  is  no  difficulty  in  answering  this  question  in  favor  of  the 
latter  view.  In  such  cases  as  those  of  the  chorda  tympani  and 
nervi  erigentes,  stimulation  of  the  perijjheral  portion  of  the  nerve 
brings  about  a  dilation  far  exceeding  that  resulting  from  simple 
section. 

Further,  Luchsinger,^  reviving  and  extending  a  very  old  ex- 
periment of  Schiir's,^  linds  that  when  an  animal,  a  kitten,  is 
warmed  in  a  heated  chamber  till  the  feet  become  red  from  dila- 
tion of  the  bloodvessels,  division  of  the  sciatic  nerve  causes  the 
foot  of  the  same  side  to  become  paler.  Similarly  if  the  sciatic  on 
one  side,  say  the  left,  is  tirst  divided,  the  left  foot  in  consequence 
becoming  warmer  and  redder,  and  the  animal  then  exposed  to 
heat,  not  only  does  the  right  foot  become  redder,  but  the  left  foot 
(in  consequence  of  the  blood-current  being  diverted  to  other 
parts)  even  paler  than  before,  so  that  the  diilerence  in  respect  to 
dilation  in  favor  of  the  right  foot  becomes  ver}-  marked.  That 
is  to  say,  the  influence  of  the  heat  on  the  central  nervous  system 
produces  l)y  the  agency  of  vaso-motor  nerves  a  dilation  greater 
than  that  which  results  from  the  mere  loss  of  central  tonicity 
through  severance  of  the  peripheral  vessels  from  the  central 
nervous  system. 

2.  The  more  difficult  question  then  arises  :  Is  the  dilation 
which  follows  section  of  a  nerve  always  due  to  the  section  acting 
as  a  stimulus  to  dilator  fibres,  or  may  it  in  some  cases  at  least 
have  its  origin  in  a  loss  of  central  tonicity,  or  may  it  in  still  a 
third  class  of  cases  be  brought  about  by  botli  causes  combined  ? 

Goltz''  was  led  to  insist  on  the  view  that  dilation  following  sec- 
tion is  the  result  of  the  stimulation  of  dilator  fibres,  from  the 
following  experiment.  The  sciatic  of  a  dog  is  divided  and  care- 
fully replaced  in  the  wound.     In  the  course  of  a  few  days,  when 

'  Pfluger's  Arehiv,  xiv  (1877),  391. 

2  Mitth.  d.  Natiirforsch.  Gesellsch.  in  Bern.,  1856,  p.  69. 

'  Pfliiger's  Arehiv,  ix  (1874),  p.  174;  xi  (1875),  p.  52. 


VASO-MOTOR    NERVES.  281 


the  vascular  tone  of  the  foot  has  been  regained,  the  nerve  is 
again  laid  bare,  and  a  cut  made  in  the  peripheral  stump  ;  forth- 
with the  vessels  of  the  foot  dilate,  and  if  the  nerve  be  crimped 
by  a  series  of  cuts  carried  successively  downwards,  a  very  marked 
dilation  of  the  bloodvessels  and  rise  of  temperature  in  the  foot 
is  observed.  The  question  why  dilation  only  results  under  these 
circumstances,  whereas  when  the  nerve  is  in  the  first  instance 
divided  a  passing  constriction  followed  by  the  more  lasting  dila- 
tion is  observed,  is  answered  b}^  the  hypothesis  that  the  constric- 
tor fibres,  which  are  present  in  the  nerve  together  with  the 
dilator  fibres,  degenerate  rapidly,  so  that  at  the  time  the  crimp- 
ing produces  dilation,  the  latter  fibres  only  are  in  functional 
activity.  This  experiment  undoubtedly  shows  that  the  effects  of 
mere  section  in  the  wa}'  of  a  stimulus  must  not  be  underrated  ; 
but  is  not  valid  as  an  argument  against  the  view  that  dilation 
may  be  the  result  of  mere  loss  of  central  tonicit}^  For  besides 
the  fact  that  the  dilation  which  follows  upon  crimping  is  far 
more  transient  than  the  initial  dilation  which  results  from  the 
primary  division  of  the  nerve,  section  of  an  undoubted  dilator 
nerve  such  as  the  chorda  tympani  does  not  produce  anything 
more  than  the  slightest  and  briefest  dilation,  and  even  that  some- 
times is  absent.^  Moreover  if  mere  section  were  so  powerful  a 
stimulus  to  dilator  fibres,  it  ought,  unless  the  contrary  can  be 
shown,  to  act  similarly  as  a  stimulus  to  constrictor  fibres  when 
these  are  in  functional  activity  ;  and  indeed  such  an  eftect  on 
constrictor  fibres  may  be  supposed  to  be  indicated  by  the  initial 
constriction  which  sometimes  may  be  seen  to  precede  the  dilation 
following  on  section  of  the  sciatic.  But  in  a  section  of  a  purely 
constrictive  nerve,  like  the  cervical  sympathetic,  the  initial  con- 
striction, which  is  sometimes  but  not  always  seen  to  precede  the 
more  lasting  dilation,  is  of  the  slightest  kind. 

We  must  therefore  conclude  that  the  dilation  which  follows 
section  of  the  nerve  is  due  largely,  and  probably  in  some  cases 
exclusively,  to  actual  loss  of  central  tonicity. 

3.  The  third  question  suggested  is.  What  is  the  nature  and 
mode  of  action  of  vaso-dilator  and  vaso-constrictor  fibres  respec- 
tively ?  Are  they  separate  and  distinct  fibres,  with  altogether 
difl:erent  mechanisms  ?  Or  ma}'  the  same  fibre  according  to  cir- 
cumstances act  now  as  a  dilator,  now  as  a  constrictor  ? 

In  reference  to  this  the  following  facts  deserve  attention. 
When  the  sciatic  nerve  is  stimulated  with  an  interrupted  current 
immediately  after  division,  constriction  in  the  vessels  of  the  foot, 
as  siiown  by  a  fall  of  temperature,  or  diminished  injection  of 
vascular  surfaces,  or  diminished  outflow  from  an  incision,  is  the 
result  which  has  been  observed  by  nearly  all  experimenters.  In 
a  degenerating  nerve  [i.  e.,  one  which  has  been  divided  some  days 


^  Kendall  and  Luclisinger,  Pfiugers  Archiv,  xiii  (187G),  p.  19" 


282  THE    VASCULAR    MECHANISM. 


lireviously),  stiinuliitioii  in-odiices  dilation. '  Indeed  the  same 
stimulation  ^vllieh  on  an  early  day  after  division  causes  constric- 
tion may  on  a  later  day  <j;ivc  rise  to  dilation. ^  Single  induction- 
shocks  repeated  at  intervals  (one  or  two  seconds)  applied  to  a 
fresh  nerve  give  Mhen  weak  dilation,  when  strong  constriction  ; 
the  same  rhythmical  stimulus,  however  strong,  apjjlied  to  a  de- 
generating nerve  causes  dilation,  even  in  cases  where  the  inter- 
rupted current  still  gives  rise  to  constriction. ^  Similarly  with 
the  degenerating  i)eripheral  stump  of  the  miriciddris  nuuiuux  in 
the  rabhit  weak  stimulation  sometimes  causes  dilation,  strong 
stimulation  constriction.  So  that  in  general  when  the  stimulus 
is  weak  in  relation  to  the  irritability  of  the  nerve,  dilation  re- 
sults ;  when  it  is  strong,  constriction.  When  the  stimulus  is 
very  strong  and  prolonged  the  constriction  may  be  followed  by 
dilation,  but  this  appears  to  be  merely  the  result  of  exhaustion.-* 

On  the  other  hand,  stimulation  of  the  chorda  tympani  pro- 
duces dilation,  never  constriction,  whatever  be  the  strength  of  the 
stimulus;  and  stimulation  of  the  cervical  sympathetic  similarly 
always  causes  constriction. 

In  the  case  of  the  mylo-hyoid  of  the  frog  stimulation  of  the 
nerve  always  produces  dilation,  though  constriction  may  ])e 
brought  about  by  applying  the  electrodes  directly  to  the  muscle.^ 

So  far  facts  are  compatible  with  the  hypothesis  that  while  the 
cervical  sympathetic  contains  only  constrictor  and  the  chorda 
tympani  only  dilator  fibres,  the  sciatic  nerves  contain  both  kinds 
of  fibres,  the  constrictor  fibres  being  less  irritable,  and  degener- 
ating sooner,  the  dilating  effects  in  consequence  appearing  as 

^  Goltz,  op.  cit.  '  Kendall  and  Luchsinger,  op.  cit. 

'^  Kendall  and  Luchsin.c;er,  op.  cit. 

*  Dastre  and  Morat  (Compt.  Rend.,T.  87  (1878),  p.  771,  p.  880)'judg- 
ing  of  the  condition  of  the  vessels  governed  by  the  cervical  sympathetic, 
by  relative  variations  in  the  arterial  and  venous  pressure  of  the  region, 
find  that  the  constriction  which  is  caused  by  stimulation  of  the  sympa- 
thetic is  of  short  duration,  and  is  followed  even  before  the  removal  of 
the  stimulus  when  this  is  of  long  duration,  by  a  dilation  greater  than 
that  which  existed  before  the  application  of  the  stimulus,  by,  in  fact,  a 
super-dilation.  The  same  phenomena  was  seen  in  the  vessels  of  the  foot 
(of  the  horse  or  ass)  when  the  posterior  tibial  nerve  was  stinmlated,  and 
it  may  he  remarked  that  the  authors  never  in  any  case  saw  the  stimulus 
fail  to  produce  constriction ;  whether  the  stimulus  was  weak  or  strong, 
rhythmic  or  tetanic,  whether  the  nerve  had  been  divided  recently,  or 
for  days  before,  stimulation  always  caused  constriction;  dilation  never 
occurred  otherwise  than  as  subsequent  super-dilation.  The  effects  then 
observed  by  these  authors  on  stimulating  this  smaller  branch  in  the  horse 
are  opposed  to  those  of  stimulating  the  sciatic  trunk  in  other  animals, 
for  the  dilation  spoken  of  above  has  been  repeatedly  observed  without 
any  previous  constriction,  even  when  the  state  of  the  vessels  was  judged 
by  inspection  of  the  unpigmented  feet,  and  not  merely  inferred  from  a 
rise  of  temperature. 

«  Gaskell,  Journ.  Anat.  Phys.,  xi  (1877),  p.  720. 


VASO-MOTOR    NERVES.  283 


degeneration  is  setting  in  and  when  the  stimulus  used  is  too 
weak  to  excite  the  constrictor  fibres.  But  Burnstein^  finds  tliat 
the  transition  from  constriction  may  be  effected  without  any 
change  in  the  nerve-trunk  itself,  it'^is  simply  sufficient  in  the 
case  of  the  sciatic  of  the  dog  to  reduce  the  temperature  of  the 
'foot  by  plunging  it  into  a  cold  bath,  in  order  that  stimulation  of 
even  the  just  divided  sciatic,  whether  by  rhythmical  induction- 
shocks,  or  by  the  interrupted  current,  or  by  crimping,  may  bring 
about  dilation.  And  Lepine^  had  previously  arrived  at  a  similar 
conclusion  with  regard  to  the  sciatic  of  the  frog.  From  this  we 
may  infer  that  the  same  libre  may  act  as  dilator  or  constrictor 
according  to  the  condition  of  the  peripheral  mechanism  ;  at  all 
events,  these  results  throw  great  doubt  on  the  necessity  of  sup- 
posing the  existence  of  two  kinds  of  fibres.  Moreover  were  the 
two  kinds  of  fibres  distinct  we  should  expect  to  find  them  run- 
ning, in  some  part  of  their  course  at  least,  in  ditTerent  tracts  ; 
butthis  has  not  as  yet  been  observed,  as  will  appear  from  the 
following  paragraph. 

The  Course  of  Vaso-motor  Fibres .—SchitY^  concluded  that  the 
vaso-motor  fibres  for  the  front  and  hind  limbs  passed  partly 
directly  from  the  cord  through  the  anterior  roots  of  the  nerves 
forming  the  sciatic  and  brachial  plexuses  respectively,  and  partly 
indirectly  from  the  anterior  roots  of  the  last  three  or  five  dorsal 
nerves  to  the  abdominal  sympathetic  and  thus  to  the  trunk  of 
the  sciatic,  and  from  the  anterior  roots  of  the  3d,  4th.  5th,  or 
sometimes  (3th  dorsal  nerves  to  the  thoracic  sympathetic,  and 
thence  by  the  stellate  or  first  thoracic  ganglion  to  the  brachial 
plexus.  Schiff  made  no  distinction  between  the  paths  of  con- 
strictor and  dilator  fibres  ;  he  supposed  the  fibres  of  direct  origin 
to  supply  the  lower  parts,  those  of  indirect  origin  the  upper  and 
middle  parts,  of  the  respective  limbs.  Bernard,^  on  the  con- 
trary, found  that  all  the  fibres  for  both  limbs  took  the  indirect 
course  through  the  sympathetic.  And  subsequent  observers 
have  supported  now  one,  now  the  other  view.  E.  Cyon^  in 
respect  to  the  fore  limb  (the  fibres  running  in  a  single  nerve  pass- 
ing from  the  thoracic  chain  to  the  stellate  ganglion),  and  Ostrou- 
moff^  in  respect  to  the  hind  limb,  support  Bernard  ;  while  Luch- 
singer  and  Puelma '  agree  with  Schiff  in  so  f\ir  that  some  of  the 
fibres  issue  from  the  cord  through  the  proper  anterior  roots  of 
the  nerve.  Heidenliain  and  Gaskell^  find  that  the  vaso-motor 
nerves  of  the  muscles  of  the  leg  run,  in  the  dog,  in  the  abdominal 

^  Pfliiger's  Archiv,  xv  (1877),  p.  575. 
2  Compt.  Eend.  8oc.  Biol.,  March  4th,  1876. 

^  Comptes  Kendus,   1862,  ii,  p.  400,  p.  425,  and  previously,  Unter- 
such.  z.  Phvsiol.  d.  Nerven-Svstem,  1855. 
*  Comptes  Kendus,  1862,  ii,  p.  228,  p.  305. 
^  Lndwig's  Arbeiten,  1868,  p.  62. 
^  Pfliiger's  Archiv,  xii  (1876),  p.  219. 
'  Pfliiger,  xviii  (1878),  p.  489.         ^  Journ.  Physiol.,  i  (1878),  p.  262. 


284  THE    VASCULAR    MECIIANISiM. 


synipatlu'tic,  but  jippnrently  not  exclusively  so.  All  these  ob- 
servers either  liiul  constrictors  and  dilators  running  in  the  same 
tract,  or  at  least  make  no  dillcrence  between  them.  The  evi- 
dence, however,  as  to  the  exact  course  is  more  satitactory  in  the 
case  of  the  constrictors  than  in  the  case  of  the  dilators.  The 
view  of  Strieker,'  that  dilator  fibres  for  the  hind  limb  run  in  the 
poi'tterior  roots  of  the  4th  and  oth  luml)ar  nerves,  has  been  con- 
tested l)y  Crossy-  and  Yulpian.^  In  the  frog  the  vaso-motor 
fibres  for  the  hind  limb,  at  least  the  web,  appear  to  leave  the  cord 
through  the  anterior  roots  of  the  sciatic  nerve. '*  Lastly  it  may 
be  observed  that  Bernard^  traces  the  vaso-motor  fibres  of  the 
cervical  sympathetic  into  the  first  thoracic  ganglion  on  their  way 
from  the  spinal  cord. 

Spinal  Vaso-motor  Centres. — Evidence  has  already  been  given 
(p.  279)  of  the  existence  even  in  the  mammal  of  spinal  vaso-motor 
centres,  in  addition  to  the  medullary  centre.  In  the  frog  this 
power  of  the  si)inal  cord  to  act  as  a  vaso-motor  centre  is  still 
more  marked  and  general.^  And  even  the  statement  on  p.  277, 
that  the  rise  of  pressure  following  upon  stimulation  of  an  afferent 
nerve  is  absent  or  very  slight  \vhen  the  medullary  vaso-motor  has 
been  removed,  does  not  apply  in  certain  conditions.  Thus  in 
strychnized  animals,  such  a  rise  when  an  afferent  nerve  is  stim- 
ulated is  quite  distinct.''  A  rise  of  pressure  is  similarly  observed, 
in  the  absence  of  the  medulla,  as  a  consequence  of  dyspnoea,^ 
and  as  the  direct  result,  without  any  concomitant  stimulation  of 
afferent  nerves,  of  poisoning  by  picrotoxin,^  and  by  antiarin,  ° 
and  by  strychnia.'^  It  is  probable,  at  all  events,  that  in  these 
cases  the  rise  in  blood-pressure  is  due  to  constrictive  imi)ulses  pass- 
ing down  the  splanchnic  nerves.  If  so,  then  the  vaso-motor 
mechanism  of  the  spinal  cord  would  bear  to  the  ordinary  retlex 
mechanisms  by  which  the  skeletal  muscles  are  worked,  the  addi- 
tional analogy  that  the  paths  along  which  the  impulses  of  affer- 
ent or  central  origin  issue  as  efferent  impulses  are  determined  in 

Wien.  Sitzungsberichte,  Ixxiv  (Julv,  187G). 

2  Archives  de  Phvsiolog.,  iii  (1876),*p.  832. 

3  Ibid.,  V  (1878),  p.  3G. 

^  Pllu;^er,  Allg.  Med.  Central  Zeitiing,  Jalirg.,  xxiv,  Xo.  687G.  Xnss- 
baum,  Plliiger's  Archiv,  x  (1875),  p.  374. 

^  ComDtes  Rendus,  18G2,  ii,  j).  381. 

«  Cf.  Lister,  Phil.  Trans.,  1858,  ii,  p.  G07 ;  Nussbaum,  Pfliiger's 
Archiv,  x  (1875),  p.  374. 

'  Schlesinger,  Wien.  Med.  Jahrb.,  1874 ;  Ileidenhain,  Plliiger's  Ar- 
chiv, xiv  (1S7G),  p.  518. 

^  Schlesinger,  op.  cit. ;  Luchsinger,  Pliiiger's  Archiv,  xvi  (1877),  p. 
510. 

^  Luchsinger,  op.  cit. 

^°  Strieker,  Wien.  Sitznngsbericlite,  Ixxv,  March,  1877  ;  Schroff,  Wien. 
Med.  Jahrb.,  1874,  p.  259.' 

''  Strieker,  op.  cit. 


VASCULAR    CONSTRICTION    AND    DILATION.       285 


part  by  the  condition  of  the  cord  and  the  character  of  the  afferent 
impulses  or  of  the  central  disturbances.^ 

[Digitalis,  chloral,  belladonna  (small  doses),  and  ergot  stimu- 
late the  vaso-motor  centres  in  the  medulla  oblongata.  Vera- 
tria  primarily  stimulates,  secondarily  depresses  these  centres. 
Alcohol,  chloroform,  and  jervia.  paralyze  the  centres.  Strychnia 
stimulates  both  the  vaso-motor  centres  in  the  medulla  and  spinal 
cord.  Nitrite  of  anud  paralyzes  the  vaso-motor  centres  in  the 
medulla,  and  the  muscles  of  the  arterioles.  Belladonna  in  large 
doses  paralyzes  the  muscles  of  the  arterioles.] 

The  Effects  of  Local  Vascular  ConHtriclion  or  Dilation. 

Whatever  be  determined  ultimately  to  be  the  modus 
operandi  of  vasomotor  mechanisms,  the  following  funda- 
mental facts  remain  of  prime  importance. 

The  tone  of  any  given  vascular  area  may  be  altered,  pos- 
itively in  the  direction  of  augmentation  (constriction),  or 
negatively  in  the  way  of  inhibition  (dilation),  quite  inde- 
pendentl}^  of  what  is  going  on  in  other  areas.  The  change 
may  be  brought  about  by  (1)  stimuli  applied  to  the  spot 
itself,  and  acting  either  directly  on  some  local  mechanism, 
or  indirectly  by  reflex  action  through  the  general  central 
nervous  system  ;  (2)  b}^  stimuli  applied  to  some  other  sen- 
tient surface,  and  acting  by  reflex  action  through  the  central 
nervous  system;  (3)  by  stimuli  (chemical,  blood  stimuli) 
acting  directly  on  the  central  nervous  system. 

The  effects  of  local  dilation  are  local  and  general. 

Local  Effects  of  Dilation. — The  arteries  in  the  area  being 
dilated,  offer  less  resistance  than  before  to  the  passage  of 
blood.  Consequently,  more  blood  tlian  usual  passes  through 
them,  filling  up  the  capillaries  and  distending  the  veins. 
Owing  to  the  diminution  of  the  resistance,  the  fall  of  pres- 
sure in  passing  from  the  arteries  to  the  veins  will  be  less 
marked  tiian  usuftl ;  that  in  the  small  arteries  themselves 
will  be  lowered,  tiiat  in  the  corresponding  veins  heightened. 
The  lowering  of  the  pressure  in  the  arteries  means  that 
their  elastic  coats  are  not  put  to  the  stretch  as  much  as 
usual,  i.  e.,  tiieir  elasticity  is  not  called  into  play  to  the 
same  extent  as  before.  Now,  as  has  been  seen,  every  por- 
tion of  the  arterial  wall  has  its  share  in  destroying  the 
pulse  by  converting  the  intermittent  into  a  continuous 
flow.     Hence,  the  dilated  arteries,  their  elasticit}-  not  being 

^  Cf.  Ileidenliain,  Pfliiger's  Archiv,  xiv  (1877),  p.  olS. 


286  THE    VASCULAR    MECHANISM. 


Cfilled  into  play  so  niucli  as  hofore,  will  not  conlribute  tlieir 
usual  share  towards  destroyinu;  the  pulsations  whieii  reacii 
them  at  the  cardiac  side.  The  i)ulsations  will  travel  through 
them  less  changed  than  before,  and  may,  in  certain  cases, 
pass  right  on  into  the  veins.  This  is  frecpiently  seen  in  the 
submaxillary  gland,  when  the  cliorda  tympani  is  stimulated. 
The  ciiannels  being  wider,  resistance  being  less,  and  the 
force  of  the  heart  behind  remaining  the  same,  more  blood 
tlian  before  passes  through  the  area  in  a  given  time  ;  or, 
put  differently,  the  same  quantity  of  blood  passes  through 
the  area  in  a  shorter  time.  Tiie  blood,  consequently,  as  it 
passes  into  the  veins  is  less  changed  than  in  the  normal 
condition  of  the  area.  Usually  the  How  is  so  rapid  tliat  the 
oxy-ha^moglobin  of  tiie  corpuscles  is  deoxidized  to  a  much 
less  extent  than  usual,  and  the  venous  blood  still  possesses 
an  arterial  hue.  On  tiie  other  hand,  since  more  blood 
passes  in  a  given  time,  there  is  an  opportunit}'  for  an  in- 
crease in  the  total  interchange  between  the  blood  and  the 
tissue.  Thus  the  total  work  may  be  greater,  tiiougli  the 
share  borne  by  each  quantity  of  l)lood  is  less. 

General  Effects  of  Dilation. — Supposing  that  the  total 
quantity  of  blood  issuing  from  the  ventricle  remains  the 
same,  that  is  to  say,  supposing  that  the  quantity  of  blood 
put  into  circulation  is  constant,  the  surplus  passing  through 
the  dilated  area  must  be  taken  away  from  the  rest  of  the 
circulation.  Consequently  the  fulness  of  the  dilated  area 
will  lead  to  an  emptying  of  the  other  areas.  This  is  seen 
very  clearly  when  the  dilated  area  is  a  capacious  one.  At 
the  same  time,  local  dilation  causes  a  local  diminution  of 
peripheral  resistance.  This  in  turn  causes  a  lowering  of  the 
general  arterial  pressure  ]  to  this  we  have  already  called 
attention. 

The  effects  of  local  constriction,  similarly  local  and  gen- 
eral, are  naturall}'  the  reverse  of  those  of  dilation. 

In  the  vascular  area  directly  affected,  less  blood  passes 
through  the  capillaries  in  a  given  time,  and  in  consequence 
less  total  interchange  between  the  blood  and  the  tissues 
takes  place,  though  each  unit  volume  of  blood  which  does 
pass  through  is  more  deeply  affected.  Tlie  blood-pressure 
in  the  corresponding  arteries  is  increased,  and,  if  the  area 
be  large,  the  pressure  in  even  distant  arteries  may  be 
heightened. 


CHANGES    IN    THE    CAPILLARIES.  287 

Thus,  to  indicate  results  in  a  general  manner,  local  dila- 
tion encourages  a  copious  flow  of  blood  through  the  area 
where  the  dilation  is  taking  place,  and,  by  reducing  the 
blood-pressure,  liinders  the  flow  of  blood  into  other  areas. 
Local  constriction,  on  the  other  hand,  lessens  the  flow  of 
blood  in  the  particular  area,  and  by  heightening  the  blood- 
pressure  tends  to  throw  the  mass  of  the  blood  on  to  other 
areas.  Hence  the  great  regulative  value  of  the  vasomotor 
system.  By  augmenting  or  inhibitory  influences  (constric- 
tor or  dilating)  applied  either  to  peripheral  mechanisms  or 
to  cerebro-spinal  centres,  and  called  forth  by  stimuli  either 
intrinsic  and  acting  tlirough  the  blood,  or  extrinsic  and 
acting  through  nervous  tracts,  the  supply  of  blood  to  this 
or  that  organ  or  tissue  may  be  increased  or  reduced  ;  the 
surplus  or  deficit  being  carried  away  to.  or  l)rought  up  from, 
either  the  rest  of  the  body  generall}',  or  some  other  special 
orsran  or  tissue. 


Sec.  6.  Changes  in  the  Capillary  Districts. 

Possessing  no  muscular  element  in  tlieir  texture,  the 
capillaries,  unlike  the  arteries,  are  subject  to  no  active 
cliange  of  calibre.  They  are  expanded  when  a  large  suppl}'' 
of  blood  reaches  them  through  the  supj)lying  arteries,  and, 
b}'  virtue  of  their  elasticity,  shrink  again  when  the  supply 
is  lessened  or  witiidrawn  ;  in  both  these  events  their  share 
is  a  passive  one. 

It  is  true  that  certain  active  changes  of  form,  due  to  move- 
ments in  the  protoplasm  of  their  walls,  have  been  described  ; 
but  the  eflects  of  any  such  changes,  even  if  common,  must  be 
quite  subordinate. 

Xevertheless  the  capillaries  do  possess  active  properties 
of  a  certain  kind,  which  cause  them  to  play  an  important 
part  in  the  work  of  the  circulation.  They  are  concerned  in 
maintaining  the  vital  equilibrium  which  exists  between  the 
intra-vascular  blood  and  the  extra-vascular  tissue,  an  equilil)- 
r:um  which  is  the  central  fact  of  a  normal  capillar^'  circula- 
tion, of  a  normal  interchange  between  the  blood  and  the 
tissue,  and  thus  of  a  normal  life  of  the  tissue.  The  exist- 
ence of  this  equilibrium  is  best  shown  \vhen  it  is  overthrown, 
as  in  the  condition  known  as  inflammation. 


288  TUE    VASCULAR    MECHANISM. 

If  an  irritant,  sucli  as  silver  nitrate,  or  mustar;!,  etc.,  be 
applied  to  a  small  i)orti()n  of  a  frocr's  web,  or  a  frog's  tongne, 
intiamination  is  set  up  over  a  circumscribed  area.  In  this 
area  the  following  changes  may  be  successively  observed 
under  the  microscope.  The  first  effect  that  is  noticed  is  a 
dilation  of  the  arteries,  accoin[)anied  by  a  quickening  of  the 
stream.  The  cai)illaries  become  filled  with  corpuscles,  and 
many  passages  previously  invisible  or  nearly  so  on  account 
of  their  containing  no  corpuscles  come  into  view.  The  veins 
at  the  same  time  appear  enlarged  and  full.  These  events, 
the  filling  of  the  capillaries  and  veins,  and  the  quickening 
of  the  stream,  are  all  sim[)ly  the  results  of  the  diminution 
of  peripheral  resistance  caused  by  the  dihition  of  the  small 
arteries.  If  the  stimulus  be  very  slight,  this  may  all  pass 
away,  the  arteries  gaining  their  normal  constriction,  and  the 
capillaries  and  veins  in  consequence  retuining  to  their  half- 
filled  condition  ;  in  other  words,  the  effect  of  the  stimulus 
in  such  a  case  is  rather  a  temporary  blush  than  actual  in- 
flammation. When  the  stimulus  however  is  stronger,  the 
quickening  of  the  stream  gives  way  to  a  slackening  ;  this 
is  not  due  to  any  returning  constriction  of  the  arteries,  for 
they  still  continue  dilated.  The  capillaries  and  veins  get 
more  and  more  crowded  with  corpuscles,  the  stream  becomes 
slower  and  slower,  until  at  last  the  movement  of  the  blood 
in  the  now  distinctly  infiamed  area  ceases  altogether.  The 
phase  of  accelerated  flow  has  given  place  to  sfaf^is.  The 
capillaries,  veins  and  small  arteries  are  choked  with  corpus- 
cles, and  it  may  now  be  remarked  that  the  red  cori)uscles 
seem  to  run  together,  so  that  their  outlines  ai-e  no  longer 
distinguishable;  they  appear  to  have  become  fused  into  a 
yellow  homogeneous  mass.  The  large  number  of  white 
corpuscles  in  the  capillaries  and  veins  is  also  a  conspicuous 
feature.  This  stasis,  this  arrest  of  the  current,  is  not  due 
to  any  lessening  of  the  heart's  beat ;  the  arterial  pulsations, 
or  at  least  the  arterial  flow,  may  be  seen  to  be  continued 
down  to  the  inflamed  area,  and  there  to  cease  very  suddeidy. 
It  is  not  due  to  any  increase  of  peripheral  resistance  caused 
by  constriction  of  the  small  arteries,  for  these  continue  di- 
lated rather  than  constricted.  It  must  therefore  be  due  to 
some  new  and  unusual  resistance  occurring  in  the  capillary 
area  itself.  The  increase  of  resistance  is  not  caused  by  any 
change  confined  to  the  cor[)uscles  themselves  ;  for  if  after 
a  temporary  delay  one  set  of  corpuscles  has  managed  to 
pass  away  from  the  inflamed   area,  the  next  set  of  corpus- 


CHANGES    IN    THE    CAPILLARIES.  289 

eles  is  subjected  to  the  same  delay  and  the  same  apparent 
fusion. 

The  cause  of  the  resistance  must,  therefore,  lie  in  the 
capillary  walls,  or  in  the  tissue  surrounding  them  ;  or,  to 
speak,  perhaps,  more  correctl}',  it  depends  on  a  disturbance 
of  the  relations  which  in  a  healthy  area  subsist  between  the 
blood  in  the  capillaries  on  the  one  hand,  and  the  capillary 
walls,  with  the  tissue  of  which  they  are  a  part,  on  the  otlier. 
After  stasis  has  continued  for  some  time,  the  tissue  outside 
the  capillary  wall  is  seen  to  become  crowded  with  white 
corpuscles,  and  in  tlie  tissue  outside  the  veins  are  seen  not 
only  white,  but  also  red  corpuscles.  There  can  be  no  doubt 
that  these  have  passed  through  the  capillary  and  venous 
walls  ;  they  may,  indeed,  be  seen  in  transit,  but  the  mechan- 
ism of  their  passage  is  not  exactly  known.  We  have  no  clear 
proof  that  any  distinct  pores  do  exist  in  the  vascular  walls  ; 
and  it  seems  probable  that  in  the  protoplasmic  tissue,  which 
constitutes  these  walls,  a  temporary  breach  made  by  the  pas- 
sage of  a  corpuscle  may  be  immediately  and  completely 
obliterated,  just  as  a  body  may  be  tlirust  through  a  film 
such  as  that  of  a  soap-bubble,  and  yet  leave  tlie  film  appar- 
entl}'  entire,  the  internal  cohesion  of  the  film  at  once  repair- 
ing the  breach. 

Except  in  cases  where  the  stimulus  produces  permanent 
mischief,  the  inflammation  after  awhile  subsides.  The  out- 
lines of  the  corpuscles  become  once  more  distinct;  those 
on  the  venous  side  of  the  block  gradually  drop  away  in  the 
neighboring  currents;  little  l)y  little  the  whole  obstruction 
is  removed  ;  the  current  through  tlie  area  is  re-establislied  ; 
and,  though  the  arteries  and  capillaries  remain  dilated  tor 
some  considerable  time,  they  eventually  return  to  their 
normal  calibre.  Thus  it  is  evident  that  the  peripheral  re- 
sistance in  the  capillaries  (and  consequently  all  that  depends 
on  peripheral  resistance)  is  not  merel}'  a  matter  of  the  me- 
chanical friction  of  the  blood  against  the  smooth  walls  of 
the  bloodvessels,  but  is  concerned  with  the  vital  condition 
of  the  tissues.  When  the  tissue  is  in  health,  a  certain  re- 
sistance is  offered  to  the  passage  of  blood  through  the  capil- 
laries, and  the  whole  vascular  mechanism  is  adapted  to 
overcome  this  resistance  to  such  an  extent  that  a  normal 
circulation  can  take  place.  When  tlie  tissue  becomes  in- 
flamed, the  disturbance  of  the  equilibrium  between  the  tissue 
and  the  blood  so  augments  the  resistance  that  the  passage 
of  the  blood  becomes  diflicnlt  or  impossible.    And  it  is  quite 


290  TUE    VASCULAR    MECHANISM. 

open  to  us  to  suppose  that  there  are  conditions  tlic  reverse 
ol"  inllannnation,  in  which  the  resistance  may  he  lowered 
below  the  normal,  and  the  circulation  in  the  area  quickened. 

Such  a  diminution  of  peripheral  resistance  may  possibly  in  part 
exi)lain  the  remarkable  (piickenini^  of  the  tlow  of  blood,  wdiich  is 
seen  in  any  tissue  after  a  temi)orary  interruption  of  the  stream, 
and  which  is  also  witnessed  in  the  case  of  an  artificial  stream 
kept  up  in  an  organ,  such  as  the  liver  or  kidney,  removed  from 
the  body.  Mosso,'  by  means  of  the  Plethysmograph,'^  deter- 
mined that  the  amount  of  resistance  offered  to  the  artificial  tlow 
of  blood  throuuh  an  excised  kidney  depends  upon  the  gases 
present  in  the  blood  passed  through,  the  resistance  being  greater 
in  proportion  to  the  amount  of  carbonic  acid,  irrespective  of  the 
cpiantity  of  oxygen. 

Thus  the  vital  condition  of  the  tissue  becomes  a  factor 
in  the  maintenance  of  the  circulation. 

It  is,  perhaps,  hardly  necessary  to  observe  that  the  consider- 
ations urged  above  arc  quite  distinct  from  what  is  sometimes 
spoken  of  under  the  name  of  ''capillary  "  force  as  an  agent  of  the 
circulation.  If  by  capillary  force,  it  is  intended  to  refer  to  the 
rise  of  fluids  in  capillary  tubes,  it  is  evident  that  since  such  phe- 
nomena are  the  results  of  adhesion,  capillarity  can  only  be  a 
greater  or  less  hindrance  to  the  tlow  of  blood,  seeing  that  this  is 
l)ropelled  b}'  a  force  (the  heart's  beat)  which  has  been  proved  by 
experiment  to  be  equal  to  the  task  of  driving  the  blood  from  ven- 
tricle to  auricle  through  the  capillary  regions.  If  by  capillary 
force  it  is  meant  that  the  tissues  have  some  vital  power  of  w^ith- 
drawing  the  tluid  parts  of  the  blood  from  the  small  arteries,  and 
thus  of  assisting  an  onward  tlow,  it  becomes  necessary  also  to 
assume  that  they  have  as  well  the  power  of  returning  the  fluid 
parts  to  the  veins.  Both  these  assumptions  are  unnecessary  and 
without  foundation. 

Sec.  7.  Changes  in  the  Quantity  of  Blood. 

In  an  artificial  scheme  changes  in  the  total  quantity  of 
fluid  in  circulation  will  have  an  immediate  and  direct  effect 

'   Ludwig's  Arbeiten,  1874. 

2  By  this  instrument  variations  in  volume  are  measured,  and  where 
these  depend  on  variations  in  the  quantity  of  blood  passing  the  organ 
■Nvliich  is  being  studied,  changes  in  the  circulation  may  thereby  be  inves- 
tigated. Cf.  Mosso,  "  iSopra  un  nuovo  mctodo  per  scrivere  movimenti 
dei  vasi  sanguigni  nell'  uomo,"  Atti  d.  Real.  Accad.  d.  Sci.  d.  Torino,  vol. 
xi ;  Frangois-Franck,  Marev's  Travaux  du  Laborat.,  vol.  ii,  p.  1 ;  and 
the  earlier  memoir  of  Fick,  Untersuch.  Zurich.  Physiol.  Lab.,  Hft.  i,  p.  51. 


CHANGES    IN    THE    QUANTITY    OF    BLOOD.  291 

on  the  arterial  pressure,  increase  of  the  quantit}^  heighten- 
ing and  decrease  diminishing  it.  This  effect  will  be  produced 
partl}^  by  the  pump  being  more  or  less  filled  at  each  stroke, 
and  partly  by  the  peripheral  resistance  being  increased  or 
diminished  by  the  greater  or  less  fulness  of  the  capillaries. 
The  venous  pressure  will,  under  all  circumstances,  be  raised 
with  the  increase  of  fluid  ;  but  the  arterial  pressure  will  be 
raised  in  proportion  onl}'  so  long  as  the  elastic  walls  of  the 
arterial  tubes  are  able  to  exert  their  elasticity. 

In  the  natural  circulation,  the  direct  results  of  change  of 
quantity  are  obscured  b}'  compensatory  arrangements. 
Thus  experiment  shows^  that  when  an  animal  with  normal 
blood-pressure  is  bled  from  one  carotid,  the  pressure  in  the 
other  carotid  sinks  so  long  as  the  bleeding  is  going  on  (this, 
of  course,  not  so  much  from  loss  of  blood  as  from  diminu- 
tion of  peripheral  resistance  in  the  open  artery),  and  re- 
mains depressed  for  a  brief  period  after  the  bleeding  has 
ceased.  In  a  short  time,  however,  it  regains  or  nearly  re- 
gains the  normal  height.  This  recover}'  of  Idood-pressure, 
after  hjemorrhage,  is  witnessed  until  the  loss  of  blood 
amounts  to  about  3  per  cent,  of  the  body-weight.  Beyond 
that,  a  large  and  frequently  a  sudden  dangerous  permanent 
depression  is  observed. 

The  restoration  of  the  pressure  after  the  cessation  of  the 
bleeding  is  too  rapid  to  permit  us  to  suppose  that  the 
quantity  of  fluid  in  the  bloodvessels  is  repaired  by  the  with- 
drawal of  lymph  from  the  extra-vascular  elements  of  the 
tissues.  In  all  probabilit}^  the  result  is  gained  by  an  in- 
creased action  of  the  vaso-motor  nerves,  increasing  the 
peripheral  resistance,  the  vaso-motor  centres  being  thrown 
into  increased  action  by  the  diminution  of  their  blood  sup- 
ply. When  the  loss  of  blood  has  gone  beyond  a  certain 
limit,  this  vaso-motor  action  is  insutiicient  to  compensate 
the  diminished  quantity  (possibly  the  vaso-motor  centres  in 
part  become  exliausted),  and  a  considerable  depression  takes 
place;  but  at  this  epoch  the  loss  of  blood  frequently  causes 
anaemic  convulsions. 

Similarly  when  an  additional  quantity  of  l)lood  is  injected 
into  the  vessels,  no  marked  increase  of  blood-pressure  is 
observed  so  long  as  the  vaso-motor  centre  in  the  medulla 
oblongata  is  intact.     If,  however,  the  cervical  spinal  cord 

^  Worm  Miiller,  Ludwig's  Arbeiten,  1873,  p.  159.  Lesser,  ibid.,  1874, 
p.  50. 


292  THE    VASCULAR    MECHANISM. 

be  divided  previous  to  tlio  injection,  tlie  pressure,  which  on 
account  of  tiie  removal  of  the  medullary  vasomotor  centre, 
is  very  low,  is  permanently  raised  hy  the  injection  of  blood. 
At  each  injection  the  pressure  rises,  falls  somewhat  after- 
wards, but  eventually  remains  at  a  higher  level  than  before. 
This  rise  continues  until  the  amount  of  blood  in  the  vessels 
above  the  normal  quantity  reaches  from  2  to  3  per  cent,  of 
the  body-weiyht.  IJeyond  this  point  there  is  no  further  rise 
of  pressure. 

These  facts  show,  in  the  first  place,  that  when  the  volume 
of  the  blood  is  increased,  comi)ensation  is  effected  by  a 
lessening  of  the  peri})heral  resistance  by  means  of  a  dimin- 
ished action  of  the  vaso-motor  centres,  so  that  the  normal 
blood-j)ressure  remains  constant.  They  further  show  that 
a  much  greater  quantity  of  blood  can  be  lodged  in  the  blood- 
vessels than  is  normally  present  in  them.  That  the  addi- 
tional quantity  injected  does  remain  in  the  vessels  is  proved 
by  the  absence  of  extravasations,  and  of  any  considerable 
increase  of  the  extra-vascular  lymphatic  fluids.  It  has  al- 
ready been  insisted  that  the  bloodvessels  are,  in  health,  but 
partially  filled,  that  the  veins  and  capillaries  are  alone  able 
to  receive  all  the  blood  in  the  body.  In  these  cases  of  large 
addition  of  blood,  the  extra  quantity  appears  to  be  lodged 
in  t!ie  small  veins  and  capillaries  (espe(;ially  of  the  internal 
organs),  which  are  abnormall}'  distended  to  contain  the 
surplus. 

We  learn  from  these  facts  the  two  practical  lessons,  first, 
that  blood-pressure  cannot  be  lowered  directly  by  bleeding, 
unless  the  quantity  lemoved  be  dangerously  large ;  and 
secondly,  that  there  is  no  necessary  connection  between  a 
high  blood-pressure  and  fulness  of  blood  or  plethora,  since 
an  enormous  quantity  of  blood  may  be  driven  into  the  ves- 
sels without  any  marked  rise  of  pressure. 


The  Mutual  Relations  and  the  Co-ordination  of  the 
Vascular  Factors. 

The  foregoing  considerations  show  how  complicated  and 
sensitive,  and,  therefore,  how  useful  is  the  vascular  mechan- 
ism. It  ma}'  be  worth  while  briefly  to  summarize  the  rela- 
tions of  the  different  factors,  and  to  point  out  the  manner 
in  which  they  are  made  to  work  in  harraon}-  for  the  good  of 
the  body. 


RELATIONS  OF  THE  VASCULAR  FACTORS.   293 

Two  facts  stand  out  prominent  above  all  others :  (1)  The 
heart's  beat  may  be  made  slow  by  vagus  inhibition,  and 
probably  quickened  by  withdraw^al  of  the  constant  inhibitory 
influence  exercised  by  the  cardio-inhibitory  centre  in  the 
medulla.  (2)  The  peripheral  resistance  ma}'  be  diminished 
by  diminished  action  (dilating  action)  of  the  vaso-motor 
centres,  and  increased  by  increased  action  (constricting 
action)  of  the  same  centres. 

These  two  facts  are,  by  the  mediation  of  the  nervous  S3's- 
tem,  placed  in  mutual  regulative  dependence  on  each  other. 
Thus,  if  with  a  given  peripheral  resistance,  and  proportion- 
ate blood-pressure,  the  heart  begins  to  beat  violently, afferent 
impulses  passing  up  the  depressor  nerves  diminish  periph- 
eral resistance  (by  opening  the  splanchnic  flood-gates),  and 
prevent  the  rise  of  blood-pressure  which  w^ould  otherwise 
take  place.  In  this  way  a  delicate  organ,  such  for  instance 
as  the  retina,  is  sheltered  from  the  turbulence  of  the  heart 
by  a  change  in  the  flow  of  blood  through  the  less  nol.le 
organs  of  tlie  abdomen.  Conversely,  if  peri])lieral  resist- 
ance be  in  an}'  area  increased,  the  general  blood-pressure  is 
prevented  from  rising  too  high  by  reason  of  the  actual  in- 
crease of  blood-i)ressure  so  affecting  the  medulla,  that 
inhibitory  impulses  descend  the  vagus,  and  b}'  producing  a 
less  frequent  pulse,  tone  down  the  distension  of  the  arteries. 

The  more  we  learn  of  the  working  of  the  body,  the  more 
aware  we  become  of  the  fact  that  it  is  crowded  with  regula- 
tive and  compensating  arrangements  no  less  striking  and 
exquisite  than  the  two  we  have  just  described.  Some  of 
these  will  be  seen  in  the  following  almost  tabular  statement 
of  the  various  modifications  of  the  vascular  factors,  and  of 
their  causes. 

A.  The  heat  of  the  heart  is  aflfected 

1.  By  the  amount  of  distension  of  the  ventricular  cavities 
preceding  the  systole.     This  will  depend  on 

a.  The  quantity  of  blood  passing  into  the  ventricular 
cavities  during*  the  diastole.  This  in  turn  is  determined  by 
the  flow  of  blood  through  the  veins,  the  flow  itself  being  in- 
fluenced b}'  the  arterial  pressure,  respiratory  movements, 
etc. 

h.  The  force  of  the  auricular  contractions.^ 

c.  The  amount  of  resistance  which  has  to  be  overcome  by 

1  Cf.  KoY,  Journ.  Physiol.,  i  (1878),  p.  452. 
25 


294  THE    VASCULAR    MECHANISM. 

the  systole.     I'liis  is  determined  by  tlie  mean  firterial  pres- 
sure, and  is  intlneneed  by  everything  whicli  inlluenees  that. 

2.  By  the  quantity  of  the  blood  passing  through  the  coro- 
nary arteries.  In  tlie  frog  the  thin  walls  of  the  auricle  and 
the  spongy  texture  of  the  ventricle  i)erniit  the  nourishment 
of  the  cardiac  substance  to  be  carried  on  by  direct  contact 
with  the  blood  in  the  cavities.  In  mammals  this  mode  of 
nutrition  must  be  insignificant.  In  tliem  the  condition  of 
the  cardiac  muscles  and  nervous  appendages  depends  almost 
exclusively  on  the  blood  distributed  by  the  coronary  ar- 
teries. Putting  aside  the  vaso-motor  supply  of  the  coro- 
nary arteries,  of  which  we  know  nothing,  we  may  say  that 
the  amount  so  sent  will  depend  on  the  arterial  pressure  in 
the  aorta. 

If  the  blood-current  through  the  muscles  of  the  heart  be  inter- 
mittent, instead  of  constant  as  in  other  muscles,  the  beat  of  the 
heart  must  be  itself  self-regulative,  and  the  whole  matter  becomes 
very  complicated.^ 

3.  By  the  quality  of  the  blood  passing  through  the  coro- 
nary arteries,  and  acting  upon  simpl}^  the  muscular  tissue, 
or  upon  the  various  nervous  mechanisms,  or  upon  both. 
This  is  well  illustrated  by  the  action  of  poisons  (see  pp.  242 
and  248).  The  quantitative  relations  of  the  normal  and 
presence  of  abnormal  constituents  must  of  necessity  pro- 
foundly affect  the  heart's  beat. 

4.  Through  the  inhibitory  fibres  of  the  vagus. 

a.  By  the  blood  directly  stimulating  [or  depressing]  the 
endings  of  the  vagus  fibres.  This  is  only  seen  in  the  case 
of  poisons  (pp.  247  and  248^. 

h.  By  the  blood  [or  poisons,  p.  248]  directly  affecting  the 
cardio-inhiliitory  centre  in  the  medulla  oblongata,  either 
positively  by  augmenting  the  normal  inhibitory  influences 
and  so  slowing  the  heart,  or  negatively  by  depress^ing  those 
influences  and  so  quickening  the  heart. 

c.  By  reflex  stimulation  of  the  same  centre.  Cases  of  ex- 
altation through  reflex  stitnulation  have  already  been  quoted. 
Instances  of  depression  leading  to  quickening  of  the  heart's 
beat  are  not  so  clear.  The  afferent  impulses  may  be  started 
in  any  part  of  the  body  ;  but,  as  we  have  seen,  there  seems 
to  be  a  special  connection  between  this  centre  and  the  ali- 
mentary canal. 

'  Cf.  Garrod,  Journ.  Anat.  and  Phys.,  vii,  p.  219,  viii,  p.  54. 


RELATIONS    OF    THE    VASCULAR    FACTORS.        295 

5.  By  the  accelerator  nerves  [as  is  seen  in  the  action  of 
poisons,  p.  254].  We  have,  however,  at  present,  no  evidence 
of  the  natural  activity  of  this  nerve. 

B.  The  peripheral  resistance  is  affected 

1.  By  the  vital,  2.  e.,  the  nutritive  condition  of  the  tissue 
of  the  part.     This  is  again  influenced  b_y 

a.  The  qualit}'  (and  quantity  ?)  of  the  blood  brought  to  it. 
h.  Through  the  agency  of  the  nervous  system,  as  in  cases 
of  inflammation  caused  by  nervous  influences. 
Both  these  points  are  very  obscure. 

2.  By  the  varying  calibre  (constriction,  dilation)  of  the 
minute  arteries,  brought  about 

a.  By  the  blood  or  other  stimulus  [or  poisons,  p.  284] 
acting  directly  on  the  peripheral  vaso-motor  mechanism. 

h.  By  the  blood  [or  poisons,  p.  284]  acting  directly  on  the 
vasomotor  centres  in  the  central  nervous  system. 

c.  By  reflex  stimulation  of  the  vaso-motor  centres. 

d.  It  is  more  than  probable  that  the  peripheral  resistance, 
i,  e.,  the  amount  of  constriction  of  the  minute  arteries,  is  di- 
rectly dependent  on  the  blood-pressure  itself.  In  common 
with  all  muscles,  the  contraction  of  the  circular  muscles  of 
the  arteries  will  be  greater  when  the  resistance  is  greater, 
i.  e.,  when  the  distension  of  the  vessels  is  greater.  That  is 
to  say,  other  things  being  equal,  with  an  increase  of  pres- 
sure, due  for  instance  to  an  increase  of  heart-beat,  the  dis- 
tension so  caused  will  be  more  than  counterbalanced  b3'  the 
increased  contraction  of  the  muscular  fibre,  and  thus  the 
l)ressure  still  further  increased.  This,  of  course,  will  take 
place  within  certain  limits  only.^ 

Through  these  intricate  ties  it  comes  to  pass  that  an  event 
which  takes  place  in  one  part  of  the  body  is  felt,  to  a  greater 
or  less  extent,  by  all  parts.  To  take  a  simple  instanc^e  ;  a 
change  in  the  condition  of  the  skin  at  any  one  spot,  such  as 
that  produced  by  the  application  of  cold  or  lieat,  may  lead, 

a.  By  direct  local  action  to  a  constriction  or  dilation  of  the 
vessels  of  the  part,  giving  rise  to  local  pallor  or  suftusion. 

,5.  By  reflex  action  througli  the  central  nervous  system, 
to  an  increase  of  the  same  local  effects,  and  in  addition  to  a 
change  in  the  calibre  of  the  bloodvessels  in  other  parts. 
This  distant  reflex  change  may  be  of  the  same  or  the  oppo- 
site nature  as  the  local  change. 

^  Cf.  .Latschenberger  and  Deabna,  Pfliiger's  Archiv,  xii  (1876),  j). 
157. 


296  THE    VASCULAR    MECHANISM. 

y.  \\\  reflex  action  to  a  qiiickoiiiiiti:  or  slowin<r  of  the 
heart's  beat,  tliougli  the  heart  is  in  this  respect  less  inti- 
mately connected  with  the  skin  than  with  other  parts. 

Out  of  these  primary  effects  there  may  arise  secondary 
effects;  the  constriction  or  dilation  [produced  locally  will 
affect  the  general  blood-pressure,  which  in  turn  will  produce 
all  its  effects. 

The  modifications  of  the  heart-beat  will  not  only  affect  the 
general  blood-i)ressure,  but  in  a  reflex  manner  may  affect 
the  peripheral  resistance,  and  hence  the  flow  of  blood  in  par- 
ticular areas  {e.  g.^  the  splanchnic  area).  The  modifications 
of  the  flow  through  the  area  dircclly,  and  also  through  those 
secondarily  affected,  will  influence  the  tem[)erature  and 
chemical  changes  of  the  blood,  and  those  again  will  produce 
their  effects  everywhere.     And  so  on. 

On  the  other  hand,  the  turbulence  which  would  be  the 
natural  outcome  of  all  these  events  is  softened  down,  by 
the  compensating  effects  of  which  we  have  spoken,  into  the 
smoothness  whicli  we  call  health.  Still  the  greatness  of  the 
possibilities  of  change  which  lie  hidden  in  the  body  are 
clearly  enough  shown  by  the  violence  of  disease,  wdien  com- 
pensation fails  of  accomi)lishment. 

The  proofs  of  the  circulation  brought  forward  by  Harvey  (1628) 
required  for  their  completion  an  explanation  of  the  manner  in 
which  the  blood  passed  from  the  small  arteries  to  the  small  veins. 
For  this  the  use  of  the  microscope  was  necessary,  and  Malpighi 
(1601)  was  the  first  to  demonstrate  the  capillary  circulation. 
Leuwenhoek  afterwards  (1074)  more  fully  described  the  passage 
of  blood  through  the  capillaries  as  seen  in  the  web  of  the  frog's 
foot,  in  the  fin  of  the  fish's  tail,  and  in  other  transparent  struc- 
tures. 

Observations  on  Blood-Pressure  w^ere  first  made  by  Dr.  Stephen 
Hales,'  who  inserted  a  tall  tube  into  the  crural  artery  of  a  mare, 
and  observed  the  height  (more  than  eight  feet)  to  which  the  col- 
umn of  blood  rose.  lie  thus  used  not  a  mercury,  nor  a  water, 
but  a  blood  manometer.  Poiseuille'  introduced  the  mercury 
manometer,  and  to  him  we  are  indebted  for  our  knowledge  of  the 
fundamental  principles  of  the  subject.  The  elaborate  treatise  of 
Volkmann^  helped  to  formulate  our  knowledge  ;  and  we  are  in- 
debted to  Ludwig  for  many  of  our  present  methods  of  investiga- 
tion. 


'  Statical  Essays,  vol.  ii  (1732). 

2  Rech.  s.  1.  Causes  du  Mouveiiient  dn  Sang,  1831. 

^  Hamodvnamik,  1850. 


RELATIONS  OF  THE  VASCULAR  FACTORS. 


Claude  BernarcP  was  the  first  to  observe  that  section  of  tlie 
cervical  sympathetic  on  one  side  of  the  neck  was  followed  by  a 
rise  of  temperature  and  dilation  of  the  bloodvessels  of  the  same 
side  of  the  head.  Brown-Sequard  in  the  same  yeav-  was  appar- 
ently the  first  to  observe  tliat  stimulation  of  the  peripheral  por- 
tion"^of  the  divided  sympathetic  brought  about  a  return  of  the 
pallor  and  a  fall  of  temperature  :  he  clearly  recognized  that  the 
eflects  of  the  section  of  the  sympathetic  were  the  results  of  a 
parah'sis  of  the  bloodvessels.  Bernard  himself,  somewhat  later,^ 
observed  the  effects  of  galvanic  stimulation  of  the  divided  nerve, 
though  he  seems  not  to  have  obtained  so  distinct  a  grasp  of  the 
matter  as  did  A.  Waller. ^  who  in  February*  1853,  clearly  recog- 
nized the  vaso-motorial  functions  of  tlie  cervical  sympathetic, 
and  tlie  relation  of  these  functions  to  the  action  of  the  same 
nerve  on  the  iris.  These  discoveries  formed  the  beginning  of  our 
knowledge  of  the  vaso-motor  nerves.  Among  the  numerous  in- 
vestigations which  have  since  been  carried  on,  none  can  be  con- 
sidered more  important  than  those  for  which  we  are  indebted  to 
Ludwig  and  his  pupils. 


^  Comptes  Eendiis,  xxxiv  (1852),  p.  472. 

-  Philadelphia  Medical  Examiner,  Aug.  1852,  p.  489,  quoted  in  Ex- 
perimental Eesearches  applied  to  Physiology  and  Pathology,  New  York, 
1853,  p.  9. 

^  Comptes  Eendns  de  la  Societe  de  Biologie,  Nov.,  1852. 

*  Comptes  Rendus,  xxxvi  (^1853),  p.  378. 


BOOK   II. 

THE  TISSUES  OF  CHEMICAL  ACTION  WITH 

THEIR  RESPECTIVE  MECHANISMS. 

NUTRITION. 


CHAPTER    I. 
[THE  EPITHELIA. 

The  epitbelia  are  found  in  the  body  as  single  or  multiple 
la^'ers  of  nucleated  protoplasmic  cells.  They  have  a  large 
area  of  distribution  in  the  economy,  and  play  a  ver3'  im- 
portant part  in  many  of  the  vital  processes.     These  cells 


[Fig.  so. 


Fig.  81. 


Fig.  80.— Fragment  of  Epithelium  from  a  Serous  Membrane  (peritoneum) ;  magni- 
fied 410  diameters,    o,  cell ;  ft,  nucleus;  c,  nucleoli.— Henle. 

Fig.  81.— Epithelium  Scales  from  the  Inside  of  the  Mouth  ;  magnified  260  diam- 
eters.— Henle. 


are  more  or  less  modified  in  form  and  structure  in  the  dif- 
ferent epitbelia,  and  so  differentiated  in  their  "amoebiform 
units  "  as  to  perform  very  diverse  functions. 


300 


EPITHELIUM. 


Tlicy  liavo  1)0011  divided  into  four  i)riii('ii)al  varieties,  dis- 
tiiiirnished  by  eertain  characteristic  appearances  of  the  cells. 
Tiieyare  generally  known  as  pavement^  tcsseUnlcd  or  squavi- 
ou.s :  cohonnar  or  cijliinlricdl :  cilialcd;  and  ><pheroidal 
epithelia. 

ravrment^   ta^i^ellaled  or  stjnaniou^^   epitiieliuni    is  found 

Fig.  82. 


\ 


Cylindrical  Epithelium  from  lutostinal  Villus  of  a  Rabbit ;  luagnificd  300  diameters. 
After  KoLi.iKKR. 

widely  distributed,  forming  the  epidermal  covering,  the 
lining  of  the  bloodvessels,  serous  sacs,  many  of  tlie  mucous 
membranes,  etc.     This  form  of  epiLhelium  consists  of  irreg- 


Fk;.  83. 


Ciliated  Epithelium  from  Trachea  (magnified),  a,  basement  membrane ;  6,  c,  d, 
cells  in  several  stages  of  development,  and  which  will  ultimately  be  fully  developed 
ciliated  cells,  and  take  the  place  of  the  matured  ones  which  will  be  thrown  off;  e, 
shows  fully  developed  cells. 

ular,  polygonal  flattened  cells,  which  are  overlapped,  or 
more  or  less  merged  into  each  other  at  their  edges.  (Figs. 
80  and  81.) 

Columnar  or  cylindrical  epithelium  (Fig.  82)  is  found  in 


EPITHELIUM.  301 


the  form  of  elonirfited  cylindrical  cells,  which  are  more  or 
less  angular  on  their  sides  from  mutual  compression  ;  they 
are  placed  parallel  with  each  other,  and  vertically  on  the 
Itasenient  membrane.  Tiiis  form  of  epithelium  is  found 
principalh'  as  a  lining  of  tlie  mucous  membrane  of  the  gas- 
tro-intesLinal  tract,  and  of  many  of  the  ducts. 

Cilintt'd  epithelium  (Fig.  83)  usualh'  is  found  in  a  form 
similar  to  that  of  the  columnar  variety.  These  cells  have 
projecting  from  their  free  extremities  very  numerous  hair- 
like bodies  or  cilia.  If  these  cells  be  examined  with  a  mi- 
croscope during  life  or  immediately  after  death,  the  cilia  will 
be  seen  to  be  in  a  state  of  constant  vibratiie  motion.  This 
form  of  epithelium  is  found  in  the  greater  portion  of  the  re- 
si)ii-atory  tract,  in  the  Fallopian  tubes,  etc. 

Spheroidal  or  glandular  (Fig.  92)  epithelium  is  in  the 
form  of  somewhat  globular  or  spheroidal  cells,  which  are 
more  or  less  angular  on  their  sides,  from  compression  of  ad- 
joining cells.  This  epithelium  is  found  principally  in  the 
secretory  portions  of  the  glands,  and  in  many  of  them  it 
forms  the  essential  ph3'siological  constituent. 

The  functions  of  these  different  epithelia  are  as  diverse  as 
are  their  foims  and  structures.  Pavement  epithelium  is 
so  distributed  that  its  use  often  appears  to  be  of  a  physical 
character.  Tims  in  the  skin  it  consists  of  numerous  stratifica- 
tions of  cells  which  form  a  tough,  more  or  less  impermeable 
layer,  which  pi-otects  the  true  skin  from  effects  of  friction, 
and  at  the  same  time  protects  the  l)ody  from  overloss  of 
water  by  evaporation.  The  horns  of  animals,  the  nails  and 
hairs,  are  all  modifications  of  this  foim  of  epithelium.  In 
the  bloodvessels  it  forms  a  smooth  lining  membrane  and 
seems  to  be  endowed  with  a  vital  property  in  preventing  an 
intravascular  coagulation  of  the  blood.  Jn  the  cajjillaries  it 
also  pla^s  a  very  important  part  in  the  interchange  of  the 
secretive  and  excretive  materials  which  are  conveyed  in  the 
blood.  In  both  tiie  systemic  and  pulmonic  capillaries  it  is 
an  active  agent  in  the  interchange  of  gases,  and  is  therefore 
a  re.spir'atory  tissue.  In  the  bladder,  where  its  form  is  some 
what  modified,  it  forms  a  membrane  which  prevents  the  re- 
absorption  of  urine. 

Other  ei)ithelia,  sucii  as  the  spheroidal,  are  principally 
aecretive^  and  possess  the  power  of  selecting  certain  elements 
froin  the  blood,  and  by  a  process  of  metabolism  convert 
them  iiito  new  substances.  In  certain  glands  these  cells 
themselves  undergo  certain  metamorphoses  and  are  elabor- 

26 


;02 


EPITHELIUM. 


nted  ns  eloiionts  of  tlio  secrelioii.  Tlie  rimction  oftliis  o|)itho- 
liniii  in  some  of  the  uplands  is  cxcretor;/.  Tlie  spiieroidal  and 
coluMinai-  varieties  are  the  principal  secretory  epitiielia. 

Af>.<(frj)(io)}  is  the  function  par  c.rceUence  of  others.  The 
intestinal  villi,  which  are  covered  with  a  layer  of  columnar 
epithelial  cells,  are  intimately  connected  vvith  the  function 
of  absorption.  It  is  through  tiiese  cells  tliat  tlie  chyle  passes 
to  reach  the  lacteals,  and  through  which  other  products  of 
digestion    pass  to   reach    the   intestinal    ca[)illaries   of  the 

.  .H4. 


Section  of  a  Villus  from  the  Intestine  of  a  Rabbit.  Above  (a)  is  the  central  canal 
boundeil  on  eitiier  side  by  the  matrix  (h),  which  again  is  covered  by  long  columnar 
cells  (c),  containing  a  nucleus  and  granules.  The  outer  surface  of  these  cells  is  seen 
to  be  striated. 

portal  vein.  The  cells  in  this  position  are  somewhat  modi- 
fied !)>'  possessing  a  striated  outer  surface  (Fig.  84).  The 
striffi  are  supposed  by  some  physiologists  to  be  minute  canals 
which  lead  into  the  intracellular  protoplasm.  These  cells 
during  fasting  contain  clear  granular  protoplasm,  but  during 
digestion  they  are  seen  to  contain  very  numerous  fat-glob- 
ules.    They  will  be  referred  to  more  full}'  hereafter. 

The  ciliated  epitiielia  possess  a  special  function  by  virtue 
of  their  ciliary  api)endages.  In  the  respiratory  tract  tiiey 
assist  in  the  expulsion  of  mucus  and  foreign  bodies,  also  in 
the  expiration  of  air.     In  the  Fallopian  tubes  they  are  prob- 


ANATOMY    OF    THE    SALIVARY    GLANDS.  303 

ably  active  agents  in  propelling  tlie  ovule  along  the  interior 
of  the  tubes  to  the  uterine  cavity. 

Tlieepithelia  have  no  bloodvessels,  and  must  therefore  ob- 
tain their  nutriment  by  diffusion  from  the  adjoining  tissues. 

After  epithelium  cells  are  matured,  and  no  longer  capaci- 
tated for  the  performance  of  their  proper  functions,  the}'  are 
cast  off  and  replaced  bv  cells  which  are  produced  beneath. 
(See  Fig.  83.)] 

THE  TISSUES  AXD  MECHANISMS  OE  DIGESTION. 

The  food,  in  passing  along  the  alimentary  canal,  is  sub- 
jected to  the  action  of  certain  juices  which  are  the  products 
of  the  secretory  activity  of  the  epithelium  cells  of  the  ali- 
mentary mucous  membrane  itself,  or  of  the  glands  which 
belong  to  it.  These  juices  (viz.,  saliva,  gastric  juice,  bile, 
pancreatic  juice,  succus  entericus,  and  the  secretion  of  tiie 
large  intestine),  poured  upon  and  mingling  with  the  food, 
produce  in  it  such  changes  that,  from  being  hirgely  insol- 
uble, it  becomes  largely  soluble,  or  otherwise  modify  it  in 
such  a  way  that  the  larger  part  of  what  is  eaten  passes  into 
the  blood,  eitlier  directly  by  means  of  the  capillaries  of  the 
alimentar}'  canal,  or  indirectly  by  means  of  the  lacteal  sys- 
tem, while  the  smaller  part  is  discharged  as  excrement. 

We  have,  therefore,  to  consider:  1st,  the  properties  of 
the  various  juices,  and  the  changes  they  bring  about  in  the 
food  eaten  ;  2d,  the  nature  of  tlie  processes  by  means  of 
which  tlie  various  epithelium  cells  of  the  various  glands  and 
various  tracts  of  tlie  canal  are  able  to  manufacLure  so  many 
various  juices  out  of  the  common  source,  the  blood,  and  the 
manner  in  which  the  secretory  activity  of  the  cells  is  regu- 
lated and  subjected  to  the  needs  of  the  economy;  3d,  the 
mechanisms,  here  as  elsewhere,  chiefly  of  a  muscular  nature, 
by  which  the  food  is  passed  along  tiie  canal,  and  most  efH- 
cieutly  brought  in  contact  with  successive  juices;  and  4th 
and  lastly,  the  metins  by  which  the  nutritious  digested  ma- 
terial is  separated  from  the  indigested  or  excremeutal  mate- 
rial, and  iusorbed  into  the  blood. 

Sec.  1.    The  Properties  of  the  Digestive  Juices. 
\_Phiji<iolocjical  Anatomy  of  the  SaJiimry  Gland.-<. 

The  saliva  is  a  compound  secretion,  being  the  product  of 
four  distinct  sets  of  glands.  Three  of  these  exist  in  pairs, 
and  are  termed  respectively  the  parotid^  suhmaxiUary^  and 
sublingual.     The  fourth  set  comi)rises  the  simple  follicular 


P>OA      THE    TISSUES    AND    MECHANISMS    OF    DIGESTION. 


"lands,  \vl»i{;li  are  ver}'  iiiimeroiis  and   fonnd   in  the  buccal 

mncoMS  nienibrane. 

The  larger  salivary  glands  are  composed  of  lobes,  which 
are   subdivided    into    lobules.     The 
^'"'  '''*■  lobules    are    coni[)osed    of     smaller 

vesicular  divisions,  which  are  termed 
the  alveoli.  The  clustered  appear- 
ance of  the  alveoli,  which  compose 
the  lobule,  resembles  somewhat  the 
form  of  a  bunch  of  grapes,  lience 
tliey  have  been  termed  racemose 
glands.  (Fig.  85.)  The  alveoli  are 
composed  of  a  delicate  basement 
membrane,  lined  by  spheroidal  epi- 
thelium, which  is  the  j)roper  secretory 
l)ortion  of  the  organ.  These  cells  con- 
tain non-granular  protoplasm,  with 
an  eccentric  nucleus.  In  some  of 
the  alveoli  granular  protoplasmic 
cells,  with  centric  nuclei  are  found. 

(Fig.   80.)      Within    the    alveolar    vesicles    containing   the 

spheroidal  cells  there  are  frequentl}^  found  halfmoon-shaped 


Lol.ule  (.!■  Parotid  (ilaiid  of 
a  Newborn  Infant,  injected 
with  Mercury.    (Magnified.) 


Submaxillary  gland  of  a  dog.  a,  raucous  cells;  b,  j)rotoplasmic  cells;  c.  demilune 
cells  ;  d,  transverse  section  of  an  excretory  duct,  with  its  peculiar  columnar  epithe- 
lial cells. 


ANATOMY    OF    THE    SALIVARY    GLANDS. 


305 


cells,  which  are  CTlled  demilune  cells.  These  are  always 
found  external  to  the  spheroidal  cells,  and  are  supposed  to 
}>e  young  spheroidal  cells  in  rapid  growth,  wiiich  will  re- 
place che  old  cells  wlien  they  have  matured.  The  alveoli  of 
a  lobule  empty  their  secretion  by  a  common  duct,  which  by 
uniting  with  the  ducts  from  other  lobules  forms  tlie  common 
duct  or  ducts  of  the  gland.  Tliese  ducts  are  all  lined  by 
columnar  epithelium.  The  sublingual  gland  has  multiple 
ducts.    The   parotid   and   submaxillary  glands  each  have  a 


single  duct. 


Fig.  87. 


Modes  of  termination  of  the  nerves  in  the  salivary  glands.  1  an-l  2,  branching  of 
the  nerves  between  the  salivary  cells;  3,  termination  of  the  nerve  in  the  niichus; 
4,  union  of  a  ganglion  cell,  with  a  salivary  cell ;  5,  varicose  nerve  fibres  entering  the 
cylindrical  cell  of  the  excretory  ducts. 


The  alveoli  are  surrounded  by  dense  plexuses  of  capilla- 
ries, in  tlie  meshes  of  which  arise  the  lymphatics.  The 
stdistance  of  the  gland  is  closely  liound  togetlier  by  a 
fibro-areolar  tissue.  The  mode  b^-  whicii  the  nerves  termi- 
nate in  these  glands  is  as  3'et  undetermined.  Pfliiger  be- 
lieves that  the  medulla  of  the  nerve  penetrates  the  cells  and 
unites  with  the  nucleus  (Fig.  87,  1  and  2);  that  others  (4) 
(probably  from  tlie  si/mpathetic  .<ysfem)  terminate  in  multi- 
polar ganglion  cells,  which  send  prolongations  into  the  nuclei 
of  the  gland  cell ;  other  nerves  (3)  terminate  in  an  expanded 
extremitv,  which  lie  considers  an  intermediate  organ  ;  others 


3 


G 


30(]      THK    TISSUES    AND    MECHANISMS    OF    DIGESTION. 

(5)  terniinato  in  tl)C  coliiiniiar  ot'lls  linino;  tho  ducts.  Wliollior 
tliese  sii|ii)ost'tl  tiTiDiiialions  of  llie  nerves  are  tlie  real  ones 
or  not  is  still  a  question  involved  in  much  doubt.] 

So  lira. 

Mixed  saliva,  as  it  appears  in  the  mouth,  is  a  thick.  ,i2:lairv, 
generally  fi'othy  and  turbid  fluid.  Under  the  microscope 
it  is  seen  to  contain,  beside  tiie  molecular  debris  of  food 
(and  frequently  cryptogamic  si)ores),  ei)ilhelium  scales, 
mucus-corpuscles  and  granules,  and  the  so-called  salivary 
corpuscles.  (Fig.  88.)  Its  reaction  in  a  healthy  subject  is 
allxaline.  especially  when  the  secre- 
^^^^''  ^^;  tion  is  abundant.    When  the  saliva 

--  .-»=>--.i  '   ''  ~  ^    ^  is  scanty,  or  when  the  sulject  suf- 

fers from  dyspepsia,  the  reaction 
of  the  mouth  may  be  acid.  Saliva 
contains  but  little  solid  matter,  on 
an  average  probably  about  .5  ))er 
cent.,  the  specific  gravity  varving 
-._>'  fi'om  1.002  to  l.OOG.  Of"thesesoi- 
"i!^     -:    ^vs^  "  jdg^  rather  less  than  half,  about  .2 

Nahv.ir>  corpuscles.  epiUiLiKd       p^,,.   ^<,„|-^^  ^re   salts   (includin£r  a 

scales  and  granules.]  n  ,•■  e         .         •  '     i 

^  small   quantity  or  potassium   sul- 

phocyanate).  The  organic  bodies  which  can  be  recognized 
in  it  are  chiefly  mucin,  with  small  quantities  of  globulin  and 
serum-albumin. 

The  chief  purpose  served  b^-  the  saliva  in  digestion  is  to 
moisten  the  food,  and  to  assist  in  mastication  and  degluti- 
tion. In  some  animals  this  is  its  only  function.  In  other 
animals  and  in  man  it  has  a  specific  solvent  action  on  some 
of  the  food-stuffs.  Such  minerals  as  are  soluble  in  slightly 
alkaline  fluids  are  dissolved  by  it.  On  fats  it  has  no  effect 
save  that  of  producing  a  very  feeble  emulsion.  On  proteids 
it  has  also  no  action.  Its  characteristic  propert}-  is  that  of 
converting  starch  into  sugar  (grape-sugar,  glucose,  dex- 
trose). 

Action  of  Saliva  on  Starch. — If  to  a  quantity  of  thin  boiled 
starch,  which  has  been  ascertained  to  be  free  from  sugar,  a 
small  quantit}'  of  saliva  be  added,  it  will  be  found  after  a 
time  that  the  whole  of  the  starch  has  disappeared,  having 
been  replaced  b}-  a  quantit}'  of  grape-sugar.  The  mixture 
no  longer  gives  any  blue  color  with  iodine,  but  when  boiled 
with  Fehling's  fluid  (cnpric  sulphate  dissolved  in  an  excess 


SALIVA.  307 

of  a  concentrated  solution  of  sodium  or  potassium  hydrate), 
gives  a  copious  red  or  yellow  deposit  of  cuprous  oxide.  If 
iodine  he  added  to  the  mixture  in  the  early  stages  of  the 
action  of  the  saliva,  a  red  or  violet  color  (more  or  less  ob- 
scured by  the  blue)  will  be  observed.  This  indicates  the 
presence  of  dea-trin^  which,  at  a  later  stage,  like  the  starch 
itself,  disappears.  In  fact,  the  saliva  either  converts  the 
starch  into  dextrin  and  then  into  sugar,  or  first  splits  the 
starch  into  dextrin  and  sugar,  and  then  changes  the  dextrin 
into  sugar.  The  essence  of  both  changes  is  the  assump- 
tion of  a  molecule  of  water.  Thus  starch,  Cj;H,oO-,  or  more 
probably 

(Grape-sngar.)     (Dextrin.") 
CisHsoOia  +  3H2O  =  CeHi A-h  2( CeH,o05)  +  2H,0  =  3(CeH,A). 

While  boiled  starch  is  thus  converted  into  grape-sugar  with 
considerable  rapidity,  raw,  unboiled  starch  also  suffers  the  same 
change,  though  more  slowly.  If  a  quantity  of  raw  starch  be 
suspended  in  water  and  saliva  be  added,  the  water  will  after  a  time 
be  found  to  contain  sugar.  If  the  water  be  replaced  from  time  to 
time,  the  starch  will  gradually  disappear,  until  a  remnant  is  left 
which  gives  no  blue  color  witii  iodine,  unless  acid  be  previously 
added.  The  starch-corpuscle  consists  of  {jramdose  giving  a  blue 
color  with  iodine  alone,  and  celltdose  giving  a  blue  color  with 
iodine  on  the  addition  of  sulphuric  acid.  The  saliva  acts  on  the 
granulose,  converting  it  into  sugar  ;  it  is  unable  to  act  on  the  cel- 
lulose. When  starch  is  boiled  the  cellulose  coats  of  the  starch- 
corpuscle  are  ruptured  and  the  saliva  has  ready  access  to  the 
granulose.  Hence  the  comparative  rapidity  of  the  action.  In 
raw  starch  the  saliva  can  only  get  at  the  granulose  by  traversing 
the  coat  of  cellulose. 

Brlicke'  distinguishes  in  the  starch-corpuscle,  besides  granulose 
and  cellulose,  a  third  body  which  he  calls  erytkrogranidose.  This 
gives  a  red.  not  a  blue  color  with  iodine,  not  usually  seen  when 
iodine  is  added  to  starch,  because  erythrogranulose  is  much  less 
abundant  than  ordinary  granulose.  Er3'throgranulose  is  con- 
verted by  saliva  into  grape-sugar,  but  not  so  readily  as  granulose. 
Bracke  further  regards  dextrin  resulting  from  the  conversion  of 
starch  as  a  mixture  of  erythrodextrin  giving  a  red  color  with 
iodine,  uchroodextrin  w^hich  is  not  colored  by  iodine.  The  former 
is  readily  converted  b}- saliva  and  similar  agents  into  grape-sugar, 
the  latter  with  considerable  ditiiculty,  if  at  all ;  so  that  a  fluid 
originally  containing  starch,  alter  it  has  been  acted  upon  by  saliva 
until  iodine  gives  no  longer  either  a  blue  or  red  color,  may  still 
contain  a  considerable  quantity  of  dextrin  in  the  form  of  achroo- 
dextrin.     When  starch  is  actecl  upon  by  dilute  acids,  the  conver- 

^  Vorlesungen,  i,  p.  221. 


308      THE    TISSUES    AND    MECHANISMS    OF    LIGESTION. 


sion  into  dextrin  is  prccedod  by  the  api)earancc  of  soluhlc  starrh^ 
i.  €..  of  starch  which,  like  dextrin,  forms  a  clear  soUition  with 
water,  but,  unlike  dextrin,  gives  a  blue  color  with  iodine. 

There  is,  moreover,  some  doubt  whether  the  sugar  resulting 
from  the  action  of  saliva  on  starch  is  all,  or,  indeed,  even  in  ])art 
true  grape-sugar  or  dextrose.  According  to  Musculus  and  v. 
Mering,'  the  products  are  a  small  quantity  of  true  grape-sugar, 
a  large  quantity  (70  per  cent.)  of  the  kind  of  sugar  known  as 
maltose  and  achnxxlextrin.  Maltose,  which,  as  its  name  implies, 
is  produced  by  the  action  of  diastase  on  starch,  is  a  sugar  with 
stronger  rotary  power,  but  with  less  reducing  power  tlian  dex- 
trose ;  it  may  be  converted  into  dextrose  by  the  action  of  dilute 
acids.  ^-  Other  observers''  also  affirm  that  the  sugar  produced  by 
the  action  of  saliva  is  not  true  dextrose,  though  they  do  not  ad- 
mit that  it  is  maltose.  It  is  very  probable  that  future  researches 
may  bring  to  light  many  varieties  of  sugar  allied  to  dextrose, 
possibly  having  different  physiological  properties,  as  well  as  many 
varieties  of  dextrin.  Since  achroodextrin,  which  appears,  ac- 
cording to  all  observers,  to  be  one  of  the  products  of  the  action 
of  saliva,  itself  resists  the  further  action  of  the  ferment,  all  the 
starch  subjected  to  the  action  of  saliva  does  not  pass  into  sugar. 

The  conversion  of  starch  into  sugar,  or  the  amylolytic 
action  of  saliva  will  go  on  at  tiio  ordinary  tem[)erature  of 
the  atmosphere.  The  lower  the  temperature  the  slower  the 
cliange,  and  at  about  0°  C.  the  conversion  is  indefinitely 
prolonged.  After  exi)osure  to  cold  of  even  as  much  as  some 
degrees  below  0^,  when  the  temperature  is  again  raised  the 
action  recommences.  Increase  of  temperature  up  to  about 
85^-40^,  or  even  iiigher,  favors  the  change.  Beyond  60'^  or 
70^  increase  of  temperature  is  injurious,  and  saliva  which 
has  been  boiled  for  a  few  minutes  not  only  has  no  action  on 
starch  while  at  that  temperature,  but  does  not  regain  its 
powers  on  cooling.  By  being  boiled,  the  amylolytic  activity 
of  saliva  is  permanently  destroyed. 

The  action  of  saliva  on  starch  is  favored  by  a  slightly 
alkaline  medium.  It  will,  liowever,  still  go  on  even  in  the 
presence  of  a  small  quantity  of  free  acid.  Increase  of 
acidity,  however,  checks  it.  Thus,  in  a  mixture  containing 
.1  percent,  of  free  hydrochloric  acid,  the  conversion  of  starch 
is  arrested.  After  a  short  exposure  to  a  dilute  acid,  saliva 
will  regain  its  powers  on  neutralization.  Its  activity  is, 
however,  permanently  destroyed  by  long  exposure  to  weak, 

'  Zt.  f.  Physiol.  Chem.,  ii  (1879),  p.  403.  ^  f^eg  Appendix. 

3  Nasse,  PHiiger's  Archiv,  xiv  (1877),  p.  473.  Seegen,  il)id.,  xix 
(1879),  p.  106. 


SALIVA.  309 

or  by  shorter  exposure  to  strong  acids.     Strong  alkalies  also 
destroy  it. 

Tlie  action  of  saliva  is  ham[)ered  by  tlie  concentrated 
presence  of  the  product  of  its  own  action,  that  is,  of  sugar. 
If  a  small  quantity  of  saliva  be  added  to  a  thick  mass  of 
boiled  staich,  the  action  will  after  awhile  slacken,  and  even- 
tually come  to  almost  a  standstill  long  before  all  the  starch 
has  been  converted.  On  diluting  the  mixture  with  water, 
the  action  will  recommence.  If  tlie  products  of  action  be 
removed  as  soon  as  they  are  formed,  a  small  quantity  of 
saliva  will,  if  sutticient  time  be  allowed,  convert  into  sugar 
a  very  large,  one  might  almost  sa}'  an  indefinite  quantity  of 
starch. 

It  is  at  present  uncertain  whether  the  constituent  of  the  saliva, 
on  which  its  activit}'  depends,  is  at  all  ccmsumed  in  its  action. 
Paschutin^  argues  that  it  is  ;  but  other  observers  litive  come  to  a 
contrar}^  conclusion. 

On  what  ci)nstituent  do  the  amylolytic  virtues  of  saliva 
depend  ? 

If  saliva,  filtered  and  thus  freed  from  mucus  and  the 
formed  constituents,  be  treated  with  ten  or  fifteen  times  its 
bulk  of  alcohol,  a  j^recipitate  containing  all  the  proteid  mat- 
ters takes  place.  Upon  standing  under  the  alcohol  for  some 
time  (several  days,  or  better,  weeks),  tlie  proteids  thus  pre- 
cipitated become  coagulated  and  insoluble  in  water.  Hence, 
an  a([ueous  extract  of  the  precipitate,  made  after  this  inter- 
val, contains  little  or  no  proteid  material.  Yet  it  is  as  ac- 
tive, or  almost  as  active,  as  the  original  saliva  (the  solution 
being  brought  to  the  same  bulk  as  the  saliva).  If  the  pre- 
cipitate be  treated  with  concentrated  glycerin,  very  little 
passes  into  solution.  Xevertlieless,  tlie  glycerin  diluted  with 
water  is  found  to  be  highly  amylolytic.  Now  we  cannot 
say  that  even  this  small  quantity  of  matter  which  is  thus 
soluble  in  glycerin  is  entirely  composed  of  the  really  active 
constituents;  it  may  be,  and  probably  is  a  mixture  of  tiiis 
with  other  l)odies.  An  amylolytic  solution,  free  from  pro- 
teid matter,  may  also  be  prepared  by  Briicke's  method  for 
isolating  pepsin  (see  p.  322);  but  this  also  prol)ably  contains 
other  bodies  besides  the  really  active  constituent;  whatever 
the  active  substance  be  in  itself,  it  exists  in  such  extremely 


Centrbt.  f.  Med.  Wissen.,  1H71. 


oU)     THE    TISSUES    AND    MECHANISMS    OF    DIGESTION. 

small  (luautitios  that  it  has  nevor  yet  hvcu  satisfactoi-ily 
isohitiMl  ;  and,  indci'd,  the  only  evidence  we  have  of  its  ex- 
istence is  the  nianile.station  ol' its  peculiar  powers. 

The  salient  features  of  this  hody,  which  we  ma}^  call 
ph/alin^  aie  then  1st,  its  presence  in  minute  and  almost  in- 
appreciable quantity  ;  2d,  the  close  de}jendence  of  its  activity 
on  temperature  ;  8d,  its  permanent  and  total  destruction  hy 
a  high  temperature  and  hy  chemical  reagents  such  as  strong 
acids  ;  4th.  the  want  of  any  clear  proof  that  it  itself  under- 
goes any  change  during  tiie  manifestation  of  its  powers; 
that  is  to  say,  the  energy  necessary  for  the  transformation 
which  it  etiects  do  s  not  come  out  of  itaclf.  If  it  is  at  all 
used  up  in  its  action,  the  loss  is  rather  that  of  sin.ple  wear 
and  tear  of  a  machine  than  that  of  a  substance  expended  to 
do  work  ;  5th,  the  action  which  it  induces  is  of  such  a  kind 
(s|)litting  up  of  a  molecule  with  assumption  of  water)  as  is 
etlected  by  the  agents  called  catalytic,  and  by  that  particular 
class  of  catalytic  agents  called  hydrolytic 

These  features  mark  out  the  amylolytic  active  body  of 
saliva  as  belonging  to  the  class  of /(^r»i(^/?/.s/'and  we  may 
henceforward  speak  of  the  amylolytic  ferment  of  saliva. 

Mixed  saliva,  whose  i)r(jperties  we  have  just  discussed,  is 
the  result  of  the  mingling  in  various  proportions  of  saliva 
from  the  parotid,  sulnnaxillary,  and  sublingual  glands  with 
the  secretion  from  the  buccal  glands. 

Parotid  saliva,  as  obtained  by  introducing  a  canula  into  the 
Stenonian  duct,  is  clear  and  limpid,  not  viscid  ;  the  reaction  of 
the  first  drops  secreted  is  always  acid,  and  according  to  some 
observers  the  succeeding  portions  are  also  faintly  acid,  except 
when  the  tlow  is  very  copious  ;  other  observers  however  lind 
with  even  a  moderate  tlow  an  alkaline  reaction  after  the  tirst 
drops.''  On  standing,  it  becomes  turbid  from  a  precipitate  of 
calcic  carbonate,  due  to  an  escape  of  carbonic  acid.     It  contains 

^  Ferments  may,  for  the  present  at  least,  be  divided  into  two  classes, 
commonly  called  oryaaized  and  uiiorrjanized.  Of  the  ibrmer,  yeast  may 
be  taken  as  a  well-known  example.  The  fermentative  activity  of  yeast 
which  leads  to  the  conversion  of  sugar  into  alcohol,  is  dependent  on  the 
life  of  the  yeast-cell.  Unless  the  yeast-cell  be  living  and  functional, 
fermentation  does  not  take  place  ;  wlien  the  yeast-cell  dies  fermentation 
ceases;  and  no  snbstance  ol)tainetl  from  yeast,  1)V  precipitation  with  al- 
cohol or  otherwise,  will  give  rise  to  alcoholic  iermcntation.  The  sali- 
vary ferment  belongs  to  tlie  latter  class;  it  is  a  substance,  not  a  living 
organism  like  veast. 

«  Astasciiewsky,  Cbt.  Med.  Wiss.,  1878,  p.  2o7. 


SALIVA.  311 


globulin  and  some  other  forms  of  albumin,  with  little  or  no  mu- 
cin. Potassium  sulphocyanate  is  present,  but  structural  ele- 
ments are  absent.     In  man,  at  least,  it  acts  powerfully  on  starch. 

Submaxillary  saliva,  as  obtained  by  introducing  a  canula 
into  the  duct  of  Wharton,  dilfers  from  parotid  saliva  in  being 
more  alkaline  and,  from  the  presence  of  mucus,  more  viscid  ;  it 
contains,  often  in  abundance,  salivary  corpuscles,  and  amor- 
phous masses  of  proteid  material.  The  so-called  chorda  saliva 
in  the  dog  (see  Sec.  2)  is  under  ordinary  circumstances  thinner 
and  less  viscid,  contains  less  mucus,  and  fewer  structural  ele- 
ments, than  the  so-called  sympathetic  saliva,  which  is  remarkable 
for  its  viscidity,  its  structural  elements,  and  for  its  larger  total  of 
solids. 

Sublingual  saliva  is  more  viscid,  and  contains  more  mucin  and 
more  total  solids  (in  the  dog  2.75  per  cent.),  than  even  the  sub- 
maxillary saliva. 

Tiie  action  of  saliva  varies  in  intensity  in  different  ani- 
mals. 

Thus  in  man,  the  pig,  the  guinea-pig,  and  the  rat,  both  parotid 
and  submaxillary  and  mixed  saliva  are  amylolytic  ;  the  submax- 
illary saliva  (or  infusion  of  gland)  being  in  most  cases  more 
active  than  the  parotid/  In  the  rabbit  the  submaxillary  saliva 
is  said  to  have  scarcely  any  action,  while  that  of  the  parotid  is 
energetic.  In  the  dog  parotid  saliva  is  wholly  inert  on  starch, 
submaxillary  and  mixed  saliva  have  a  slight  etfect  only  ;  the 
saliva  of  the  cat  is  more  active  than  that  of  the  dog.  In  the 
horse,  sheep,  and  ox  the  amylolytic  powers  of  eiiher  mixed 
saliva,  or  of  an}*  one  of  the  constituent  juices,  are  extremely 
feeble. 

Wiiere  the  saliva  of  any  gland  is  active,  an  aqueous  infu- 
sion of  the  same  gland  is  also  active.  The  importance  and 
bearing  of  this  statement  will  be  seen  later  on.  From  the 
aqueous  infusion  of  the  glaiul,  as  from  saliva  itself,  the  fer- 
ment may  be  approximate!}^  isolated. 

In  some  cases  at.  least  a  ferment  may  be  extracted  from  the 
'gland  even  when  the  secretion  is  itself  inactive. 

The  readiest  method  indeed  of  preparing  from  the  gland 
a  highly  amylolytic  liquid  as  free  as  possible  from  proteid 
and  other  impurities,  is  to  mince  the  gland  finely,  dehydrate 
it  b}'  allowing  it  to  stand  under  absolute  alcohol  for  some 
days,  and  then,  having  poui-ed  off  most  of  the  alcohol,  and 

^  Griitzner,  Pfliiger's  Archiv,  xvi,  1877,  p.  105. 


312      THE    TISSUES     AND    MECHANISMS    OF    DIGESTION. 

rcuiovLM]  the  reinaiiuUu'  hy  evaporalion  at  a  low  tcmporature, 
to  cover  tlie  [)ieces  of  gland  with  strong  glycerin.  A  mere 
drop  of  such  a  glycerin  extract  rapidly  converts  starch 
into  gra[)e-sugar. 

IPht/fiioIof/icaJ  Anafomij  of  (he  Mucous  Membrane  of  the 
Stomach. 

The  mucous  membrane  of  the  stomach  is  soft  and  velvety, 
and  of  a  pale  grayisli  color.  It  is  lined  throughout  witii  col- 
umnar epithelium.   When  the  stomach  is  empty,  the  muscular 


Fl(i.  89. 


Fig.  9a. 


.\.L'     :%^-      --^ 


Fir,.  89.— Capillary  Network  of  the  Lining  Membrane  of  the  Stomach,  with  the 
Orifices  of  the  Gastric  Follicles. 

Fig.  90.— Vertical  Section  of  the  Mucous  Membrane  of  the  Stomach,  near  the 
Pylorus  ;  maj^nified  20  times. 


walls   contract  and  cause  the  mucous  membrane    to  form 
numerous  longitudinal  folds,  which  are  termed  rugte.   If  the 


THE    MUCOUS    MEMBRANE    OF    THE    STOMACH.      313 

surface  be  examined  with  the  aid  of  a  lens,  numerous  vas- 
cular ridges  or  processes  will  he  seen,  at  the  bases  of  which 
are  numbers  of  minute  openings,  which  are  the  orifices  of 
the  gadric  follicles  or  glands  (Fig.  89).     If  a  vertical  sec- 


FiG.  91. 


L 


■J 


FiCi.  92. 


''  ^  {.^  -j'l 


Fig.  93. 


Fig.  91.— Peptic  Gastric  Gland,  a,  common  trunk;  h,  h,  its  chief  branches;  c,  c, 
terminal  caeca  with  spheroidal  or  "peptic"  gland-cells. 

Fig.  92. — Portions  of  one  of  the  Cseca  more  highly  magnified,  as  seen  longitudi- 
nally (a),  and  in  transverse  section  (b).  a,  basement-membrane  ;  h,  large  glandular 
or  peptic  cell ;  c,  small  "  central  "  epithelium  cells  surrounding  the  cavity. 

Fig.  93.— Mucous  Gastric  Gland,  with  Cylinder  Epithelium,  a,  wide  trunk  ;  ft,  h,  its 
caecal  appendages. 


tion  be  made  of  the  membrane  (Fig.  90),  it  will  be  seen  to 
consist  of  tubuli  closely  arranged  side  by  side,  and  resting 
upon  a  sul)mucous  fibrous  tissue  which  contains  a  layer  of 
unstriated   muscular  fibres,  called  the  muscularis  mucosas. 


314      THE    TISSUES    AND    MECHANISMS    OF    DIGESTION. 

Those  muscular  fibres  are  entirely  distiuct  from  the  museles 
fonniui!;  the  stouiaehial  walls.  The  tul)uli  or  <:;astric  glands 
forui  the  greater  [)ortion  of  the  thickness  of  the  mucous  mem- 
brane, and  according  to  Sappey,  they  number  about  five 
millions.  They  are  bound  togetlnu-  l)y  an  adenoid  tissue  and 
surrounded  by  plexuses  of  capillaiies.  The  nerves  are  de- 
rived from  the  })neumogastric  and  sym]iathetic. 

The  gastric  glands  consist  of  two  })i"incii)al  kinds  :  the 
prptic  and  mucous.  The  peptic  glands  (Figs.  91  and  *.)2)  are 
distributed  over  nearly  the  whole  area  of  the  mucous  mem- 
brane. Near  the  indorus  the  peptic  glands  are  al>sent.  They 
consist  of  a  trunk  with  its  branching  divisions  and  terminal 
canals,  or  cteca.  Tiie  trunk  at  the  superficial  extremity  has 
an  open  orifice  on  the  surface  of  the  membrane,  at  the  other 
extremity  it  terminates  in  two  or  more  branching  divisions; 
these  divisions  are  again  subdivided  into  small  canals,  which 
are  the  cteca.  The  canals  are  lined  by  a  wall  of  small  epithe- 
lium cells.  Surrounding  this  wall  is  a  compact  layer  of  larger 
spheroidal  nucleated  or  ovoidal  granular  protoplasmic  cells. 
These  cells  are  i)robably  the  cells  which  secrete  the  gastric 
juice.  The  trunk  and  its  primary  divisions  are  lined  with 
columnar  epithelium. 

The  mucous  glands  are  found  in  greatest  number  about 
the  region  of  the  cardia  and  pylorus.  Their  princi|)al  struc- 
tural difference  from  the  peptic  glands  is  in  the  c;ecal  ap- 
pendages and  in  the  epithelial  lining.  (Fig.  93).  The  cffical 
appendages  are  very  short  as  compared  vvith  those  of  tiie 
peptic  glands,  and  the  glands  are  lined  throughout  with 
columnar  epithelium.  The  function  of  the  mucous  glands 
and  probably  of  the  columnar  epithelium  of  the  peptic  glands 
is  to  secrete  mucus. 

Within  the  membrane  are  found  a  variable  number  of  small 
lenticular  glands.  These  are  closed  sacs,  and  are  similar  in 
structure  to  the  solitary  glands  of  the  small  intestines.  They 
are  probably  accessories  of  the  lymphatic  system.] 

Gastric  Juice. 

Gastric  juice,  obtained  bj'  artificial  stimulation  from  the 
healthy  stomach  of  a  fasting  dog,  by  means  of  a  gastric  fistula, 
is  a  thin  almost  colorless  fluid  with  a  sour  taste  and  odor. 

In  the  operation  for  gastric  fistula,  an  incision  is  made  through 
the  abdominal  walls,  along  the  linea  alba,  the  stomach  is  opened, 
and  the  lips  of  the  gastric  wound  securely  sewn  to  those  of  the 
incision  in  the  abdominal  walls.     Union  soon  takes  place,  so  that 


GASTRIC    JUICE.  315 


a  permanent  opening  from  the  exterior  into  the  inside  of  the 
stomach  is  established.  A  tube  of  proper  construction,  intro- 
duced at  the  time  of  the  operation,  becomes  finnl}^  secured  in 
place  by  the  contraction  of  healing.  Through  the  tube  the  con- 
tents of  the  stomach  can  be  received,  and  the  mucous  membrane 
stimulated  at  pleasure. 

When  obtained  from  a  natural  fistula  in  man,  its  specific 
gravity  has  lieen  foumi  to  differ  little  from  that  of  water, 
varyingr  from  1.00 1  to  1.010,  and  the  amount  of  solids  pres- 
ent to  be  ver}'  small,  viz.,  about  .56  per  cent. 

In  the  dog.  Bidder  and  Schmidt'  found  the  amount  of  solids 
to  be  as  much  as  2.7  per  cent.,  and  in  the  sheep  1.9  ;  from  this  it 
might  be  inferred  that  the  estimate  given  above  for  man  repre- 
sents not  a  thoroughly  healthy  but  a  diluted  juice.  But  Heid- 
enhain-  finds  in  the  dog,  that  the  secretion  of  the  isolated  fundus 
of  the  stomach  does  not  contain  more  than  .45  percent,  of  solids, 
and  the  higher  figures  of  Bidder  and  Schmidt  are  probably  due 
to  an  admixture  with  remnants  of  digested  food  and  secretions 
of  the  oesophagus  and  mouth. 

Of  these  about  half,  .24  per  cent.,  are  inorganic  salts, 
chiefly  alkaline  (^sodium)  chlorides,  with  small  quantities  of 
phosphates.  The  organic  material  consists  of  pepsin,  a  body 
to  he  described  immediately,  mixed  with  other  substances 
of  nndetermined  nature.  In  a  healthy  stomach  gastric  juice 
contains  a  very  small  quantity  only  of  mucus,  unless  some 
submaxillary  saliva  lias  been  swallowed. 

The  reaction  is  distinctly  acid,  and  the  acidity  is  nor- 
mally due  to  free  hydrochloric  acid.  This  is  proved  by  the 
fact  that  the  amount  of  hydrochloric  acid  is  more  than  can 
be  neutralized  by  the  bases,  and  the  excess  corresponds  to 
the  quantity  of  free  acid  present.''  Lactic  and  butyric,  and 
other  acids  when  present,  are  secondary  products,  arising 
either  by  their  res|^)ective  fermentations  from  articles  of  food, 
or  from  decomposition  of  their  alkaline  or  other  salts.  In 
man  the  amount  of  free  hydrochloric  acid  in  healthy  juice 
is  probably  about  .2  per  cent.* 

^  Bidder  u.  Schmidt,  Die  Verdauungssafte,  p.  73. 

2  Pfliiger's  Archiv,  xix,  1879,  p.  148. 

3  Bidder  u.  Schmidt,  op.  cit.  Ricliet,  Journ.  de  I'Anat.  et  de  la 
Phy.siol.,  xiv  (1878),  p.  170.  Szaho,  Zt.  f.  Phvsiol.  Chem.,  i  (1877),  p. 
140.     Reoch,  Journ.  of  Anat.  and  PliysioL,  viii  (1874),  p.  274. 

*  liicliet,  op.  cit.     Szabo,  op,  cit. 


^1()      THE    TISSUES    AND    MECHANISMS    OF    DIGESTION. 


Tlie  aincnint  of  free  acid  actunlly  found  l)y  ]jid(l(T  and  Sdimidt 
in  the  Juice  whose  speeilic  m-avily  is  uiveii  al)ov(!  was  only  .02  per 
per  cent.,  but  this  is  iindouhledly  below  the  normal  of  health, 
and,  indeed,  in  the  doi:;.  Bidder  and  Schmidt'  found  free  acid  to 
the  extent  of  .3  per  cent.,  and  in  the  sheej)  .123  per  cent.,  while 
Ileidenhain^  obtained  by  his  method  a  percentage  in  the  dog  as 
high  as  ."). 

According  to  Richet,'  the  acid  does  not  behave  exactly  as  does 
absolutely  fn^e  hydrochloric  acid  ;  he  infers  that  it  exists  in  com- 
bination with  some  substance  which  does  not  destroy  its  free 
acidity.  The  same  observer  states  that  lactic  acid  makes  its  ap- 
pearance in  gastric  juice  on  keeping,  even  when  unmixed  with 
food. 

On  starch  gastric  juice  has,  ppr  .vp.  no  effect  whatever; 
indeed,  the  acidity  of  the  juice  tends  to  weaken,  and  may 
possibly  be  sullicient  to  arrest  the  amylolytic  action  of  aiiy 
saliva  with  which  it  may  be  mixed. 

On  gia[)e-sugar  and  cane  sugar  health}'  gastric  juice  has 
no  elkct. 

When  the  stomach  contains  mucus,  gastric  juice  has  the  power 
of  converting  cane-sugar  into  grai)e-sugar.  This  power  seems  to 
be  due  to  the  presence  in  the  nuicus  of  a  special  ferment,  anal- 
ogous to,  but  quite  distinct  fr(jm  the  ])tyalin  of  saliva.  An  ex- 
cessive quantity  of  cane-sugar  introduced  into  the  stomach  causes 
a  secretion  of  mucus,  and  hence  provides  for  its  own  conversion.* 

On  fats  gastric  juice  is  powerless.  They  undergo  by  rea- 
son of  it  no  change  whatever  in  themselves.  When  adipose 
tissue  is  eaten,  all  that  happens  in  the  stomach  is  that  the 
proteid  and  gelatin iferous  envelopes  of  the  fat-cells  are  dis- 
solved and  the  fats  set  free;  the  fat  itself  undergoes  no 
change  except  the  very  slightest  emulsion. 

Such  minerals  as  are  soluble  in  free  hydrochloric  acid  are 
for  the  most  part  dissolved  ;  though  there  is  a  difference  in 
this  respect  between  gastric  juice  and  simple  free  hydro- 
chloric acid  diluted  with  water  to  the  same  degree  of  acidity 
as  the  juice. 

The  essential  property  of  gastric  juice  is  the  power  of 
dissolving  proteid  matters,  and  of  converting  them  into  a 
substance  called  peptone. 

'  Op.  cit.  2  Op.  cit.  ^  Op.  cit. 

*  Huppe-Seyler,  Yircliow's  Arcliiv,  x  (185G),  p.  144. 


GASTRIC    JUICE.  317 

Action  of  Gastric  Juice  on  Proteids. — The  results  are  es- 
sentially the  same  whether  natural  juice  obtained  by  means 
of  a  fistula  or  artificial  juice,  i.  e.,  an  acid  infusion  of  the 
raucous  membrane  of  the  stomach  be  used. 

Artificial  gastric  juice  may  be  prepared  in  any  of  the  following 
ways  : 

1.  B}'  scraping  the  surface  of  a  (pig's  or  dog's)  stomach,  rub- 
bing up  the  scrapings  with  pounded  glass  and  water  in  a  mortar, 
filtering,  and  adding  hydrochloric  acid,  till  the  filtrate,  which  is 
in  itself  simiewhat  acid,  has  a  free  acidity  corresponding  to  .2  per 
cent,  of  hydrochloric  acid.  The  juice  thus  prepared  contains  but 
little  peptone,  but  is  not  verj'  potent. 

2.  By  removing  the  mucous  membrane  from  the  muscular  coat, 
mincing  the  fornier  finely,  and  allowing  it  to  digest  at  35^  C.  in 
a  largequantity  of  hydrochloric  acid  diluted  to  .2  per  cent.  The 
greater  part  of  the  membrane  disappears,  shreds  only  being  left, 
and  the  somewhat  opalescent  liquid  can  be  decanted  and  filtered. 
The  filtrate  has  powerful  digestive  (peptic)  properties,  but  con- 
tains a  considerable  amount  of  the  products  of  digestion  (pep- 
tone, etc.),  arising  from  the  digestion  of  the  mucous  membrane 
itself.  1 

3.  From  the  mucous  membrane,  similarly  prepared  and  minced, 
the  superfluous  moisture  is  removed  with  blotting-paper,  and  the 
pieces  are  thrown  into  a  comparatively  large  quantity  of  concen- 
trated glycerin,  and  allowed  to  stand.  The  membrane  may  be 
previously  dehydrated  by  being  allowed  to  stand  under  alcohol, 
but  this  is  not  necessary.  The  decanted  clear  glycerin,  in  which 
scarcely  any  of  the  ordinar}-  proteids  of  the  mucous  membrane 
are  dissolved,  if  added  to  hydrochloric  acid  of  .2  per  cent,  (a  few 
drops  of  glycerin  to  100  cc.  of  the  dilute  acid  are  sufficient), 
makes  an  artificial  juice  free  from  ordinarj^  proteids  and  peptone, 
and  of  remarkable  potency,  the  presence  of  the  glycerin  not  in- 
terfering with  the  results. 

If  a  few  shreds 'of  fibrin,  obtained  by  whii)ping  blood, 
after  being  thoroughly  washed  and. boiled,  be  thrown  into  a 
quantity  of  gastric  juice,  and  the  mixture  exposed  to  a  tem- 
perature of  from  35°  to  40°  C,  the  fibrin  will  speedily,  in 
some  cases  in  a  few  minutes,  be  dissolved.  The  shreds  first 
swell  up  and  become  transparent,  then  fall  to  pieces  into 
flakes  especially  when  the  vessel  containing  them  is  shaken, 

^  These,  hovrever,  may  be  removed  by  concentration  at  40°  C,  and 
subsequent  dialysis. 

27 


818      THE    TISSUES    AND    xMECUANISMS    OF    DIGESTION. 

and  rmjilly  disappear  willi  the  exception  of  a  little  granular 
debris,  tiie  amount  of  whicii  varies  according  to  circuni- 
vStances. 

If  small  morsels  of  coagulated  albumen,  sucli  as  winte  of 
egg,  be  treated  in  the  same  way,  the  same  solution  is  ob- 
served. The  pieces  become  trans[)arent  at  their  surfaces; 
this  is  especially  seen  at  the  edges,  which  gradually  become 
rounded  down  ;  and  solution  steadily  i)rogresses  from  the 
outside  of  the  pieces  inwards. 

If  any  other  form  of  coagulated  all)umin  (c.  f/.,  precipi- 
tated acid  or  alkali  albumin,  suspended  in  water  and  boiled) 
he  treated  in  the  same  way,  a  similar  solution  takes  place. 
The  readiness  with  which  the  solution  is  elfected  will  de- 
pend, CrPleris  parihuii^  on  the  smallness  of  the  i)ieces.  or 
lather  on  the  amount  of  surface  as  compared  with  bulk, 
which  is  presented  to  the  action  of  the  juice. 

Gastric  juice  then  readily  dissolves  coagulated  proteids, 
which  otherwise  are  insoluble,  or  soluble  onl\',  and  that  with 
ditticulty,  in  very  strong  acids. 

Nature  of  the  Change  as  shown  by  the  Products  of  the 
Action  — If  raw  white  of  Qg'^,  largely  diluted  with  water  and 
strained,  l)e  treated  with  a  suMicient  quantity  of  dilute  hydro- 
cldoric  acid,  the  opalescence  or  turbidity  which  ai)peared  in 
the  white  of  agg  on  dilution,  and  which  is  due  to  the  pre- 
cipitation of  various  foi-ms  of  globulin,  disappears,  and  a 
clear  mixture  results.  If  a  portion  of  the  mixture  be  at 
once  boiled,  a  large  deposit  of  coagulated  albumin  occurs. 
If,  however,  the  mixture  be  exposed  to  35^  or  40^  C.  for 
some  time,  the  amount  of  coagulation  which  is  produced  by 
l)oiling  a  specimen  becomes  less,  and,  finally,  boiling  pro- 
duces no  coagulation  whatever.  By  neutralization,  how- 
ever, the  whole  of  the  albumin  (with  such  restrictions  as  the 
presence  of  certain  neutral  salts  may  cause)  may  be  oli- 
tained  in  the  form  of  aci<l-albumin  or  syntonin,  the  filtrate 
after  neutralization  containing  no  proteids  at  all  (or  a  veiy 
small  quantit}')-  Thus  the  whole  of  the  albumin  present  in 
the  white  of  egg  is  converted,  by  the  simple  action  of  dilute 
hydrochloric  acid,  into  acid-ali)umin  or  syntonin.  • 

If  the  snme  white  of  egg  be  treated  with  gastric  juice  in- 
stead of  simple  dilute  hydrochloric  acid,  the  events  for  some 
time  seem  the  same.  Thus  after  awhile  boiling  causes  no 
coagulation,  while  neutralization  gives  a  considerable  pre- 
cipitate of  a  proteid   body,  which,  being  insoluble  in  water 


GASTRIC    JUICE.  319 


and  ill  dilute  sodium  chloride  solutions,  and  soluble  in  dilute 
alkali  and  acids,  at  least  closely  resembles  syntonin.  But  it 
is  found  that  only  a  portion  of  the  proteids  originally  present 
in  the  white  of  egs;  can  thus  be  regained  by  precipitation. 
A  great  deal  is  still  retained  in  tiie  filtrate  after  neutraliza- 
tion, in  the  form  of  what  is  called  peptone^  and.  on  the  whole, 
the  longer  the  digestion  is  carried  on  the  greater  is  the  i)ro- 
portion  borne  by  the  peptone  to  the  precipitate  thrown 
down  on  neutralization  ;  indeed,  in  some  cases  at  all  events, 
all  the  proteids  are  brought  into  the  condition  of  peptone. 

Peptone  is  a  proteid,  having  the  same  approximate  tde- 
mentar\*  composition  as  other  proteids,  and  giving  most  of 
the  usual  proteid  reactions. 

It  is  distinguished  from  other  proteids  by  the  following 
marked  features  ; 

1st.  It  is  not  precipitated  by  potassium  ferrocyanide  and 
acetic  acid,  as  are  all  other  proteids. 

2d.  Though  soluble  in  distilled  water  and  in  neutral  saline 
solutions,  even  the  most  dilute,  and  therefore  not  precipi- 
tated from  its  acid  or  alkaline  solutions  by  neutralization, 
it  is  not,  like  the  other  similarly  soluble  proteids  coagulated 
by  heat. 

3d.  It  is  highly-  diffusible,  passing  through  membranes 
with  the  greatest  ease.  (For  the  other  less  important  reac- 
tions see  Appendix.) 

The  neutralization  precipitate  resembles,  in  its  general 
characters,  acid  albumin  or  syntonin.  Since,  however,  it 
probably  is  distinguishable  from  the  body  or  bodies  produced 
by  the  action  of  simple  acid  on  muscle  or  white  of  egg,  it  is 
best  to  reserve  for  it  the  name  of  2^araj)eptone.  Thus  the 
digestion  by  gastric  juice  of  white  of  egg  results  in  the  con- 
version of  all  the  proteids  present  into  peptone  and  para- 
peptone,  of  which  the  former  must  be  considered  as  the  final 
and  chief  product,  the  latter  a  by-product  or  initial  product 
of  variable  occurrence  and  importance.  The  gastric  diges- 
tion of  fibrin,  either  raw  or  boiled,  and  of  all  forms  of  coag- 
ulated albumin,  gives  rise  to  the  same  products,  peptone 
and  parapeptone.  Milk  when  treated  with  gastric  juice  is 
first  of  all  coagulated  or  curdled.  This  is  the  result  partly 
of  the  action  of  the  free  acid  and  partly  of  the  special  action 


320      THE    TISSUES    AND    MECHANISMS    OF    DIGESTION. 

of  a  i)articiilar  constituent  of  <;asti'ic  juice,  of  which  we  shall 
speak  hereafter.  Tl»e  conouhited  milk  is  subsecjuently  dis- 
solved with  the  same  appeaniiice  of  peptone  and  j)arapep- 
tone  as  in  the  case  of  other  proteids.  Jn  fact,  the  (ligeslion 
by  gastric  juice  of  all  the  varieties  of  proteids  consists  in  the 
conversion  of  the  proteid  into  peptone,  with  the  concomitant 
appearance  of  a  certain  variable  amount  of  parapeptone. 

AVhen  raw  unboiled  fibrin  is  treated  witb  gastric  juice,  the  di- 
gesting mixture  is  found,  when  examined  immediately  after  the 
solution  of  the  Iil)rin,  to  contain,  in  addition  to  peptone  and  ])ara- 
peptone,  soluble  albumin  coagulable  by  heat.  No  such  soluble 
albumin  is  formed  during  the  digestion  of  boiled  tibrin  or  of  any 
form  of  coagulated  albumin. 

Circumstances  Affecting  Gastric  Digestion. — In  order  to 
come  to  a  satisfactory  conclusion  on  tiiis  matter  it  is  de- 
sirable to  use  the  same  proteid  in  all  the  experiments;  and 
of  all  proteids  fibrin  is  most  convenient.  It  should  be  boiled 
rather  than  raw,  because  the  latter  is,  for  reasons  of  which 
we  shall  speak  presently,  soluble  to  a  certain  extent  in  dilute 
acids  alone.  Since,  as  will  be  seen,  a  given  amount  of  gas- 
tric juice  may.  by  proper  management,  be  made  to  digest 
an  almost  indefinite  cpiantity  of  fibrin  if  sulficient  time  be 
allowed,  we  are  obliged  to  take,  as  a  measure  of  the  activity 
of  a  specimen  of  gastric  juice,  the  rapidity  with  which  it  dis- 
solves a  given  quantity  of  fibrin. 

The  greater  the  surface  presented  to  the  action  of  the 
juice  the  more  rapid  the  solution.  Hence  minute  division 
and  constant  movement  favor  digestion.  Neutralization  of 
the  juice  wholly  arrests  digestion.  Fibrin  may  be  submitted 
for  an  almost  indefinite  time  to  the  action  of  neutralized 
gastric  juice  without  being  digested.  If  the  neutralized  juice 
be  again  properly  acidified  it  becomes  quite  as  active  as  be- 
fore. Digestion  is  most  rapid  with  dilute  hydrochloric  acid 
of  .2  per  cent  (the  acidity  of  natural  gastric  juice).  If  the 
juice  contains  much  more  or  much  less  free  acid  than  this 
its  activit}^  is  visibly  im[)aired.  Other  acids,  lactic,  phos- 
phoric, etc.,  may  be  substituted  for  hydrochloric;  but  they 
are  not  so  effectual,  and  the  degree  of  acidity  most  useful 
varies  with  the  difierent  acids.  The  presence  of  neutral  salts, 
especially  sodium  chloride,  in  excess  is  injurious.'  The  pres- 
ence in  a  concentrated  form  of  the  [)roducts  of  digestion  hin- 


•   A.  Schmidt,  Pfluger's  Archiv,  xiii  (1876),  p.  93. 


GASTRIC    JUICE.  321 

ders  the  process.  If  a  large  quantity  of  fibrin  be  placed  in 
a  small  quantity  of  juice  digestion  is  soon  arrested  ;  on  dilu- 
tion vvith  the  normal  hydrochloric  acid  (.2  per  cent.),  or  if 
the  mixture  be  submitted  to  dial^  sis,  and  its  acidity  be  kept 
up  to  the  normal,  the  action  recommences.  Digestion  is 
most  rapid  at  about  o5°-40^  C. ;  at  the  ordinary  temper- 
ature it  is  much  slower,  and  at  about  0^  C.  ceases  altogether. 
Gastric  juice  may  be  kept,  however,  at  0°  C.  for  an  indeti- 
nite  period  without  injury  to  its  powers. 

The  gastric  juice  of  cold-blooded  vertebrates  is  relatively  more 
active  at  low^  temperatures  than  that  of  warm-blooded  mammals 
or  birds  ;  whether  this  is  due  to  a  diflerent  nature  of  the  gastric 
juice,  or  to  attendant  circumstances,  is  uncertain.^  The  digestive 
tiuids  in  the  stomachs  or  intestines  of  invertebrata  frequently  con- 
tain a  ferment  Avholly  similar  to  pepsin,  but  mixed  with  another 
proteolytic  ferment  resembling  that  of  the  pancreas.-^ 

At  temperatures  much  above  40°  or  45^  the  action  of  the 
luice  is  impaired.  By  boiling  for  a  few  minutes  the  activity 
of  the  most  powerful  juice  is  irrevocably  destroyed.  By 
removing  the  products  of  digestion  as  fast  as  they  are 
formed,  and  by  keeping  up  the  acidity  to  the  normal,  a  given 
amount  of  gastric  juice  may  be  made  to  digest  an  almost 
unlinnted  quantity  of  proteid.  This  shows  that  the  energies 
of  the  juice  are  not  exhausted  by  the  act  of  digestion. 

It  has  been  debated  whether  this  statement  is  absolutely  true. 
Eansome,^  however,  thinks  that  the  powers  of  the  juice  are  even 
increased  by  action. 

Nature  of  the  Action. — All  these  facts  go  to  show  that  the 
digestive  action  of  gastric  juice  on  proteids,  like  that  of 
saliva  on  starch,  is  a  ferment  action  ;  in  other  words,  that 
the  solvent  action  of  gastric  juice  is  essentially  due  to  the 
l)resence  in  it  of  a  ferment  bcjdy.  To  this  ferment  body, 
whicii  as  yet  has  been  oidy  approximately  isolated,  the  name 
of  pejjfiiii  has  been  given.  The  glycerin  extract  of  mucous 
membrane,  especially  of  that  which  has  been  dehydrated, 
contains  a  minimal  quantity  of  proteid  matter,  and  yet  is 
intensely  active.  The  elaborate  method  of  Briicke  gives  us 
a  residue  which  possesses  none  of  the  ordinary  proteid  re- 
actions, and  yet  in  concert  with  normal  dilute  hydrochloric 
acid  is   peptic  in  the  highest  degree.     We  may,  therefore, 

1  Fick,  Arbehen  Physiol.  Lab.  Wurz.  ii  (1873),  p.  181. 

2  Krukenberg,  Unt.  Phys.  Jnst.  Heidelberg,  i  (1877),  p.  327,  ii  (1877), 
p.  1,  p.  261  ;  also  Hoppe-'Seyler,  Priiiger's  Archiv,  xiv  (1877),  p.  395. 

^  Journ.  Anat.  Phys.  (1876),  vol.  x. 


3:22    THE  TISSUES   and  mechanisms  of  digestion. 

safely  assert  that  pepsin  is  not  a  proteid.  IJiiicke's  residue 
contained  nitrogen,  but  it  would  be  hazardous  to  assert  that 
that  residue  was  nothing  but  pepsin.  At  present  the  mani- 
festation of  peptic  powers  is  our  only  test  of  the  presence 
of  pepsin. 

Bruckc"'s'  method  is  as  follo\vs  :  Gastric  mucous  membrane  is 
digested  with  dilute  iihosjjhoric,  instead  of  hydrochloric,  acid.  To 
the  filtered  digest  clear  lime-water  is  added, until  a  viok't  reaction 
with  litmus  is  gained.  The  bulky  precipitate  of  calcium  phos- 
phate carries  down  with  it  mechanically  the  greater  part  of  the 
pepsin  ;  the  supernatant  tiuid  when  reacidified  has  very  little 
peptic  power.  The  precipitate  is  collected,  pressed,  suspended 
in  water,  and  redissolved  carefully,  with  a  minimal  quantity  of 
dilute  hydrochloric  acid,  and  reprecipitated  with  lime-water ; 
much  of  the  peptone  which  went  down  with  the  tirst  })recipitate 
is  thus  left  behind,  wdiile  the  pepsin  still  clings  to  the  calcic  salt. 
The  precipitate  is  ao;ain  dissolved  in  dilute  hydrochloric  acid, 
placed  in  a  tlask,  and  a  solution  of  cholesterin  in  4  parts  alcohol 
to  1  ether  is  poured  in  slowly  through  a  long  funnel  reaching  to 
the  bottom  of  the  flask.  The  cholesterin  rises  as  a  bulky  mass 
to  the  top  of  the  liquid,  carrying  the  pepsin  with  it.  After  sev- 
eral shakings  the  cholesterin  is  collected,  washed  with  water 
acidulated  with  acetic  acid,  and  then  with  pure  water.  While 
still  moist  it  is  transferred  to  a  vessel  and  shaken  with  alcohol- 
free  ether,  wdiich,  dissolvins:  the  cholesterin  and  floating  on  the 
top,  leaves  a  watery  stratum  below^  This  must  be  repeated  until 
all  the  cholesterin  is  dissolved.  The  ether  is  removed,  and  the 
watery  residue  is  filtered.  The  filtrate,  though  it  does  not  give 
the  ordinary  reactions  of  proteids,  is,  when  acidulated,  most 
strongly  peptic.  By  dialysis  it  may  be  still  further  purified  (for 
pepsin  will  not  pass*^  through  ordinary  dialysis  paper)  ;  but  even 
the  dialyzed  fluid  gives  a  precipitate  with  basic  and  neutral  lead 
acetate. 

In  one  important  respect  pepsin,  the  ferment  of  gastric 
juice,  differs  from  ptyalin,  the  ferment  of  saliva.  Though 
saliva  is  most  active  in  a  faintly  alkaline  medium,  there 
seems  to  be  no  special  connection  between  the  ferment  and 
any  alkali.  In  gastric  juice,  however,  there  is  a  strong  tie 
between  the  acid  and  the  ferment,  so  strong  that  some 
writers  speak  of  pepsin  and  hydrochloric  acid  as  forming 
together  a  compound,  peptodiydrochloric  acid. 

In  the  absence  of  exact  knowle<lge  of  the  constitution  of 
proteids,  we  cannot  state  distinctly  what  is  the  precise  na- 
ture of  the  change  into  peptone.  Judging  from  the  analogy 
with  the  action  of  saliva  on  starch,  we  ma}'  fairly  suppose 


Moleschott's  Untersach.,  vi  (18o9j,  p.  479. 


GASTRIC    JUICE.  323 

tliat  the  process  is  at  bottom  one  of  hydration  ;  but  we  liave 
no  exact  proof  that  it  is,  and  it  is  at  least  quite  as  prol)able 
that  peptone  arises  b}-  a  sitnple  splittino-  up  of  hiro^er  pro- 
teid  molecules.  Peptone  closely  resemblino-,  if  not  identical 
with,  that  obtained  by  gastric  digestion,  may  be  obtained 
by  the  action  of  sti'ong  acids,  by  the  prolonged  action  of 
dilute  acids  especially  at  high  temperature,  or  simply  by 
digestion  with  superheated  water  in  a  Papin's  digester. 
The  role  of  pepsin  therefore  is  only  to  facilitate  a  change 
wdiich  may  be  effected  without  it.  Since,  in  the  act  of  diges- 
tion, the  pepsin  itself  is  not  exhausted,  it  is  clear  that  the 
energy  which  is  spent  in  the  conversion  of  the  proteid  into 
pe[)tone  does  not  come  from  the  ferment. 

We  have  seen  that  a  particular  acid  and  a  particular  dilution 
are  most  favorable  to  digestion.  We  may  add,  that  the  natural 
action  of  the  acid  is  modified  b}'  the  presence  of  the  pepsin.  It 
is  not  that  in  digestion  the  acid  converts  the  proteid  into  acid- 
albumin,  wdiich,  in  turn,  is  converted  b}'  the  pepsin  into  peptone. 
Ordinary  albumin  is  less  readil}'  converted  into  neutralization 
products  when  pepsin  is  present,  than  when  pepsin  is  absent,  and, 
as  we  shall  see,  the  neutralization  products  probably  differ  also 
in  nature  in  the  two  cases.  When  bones  are  treated  with  simple 
hydrochloric  acid,  the  earthy  salts  are  dissolved  out,  and  the 
animal  basis  left ;  when  bones  are  treated  with  gastric  juice,  the 
animal  basis  is  acted  on  more  speedily  than  the  earthy  salts. ^ 
The  nature  of  peptic  digestion  will  hmvever  be  more  fully  dis- 
cussed under  pancreatic  digestion. 

All  proteids,  as  far  as  we  know,  are  converted  by  pepsin 
into  pei)tone.  Of  its  action  on  other  nitrogenous  substances 
not  truly  proteid  in  nature,  we  need  only  say  that  mucin, 
nuclein,  and  the  chemical  basis  of  horny  tissues  are  wholly 
unaffected  b}'  it,  but  that  the  gelatiniferous  tissues  are  dis- 
solved and  changed  into  a  substance  so  far  analogous  with 
peptone,  that  the  characteristic  properl}'  of  gelatinization  is 
entirely  lost. 

Chondrin  and  the  elastic  tissues  are  also  dissolved.'' 

Milk  is  peculiarly  affected  by  gastric  juice,  whether  natu- 
ral or  artificial.  It  is  curdled,  that  is  to  say,  its  casein  is 
precipitated.  The  change  will  go  on  at  the  ordinary-  tem- 
perature, l>ut  is  favored  by  that  of  35°-40'^.  This  property 
of  gastric  juice  (which  has  long  betn  known  in  domestic 
life,  the  rennei  used  for  the  purpose  of  curdling  milk  in  the 

'   Kuhne,  Lehrb.,  p.  40.  ^  Etzinger,  Zt.  f.  Biolog.,  x  (1874),  84. 


324     THE    TISSUES    AND    MECHANISMS    OF    DIGESTION. 

Ill  a  nil  fad  lire  of  cliccsc,  or  for  oilier  purposes,  Itciiig  an  infu- 
sion  of  cah'cs'  stomach)  does  not  depend  on  the  acidity  of 
the  juice,  ?'.  r.,  the  casein  is  not  directly  p/iecipitated  by  the 
free  acid  of  the  Juice;  for  neutralized  gastric  juice  is  etlica- 
cious.  Since  the  property  is  lost  when  the  neutralized  juice 
is  boiled,  and  the  effects  are  so  closely  dependent  on  tem- 
perature, it  seems  probable — and  the  conclusion  is  supported 
1>V  other  facts — that  the  ettect  is  produced  b}'  the  action  of 
a  sjiecial  ferment. 

This  ferment  is  not  identical  with  pepsin,  and  ITammarsten' 
has  succeeded  in  separatini;  the  two.  According  to  him  the 
jiresence  of  milk-sugar  is  not  necessary  to  the  change,  and  the 
ferment  itself  does  not  give  rise  to  a  lactic  acid  fermentation. 
He  therefore  docs  not  regard  the  curdling  as  the  mere  })recipita- 
tion  of  casein  caused  by  the  develoi)ment  of  lactic  acid.  He 
believes  the  process  to  be  a  sjiecies  of  coagulation,  in  which  an 
insoluble  casein  arises  from  the  si)litting  up,  under  the  intluence 
of  the  terment,  of  a  previously  soluble  body. 

IP hy biological  Anatomy  of  the  Live7\ 

The  liver  is  the  largest  gland  in  the  body.  Tt  is  very  vas- 
cular, receiving  not  only  the  arterial  blood  from  the  hepatic 

A  Fig.  94-  B 


•'':3 


..•?^?^!>. 


w 


A.  Portion  of  ;i  Hepatic  Column,  from  Human  Liver,  sliowing  its  comjmnent 
socreliuK  cells,  b.  Secreiing  cells  detached.  «,  in  their  normal  slate;  6,  a  cell  more 
highly  magnified,  showing  the  nucleus  aud  distinct  oil-particles;  c,  in  variousstages 
of  fatty  degeneration. 


^  Upsala  Liikareforenings  Forhandlingar,  Bd.  viii  (1872),  p.  63. 


LIVER. 


325 


artery  for  its  own  nutrition  but  also  tlie  Mood  of  tlie  poi'tal 
vein,  whicli  contains  tlie  great  j^ortion  of  the  in-oduets  of 
digestion.  The  blood  is  conveyed  from  the  liver  by  the 
hepatic  veins  which  emi>ty  into  the  inferior  vena  cava.  The 
bile,  which  is  the  principal  secretion  of  the  organ,  is  con- 
ducted from  the  liver  through  two  ducts  which  unite  to  form 
the  hepatic  duct. 


Fig. 


%^ 


^^^ 

M^W 


Cross-section  of  a  Lobule  of  the  Huinan  Liver,  in  whic]!  the  capillary  network  be- 
tween the  Portal  and  Hepatic  Veins  has  been  fully  injected  (from  Sappey)  ^j.  1, 
section  of  the  iH^m-lohular  vein  ;  2,  its  smaller  branches  collecting  blood  from  the 
capillary  network;  3,  m/^7--Iobular  branches  of  the  vena  j)Oitae  with  their  smaller 
ramifications  passing  inwards  towards  the  capillary  network  in  the  substance  of  the 
lobule  — After  Kiukk. 


The  liver  is  covered  with  a  delicate  areolar  tissue  which 
sends  processes  or  trabecul^g  into  its  sulistance  between  the 
lobules.  A  prolongation  of  this  areolar  tissue  accompanies 
the  vessels  as  a  sheath  into^the  organ,  and  is  called  Glisson's 
capsule.  The  liver  is  partially  covered  with  peritoneum, 
which  by  its  reduplications  formsthe  hepatic  ligaments  which 
susi)end  the  viscus  in  the  al)d<;minal  cavity. 

The  sul'Stance  of  the  liver  is  composed  of  lobules  having 
a  polygonal  outline.  These  lobules  are  composed  of  irregu- 
lar polyhedral  rounded  cells,  which  are  granular  and  nucle- 
ated, sometimes  contaiuingtwo  or  moie  nuclei.  (Fig. 91.)  The 

28 


320    THE  TISSUES  and  mechanisms  of  digestion. 


coll  fontonts  are  viscid,  vcllowisli,  and  contain  oil-iilohules. 
Those  colls  comprise  the  secretory  portion  of  tlie  liver. 

Tiie  lolinles  are  extremely  vascular,  and  the  distribution 
of  the  bloodvessels  to  them  is  very  complex.  They  are  ob- 
served to  have  a  large  vessel  in  the  centre,  which,  througli 
its  capillaries,  communicates  with  the  capillaries  of  an  intri- 
cate plexus  of  vessels  coming  from  the  circumference.  The 
portal  vein,  lie[)atic  artery,  and  hepatic  duct  run  in  compau}' 

Fig. 96. 


Longitudinal  Section  of  a  small  Portal  Vein  and  Canal,  a,  portions  of  the  canal 
from  which  the  vein  has  been  removed  ;  b,  the  side  of  the  portal  vein  in  contact  with 
the  canal;  c,  the  side  of  the  vein  which  is  separated  from  the  canal  by  the  hepatic 
artery  and  duct,  with  areolar  tissue  (Glisson's  Capsule);  d,  internal  surface  of  the 
portal  vein,  through  which  are  seen  the  outlines  of  the  lobules  and  the  openings  (e) 
of  the  interlobular  veins;/,  vaginal  veins  of  Kiernan;  g,  liepatic  artery;  h,  hepatic 
duct. 

in  their  distribution.  The  liepatic  vein  and  its  ramifications 
run  independently  of  the  other  vessels.  In  Fig.  96  is  shown 
a  longitudinal  section  of  a  portal  canal,  which  contains  a 
portal  vein,  liepatic  artery,  and  hepatic  duct. 

The  portal  vein  sends  its  branches  between  the  lobules, 
and  are  called  the  wie7--\ohn\aY  veins.  These  veins  form  a 
dense  plexus  of  capillaries  in  the  substance  of  the  lobule,  and 
are  seen  to  communicate  with  other  capillaries  which  con- 
verge and  form  one  large  vein  in  the  centre,  termed  an 
intra-lohiilar  vein.    Between  the  meshes  of  this  intra-lobular 


LIVER, 


327 


capillary  plexus  are  founrl  the  hepatic  cells  (Fig.  95).  The 
inlraAohular  vein  empties  into  a  larger  vein  at  the  base  of 
tlie  lobule,  which  is  called  a  8u6-lobular  vein.  These  sub- 
lobular  veins  unite  to  form  the  hepatic  veins.  (Fig.  97.) 
The  walls  of  the  hepatic  veins  are  very  thin,  and,  unlike  the 


Section  of  a  Portion  of  Liver  passing  longitudinally  through  a  large  Hepatic 
Vein,  from  the  Pig  (after  Kiernan)  f .  H,  hepatic  venous  trunk,  against  which  the 
sides  of  the  lobules  are  applied;  6,  sub-lobular  hepatic  veins,  on  which  the  bases 
of  the  lobules  rest,  and  through  the  coats  of  which  they  are  seen  as  polygonal 
figures ;  a,  a,  walls  of  the  hepatic  venous  canal,  formed  by  the  polygonal  bases  of  the 
lobules. 

portal  veins,  haVe  ho  areolar  investment.  The  distribution 
of  the  hepatic  artery  and  of  the  larger  branches  of  the 
hepatic  duct,  is  similar  to  that  of  the  portal  vein. 

The  larger  branches  of  the  hepatic  ducts  are  lined  with 
cylindrical  epithelium ;  the  smaller  branches  are  lined 
with  spheroidal  epithelium.  The  relation  which  the  ter- 
minal filaments  of  the  duct  bear  to  the  cells  has  not  as 
yet  been  definitely  determined.  The  smaller  biliary  ducts 
form  a  capillary  plexus,  within  the  meshes  of  which  are 
the  hepatic  cells.  (Fig.  98.)     The  ultimate  biliary  ducts  are 


328      THE    TISSUES    AND    MECHANISMS    OF    DIGESTION. 

supposed  to  be  mere  intercellular  passas^es,  haviiifj  no  cell 
wall,  and  measurino;  ahont  2.5  niinin.  in  diameter  (Fiji;.  i)-l). 
The  liver  is  supplied  with  nerves  from  the  sympathetic,  the 
pneumogastric  (the  left  especially),  and  the  right  phrenic. 

On  the  interior  surface  of  the  liver  is  an  accessory  organ, 
called  the  gall-Madder,  which,  during  the  intervals  of  diges- 
tion, serves  as  a  receptacle  for  the  bile.  The  mechanism  by 
which  the  bile  is  carried  into  the  gall-bladder  is  somewhat 
obscure.  The  bile  is  conveyed  from  the  liver  through  the 
hepatic  duct,  which,  uniting  with  the  cystic  duct  of  the  gall- 
bladder, forms  the  ducfus  communis  choledochua^  which 
conveys  the  bile  during  digestion  to  the  duodenum.  The 
mechanismby  which  the  bile  gets  into  the  gall-bladder  is  prob- 


FiG.  98. 


Fig.  9D. 


Fig.  98.— Injected  Biliary  Capillaries  of  the  Liver  of  the  Rabbit.      Part  of  a  lobule 

showing  the  arrangement  of  the  biliary  ducts  in  relation  to  the  hepatic  cells,    a, 

apillaries  of  the  biliary  ducts;  6,  hepatic  cells;  c,  biliary  ducts;  d,  capillary  bluod- 


FiG.  99. — Section  of  Rabbit's  Liver  Injected,     c,  blood  capillaries;  h,  bile  passages; 
n,  nucleus  of  hepatic  cell. 

ablv  due  to  both  a  tonic  condition  of  the  sphincteric  mus- 
cular tilires  surrounding  the  outlet  of  the  ductus  comm^Jnis 
choledochus^  and  a  reversed  peristalsis  of  the  muscular  fibres 
in  the  wall  of  the  duct. 

The  function  of  the  liver  is  both  secretive  and  excretive. 
Its  principal  secretions  are  the  bile  and  a  peculiar  amyloid 
substance  called  glycogen.  Its  principal  excretion  is  an 
alcohol  called  cholesterin.  It  is  supposed  by  Prof.  A.  Flint, 
Jr.,  that  this  substance  is  converted  in  the  intestine  into  a 
new  substance  which  he  calls  stercorin.] 

Bile. 
The  quality  of  bile  varies  much,  not  only  in  different ani 


mals,  but  in  the  same  animal  at  different  times. 


It  is  more- 


BILE.  329 

over  affected  by  the  lengtli  of  the  sojourn  in  the  gall-bladder  ; 
bile  taken  direct  from  tlie  hepatic  duct,  especially  when 
secreted  rapidly,  contains  little  or  no  miieus  :  that  taken 
from  the  gall-bladder,  as  of  slaughtered  oxen  or  slieep,  is 
loaded  with  mucus.  The  color  of  the  bile  of  carnivorous 
and  omnivorous  animals,  and  of  man,  is  a  bright  golden- 
red  ;  of  graminivorous  animals,  a  golden-green,  or  a  bright 
green,  or  a  dirty  green,  according  to  circumstances,  being 
ranch  modified  by  retention  in  the  gall-bladder.  The  reac- 
tion is  alkaline.  The  following  may  be  taken  as  the  average 
composition  of  human  l)ile  (Frerichs). 

In  inoo  parts. 

Water,  859.2 

Solids  : 

Bile  Salts, 91.4 

Fats,  etc., 9.2 

Cholesterin, 2.6 

Mucus  and  pigment,  ....     29.8 

Inorganic  salts, 7.8 

140.8 

The  entire  absence  of  proteids  is  a  marked  feature  of  bile. 
With  regard  to  the  inorganic  salts,  the  points  of  interest 
are  the  presence  of  a  large  quantity  of  sodium  chloride  (.2 
to  .27  per  cent.),  the  presence  of  phosphates,  of  ii'on  (about 
.006  per  cent.  Fe),  manganese,  and  occasionally,  at  all  events, 
of  copper.  The  ash  contains  soda  in  a  very  large  amount, 
and  also  suli)hates.  both  coming  from  the  bile-salts.  The 
constituents  wiiich  deserve  chief  attention  are  the  pigments 
and  the  bile  salts. 

Pigments  of  Bile. — The  natural  golden-red  color  of  normal 
human  or  carnivorous  bile  is  due  to  the  presence  of  Bili- 
ruhin.  This,  which  is  also  the  chief  pigmentary  constituent 
of  gallstones,  and -occurs  largely  in  the  urine  of  jaundice, 
ma}'  be  obtained  in  the  form  either  of  an  orange-colored 
powder,  or  of  well-formed  rhombic  tablets  and  prisms.  In- 
soluble in  water,  and  but  little  soluble  in  ether  and  alcohol, 
it  is  readily  soluble  in  chloroform,  and  in  alkaline  fluids. 
Its  composition  is  CjgH^sXP3.  Treated  with  oxidizing 
agents,  such  as  nitric  acid  yellow  with  nitrous  acid,  it  dis- 
plays a  succession  of  colors  in  order  of  the  spectrum.  The 
yellowish  golden  red  becomes  a  green,  this  a  greenish-blue, 
then  blue,  next  violet,  afterwards  a  dirty  red,  and  finally  a 


OoO     THE    TISSUES    AND    MECHANISMS    OF    DIGESTION. 

I)ale  yellow.  T\\\^  clinractcristic  roacLion  of  l)iliiul)in  is  the 
liasis  of  the  so-ealled  (iiuelin's  test  for  liile-pigments.  Each 
of  these  staovs  represents  ji  distinct  pigmentarv  substance. 
An  alkaline  solution  of  bilirnhin,  exposed  in  a  shallow  vessel 
to  the  action  of  the  air,  turns  green,  becoming  converted 
into  Biliverdin  (C,gH,„N.,0-  or  C,JI,^N.,0^  ^lalyj,  the  green 
pigment  of  the  herbivorous  bile.  Biliverdin  is  also  found 
in  the  edges  of  the  placenta  of  the  bitch,  and  at  times  in  the 
urine  of  jaundice,  and  is  [)robably  the  bod\'  wliich  gives  to 
bile  which  has  been  exposed  to  the  action  of  gastric  juice, 
as  in  biliary  vomits,  its  characteristic  green  hue.  It  is  the 
first  stage  of  the  oxidation  of  l)ilirul)in  in  Gmelin's  test. 
Treated  with  oxidizing  agents  biliverdin  runs  through  the 
same  series  of  colors  as  bilirubin,  with  the  exception  of  the 
initial  golden-red. 

We  have  already  discussed  (p.  58),  the  relation  of  bilirubin  to 
h?ematoidin.  Other  pigments,  bilifascin^  bili2Jrasin,  have  been 
found  in  small  quantities  in  gallstones. 

Fresh  normal  bile,  either  of  man,  the  cow,  the  pig,  or  dog,  ex- 
hibits no  absorption  bands,  though  these  make  their  appearance 
in  the  alcoholic  extracts,  and  when  the  bile  has  become  altered. 

AVhen  bilirubin  has  been  oxidized  down  to  the  last  (yellowish) 
stage  in  Gmelin's  test,  the  liquid  is  found  to  contain  a  body  with 
characteristic  absorption-bands.  To  this  the  name  of  choletelin} 
has  been  given.  Bilirubin  treated,  on  the  other  hand,  with 
reducing  agents  (sodium  amalgam)  is  converted  into  a  body  called 
urobilin  (hydrobilirubin),  also  with  characteristic  spectrum  ap- 
pearances.- 

The  Bile-salts. — These  consist,  in  man  and  many  animals, 
of  sodium  glycocholate,  and  taurocholate^  the  proportion  of 
the  two  varying  in  different  animals.  In  man  both  the  total 
quantity  of  bile-salts  and  the  proportion  of  the  one  bile-salt 
to  the  other  seem  to  var}-  a  good  deal,  but  the  glycocholate  is 
always  the  more  abundant.''  In  ox-gall,  sodium  glycocho- 
late is  abundant  and  taurocholate  scanty.  The  l)ile-salts 
of  the  dog,  cat,  bear,  and  other  carnivora  consist  exclu- 
sively of  the  latter,  the  former  being  entirely  absent. 

In  the  bile  of  the  pig  two  peculiar  acids  are  present,  in  union 
with  sodium,  viz.,  glycohyocholic  and  taurohyocholic,  differing, 

1   Maly,  Wien.  Sitzun.c;sberichte,  Bd.  50  (1869).  2  See  p.  58. 

^  Cf.  jacobsen,  Ber.  d.  dentsch.  C'heni.  Gfcsell.  vi,  p.  1026.  Trifa- 
nowski,  Pfliiger's  Archiv,  ix  (1874),  p.  492.  Socoloff",  ibid.,  xii  (1875), 
p.  54.     Hoppe-Seyler,  Lehrb.  (1878),  p.  301. 


BILE.  331 


however,  but  slightly  from  the  above.     Similarly,  the  bile  of  the 
goose  contains  taurochenoeholic  acid. 

Insoluble  in  ether  but  soluble  in  alcobol  and  in  water, 
the  aqueous  solutioi.s  having  a  decided  alkaline  reaction, 
both  salts  ma}'  be  obtained  by  crystallization  in  fine  acic- 
ular  needles.  They  are  exceedingh'  deliquescent.  The 
solutions  of  both  acids  have  a  dextro-rotary  action  on  polar- 
ized light. 

Preparation. — Bile,  mixed  with  animal  charcoal,  is  evaporated 
to  dryness  and  extracted  with  alcohol.  If  not  colorless,  the  alco- 
holic filtrate  must  be  lurther  decolorized  with  animal  charcoal 
and  the  alcohol  distilled  off.  The  dry  residue  is  treated  with 
absolute  alcohol,  and  to  the  alcoholic  filtrate  anhydrous  ether  is 
added  as  long  as  an}-  precipitate  is  formed.  On  standing  the 
cloudy  precipitate  becomes  transformed  into  a  cr^'stalline  mass 
at  the  bottom  of  the  vessel.  If  the  alcohol  be  not  absolute,  the 
crystals  are  very  apt  to  be  changed  into  a  thick  syrupy  fluid. 
This  mass  of  crystals  has  been  often  spoken  of  as  bilin.  Both 
salts  are  thus  precipitated,  so  that  in  such  a  bile  as  that  of  the 
ox  or  man  bilin  consists  both  of  sodium  glycocholate  and  sodium 
taurocholate.  The  two  may  be  separated  b}^  precipitation  from 
their  aqueous  solutions  with  sugar  of  lead,  which  throws  down 
the  former  much  more  readily  than  the  latter.  [Both  of  these 
salts  are  precipitated  by  lead  subacetate.  The  acetate  has  no 
effect  on  the  taurocholate,  but  precipitates  the  glycocholate.  If, 
therefore,  the  glycocholate  be  precipitated  first  with  lead  acetate, 
the  taurocholate  can  be  obtained  from  the  filtered  liquid  by 
means  of  the  lead  subacetate.]  The  acids  may  be  separated 
from  their  respective  salts  by  dilute  sulphuric  acid,  or  by  the 
action  of  lead  acetate  and  sulphydric  acid. 

On  boiling  with  dilute  acids  (sulphuric  liydrocliloric),  or 
caustic  potash,  or  baryta-water,  glycocholic  acid  is  split  up 
into  cholalic  (cholic)  acid  and  glycin.  Taurocholic  acid 
may  similarl}-  be  sjjlit  up  into  cholalic  acid  and  taurin. 
Thus: 

(Glvcocholic  3cid.)        (Cholalic  acid  )    (-jlvcin.) 
(Taurocholic  acid.)        (Cholalic  acid.)    (Taurin.) 

C,6H,5XSO,  +  n.p  =  a,H,o05  +  aH.XSOs. 

Both  acids  contain  the  same  nitrogenless  acid,  cliolalic 
acid  ;  but  this  acid  is  in  the  first  case  associated  or  conju- 
gated with  the  important  nitrogenous  body  glycin,  or  ami(k)- 
acetic  acid,  and  in  the  second  case  witli  taurin,  or  amido- 
isethionic  (amidoetiiyl-sulpliuric)  acid.  The  decomposition 
of  the   bile   acids  into  cholalic  acid  and  taurin   or  glycin 


332      THE    TISSUES     AND    MECHANISMS    OF    DIGESTION. 

respectively  takes  pl.-iee  nntiirally  in  the  intestine-/  so  that 
from  the  two  iieids,  after  tliey  have  served  their  purpose  in 
digestion,  the  two  ammonia  compounds  are  returned  into 
the  l)lood.  Either  of  tlie  two  acids,  or  cholalic  acid  alone, 
when  treated  with  sulphuric  acid  and  cane-sugar,  gives  a 
magnificent  purple  color  (I*ettenkofer's  test)  with  a  charac- 
teristic spectrum.  A  similar  color  is  produced  by  the  action 
of  the  same  bodies  on  albumin, amy  1  alcohol,  and  some  other 
organic  bodies. 

By  dehydration  cholalic  acid  is  converted  into  choloidic  acid 
C,4H3,0„  or  into  dyslysin  C,4H3,0,. 

Action  of  Bile  on  Food. — In  some  animals  at  least  bile 
contains  a  ferineut  cai>able  of  converting  starch  into  sugar; 
but  its  action  in  this  respect  is  vvlioUy  subordinate. 

On  proteids  bile  has  no  direct  digestive  action  whatever. 
But  wlien  bile,  or  a  S')lution  of  bile-salts,  is  added  to  a  fluid 
containing  the  products  of  gnstric  digestion,  a  copious  pre- 
cipitate takes  place,  consisting  both  of  parapeptone  and 
peptone  [also  all)umin.  mucin,  glycocholic  acid,  biliary  color- 
ing matter,  etc.],  the  greater  part  of  the  pepsin  present  l)eing 
at  the  same  time  carried  down  mechanically,  so  that  the 
supernatant  liquid,  even  when  reaciditled,  has  little  f)r  no 
pe[)tic  })Owers.  [In  Dalton's'^and  also  in  my  own  experiments 
on  digestion  it  was  found  that  pe^jtones  (albuminose)  were 
not  precipitated  by  bile.]  The  piecii)itate,  however,  is  re- 
dissolved  in  an  excess  of  iiile  or  solution  of  bile-salts.  The 
purpose  of  this  precipitation,  which  actually  takes  place  in 
the  duodenum,  is  probably  to  shield  the  ferment  of  the  pan- 
creatic juice  (see  below)  from  the  destructive  action  of  the 
pepsin.  And,  in  general,  the  alkaline  bile,  by  neutralizing 
the  acid  contents  of  the  stomach  as  they  pass  into  the  duode- 
num, prepares  the  way  for  the  action  of  the  pancreatic  juice. 

With  regard  to  the  action  of  bile -on  fats  the  following 
statements  may  be  made : 

Bile  has  a  sbght  solvent  action  on  fats,  as  seen  in  its  use 
by  painters.  It  has  by  itself  a  slight,  but  only  slight,  emul- 
sifying power  ;  a  mixture  of  oil  and  bile  separate  after  shak- 
ing less  rapidly  than  a  mixture  of  oil  and  water.  With  free 
fatty  acids  bile  forms  soaps.  It  is,  moreover,  a  solvent  of 
solid  soaps,  and  it  would  appear  that  the  emulsion  of  fats 

'  Hoppe-Sevler,  Virehow's  Archiv,  xxv,  181  ;  xxvi  (18G3),  519. 
*  [Human  Physiology,  sixth  edition,  1875,  p.  222.] 


PANCREATIC    JUICE.  333 

is,  under  certain  cirenmstances,  at  all  events  facilitated  hy 
the  presence  of  soaps  in  solution.  Hence  bile  is  probably 
of  much  greater  use  as  an  emulsicjn  agent  when  mixed  with 
pancreatic  juice  than  when  acting  by  itself  alone.  To  this 
point  w^e  shall  return.  Lastly,  tiie  wetting  of  memliranes 
with  bile,  or  with  a  solution  of  bile-salts,  assists  in  the  pas- 
sage of  fats  througii  membranes.  Oil  passes  with  consider- 
able ease  through  a  filter-paper  kept  wet  with  a  solution  of 
bile  salts,  vvhereas  it  i>asses  with  extreme  difficulty  through 
one  kept  constantly  wet  with  distilled  water. 

[The  Phiji^iological  Anatomy  of  the  Pancreas. 

The  physiological  anatomy  of  the  pancreas  is  cssentialh^ 
that  of  the  salivary  glands.  The  lobes  are  composed  of 
lobules,  which  are  made  up  of  alveoli.  It  possesses  a  sin- 
gle duct,  which  conveys  the  pancreatic  fluid  into  the  in- 
testine either  through  an  individual  orifice,  or  by  one  com- 
mon to  it  and  tlie  ductus  communis  choledcchus.] 

Pancreatic  Juice. 

Natural  healthy  pancreatic  juice,  obtained  by  means  of  a 
temporary  pancreatic  fistula,  difi'ers  from  the  preceding  fluids 
in  the  comparatively  large  quantity  of  proteids  which  it  con- 
tains. Its  composition  varies  according  to  the  rate  of  secre- 
tion, for  with  the  more  rapid  flow  the  increase  of  total  solids 
does  not  keep  pace  with  that  of  tlie  water,  thougli  the  ash 
remains  remarkably  constant. 

B}'  an  incision  through  the  linea  alba  the  pancreatic  duct  can 
easily  be  found  either  in  the  rabbit  or  in  the  dog,  and  a  canula 
secured  in  it.  There  is  no  dithculty  about  a  temporary  fistula  ; 
but  Bernard  found  that,  with  permanent  fistula?,  the  secretion 
altered  in  nature,  and  lost  many  of  its  characteristic  properties. 
N.  O.  Bernstein,'  ho^yever,  has  succeeded  in  obtaining  perma- 
nent fistulic  without  any  impairment  of  the  secretion. 

Healthy  pancreatic  juice  is  a  clear  viscid  fluid,  frothing 
when  shaken.  It  has  a  very  decided  alkaline  reaction,  and 
contains  few  or  no  structural  constituents. 

The  average  amount  of  solids  in  the  pancreatic  juice  of 
the  dog  when  obtained  from  a  temporary  fistula  is  about  8 
to  10  per  cent.;-  but  Bernstein^  found   in  the  thoroughly 

^  Lndwi^'s  Arbeiten,  1869.  p.  1. 

2  Bernard,  Lee.  Phys.  Exp.,  1855,  ii,  237.  ^  Op.  cit. 


334     TUE    TISSUES    AND    MECHANISMS    OF    DIGESTION. 

active  secretion  from  a  peniianont  fistula  about  2.5  per  cent. 
(1.(kS-5.39),  .8  being  inorganic  matter.  The  important  con- 
stitnents  are  albumin,  a  peculiar  form  of  casein,  or  alkali- 
albumin  (precipitahle  by  saturation  with  magnesium  sul- 
phate), leucin  ami  t>rosin,  a  small  amount  of  fats  and  s(){4)s, 
and  a  comparatively  large  quantity  of  sodium  carbonate,  to 
which  the  alkaline  reaction  of  the  juice  is  due,  and  which 
seems  to  be  i)eculiarl3'  associated  with  the  albumin. 

AVhen  cooled  to  0--  C.  it  is  apt  to  undergo  a  sort  of  coagulation, 
becoming  lluid  a<2;ain  on  being  gently  heated.' 

According  to  Kiihne,-  fresh  pancreatic  Juice  of  the  dog  always 
contains  corpuscles  similar  to  salivary  corpuscles,  and  the  coagu- 
lation observed  b}^  Bernard  is  a  true  coagulation,  resulting  in  a 
product  very  similar  to  myosin.  The  coagulum,  however,  is 
speedily  digested.  Ferfcvthj  fresh  juice,  Kuhne  states,  contains 
neither  pei)tone  nor  tyrosin,  and  only  the  barest  trace  of  leucin. 

Action  on  Food-stuffs. — On  starch,  raw  or  boiled,  pan- 
creatic juice  acts  with  great  energy,  rapidly  converting  it 
into  grape-sugar.  All  that  has  been  said  in  tliis  respect  con- 
cerning saliva  might  be  repeated  in  the  case  of  pancreatic 
juice,  except  that  the  activity  of  the  latter  is  far  greater 
than  that  of  the  former;  the  pancreatic  juice  and  the  aqueous 
infusion  of  the  gland  are  always  ca|)al)le  of  converting  starch 
into  grape-sugar,  w'hether  the  animal  from  which  they  were 
taken  be  starving  or  well  fed. 

As  in  the  case  of  saliva  (p.  308),  it  is  probable  that  the  sugar 
formed  is  not  true  grape-sugar. 

From  the  juice,  or,  by  the  glycerin  method,  from  the  gland 
itself,  an  amjdolytic  ferment  may  be  approximately  isolated. 
On  proteicU  pancreatic  juice  also  exercises  a  solvent  action, 
so  far  similar  to  that  of  gastric  juice  that  by  it  proteids  are 
converted  into  pei)tone.  If  a  few  shreds  of  fibrin  are  thrown 
into  a  small  quantitj'  of  pancreatic  juice,  they  speedily  dis- 
appear, especially  at  a  temperature  of  35^  C  ,  and  the  mix- 
ture is  found  to  contain  peptone.  The  activity  of  the  juice 
in  thus  converting  proteids  into  peptone,  is  favored  by  in- 
crease of  temperature  up  to  40^  or  thereabouts,  and  hindered 
by  low  temperatures  ;  it  is  permanently  destroyed  by  boiling. 
The  digestive  powers  of  the  juice  in  fact  depend,  like  those 

'  Bernard,  Le?.  Pliys.  Exp.,  ii,  230. 

2  Verhandl.  Heidelb.  Naturhist.  Med.  Vereins,  1876. 


PANCREATIC    JUICE.  335 

of  gastric  juice,  on  the  presence  of  a  ferment,  to  which  the 
name  trypsin  has  been  given.  A  glycerin  extract  of  pan- 
creas, prepared  in  the  same  method  as  that  of  the  gastric 
mucous  membrane,  is  (under  appropriate  conditions)  active 
on  proteids.  like  the  native  juice. 

The  appearance  of  fibrin  undergoing  pancreatic  digestion 
is,  however,  different  from  that  undergoing  peptic  digestion. 
In  the  former  case  the  fibrin  does  not  swell  up,  but  remains 
as  opaque  as  before,  and  appears  to  suffer  corrosion  rather 
than  solution.  But  tiiere  is  a  still  more  important  distinc- 
tion between  pancreatic  and  peptic  digestion  of  proteids. 
Peptic  digestion  is  essentially  an  acid  digestion  ;  we  have 
seen  that  the  action  only  takes  place  in  the  presence  of 
an  acid  and  is  arrested  by  neutralization.  Pancreatic  di- 
gestion, on  the  other  hand,  is  essentially  an  alkaline  diges- 
tion ;  the  action  will  not  take  place  unless  some  alkali  be 
present ;  and  the  activity  of  an  alkaline  juice  is  arrested  by 
acidification,  and  hindered  by  neutralization.  The  glycerin 
extract  of  pancreas  is,  under  all  circumstances,  as  inert  in 
the  presence  of  free  acid  as  that  of  the  stomach  in  the  pres- 
ence of  alkalies.  If  the  digestive  mixture  l)e  supplied  with 
sodium  carbonate  to  the  extent  of  1  per  cent.,  digestion  pro- 
ceeds rapidly,  just  as  does  a  peptic  mixture  when  acidulated 
with  hydrochloric  acid  to  the  extent  of  .2  per  cent.  Sodium 
carbonate  of  1  per  cent,  seems  in  fact  to  play  in  pancreatic 
digestion,  a  part  altogether  comparable  to  that  of  h}  dro- 
chloric  acid  .2  per  cent,  in  gastric  digestion. 

With  distilled  water  the  digestion  goes  on  but  very  slowd}-,  and 
the  addition  of  sodium  carbonate  quickens  the  change,  in  propor- 
tion to  the  quantity  added,  up  to  about  .9  or  1.2  per  cent.  Be- 
yond this,  further  alkali  is  a  hindrance,  and  large  quantities  stop 
the  process  altogether.  Bile,  which  arrests  peptic  digestion, 
seems,  if  anything,  favorable  to  pancreatic  digestion.^  When 
isolated  ferment,  as  the  glycerin  extract  of  pancreas,  is  operated 
with,  .1  per  cent,  of  free  hydrochloric  acid  is  sutticient  to  arrest 
the  action. 

Corresponding  to  this  dilference  in  the  helpmate  of  the 
ferment,  there  is  in  the  two  cases  a  difference  in  the  nature 
of  the  products.  In  both  cases  peptone  is  produced,  and 
such  differences  as  can  at  present  be  detected  i)etween  pan- 
creatic and  gastric  peptones  are  comparative!}^  slight ;  but 

^  Heidenhain,  Pfliiger's  Archiv,  x  (1875),  p.  557. 


3;](j      TIIK    TISSUES    AND    MECHANISMS    OF    DIGESTION. 


in  }):\iu'renti('  dioeslion  the  hy-prodncl  is  not,  as  in  ijaslric 
digestion,  a  i\ind  of  acid-albumin,  hut  a  body  having  more 
analogy  with  alkali  albumin. 

Before  solution  has  actually  taken  place  the  fibrin  be- 
comes altered  in  character.  It  is  solul>le  not  only  in  dilute 
acids  and  alkalies,  but  also  in  a  10  i)er  cent,  solution  of 
sodium  chloride,  and  the  solutions  obtained  by  the  latter 
reagent  arc  coagulablo  on  boiling  and  on  the  addition  of 
strong  nitric  acid.  The  first  action  of  the  pancreatic  juice, 
therefore,  seems  to  lie  to  convert  the  proteid  under  diges- 
tion into  a  body  intermediate  between  alkali-albumin  and 
ordinary  native  albumin. 

But  tliough  the  general  characters  of  pancreatic  and  gas- 
tric digestion  are  on  the  surface  so  similar,  it  is  more  than 
probal)le  that  j)rofound  differences  do  exist  l)etween  them. 
This  is  shown  by  the  ap|)earance,  in  the  pancreatic  digestion 
of  proteids,  of  two  remarkable  nitrogenous  crystalline  bodies, 
leucin  and  ti/rosin.  (Fig.  100.)  When  fibrin  (or  other  pro- 
teid)  is  submitted   to   the   action   of  pancreatic  juice,   the 

amount  of  [)eptone  which  can  be 
recovered  from  the  mixture  falls 
far  short  of  the  original  amount 
of  proteids,  much  more  so  than 
in  the  case  of  gastric  juice;  and 
the  longer  the  digestive  action, 
the  greater  is  this  apparent  loss. 
If  a  pancreatic  digestive  mixture 
be  freed  from  the  alkali-albumin 
by  neutralization,  and  after  con- 
centration by  evaporation  be 
treated  with  excess  of  alcohol, 
most  of  the  peptone  will  be  pre- 
cipitated. The  alcoholic  filtrate 
when  concentrated  gives,  on  cool- 
ing, crystals  of  tyrosin,  and  the 
mother  liquor  from  these  crystals 
will  afford  abundance  of  crystals  of  leucin.  Thus  by  the 
action  of  the  pancreatic  juice  a  considerable  amount  of  the 
proteid,  which  is  being  digested,  is  so  broken  up  as  to  give 
rise  to  products  which  are  no  longer  proteid  in  nature. 
From  its  decomposition  there  arise  leucin,  tyrosin,  and 
probably  several  other  bodies,  such  as  fatty  acids  and  vola- 
tile substances.  In  gastric  digestion  such  a  complete  de- 
struction of  proteid  material  occurs  to  a  much  less  extent ; 


^^^ 


Tyrosin.] 


PANCREATIC    JUICE.  337 

neither  leiicin  nor  tyrosin  can  at  present  be  considered  as 
natural  products  of  the  action  of  pepsin. 

As  is  well  known,  leucin  and  tyrosin  are  the  bodies  which 
make  their  appearance  when  proteids  or  gelatin  are  acted 
on  by  dilute  acids,  alkalies,  or  various  oxidizing  agents. 
i^ow  leucin  is  amido-caproic  acid,  and  thus  belongs  dis- 
tinctly to  the  fatt}'  bodies,  while  tyrosin  is  a  member  of  the 
aromatic  group,  being  closely  related  to  benzoic  acid.  So 
that  in  pancreatic  digestion  we  have  the  large  complex  pro- 
teid  molecule  split  up  into  its  constituent  fatty  acid  and 
aromatic  molecules,  and  into  its  other  less  distinctly  known 
components. 

The  presence  of  these  bodies  and  of  the  alkali-albumin  in  pan- 
creatic juice  is  probably  due  to  an  intrinsic  digestion  taking  place 
in  the  secretion  as  it  passes  along  the  duct  or  after  it  has  been 
collected.  Among  the  sup]jlementary  products  of  pancreatic  di- 
gestion may  be  enumerated  a  bod}-  which  gives  a  violet  color  with 
chlorine-water  (this  reaction  is  often  seen  in  the  juice  itself),  and 
indoh  to  which  apparently  the  strong  and  peculiarly  fa?cal  odor, 
which  makes  its  appearance  during  pancreatic  digestion,  is  due. 

Indol,  however,  unlike  the  leucin  and  t^-rosin,  is  possibly  not  a 
product  of  x)ure  pancreatic  digestion,  but  of  an  accompanying 
decomposition  due  to  the  action  of  organized  ferments.  A  pan- 
creatic digestive  mixture  soon  becomes  swarming  with  bacteria, 
in  spite  of  careful  precautions,  Avhen  natural  juice  or  an  infusion 
of  the  gland  is  used.  When  isolated  ferment  is  used,  and  atmos- 
pheric germs  excluded,  no  odor  whatever  is  produced,^  though 
carbonic  acid  and  nitrogen  are  set  free  ;  and  Krdine  found  no 
indol  produced  when  pancreatic  digestion  was  carried  on  in  the 
presence  of  salic3'lic  acid,  which  prevents  the  development  of 
bacteria  and  like'^organisms. 

After  long-continued  digestion,  especially  when  accompanied 
by  putrefactive  decomposition,  the  amount  of  proteids  which  are 
carried  beyond  the  peptone  stage  and  broken  up  may  be  very 
great.  A  slight  difference  betAveen  pancreatic  and  gastric  diges- 
tion may  be  found  in  the  fact,  that  while  fibrin  boiled  as  well  as 
raw  is  readily  acted,  on  by  pancreatic  juice,  boiled  albumin,  syn- 
tonin,  etc.,  resist  the  action  of  pancreatic  juice  to  a  much  greater 
extent  than  they  do  that  of  gastric  juice. 

Theory  of  Digestive  Proteolysis. — The  simplest  view  of  peptic 
digestion  is  that  of  Brdcke,-  that  the  fibrin  or  albumin,  etc.,  is 
first  converted  into  syntonin  (parapeptone),  and  that  the  syn- 
tonin  (parapeptone)  is  converted  into  peptone  ;  and  is  moreover 
supported  by  the  fact  that  the  final  result  of  digestion  with  a  very 

1  Hiifner,  .J.  f.  Prakt.  Chem.  N.  F.,  x,  1. 

^  Wieu.  Sitzungsbericht,  xxxvii,  13J,  xliii,  601. 


338       TIIK  TISSUES    AND    MECHANISMS    OF    DIGESTION. 


active  Juice  is  iiothini;-  l)ut  iM'j)tone 
which  show  that  so  simple  a  view  cannot  he  acctepted.  ^leissner' 
came  to  the  conclusion,  hased  on  very  lahorious  researches,  that 
the  conversion  into  syntonin  was  followed  by  the  splitting  up  of 
that  body  into  pcjtUmc  and  })ar((i>Cj)tone^  the  latter  being  distin- 
guished from  onlinary  syntonin  not  by  its  general  characters, 
but  by  the  fact  that  it  was  incapa1)le  of  being  further  converted 
into  peptone  by  the  action  of  gastric  juice,  though  it  could  undergo 
that  change  under  the  influence  of  pancreatic  juice.  He  further 
described  two  subsidiary  i)roducts,  DieldjK'jttone  and  di/speptone^ 
but  the  (;haracters  he  assigned  to  those  bodies  were  unsatisfac- 
tory. He  moreover  spoke  of  three  kinds  of  peptone,  A^  1?,  and 
O  peptone,  the  last  not  being  precipitable,  whilst  the  first  two 
are,  by  acetic  acid  and  ])otassium  ferrocyanide,  A  in  a  Aveakly 
acid,  JB  in  a  strongly  acid  solution  ;  in  other  words,  O  is  a  perfect 
peptone  and  A  and  B  are  imperfect  pei)tones.  Krdine^  is  of  opinion 
that  every  natural  proteid  consists  of,  and  may  be  split  up  into, 
two  elements,  belonging  to  what  he  calls  respectively  the  anti 
group  and  the  Jteiui  group.  AVhen  a  proteid  is  digested  by  tryp- 
sin, two  peptones  are  produced,  an  anii peptone  and  a  hemijjeptone. 
Of  these  the  first,  antipeptone,  undergoes  no  further  change 
under  the  action  of  trypsin  ;  it  remains  a  peptone.  Hemipep- 
tone  on  the  one  hand  is  readily  decomposed  by  trypsin  into  leucin, 
tyrosin,  and  the  other  products  of  pancreatic  digestion.  So  also 
when  a  proteid  is  digested  by  pepsin,  the  same  antipeptone  and 
hemipeptone  are  formed  ;  but,  unlike  tryi)sin,  pepsin  camiot  pro- 
duce any  further  change  in  the  hemipeptone.  (The  assertion  that 
leucin  and  tyrosin  appear  as  products  of  peptic  digestion,  is  ex- 
plained by  the  fact  that  pepsin  is  associated  in  tlie  gastric  mem- 
brane with  a  proteid  body,  which  gives  up  considerable  quantities 
of  leucin  and  tyrosin  when  dissolved  in  a  dilute  acid.  Trypsin 
also  is  associated  with  a  similar  body  in  the  pancreas.)  Tims  the 
results  of  peptic  and  tryptic  digestion  together  are  antipeptone 
with  leucin,  tyrosin,  etc.,'  the  latter  arising  from  the  profouuder 
tryptic  digestion  of  hemipeptone.  Between  these  peptones,  how- 
ever, and  the  original  proteid  are  various  stages,  and,  under  cer- 
tain circumstances,  various  by-products.  Thus  antipeptone  has 
for  its  antecedent  antiaJhumose  (BrUcke's  para  peptone)  agreeing 
in  its  general  characters  with  the  syntonins,  but  capable  of  con- 
version into  antipeptone  only,  never  into  hemipeptone.  Similarly 
hemipeptone  has  an  antecedent  JiemiaJhurno.He  (apparently  Meiss- 
ner's  A  peptone)  soluble  in  dilute  acids  and  alkalies  and  in  a  10 
per  cent,  sodium-chloride  solution,  and  convertible,  by  the  agency 
of  pepsin  or  trypsin,  into  hemipeptone,  and  of  trypsin  alone  into 
leucin,  tyrosin,  etc.  The  action  of  dilute  hydrochloric  acid  at 
40^  on  proteids  gives  rise,  on  the  side  of  the  hemi-group,  to  hemi- 
albumose  and  so  to  hemipeptone.     By  the  action  of  sulphuric 

'  Zt.  f.  Eat.  Med.,  vii,  1  ;  viii,  280 ;  x,  1 ;  xii,  46 ;  xiv,  .303. 
2  Yerhundl.  Naturhist.  Med.  Yereins,  Heidel.,  1876. 


PANCREATIC    JUICE.  339 


acid  at  100^  C.  the  hemi peptone  is  further  reduced  to  leucin, 
tyrosin,  etc.  On  the  side  of  the  anti-group  these  agents  give 
rise  to  a  body  whicli  Kdlme  calls  antkdhiunate.  This  substance 
also  occurs  in  digestive  mixtures  where  the  pepsin  is  insuthcient. 
It  is  not  capable  of  any  change  under  the  influence  of  pepsin, 
but  by  trypsin  is  converted  into  antipeptone.  It  is  evidently  the 
real  parapeptone  of  Meissner.  These  results  of  Kiihne  it  will  be 
seen  reconcile  some  previous  contradictions  ;  and  the  distinction 
of  the  anti-  and  hemi-groups,  if  it  prove  as  general  as  Kdhne 
supposes,  throws  a  great  light  on  proteid  metabolism.  It  may 
be  remarked,  in  passing,  that  hemialbumose  agrees  very  closely 
with  the  peculiar  proteid  body  discovered  by  Bence  Jones  in  the 
urine  of  a  case  of  osteomalacia.  According  to  Kuhne,  while  the 
activity  of  trypsin  is  entirely  destroyed  by  digestion  with  pepsin, 
trypsin  has  no  such  eftect  on  pepsin. 

On  the  gelatiniferous  elements  of  the  tissues,  unless  they 
have  been  previously  treated  with  acid  or  heated  with  water, 
pancreatic  juice  appears  to  have  no  solvent  action.  In  this 
respect  it  atfords  a  striking  contrast  to  gastric  juice.^ 

Trypsin,  unlike  pepsin,  will  dissolve  mucin.  Like  pepsin,  it  is 
inert  towards  nuclein,  horny  tissues,  and  the  so-called  amyloid 
matter. 

On  Fats  pancreatic  juice  has  a  twofold  action  ;  it  emulsi- 
fies them,  and  it  splits  up  neutral  fats  into  their  respective 
acids  and  glycerin. 

If  hog's  lard  be  gently  heated  till  it  melts  and  be  then 
mixed  with  pancreatic  juice  before  it  solidifies  on  cooling,  a 
creamy  emulsion,  lasting  for  almost  an  indefinite  time,  is 
formed.  So  also  when  olive  oil  is  shaken  up  with  pancre- 
atic juice,  the  separation  of  the  t\w)  fluids  takes  place  ver}'- 
slowl}^,  and  a  drop  of  the  mixture  under  the  microscope 
shows  the  division  of  the  fat  is  very  minute.  An  alkaline 
aqueous  infusion  of  the  gland  has  similar  emulsifying  powers. 

If  perfectly  neutral  fat  be  treated  with  pancreatic  juice, 
especially  at  the^  o.ody-temperature,  the  emulsion  speedily 
takes  on  an  acid  reaction,  and  by  appropriate  means  not 
only  the  corresponding  fatty  acids,  but  glycerin  may  be  ob- 
tained from  the  mixture.  "WHien  an  alkali  is  present,  the 
fatty  acids  thus  set  free  form  their  corresponding  soaps. 

Pancreatic  juice  contains  fats,  and  is  consequently  apt  after 
collection  to  have  its  alkalinity  reduced,  and  an  aqueous  infusion 

'  Ewald  and  Kiihne,  Verhandl.  Naturhist.  Med.  Vereins,  Heidelberg, 
Bd.  i  (1876). 


340      THE    TISSUES    AND    MECHANISMS    OF    DIGESTION. 


of  a   pancreatic   inland   (which   always  contains  a  considcrahlo 
amount  of  fat)  very  speedily  becomes  acid. 

Thus  pancreatic  juice  is  remaikalde  for  tlic  powei-  it  pos- 
sesses of  acting  on  all  the  food-stulfs,  on  starch,  hits,  and 
p rote  ids. 

The  action  on  starch  and  on  proteids  is  certainly,  and  the  split- 
tins;  up  of  fatty  at'ids  is  probably  due  to  the  presence  of  distinct 
ferinents,  and  Danilew^sky'  has  suugested  a  method  for  isolating 
these  three  ferments.  The  emulsify  ing  power,  on  the  other  hand, 
is  connected  with  the  general  comi)osition  of  the  juice  (or  of  the 
aqueous  infusion  of  the  gland),  being  probably  in  large  measure 
dependent  on  the  alkali-albumin  present.  Tlie  ])roteolytic  fer- 
ment trypsin  contains,  according  to  K.hne,  a  considerable  quan- 
tity of  nitrogen  ;  and  the  fact  tliat  it  can  be  digested  by  i)epsin 
would  seem  to  indicate  that  it  is  really  proteid  in  nature.  There 
are  no  means  of  distinguishhig  the  amylolytic  ferment  of  the 
pancreas  from  ptyalin. 

The  action  of  [)ancreatic  juice,  or  of  the  infusion  or  ex- 
tract of  the  gland,  on  starch,  is  seen  under  all  circumstances, 
whether  the  animal  be  fasting  or  not.  The  same  may  proba- 
bly be  said  of  the  action  on  fats. 

Pancreatic  jnice,  when  secreted  in  a  normal  state,  is  al- 
ways active  on  proteids.^  The  glycerin  extract  or  aqueous 
infusion  of  the  gland,  on  the  contrary,  differs  at  ditl'ercnt 
times;  prepared  from  an  animal  some  4  to  10  iiours  after 
food  has  been  taken,  it  is  very  powerful ;  i)repared  from  a 
fasting  animal,  it  exhii)its  scarcely  any  action  at  all.  To 
this  j)oint  we  sliall  return  immediatel}'. 

\_Phy biological  Anatomy  of  Uie,  Mucoua  Membrane  of  the 
iSmall  Intestine. 

The  raucous  meml)rane  lining  the  small  intestine  is  thrown 
into  numerous  transverse  folds,  which  are  called  valrulse 
connivenleti.  These  folds  are  best  marked  near  the  pyloric 
end,  and  are  relatively  few  in  the  ileum.  These  folds  aflbrd 
a  greater  surface  for  the  contact  of  food  with  the  absorbing 
surface,  while  at  the  same  time  its  passage  along  the  intes- 
tinal walls  is  retarded.  The  surface  of  the  membrane  has  a 
soft  velvety  appearance,  and  if  seen  by  the  aid  of  a  lens,  it 
appears  thickly  studded  witli  innumerable  fingerlike  projec- 
tions, which  are  called  villi.  At  the  bases  of  these  villi  are 
numerous  minute  apertures,  which  are  the  openings  of  the 

^  Virchow's  Archiv,  xxv,  p.  297.  ^  N.  O.  Bernstein,  1.  c. 


MUCOUS    MEMBRANE    OF    THE    SMALL    INTESTINE.      341 

secretiiio:  glands.  These  glands  are  of  three  kinds:  Brunner^s 
or  racem(ji<e,  simple  foIlich'f<  or  glands  of  Lieherkuhn^  and  the 
agminate.  The  glands  of  Brunner  (Fig.  101)  are  racemose 
glands,  and  are  confined  to  the  duodenum.     They  are  par- 

FiG.  101. 


Portions  of  one  of  Bruunei's  Glands,  from  the  Iliuuau  DuodenuTu. 


Fig.  102. 


tially  imbedded  in  the  submucous  tissue.     In  their  ph\-si- 
olog3'  they  are  closely  allied  to  the  pancreatic  gland. 

The  glands  of  Lieherk'uhn  or  simple  follicles  resemble 
the  finger  of  a  glove  inverted.  They  are  pro- 
fusely distributed  in  both  the  large  and  small 
intestine,  and  ai)pear  as  simj)le  depressions  of 
the  mucous  membrane.  Like  the  whole  of  the 
intestine,  they  are  lined  by  columnar  epithelium  ; 
they  are  surrounded  by  capillary  plexuses  of 
bloodvessels  and  lymphatics ;  they  are  the 
principal  glands  concerned  in  the  secretion  of  the 
succus  enter'icus  (Fig.  102). 

The  agminate ^glandx  or  Peyer's  patches  oc- 
cur as  localized  collections  of  small  white  sac- 
culi.  (Fig.  103.)  These  sacculi  are  surrounded 
by  dense  capillary  plexuses  of  bloodvessels, 
which  send  numerous  vascular  loops  into  the 
interior  which  serve  as  a  framework  for  the 
stroma  of  the  organ.  The  stroma  consists  of 
an  adenoid  tissue  containing  in  its  meshes 
lymph  corpuscles  and  an  opaque  substance 
with  oil-globules. 

29 


A  Ghind  of 
Lieberkiihu. 


342      THE    TISSUES    AND    MECHANISMS    OF    DIGESTION. 

Tlu'so  s;\('(.'iili  are  iiDbeddod  in  the  suhmucons  tissue,  and 
goneinlly  projecl  more  or  less  above  the  free  surlaee  of  llie 


Agmiuate  rullicks,  ur  iVyer'.-;  I'ateli,  in  a  ttati'  <>l'  disten.xiou  ;  luagiiiliL'd  about  five 
diameters.— Alter  Bokhm. 

mein])rane.     Encli  saccule  is  sometimes  snrrounded  at   its 
free  surface    by   an   annular   depression   or  fossa,   and  en- 


Fir;.  lot. 


Fig.  105. 


Fig.  105  — ."^ide  view  of  a  portion  of  Iiite.stinal  Mucous  ^[eml•rallo  of  a  Cat,  showing 
a  Peyei's  gland  («);  it  is  imbedded  in  the  subujucous  tissue  (/)  the  line  of  separa- 
tion between  wliitii  and  the  mucous  membrane  passes  across  tlie  ;j;land  ;  b,  one  of 
tlie  tubular  follicles,  tlie  orifices  of  which  form  the  zone  of  openi7ic(S  around  the 
gland;  c,  thp  fossa  in  the  tuucous  riieinbrane  ;  (/,  villi;  e,  follicles  of  Lieberkiihn. — 
After  P.EXDZ. 

Fig.  lO').— Solitary  <';]:\n<]  ..f  siu:ill  intestiuc— Aft(>r  P-oi:iim. 


circled  liy  a  zone  of  opeuiiigs,  wliicli  ar3  the  orifices  of  the 


MUCOUS    MEMBRANE    OF    THE    SMALL    INTESTINE.      843 


intestinal  follicles.  (Fig.  104.)  Villi  are  sometimes  seen 
on  their  surface.  Tiiese  saccnli  sometimes  exist  singly  ;  they 
are  then  termed  solitary  glands.     (Fig.  105.) 

The  function  of  the  agminate  glands  is  not  known,  but  it 
is  probable  that  they  are  accessories  of  the  lymphatic  sys- 
tem and  actively  concerned  in  absorption. 

Fig.  106. 


(Slightly  altered  from-  Teichmalin.j    A. 

Villi  of  intestine  showing  columnar  epithelium  covering  them  ;  also  adenoid  tissue, 
having  in  its  meshes  the  dark  vessels,  which  are  portal  capillaries,  and  a  lacteal  ap- 
pearing as  a  white  loop. 


The  villi  are  covered  with  columnar  epithelium,  wliich  is 
continuous  with  the  intestinal  lining*  but  is  somewhat  modi- 
fied on  its  free  surface  by  being  striated.  (Fig.  84.)  Inter- 
nall}',  the  villi  are  composed  of  a  stroma  of  adenoid  tissue, 


344      THE    TISSUES    AND    MECHANISMS    OF    DIGESTION. 

which  contains   the  bloodvessels,  muscular  fibres,  lacteals, 
and  also  til)ro-plaslic  cells  and  fat-globules.     (Fig.  lOf).) 

The  lacteals  usually  appear  as  a  single  or  double  loop, 
and  have"  no  definable  o[)enings.  They  empty  into  the 
lacteals  at  the  base  of  tiie  villi.  The  unstiiated  muscular 
fibres  are  fibres  of  the  mnsruloj'i.^  muco^^K ;  they  are  sup- 
})osed  to  be  active  elements  in  emptying  tiie  lacteals  of  the 
villi.  The  longitudinal  fibres,  in  contraction,  serve  to  pull 
the  villus  down,  and  force  its  contents  out.  Valves  in  the 
larger  vessels  [)revent  a  refiux  of  the  tluid.  The  part  which 
the  villi  take  in  the  digestive  process  is  to  al)sorb  the  pro- 
ducts of  digestion.  This  function  will  be  again  referred  to 
more  in  detail.  The  nerves  are  derived  from  the  pneumo- 
gastric  and  sympathetic] 

Succus  EnfericuH. 

When,  in  a  living  animal,  a  portion  of  the  small  intestine 
is  ligatured,  so  that  the  secretions  coming  down  from  above 
cannot  enter  its  canal,  while  yet  the  blood-supply  is  main- 
tained as  usual,  a  small  amount  of  secretion  collects  in  its 
interior.  This  is  spoken  of  as  the  auccus  entericai<.  and  is 
supposed  to  be  furnished  by  the  glands  of  Lieberkiihn. 
We  have  no  exact  knowledge,  however,  as  to  what  extent 
such  a  secretion  takes  place  under  normal  circumstances; 
and  the  statements  with  regard  to  its  action  are  conflicting. 
Probably  it  has  no  direct  action  on  either  fats  or  proteids; 
but  is  amylolytic  in  some  animals,  though  not  in  all. 

Thiry^  divided  the  small  intestine  in  two  places  at  some  dis- 
tance apart.  By  fine  sutures  he  united  the  lower  end  of  the 
upper  with  the  upper  end  of  the  lower  section,  thus  as  it  were 
cutting  out  a  whole  piece  of  the  small  intestine  from  the  alimen- 
tary tract.  In  successful  cases,  union  between  the  cut  surfeces 
took  place,  and  a  shortened  but  otherwise  satisfactory  canal  was 
re-established.  Of  the  isolated  piece  the  lower  end  was  carefully 
closed  by  sutures,  while  the  upper  was  brought  to  the  wound 
in  the  abdominal  wall  and  secured  there.  A  fistula  was  thus 
formed,  leading  into  a  short  piece  of  intestine  quite  isolated  from 
the  rest  of  the  alimentary  canal.  From  this  isolated  intestine 
Thiry  obtained  a  thin  yellowish  alkaline  albuminous  secretion 
which  dissolved  fibrin  very  much  in  the  same  way  as  does  pan- 
creatic juice,  but  was  ineffectual  on  other  proteids  and  had  no 
action  on  starch.     Masloff''  finds  that  the  juice  obtained  (from 

'  Wien.  Sitznngsbericht,  Bd.  1  (1864),  p.  77. 

2  Untei-s.  Physiol.  Inst.  Heidelberg,  ii  (1879),  p.  290. 


THE    ACT    OF    SECRETION.  345 


dogs)  by  Thiry's  method,  acts  on  starch  feebly,  but  has  no  action 
on  fibrin  or  other  proteids  in  neutral  or  alkaUne  solutions  if  putre- 
factive changes  be  carefully  avoided.  Kcilliker  and  H.  Muller 
found  that  proteids  introduced  into  the  intestines  were  digested 
in  the  case  of  carnivora,  but  not  in  the  case  of  herbivora.  Funke^ 
also  agrees  with  Thiry  that  starch  injected  into  isolated  loops  of 
rabbit's  intestine  is  not  converted  into  sugar  ;  M'hile  Frerichs  and 
Busch  came  to  the  opposite  conclusion.'-  Certainl}^  pieces  of  the 
intestine  of  the  pig  or  of  the  rabbit,  or  a  glycerin  extract  of  the 
pieces,  will  rapidly  convert  starch  into  sugar  ;  and  it  is  difficult 
to  suppose  that  this  action  is  due  to  an  admixture  of  pancreatic 
juice  which  had  not  been  thoroughly  removed  by  washing,  since 
pieces  of  the  intestine  of  the  sheep,  which  are  also  subject  to  ad- 
mixture witli  active  pancreatic  juice,  are,  when  similarl}-  treated, 
inert  as  far  as  starch  is  concerned.  Still  no  great  stress  can  be 
laid  on  this,  since  an  amylolytic  ferment  can  be  obtained  from 
almost  every  part  of  the  body  of  a  pig  or  a  rabbit. 

Suecus  entericus  has  also  been  said  to  change  cane  into 
grape  sugar,  and  by  a  fermentative  action  to  convert  cane- 
sugar  into  lactic  acid,  and  this  again  into  butyric  acid  with 
the  evolution  of  carbonic  acid  and  free  hydrogen. 

Of  the  possible  action  of  other  secretions  of  the  alimen- 
tary canal,  as  of  the  caicum  and  large  intestine,  we  shall 
speak  when  we  come  to  consider  the  clianges  in  the  alimen- 
tary canal. 

Concerning  the  secretion  of  Brunner's  glands  our  information 
is  at  presentimperfect.  The  cells  of  the  glands  closely  resemble 
the  central  cells  of  the  gastric  glands  f  and  Grlitzner*  finds  that 
an  extract  of  the  gland  will  digest  fibrin  in  an  acid  solution,  but 
has  no  distinct  amylolytic  action. 


Sec.  2.     The  Act  of  Secretion  in  the  case  of  the  Di- 
gestive Juices  and  the  Nervous  Mechanisms 
which  regulate  it. 

The  various  juices  whose  properties  we  have  just  studied, 
though  so  different  from  each  other,  are  all  drawn  ultimately 
from  one  common   source,  the  blood,  and  they  are  poured 

1  Lehrb.,  p.  190. 

■'  Cf.  also  Paschutin,  Archiv  Anat.  Physiol.,  1871,  p.  305.  Eichhorst, 
Pfliiger's  Archiv,  iv  (1871),  p.  575. 

3  Scliwialbe,  Arch.  f.  micro.  Anat.,  viii  (1872)  p.  97. 
*  Pfliiger's  Archiv,  xii  (1876),  p.  288. 


346      THE    TISSUES    AND    MECHANISMS    OF    DIGESTION. 

into  tlic  aliiiu'iilarv  canal,  not  in  a  continuous  flow,  hut 
intcrniittcnlly  as  occasion  may  demand.  The  epitlielium 
cells  which  sui)i)ly  them  have  their  periods  of  rest  and  of 
activity,  and  the  amount  and  quality  of  the  fluids  which 
these  cells  secrete  are  determined  by  the  needs  of  the  econ- 
omy as  the  food  passes  alon<^  the  canal.  \Ve  have  therefore 
to  consider  how  the  epithelium  cell  manufactures  its  special 
secretion  out  of  the  materials  supi)lied  to  it  by  the  blood, 
and  how  the  cell  is  called  into  activity  by  the  i)resence  of 
food  at  some  distance  from  itself,  or  by  circumstances  which 
do  not  bear  directly  on  itself.  In  dealing  with  these  matters 
in  connection  with  the  digestive  juices,  we  shall  have  to 
enter  at  some  length  into  the  physiology  of  secretion  in 
general. 

The  (piestion  which  presents  itself  first  is,  Does  the  epi- 
thelium cell  simply  serve  as  a  filter,  merely  draining  otf  from 
the  blood  the  already  formed  constituents  of  its  secretion, 
each  cell  being  fitted  in  some  way  to  catch  and  deliver  par- 
ticular substances'/  In  other  words,  Is  secretion  merely 
selection,  just  as  from  a  mixture  of  shots  of  various  sizes  a 
selection  might  be  made  by  [)assing  them  over  a  series  of 
sieves  with  meshes  of  vai-ying  width?  or  does  the  cell  draw 
\ipon  the  blood  for  the  nutritive  elements  recjuired  for  the 
growth  of  all  protoplasm,  and  out  of  those  common  elements 
manufacture  in  the  recesses  of  its  own  substance  the  chem- 
ical bodies  which  characterize  the  fluid  it  [jours  forth? 

This  question  is  naturally  the  first  to  be  asked,  neverthe- 
less it  will  be  of  advantage  to  defer  it  for  the  present,  and, 
while  still  bearing  it  in  mind,  to  pass  on  to  the  second  ques- 
tion :  By  what  mechanism  is  the  activity  of  the  secreting 
cells  brought  into  play  ? 

While  fasting,  a  small  quantity  only  of  saliva  is  poured 
into  the  month  ;  the  buccal  cavity  is  just  moist  and  nothing 
more.  When  food  is  taken,  or  when  any  sapid  or  stimulat- 
ing substance,  or  indeed  a  body  of  any  kind,  is  introduced 
into  the  mouth,  the  flow  induced  may  be  ver}'  copious. 
Indeed  the  (quantity  secreted  in  ordinary  life  during  24  hours 
has  been  roughly  calculated  at  as  much  as  from  1  to  2  liters. 
An  abundant  secretion  in  the  absence  of  food  in  the  mouth 
may  be  called  forth  by  an  emotion,  as  when  the  mouth  wa- 
ters at  the  sight  of  food,  or  by  a  smell,  or  l)y  events  occur^ 
ring  in  the  stomach,  as  in  some  cisesof  nausea.  Evidently 
in  these  cases  some  nervous  mechanism  is  at  work.  In 
studying  the  action  ol"  this  nervous  mechanism,  it  will  be  of 


THE    ACT    OF    SECRETION.  347 

advantage  to  confine  our  attention  at  first  to  the  submaxil- 
lary gland. 

The  submaxinary  gland  (Fig.  107)  is  supplied  witli  nerves 
from  two  sources  :  from  tiie  cervical  sympathetic  along  the 
suhmaxillary  arteries,  and  from  the  seventh  or  facial  nerve 
by  fihres,  whicli,  running  in  the  chorda  t^'mpani,  join  the 
lingual  branch  of  the  fifth  nerve,  from  which  thev  diverge 
close  under  the  lower  jaw,  and  run  as  a  small  nerve  close 
beside  the  duct  to  the  gland. 

If  a  tube  be  placed  in  the  duct,  it  is  seen  that  when  sapid 
substances  are  placed  on  the  tongue,  or  the  tongue  is  stim- 
ulated in  any  other  wa}',  or  the  lingual  nerve  is  laid  bare 
and  stimulated  with  an  interrupted  current,  a  copious  flow 
of  saliva  takes  place.  If  the  sympathetic  be  divided,  stim- 
ulation of  the  tongue  or  lingual  nerve  still  produces  a  flow. 
But  if  the  sn:iall  chorda  nerve  spoken  of  above  be  divided, 
stimulation  of  the  tongue  or  lingual  nerve  produces  no  flow. 

Evidently  the  flow  of  saliva  is  a  nervous  reflex  action,  the 
lingual  nerve  serving  as  the  channel  for  the  atferent  and  the 
small  chorda  nerve  for  the  efferent  impulses.  If  the  trunk 
of  the  lingual  be  divided  above  the  point  where  tlie  ciiorda 
leaves  it,  as  at  Fig.  107,  n.  /'.,  stimulation  of  the  tongue  pro- 
duces, under  ordinary  circumstances,  no  flow.  This  shows 
that  the  centre  of  the  reflex  action  is  higher  up  than  the 
point  of  section  ;  it  lies  in  fact  in  the  brain. 

In  the  angle  between  the  lingual  and  the  chorda,  where  the 
latter  leaves  the  former  to  pass  to  the  gland,  lies  the  small  submax- 
illar}'  ganglion  (represented  diagranunaticalh^  in  Fig.  107,  sm.  gl. ), 
from  which  branches  pass  to  the  lingual  on  the  one  hand  and  to 
the  chorda  on  the  other  ;  branches  may  also  be  traced  towards 
the  ducts  and  glands  and  towards  the  tongue.  It  has  been  much 
debated  whether  this  ganglion  can  act  as  a  centre  of  reflex  ac- 
tion. 

Bernard'  found  that  after  he  had  divided  the  conjoined  lingual 
and  chorda  at  about  one  cm.  above  the  place  where  the  chorda 
diverges  to  the  gland  (as  at  n.  /'.,  Fig.  107),  stimulation  of  the  lin- 
gual at  about  3  or  4  cm.  distance  below  the  ganglion  still  caused 
a  flow  of  saliva  ;  this  eftect  however  was  no  longer  seen  when 
the  branches  passing  from  the  ganglion  to  the  lingual  had  been 
previously  divided.  He  explained  the  result  by  supposing  that 
the  impulses  generated  b}^  the  stimulus  were  conve3"ed  by  atiferent 
flbres  in  the  lingual,  along  the  lingual  roots  of  the  ganglion  to 
the  ganglion,  and  were  thence  reflected  by  efterent  tibres  along 

'  Comptes  Rondus,  1SG2,  ii,  341. 


348      TflE    TISSUES    AND    MECHANISMS    OF    DIGESTION. 

the  branclios  from  the  gaiiijlion  to  theehorda  and  so  to  the  gland. 
The  gan<^Uon,  in  tact,  acted  as  a  rellex  centre.  ThesanK;  appar- 
ent rertex  secretion  could  also  be  induced,  but  less  readily,  by 

Flu.  107. 


c,^.^' 


Diagrammatic  Representation  of  the  Submaxillary  Gland  of  the  Dog  with  its 
Nerves  and  Bloodvessels. 

(This  is  not  intended  to  illustrate  the  exact  anatomical  relations  of  the  several 
structures.) 

sin.  gld.  The  submaxillary  gland,  into  the  duct  {sm.  d.)  of  which  a  canula  has 
been  tied.    The  sublingual  gland  and  duct  are  not  shown. 

n.l.,n.l'.  The  lingual  branch  nerve.  ch.t.,ch.t'.  The  chorda  tympani,  proceed- 
ing from  the  facial  nerve,  becoming  conjoined  with  the  lingual  at  n.  I',  and  afterwards 
diverging  and  passing  to  the  gland  along  the  duct. 

sm.  gl.  The  submaxillary  ganglion  with  its  several  roots,  n.l.  The  lingual  pro- 
ceeding to  the  tongue. 

a.  car.  The  carotid  artery,  two  branches  of  which,  a.  sm.  a.  and  r.  sm.  p.,  pass  to 
the  anterior  and  posterior  parts  of  the  gland,  v.sm.  the  anterior  and  posterior  veins 
from  the  gland,  falling  into  v.j.  the  jugular  vein. 

V.  syra.    The  conjoined  vagus  and  sympathetic  trunks. 

gl.cer.s.  The  super-cervicai  ganglion,  two  branches  of  which  forming  a  plexus 
(a./.)  over  the  facial  artery,  are  distributed  (n.  sym.  sm.)  along  the  two  glandular  ar- 
teries to  the  anterior  and  posterior  portions  of  the  gland. 

The  arrows  indicate  the  direction  taken  by  the  nervous  impulses  during  reflex 
stimulation  of  the  gland.  They  ascend  to  the  brain  by  the  lingual  and  descend  by 
the  chorda  tympani. 


pinching  the  peripheral  branches  of  the  linirual  near  the  tongue, 
or  by  dipping  them  into  concentrated  salt  solution.     In  this  case 


SUBMAXILLARY    GANGLION.  349 


also  the  secretion  failed  to  appear  if  the  Ungual  roots  of  the  gan- 
glion were  divided.  8uch  a  retlex  secretion  Avas  very  difficult  to 
obtain  bv  stimulation  of  the  mucous  membrane  of  the  tongue  ; 
but  Bernard  was  successful  when  he  stimulated  the  tongue  di- 
rectly with  a  galvanic  current  or  drew  the  tongue  out  and  placed 
ether  on  its  surface.  The  secretion  in  all  these  cases  was  accom- 
panied by  a  dilation  of  the  bloodvessels  of  the  gland,  and  the 
effect  on  the  gland  was  indeed  wholly  similar  to  that  of  directly 
stimulating  the  chorda.  Bernard  further  insisted  that  in  these 
experiments  no  anaesthetics  were  to  be  used,  and  observed  that 
the  retlex  etlect  was  no  longer  visible  when  two  or  three  days  had 
elapsed  after  section  of  the  conjoined  lingual  and  chorda  trunks. 
Both  these  facts  rather  militate  against  his  view,  since  it  seems 
improbable  that  a  spomdic  ganglion  should  be  so  susceptible  of 
anaesthetics,  or  that  degeneration  and  functional  incapacity  of 
the  ganglion  should  follow  upon  section  of  the  conjoined  lingual 
and  chorda  so  long  as  the  afferent  and  efferent  connections  of  the 
ganglion  with  the  gland  and  tongue  were  kept  up. 

Eckhard'  in  repeating  Bernard's  experiments  failed  to  obtain 
any  effect  from  dipping  the  endings  of  the  lingual  nerve  in  salt 
solution  or  from  placing  ether  on  the  tongue,  and  he  very  natur- 
ally argued  (being  supported  in  this  by  Ileidenhain'-)  that  the 
effects  seen  when  galvanic  stimulation  was  employed  were  due  to 
an  escape  of  the  current  upon  the  chorda  tibres.  Schiff  ^  did  ob- 
tain retlex  secretion  after  section  of  the  conjoined  lingual  and 
chorda,  by  direct  galvanic  stimulation  of  the  tongue  and  by  pour- 
ing ether  on  the  surface  of  that  organ  ;  but  the  currents  neces- 
sary' in  the  first  case  to  produce  any  effect  were  so  strong  that 
escape  must  have  taken  place,  and  in  the  second  case  the  secre- 
tion appeared  even  though  the  lingual  was  divided  close  under 
the  tongue,  and  when,  therefore,  this  nerve  could  not  have  been 
the  channel  for  conveying  impulses  to  the  submaxillary  ganglion. 
He  further  pointed  out  that  in  large  dogs  at  all  events,  certain 
fibres  of  the  c.iorda  after  running  along  the  conjoined  lingual 
and  chorda  do  not  leave  the  lingual  with  the  rest  of  the  fitjres 
going  straight  to  the  gland,  but  continue  in  the  lingual  close  up 
to  the  tongue,  then  bend  round  and  as  recurrent  fibres  run  back 
and  eventually  join  the  nerve  going  to  the  gland.  He  in  conse- 
quence argued  that  Bernard  in  stimulating  the  lingual  below 
the  divergence  of  the  chorda  was  in  reality  stimulating  not 
afferent  but  efferent  fibres.  But  in  such  a  case  these  recur- 
rent fibres  must  pass  to  the  chorda  through  the  ganglion,  if 
Bernard's  result  be  true  that  the  refiex  efiect  ceases  when  the 
lingual  roots  of  the  ganglion  are  divided.  Schift"  further  states, 
that  these  recurrent  fibres  degenerate  in  the  retrograde  portion 
of  their  course  when  the  lingual  is  divided  near  the  tongue,  and 

1  Zt.  f.  rat.  Med.,  xxix  (1867),  p.  74. 

^  Breslan.  Stndien,  1868. 

*  Moleschott's  Untei-suchungen,  x  (1870),  423. 

30 


150      THE    TISSUES    AND    MECHANISMS    OF    DIGESTION. 


that  MoctU'ct  follows  upon  sliinulation  of  tlie  linunal  after  section 
of  the  coiijoiiu'd  chonla  and  liiiLijual  if  the  liiiuual  iiave  some  live 
or  six  (lays  previously  hi-en  divuled  (dose  to  the  ton<^iie  so  as  to 
cause  deiieneratiou  of  the  recurrent  lihres,  jirovided  that  the 
stinuilation  he  not  so  strong  as  to  lead  to  an  es(;aj)e  of  the  current 
to  the  main  chorda,  fil)res.  In  small  dogs  Schilf  could  not  so 
readily  demonstrate  these  recurrent  lihres,  and  though  he  says 
tlie  ai)i)arent  rellex  secretion  is  more  easily  ohtained  in  large  dogs, 
such  as  ]?crnard  i)robably  used,  than  in  smaller  ones,  it  is  im- 
prol)al)le  that  mere  size  should  make  such  adilference  in  nervous 
distribution  ;  and  if  an  escape  of  current  can  explain  the  results 
in  the  one  case  it  can  also  probably  in  the  other. 

Bidder's'  account  of  the  nerves  in  the  ganglion  at  first  sight 
oilers  support  to  Bernard's  views.  In  the  dog  he  tinds,  passing 
from  the  ganglion  direct  to  the  toni^ue,  meduUated  nerve-libres 
which  do  not  degenerate  when  the  chorda  is  divided  at  its  exit 
from  the  skull.  These  fibres  accordingly  w^ould  seem  to  take 
their  origin  in  the  ganglion  and  to  be  the  afierent  nerve  required 
for  Bernard's  views.  When  ]5idder  divided  the  conjoined  lingual 
and  chorda,  he  found  the  chorda  fibres  after  about  three  weeks 
completely  degenerated,  not  only  those  forming  the  nerve  going 
to  the  gland,  but  those  also  constituting  the  branches  going  to  the 
ganglion,  L  <?.,  the  chorda  roots  of  the  ganglion.  In  the  ganglion 
and  in  the  branches  going  from  the  ganglion  to  the  gland  were 
seen  numerous  degenerated  fibres  in  the  midst  of  undegenerated 
(but  non-medullated)  fibres  which  seem  to  have  their  origin  in 
the  ganglion  itself.  Thus  after  complete  degeneration  of  the 
true  chorda  fibres,  there  still  remained  intact  (1)  the  ganglion, 
(2)  fibres  from  the  ganglion  to  the  tongue,  and  (;])  fibres  from  the 
ganglion  to  the  gland,  in  fact,  exactly  the  nervous  mechanism 
demanded  by  Bernard's  view.  But  Bidder,  like  Eckhard,  tailed 
to  obtain  a  rertex  secretion  by  pouring  ether  on  the  tongue  after 
division  of  the  conjoined  lingual  and  chorda,  and  he  found  that 
galvanic  stimulation  of  the  nerves  going  from  the  ganglion  to  the 
tongue  was  of  no  effect,  provided  that  errors  due  to  escape  of  cur- 
rent on  to  the  main  chorda  fibres  were  avoided  by  previously  in- 
ducing through  section  degeneration  of  the  chorda  fibres  includ- 
ing the  chorda  roots  of  the  ganglion.  So  that  Bidder's  results 
in  the  end  oppose  the  view  tliat  the  ganglion  can  act  as  a  centre 
of  retiex  action.  In  fact,  such  a  view  must  be  regarded  at  present 
as  not  proven. 

AVe  have,  contrary  to  our  wont,  given  this  controversy  in  de- 
tail, on  account  of  the  great  importance  of  the  subject.  The  sub- 
maxillary ganglion  is  almost  the  only  case  in  which  it  has  been 
with  any  success  attempted  to  demonstrate  by  experiment  the 
reflex  action  of  a  sporadic  ganglion,  and  the  question  whether 
sporadic  ganglia  can  or  cannot  serve  as  centres  of  reflex  action  is 
at  the  present  time  at  least  a  question  of  much  interest. 

'  Reichert  u.  Du  Bois-Eey mend's  Archiv,  1867,  p.  1. 


ACTION  OF  CHORDA  TYMPANI.         351 

Stimulation  of  the  glosso  pharvngeal  is  even  more  effectual 
than  that  of  the  Ungual.  Prohahly  this,  indeed,  is  tlie  chief 
afferent  nerve  in  ordinary  secretion.  Stimulation  of  the 
mucous  membrane  of  the  stomach  (as  b}'  food  introduced 
through  a  gastric  fistula)  or  of  the  vagus  also  produces  a 
flow  of  saliva,  as  indeed  may  stimulation  of  the  sciatic,  and 
probably  of  many  other  afferent  nerves.  All  these  cases  are 
instances  of  reflex  action,  the  cerebro-spinal  system  acting 
as  a  centre.  In  most  cases  the  centre  lies  in  the  medulla 
oblongata,  and  secretion  may  be  caused  by  direct  stimula- 
tion of  this  organ  ;  where  ideas  or  emotions  cause  a  flow, 
the  stimulation  begins  higher  up  in  the  brain  ;  and  in  cases 
where  the  sense  of  taste,  as  distinguished  from  general  sen- 
sation, is  concerned  in  the  matter,  it  is  probable  that  the 
afferent  impulses  ascend  into  tlie  brain  higher  up  than  the 
meduUa  before  the}'  return  as  efferent  impulses.  In  all  these 
cases  the  chorda  tympani  is  the  sole  efferent  nerve.  Section 
of  that  nerve,  either  where  the  fibres  pass  from  the  lingual 
nerve  and  the  submaxillar}'  ganglion  to  the  gland,  or  where 
it  runs  in  the  same  sheatli  as  the  lingual,  or  in  any  part  of 
its  course  from  the  main  facial  trunk  to  the  lingual,  puts  an 
end  at  once  (with  the  disputed  exception  mentioned  above) 
to  the  possibility  of  any  flow  being  excited  by  stimuli  ap- 
plied to  the  mouth,  or  any  part  of  the  body  other  than  the 
gland  itself 

This  statement  is  probably  too  absolute  ;  for,  though  satisfac- 
tory evidence  of  reflex  excitation  of  the  submaxillary  gland  by 
means  of  die  sympathetic  is  not  forthcoming,  it  seems  unlikely 
that  the  secretory,  as  distinguished  from  the  vaso-motor  activity 
of  this  nerve,  should  never  be  put  to  use  in  actual  life. 

In  life,  then,  tlie  flow  of  saliva  is  brought  about  by  the 
advent  to  the  gland  along  the  chorda  tympani  of  efferent 
impulses,  started  chiefly  by  reflex  actions.  The  inquiry  thus 
narrows  itself  to  the  question  :  In  what  manner  do  these 
efferent  impulses  cause  the  increase  of  flow? 

If  in  a  dog  a  tube  be  introduced  into  Wharton's  duct,  and 
the  chorda  be  divided,  the  flow,  if  any  be  going  on,  is  from 
the  lack  of  efferent  impulses  arrested.  On  passing  an  inter- 
rupted current  througii  the  peripheral  portion  of  the  chorda, 
a  copious  secretion  at  once  takes  place,  and  the  saliva  l)e- 
gins  to  rise  rapidly  in  the  tube  ;  a  ver^-  short  time  after  the 
application  of  the  current  the  flow  reaches  a  maximum,  which 
is  maintained  for  some  time,  and  then,  if  the  current  be  long 
continued,  gradually  lessens.     If  the  current  be  applied  for 


352     THE    TISSUES    AND    MECHANISMS    OF    DIGESTION. 

a  short  time  only,  the  secretion  may  last  for  some  time  after 
tiie  cinrent  has  lieen  sliul  oft'.  Tlie  saliva  thus  obtained  is 
bnt  slis2;htly  viscid,  and  contains  hut  few  salivary  corpuscles 
or  protoplasmic  lum})S.  If  the  «;land  itself  he  watched,  while 
its  activity  is  thus  roused,  it  will  be  seen  that  its  arteries 
are  dilated  and  its  capillaries  fdled.  and  that  the  blood  flows 
rapidly  through  the  veins  in  a  full  stream  and  of  bright  arte- 
rial hue,  fretpiently  with  pulsating  movements.  If  a  vein  be 
opened,  this  large  increase  of  flow,  and  the  lessening  of  the 
ordinary  deox^'genation  of  the  blood,  consequent  upon  the 
rapid  stream,  will  be  still  more  evident.  It  is  clear  that 
excitation  of  the  chorda  acts  on  some  local  vaso-motor  centre 
in  the  gland,  and  largely  dilates  the  arteries  ;  the  nerve  acts 
energetically  as  a  dilator  nerve. 

Thus  stimulation  of  the  chorda  l)rings  about  two  events, 
a  dilation  of  the  bloodvessels  of  the  gland  and  a  flow  of 
saliva.  The  question  at  once  arises,  Is  not  the  latter  simply 
the  result  of  the  former?  The  activity  of  the  epitiielial 
secreting  cell,  like  that  of  any  other  form  of  protoplasm,  is 
dei)cndent  on  blood  su|)ply.  ^V  hen  the  small  arteries  of  the 
gland  dilate,  the  capillaries  become  fuller,  more  blood  passes 
through  them  in  a  given  time,  a  larger  amount  of  nutritive 
material  passes  away  from  them  into  the  surrounding  lymph- 
spaces,  and  so  into  the  ej)ithelium  cells  (and  it  must  be  re- 
membered that  though  by  the  dilation  the  pressure  in  the 
arteries  of  the  gland  is  diminished,  that  of  the  capillaries 
and  veins  is  increased),  the  result  of  which  must  be  to 
quicken  the  processes  going  on  in  the  cells,  and  to  stir  these 
up  to  greater  activity.  This  must  be  so  :  but  it  does  not 
necessarily  follow  that  the  activity  thus  excited  should  take 
on  the  form  of  secretion.  It  is  quite  possible  to  conceive 
that  the  increased  l)lood-supply  sliould  lead  only  to  the  ac- 
cumulation in  the  cell  of  the  constituents  of  the  saliva,  or  of 
the  materials  for  their  construction,  and  not  to  a  discharge 
of  the  secretion.  A  man  works  better  for  being  fed,  but 
feeding  does  not  make  him  work  in  the  absence  of  any 
stimulus.  The  increased  blood-supply  therefore,  while  fa- 
vorable to  active  secretion,  need  not  necessarily  bring  it 
about.  Moreover,  the  following  facts  deserve  attention  : 
When  the  chorda  is  energetically  stimulated,  the  pressure 
acquired  by  the  saliva  in  the  duct  exceeds  the  arterial  blood- 
pressure  for  the  time  being;  that  is  to  say,  the  pressure  of 
fluid  in  the  gland  outside  the  bloodvessels  is  greater  than 
that  of  the  blood  inside  the  bloodvessels.     This  must,  what- 


ACTION    OF    CHORDA    TYMPANI.  353 

ever  be  tlie  exact  mode  of  transit  of  nutritive  material 
through  the  vascular  walls,  tend  to  check  that  transit. 
[It  is  also  an  interesting  fact  tiiat  tlie  temperature  of  the 
saliva  at  the  time  of  secretion  is  from  1°  to  2^  F.  higher 
than  that  of  the  arterial  hlood  supplying  the  gland.]  Again, 
if  the  head  of  an  animal  be  rapidly  cut  off.  and  the  chorda 
immediately  stimulated,  a  flow  of  saliva  takes  place  far  too 
copious  to  be  accounted  for  b}' the  emptying  of  the  salivary 
channels  through  any  supposed  contraction  of  their  walls. 
In  this  case  secretion  is  excited  in  the  absence  of  blood- 
supply.  Lastly,  if  a  small  quantity  of  atropin  be  injected 
into  the  veins,  stimulation  of  the  chorda  produces  no  secre- 
tion of  saliva  at  all,  though  the  dilation  of  the  bloodvessels 
takes  place  as  usual.  This  remarkable  fact  can  only  be  ac- 
counted for  by  sujiposing  that  the  chorda  contains  two  sets 
of  fibres,  one  secreting  fibres,  acting  directl}'  on  the  epi- 
thelium cells  only,  and  the  other  vaso-motor  or  dilating 
fibres,  acting  on  the  bloodvessels  only  ;  and  that  atro))in, 
while  it  has  no  effect  on  the  latter,  paralyzes  the  former  just 
as  it  paralyzes  the  inhibitory  fibres  of  the  vagus.  These 
facts,  and  especially  the  last,  clearly  prove  that,  when  the 
chorda  is  stimulated,  there  pass  down  the  nerve,  in  addition 
to  impulses  aflecting  the  blood-sui)ply,  impulses  affecting 
directly  the  protoplasm  of  the  secreting  cells,  and  calling 
it  into  action,  just  as  similar  impulses  call  into  action  the 
contractility  of  the  protoplasm  of  a  muscular  fibre.  Indeed, 
the  two  things,  secreting  activity  and  contracting  activity, 
are  quite  parallel.  We  know  that,  when  a  muscle  contracts, 
its  bloodvessels  dilate  ;  and,  just  as  by  atroi)in  the  secreting 
action  of  the  gland  may  be  isolated  from  the  vascular  dila- 
tion, so  by  urari  muscular  contraction  may  be  removed,  and 
leave  dilation  of  the  bloodvessels  as  the  only  effect  of  stimu- 
lating the  muscular  nerve.  In  both  cases  the  greater  flow 
of  blood  is  an  adjuvant  to,  not  the  exciting  cause  of,  the 
activit}'  of  the  protoplasm. 

If  the  chorda  acts  thus  directly  on  the  secreting  cell,  there 
must  be  a  physiological  and  probably  an  anatomical  connection 
between  tlie  cell  and  the  nerve-fibre.  Although  Pfluger'si  obser- 
vations as  to  the  actual  mode  in  which  the  nerves  end  in  the 
gland  have  not  been  generally  accepted,  nerve- fibres  have  been 
traced  to  the  exterior  of  the  alveoli,  and  Kupfter^  has  shown  that 

'  Strieker's  Histology,  Syd.  Soc.  Trans.  Art.  Salivary  Glands  (by 
Pfluger). 

^  Ludwig's  Festgabe,  p.  Ixiv. 


^54     THE    TISSUES    AND    MECHANISMS    OF    DIGESTION, 


in  the  so-called  salivary  glands  of  liJaUa^  the  nerve-fil)res  cer- 
tainly i)ass  into  the  protoplasm  and  apparently  end  in  the  nuclei 
of  the  cells. 

When  the  cervical  symi)athetic  is  stimulated,  the  vascular 
effects  are  the  exact  contraiy  of  those  seen  when  the  chorda 
is  stimulated.  The  small  arteries  are  contracted,  and  a 
small  quantity  of  dark  venous  blood  escai)es  by  the  vein. 
Sometimes,  indeed,  the  flow  through  the  inland  is  almost 
arrested.  The  sympathetic  therefore  acts  as  a  constrictor 
nerve,  and  in  this  sense  is  antagonistic  to  the  ciiorda.  We 
have  already  referred  to  the  probable  existence  of  a  local 
vasomotor  centre  situated  in  the  gland  itself,  in  which  in- 
deed there  are  found  ganglionic  cells  in  abundance.  The 
fact  that  section  of  the  cervical  sympathetic  does  not  cause 
complete  dilation  of  the  vessels  of  the  gland — the  dilating 
effects  of  stimulation  of  the  chorda  being  fully  evident  after 
previous  section  of  the  sympathetic — affords  additional  sup- 
port to  this  view.  We  may  accordingly  state  that,  while 
the  ciiorda  tympani  inhibits,  the  sympathetic  exalts,  the 
action  of  this  local  centre. 

The  antagonism  between  the  two,  as  far  as  the  blood-supply 
is  concerned,  is  very  imperfect,  the  sympathetic  being  the  more 
powerful  ;  thus  stimulation  of  the  chorda  produces  very  little 
eflect  in  altering  the  results  of  a  concomitant  strong  stimulation 
of  the  sympathetic' 

The  effects  on  the  flow  of  saliva  from  the  submaxillary 
gland  of  the  dog  brought  about  by  stimulation  of  the  sym- 
pathetic, are  very  peculiar.  A  slight  increase  of  How  is 
seen,  but  this  soon  passes  off,  and  what  saliva  is  secreted  is 
remarkabl}'  viscid,  of  higher  specific  gravity,  and  richer  in 
corpuscles  and  protoplasmic  lumps,  and  it  is  said  to  be  more 
active  on  starch  than  the  chorda  saliva.'-'  This  action  of  the 
sympathetic  is  not  affected  by  atroi)in. 

In  the  cat  on  the  contrary  the  chorda  saliva  is  distinctly 
more  viscid  than  the  sym[)athetic  saliva,  though  it  is  pro- 
duced in  greater  abundance  upon  stimulation.  The  secre- 
tory activity  of  tiie  cat's  sympathetic  is  also  arrested  by 
atropin,  though  a  larger  dose  than  that  which  pardyzes  the 
chorda  is  required.^     In  the  rabbit  both  chorda  and  sympa- 

'  Frev,  Ludwig's  Arbeiten,  1876,  p.  89. 

'  Eckhard,  Beitrage.  ii  (1860),  p.  81 ;  iii  (1864),  p.  39. 

3  Langlev,  Journ.  Phvsiol.,  i  (1878),  p.  96. 


CHORDA     AND    SYMPATHETIC.  355 

tlielic  saliva  are  free  fi'om  mncns,  tbonoh  the  latter  is  se- 
creted morescantil}'  than  the  former.  The  marked  contrast 
therefore  shoNvn  in  the  dog  between  tlie  two  kinds  of  saliva 
must  not  l)e  considered  as  of  fundamental  origin.  We  shall 
return  later  on  to  a  discussion  of  the  essential  differences 
between  chorda  and  sympathetic  action. 

Most  observers  agree  that  when  both  chorda  and  sj^mpathetic 
are  stimulated  at  the  same  time  with  strong  currents,  the  action 
of  the  chorda,  contrary  to  what  takes  place  as  far  as  the  blood- 
supply  is  concerned,  prevails  as  far  as  secretion  is  concerned,  /.  e., 
the  flow  is  copious  and  watery.  But  the  nature  of  the  differ- 
ences exhibited  by  the  chorda  and  sj-mpathelic  in  reference  to 
the  character  of  the  secretion  and  the  relations  of  the  two  will 
be  discussed  later  on,  see  p.  871. 

Bernard'  observed  that  after  section  of  all  the  nerves  going  to 
the  ghmd,  a  continuous  and  fairly  copious  secretion  of  a  watery 
sahva  soon  set  in  and  continued  for  some  time.  Heidenhain-  ob- 
served the  same  thing,  the  continuous  flow  beginning  from  four 
to  twenty-four  hours  after  section  of  the  nerves,  soon  reaching  a 
maximum,  and  after  some  weeks  decreasing  again  as  regenera- 
tion of  the  nerves  took  place.  During  this  ''  paralytic  secretion," 
as  it  is  called,  the  gland  diminishes  in  size,  and  in  some  cases 
where  the  nerves  are  not  restored  appears  to  undergo  degenera- 
tion. A  paralytic  secretion  also  appears  if  the  chorda  only  be 
divided  ;  and  urari  poisoning'  produces  a  similar  liow^.  The 
paralytic  secretion  is  watery  but  contains  both  mucin  and  sali- 
var}'  corpuscles.  The  mechanism  of  its  production  is  obscure, 
but  Heidenhain  observed  a  similar  continuous  secretion  to  result 
when  the  duct  of  the  gland  ^^as  kept  ligatured  for  twentA'-four 
hours  and  then  opened.  Heidenhain  also  observed  that  when 
the  nerves  of  the  gland  on  one  side  were  cut,  a  paralytic  secre- 
tion appeared  in  the  gland  of  the  other  side  also. 

The  natural  reflex  act  of  secietion  may  be  inhil)ited,  like 
the  reflex  action  of  the  vaso-motor  nerves,  as  its  cerebral 
centre.  Thus  when,  as  in  the  old  rice  ordeal,  fear  parches 
the  mouth,  it  is  probable  that  the  afferent  imj)ulses  passing 
from  tlie  moutheease,  througii  emotional  inhibition  of  their 
reflex  centre,  to  give  rise  to  efl'erent  impulses 

The  history  of  the  submaxillary  gland  then  teaches  us  that 
secretion  in  this  instance  is  a  reflex  action,  the  efferent  im- 
pulses of  which  directly  affect  the  secreting  cells,  and  that 
the  vascular  phenomena  may  aesist,  but  are  not  the  direct 

^  Robin's  Journal  tie  I'Anat.  et  de  la  Plivsiolog.,  i  (1864),  p.  511. 
2  Op.  cit.  2  Bernard,  op.  cit. 


356      THE    TISSUES    AND    MECHANISMS    OF    DIGESTION. 

cause  of  the  flow.  We  liave  dwelt  lonu:  on  this  gland  he- 
cause  it  has  been  more  fiuitfully  studied  tlian  any  other. 
The  nervous  meclianisnis  of  tlie  other  secretions  may  be 
passed  over  much  more  rapidl}'. 

Parotid. — The  secretion  of  this  gland,  lil<e  that  of  tlie  sub- 
maxillary, is  governed  by  two  sets  of  fibres  ;  one  of  cerebro- 
spinal origin,  running  along  the  auriculo-temporal  branch 
of  the  fifth  nerve,  but  originating  eitlier  in  the  glosso- 
pharyngeal or  the  facial,  and  the  otlier  of  sympatlietic  oi-igin 
coming  from  tlie  cervical  sympathetic.  Stimulation  of  the 
cerebro-spinal  fibres  produces  a  copious  flow  of  watery  saliva, 
free  from  mucus,  the  secretion  reaching  in  the  dog  a  pres- 
sure of  118  mm.  mercury;  sLiuiulation  of  the  cervical  sym- 
pathetic gives  rise  in  the  rabbit  to  a  secretion  free  from 
mucus  i)ut  rich  in  organic  matter  and  of  greater  amylolytic 
power  than  the  cerebro-spinal  secretion,  but  in  the  dog  little 
or  no  secretion  is  produced,  though,  as  we  shall  see  later  on, 
certain  changes  are  brought  about  in  the  gland  itself.^  In 
1)0th  animals  the  cerebro  spinal  fibres  are  vaso-dilator,  and 
the  sym[)athetic  fibres  vaso-coustrictor  in  action.  Stimula- 
tion of  the  central  end  of  the  glosso-pharyngeal  produces 
by  reflex  action  a  secretion  of  the  parotid,  but  that  of  the 
lingual  is  said  to  be  without  effect. -^ 

In  the  dog  the  secretory  fibres  of  cerebro-spinal  origin  ari.se 
from  the  glosso-pharyngeal  nerve,  pass  by  the  ramus  tympankus 
(jlossopJiari/ngei  to  the  tympanum,  and  then  join  the  nervus  petrosus 
siqyerJiciaUs  minoi\  by  which  they  reach  the  ramus  auriculo-tem- 
poralis  of  the  fifth. ^  In  the  rabbit  the  fibres  also  run  in  the  ramus 
auriculo-temporalis^  but  it  does  not  seem  clear  whether  they  spring 
from  the  glosso-pharyngeal  as  in  the  dog,  or  from  the  facial. 

Eckhard*  failed,  in  the  parotid  of  the  sheep,  to  get  any  effect, 
whatever  nerve  he  stimulated  ;  a  continuous  secretion  going  on, 
and  being  neither  increased  or  decreased  by  nerve  stimulation. 

Gastric  Juice. — The  presence  of  food  in  the  stomach  causes 
a  copious  flow  of  gastric  juice.  The  quantity  secreted  in 
man  in  the  twenty-four  hours  has  been  calculated  at  from  13 
to  14  liters.      When  the  gastric  mucous  membrane  is  stimu- 

^   Heidenhain,  Pfliiger's  Archiv,  xvii  (1878),  p.  1. 
2  Xuwrocki,  Breslau.  Studieu,  iv  (1868),  p.  125. 

^  Xawrocki,  op.  cit.  Loeb,  Eckhard's  Beitriige,  v  (18G9),  p.  1.  Hei- 
denhain, op.  cit, 

"  Beitriige,  vii  (1876),  p.  161. 


SECRETION    OF    GASTRIC    JUICE.  357 

lated  mechanically,  as  with  a  feather,  secretion  is  excited  ; 
but  to  a  very  small  amount  even  when  the  whole  interior 
surface  of  the  stomach  is  tlius  repeatedly  stimulated.  The 
most  eHicient  stimulus  is  the  natural  stimulus,  viz.,  food  ; 
but  dilute  alkalies  seem  to  have  unusually  powerful  stimu- 
lating effects ;  thus  the  swallowing  of  saliva  at  once  provokes 
a  flow  of  gastric  juice.  During  fasting  the  gastvic  mem- 
brane is  of  a  pale-gray  color;  during  digestion  it  becomes 
red  and  flushed,  and  to  a  certain  extent  tumid.  The  secre- 
tion of  gastric  juice,  therefore,  seems  to  be  accompanied  b3' 
vascular  dilation  in  the  same  way  as  in  the  secretion  of 
saliva. 

Seeing  that,  unlike  the  case  of  the  salivary  secretion,  food 
is  brouo-htinto  the  immediate  neiohboriiood  of  the  secretiug 
cells,  it  is  exceedingly  probalile  that  a  great  deal  of  the  se- 
cretion is  the  result  of  the  working  of  a  local  mechanism  ; 
and  when  a  mechanical  stimulus  is  applied  to  one  spot  of 
the  gastric  memlu'ane  the  secretion  is  limited  to  the  neigh- 
borhood of  tiiat  spot  and  is  not  excited  in  distant  parts, 
Nevertheless,  since  the  flow  of  gastric  juice  ma>'  be  excited 
or  arrested  by  events  in  distant  parts,  as  by  emotions,  the 
gastric  membrane  must  be  in  some  wa}''  or  other  brought 
into  relation  with  the  central  nervous  system  ;  and  probably 
future  inquiries  will  disclose  a  mechanism  as  complete  as 
that  of  the  submaxillary  gland.  At  present,  however,  the 
matter  is  very  imperfectly  known. 

Heidenhain^  has  succeeded  in  the  dog  in  isolating  (after  the 
manner  of  Thiry's  method  with  the  intestine)  a  portion  of  the 
fundus  from  the  rest  of  the  stomach.  He  linds  that  introduc- 
tion of  food  into  the  (main)  stomach  gives  rise  to  a  secretion  of 
gastric  juice  in  the  isolated  fundus  portion.  This  would  at  tirst 
sight  seem  to  indicate  a  nervous  action,  but  the  secretion  in  the 
isolated  fundus  is  insigniticaut  unless  the  material  introduced 
into  the  main  stomach  be  such  as  can  be  digested  and  absorbed. 
A  similar  connection  between  the  act  of  secretion  and  the  absorp- 
tion of  digested  material  is  indicated  by  the  rate  of  secretion  of 
pepsin  after  a  meal.  Grutzner-  states  that  the  rate  of  secretion 
of  pepsin,  abundant  immediately  upon  food  being  taken,  falls 
during  the  flrst  and  second  hours  afterwards,  rises  again  up  to  a 
second  maximum  at  the  fourth  or  fifth  hours,  after  which  it 
finall}'  but  gradually  sinks,  the  curve  in  fact  being  not  unlike  that 
of  the  pancreatic  secretion  (see  Fig.  108).    And  Heidenhain^  finds 

1  Pfliiger's  Archiv,  xix  (1879),  p.  14S. 

^  Untersuch.  ii.  Bildmg  u.  Aussclieidung  des  Pepsin,  1875. 

^  Op.  cit. 


358      TIIK    TISSUES    AND    MECHANISMS    OF    DIGESTION. 


this  to  be  true  also  of  the  secretion  of  tlie  isolated  fuiulus  excited 
by  the  introduction  of  food  into  the  main  stomach.  Schitf  has 
for  many  years  maintained  that  the  secretion  of  gastric  juice  is 
dependent  on  the  gastric  cells  becoming  "  laden  "  with  pepsino- 
genous material  derived  from  the  absorbed  products  of  digestion 
and  especially  from  absorbed  dextrin.  But  the  amount  either  of 
pepsin  or  pepsinogenous  material  in  the  gasti-ic  membrane  does 
not,  according  to  Grlitzner,  run  parallel  to  the  amount  of  pei)sin 
in  the  secretion. 

The  amount  of  acid  in  the  secretion  is  much  more  constant 
than  the  i)epsin,  in  fact  varies  but  slightl3^  The  increase  of 
acidity  in  the  contents  of  a  meal  is  due  sinij)ly  to  the  fact  that 
the  acid  accumulates  as  the  gastric  juice  continues  to  be  secreted. 

Eutherford'^  found  that  the  gastric  membrane,  Hushed  during 
digestion,  became  pale  when  the  vagi  were  cut.  Stimulation  of 
the  central  end  of  either  vagus  caused  a  reddening  of  the  gastric 
membrane,  but  stimulation  of  the  peripheral  end  i)roduced  no 
constant  effect.  From  these  results  we  may  infer  that  allerent 
impulses  pass  up  the  vagus  and  by  inhibiting  in  the  medulla  the 
vaso-motor  centre  governing  the  gastric  l^lood vessels,  cause  a 
dilation  of  the  latter.  The  efferent  impulses  evidently  do  not 
descend  by  the  vagus  ;  probably,  therefore,  their  path  is  along  the 
sympathetic.  After  division  of  both  vagi,  gastric  juice  of  normal 
acidity  and  peptic  power  continues  to  be  secreted.  The  same 
occurs  after  division  of  both  splanchnic  nerves,  and  even  after 
extirpation  of  the  coeliac  ganglion. 

Bile. — When  the  acid  contents  of  the  stomach  are  poured 
over  the  orifice  of  the  biliaiy  duct,  a  gush  of  bile  takes 
place.  Indeed,  stimulation  of  this  region  of  the  duodenum 
with  a  dilute  acid  at  once  calls  forth  a  flow,  whereas  alkaline 
fluids  so  applied  have  little  or  no  effect.  This,  probably,  is 
a  reflex  action  leading  to  contraction  of  the  muscular  walls 
of  the  gall-bladder  and  ducts,  accompanied  by  a  relaxation 
of  the  sphincter  of  tlie  oriflce;  it  refers,  therefore,  to  the 
discharge  rather  than  to  the  secretion  of  bile. 

When  the  secretion  of  the  bile  is  studied  by  means  of  a 
biliar}'  fistula  (which,  however,  probably  induces  errors  by 
the  total  withdrawal  from  the  body  of  the  bile  which  should 
naturally  flow  into  the  intestine),  it  is  seen  to  rise  rapidly 
after  meals,  reaching  its  maximum  in  from  four  to  ten 
hours.  There  seems  to  be  an  immediate  sudden  rise  when 
food  is  taken,  then  a  fall,  followed  subsequently  by  a  more 
gradual  rise  up  to  the  maximum,  and  ending  in  a  final  fall. 

'  See  also  Leyons  sur  la  Phvsiologie  de  la  Digestion,  ii,  1867. 
2  Phil.  Trans.  Edin.,  xxvi  fl870). 


SECRETION    OF    PANCREATIC    JUICE.  359 

It  is  exceedingly  probable  tliat  these  A'ariations  are  due  to 
the  action  of  the  nervous  system,  but  the  exact  nature  of 
the  nervous  mechanism  is  unknown. 

Stimulation' of  the  splanc-hnics  causes  an  increase  in  the  flow 
from  a  biliary  fistula,  but  this  is  probably  due  to  contraction  of 
the  bile-ducts. 

Eutherford'  finds  that  the  injection  of  various  substances, 
ipecacuanha,  podophyllin,  etc.,  into  the  duodenum  causes  an 
increase  in  the  actual  secretion,  but  the  manner  of  the  increase 
is  not  yet  explained. 

Unlike  the  case  of  saliva,  the  pressure  nnder  which  the 
bile  is  secreted  never  exceeds  that  of  the  blood,  and  is  in 
general  very  low.  When  a  water  manometer  is  connected 
with  the  gall  bladder  of  a  guinea-pig,  the  <:/?R'/?/«  choJedochui^ 
being  ligatured,  the  fluid  maj^  rise  in  the  manometer  to 
about  200  mm.  (equivalent  to  about  16  mm.  mercur}-),  but 
not  much  beyond.  If  water  be  poured  into  the  open  eud 
of  the  manometer  so  as  to  raise  tlie  pressure  much  above 
200  mm.,  resorption  into  the  circulation  takes  place,  and 
the  fluid  in  the  manometer  sinks  to,  or  even  below,  tlie 
normal  level.^  The  quantity  secreted  in  man  in  the  24 
houi's  has  been  estimated  roughly  at  about  10  kilos,  but  the 
calculations  are  based  on  very  imperfect  data. 

Pancreatic  Juice. — The  relation  of  the  nervous  system  to 
the  secretion  of  the  pancreatic  juice  lias  been  studied  rather 
more  fully.  N.  O.  Bernstein^  finds  that  in  the  dog  the  se- 
cretion, after  food  has  been  taken,  follows  the  curve  given 
in  Fig.  108.  There  is  a  sudden  m^aximum  rise  immediatel}' 
after  food  has  been  taken.  This  must  be  due  to  nervous 
action.  Then  follows  a  fall,  after  which  there  is,  as  in  bile, 
a  secondary-  rise,  the  causation  of  which  may,  or  may  not, 
be  nervous  in  nature.  The  quantity  secreted  in  24  hours 
by  man  has  been  calculated  at  300  cc.  Like  the  salivary 
glands,  the  pancreas  while  secreting  is  flushed,  through 
dilation  of  its  bloodvessels. 


'  Journ.  Anat.  Phys.,  x,  xi  (1876,  1877) ;  Brit.  Med.  J.,  1878,  1879. 
^  Friedliinder  u.  Barisch  (Heidenhain),  Du  Bois-Reymond's  Archiv, 
1860,  p.  646. 
^  Ludwio's  Arbeiten,  1869. 


3G0     THE    TISSUES    AND    MECHANISMS    OF    DIGESTION. 


Aeconlini:  to  N.  ().  Bernstein,'  the  secretion  is  :it  on(!e  stopped 
by  nausea  or  voniitinji;.  Section  of  the  vaiz;us  stops  the  secretion 
lor  a  short  time  ;  it  soon  however  recommences.  Stimulation  of 
the  central  va^us  causes  an  arrest  lasting  for  some  time  after  the 
stimulus  has  l)een  removed.  It  is  probable,  therefore,  that  the 
arrest  of  secretion  during  vomiting  is  due  to  afferent  imjnilses 
ascending  the  vagus  and  descending  by  some  other  channel.     If 


4.0 

as 

1 

3.6 

f 

3.4 

12 

3.0 

2.8 

^6 

24 

72 

f 

ZO 

1.8 

^ 

1.6 

'                                                                         /\ 

1.4 

T    \ 

1.2 

/--.                /    V    / 

1.0 

V   /            --^.               /        Ky 

0.8 

V                --.        / 

0.6 

--.    / 

0.4 

\ 

02 

\ 

0 

M 

23  1  I2l3l4|5|6|7|8l9|l0lll|l2!t3|l4llbll6ll  12 13  I4|5l6l7l8  I9|l0 

Diagram  Illustrating  the  Influence  of  Food  on  the  Secretion  of  Pancreatic  Juice. — 
After  N.  O.  Bernstein. 

The  ab.scisP8e  represent  hours  after  taking  food  ;  the  ordinates  represent  in  cc.  tlie 
amount  of  secretion  in  10  minutes.  A  marked  rise  is  seen  at  B  immediately  after 
food  was  taken,  witii  a  secondary  rise  between  tlie  4th  and  5th  hours  afterwards. 
Where  the  line  is  dotted  the  observation  was  interrupted.  On  food  being  again 
given  at  C,  another  rise  is  seen,  followed  in  turn  by  a  depression  and  a  secondary 
rise  at  the  4th  hour.    A  very  similar  curve  would  represent  the  secretion  of  bile. 

all  the  nerves  going  to  the  pancreas  around  the  pancreatic  artery 
be  severed  as  completely  as  possible,  a  continuous  paralytic  tlow, 
not  increased  but  rather  diminished  by  food,  and  very  slightly  if 
at  all  hindered  by  nausea  or  stimulation  of  vagus,  is  brought  on. 
Heidenhain^  states  that  stimulation  of  the  medulla  oblongata 
causes  an  increased  flow. 


Op.  cit. 


^  Pfliiger's  Archiv,  x  (1875),  p.  557, 


SUCCUS    ENTERICUS.  361 

Succus  Entericus. — With  regard  to  the  secretion  furnished 
by  the  intestine  itself  onr  infoimation  is  very  limited. 
Thiry^  found  tliat  in  tlie  isolated  intestine  the  secretion  was 
not  a  constant  one,  but  needed  for  its  production  some  stimu- 
lus (mechanical  or  other),  whicii  probably  acted  in  a  reflex 
manner. 

Moreau^  found  that  after  section  of  the  nerves  going  to  a  piece 
of  intestine  isolated  after  Thiry's  method,  a  coiiious  flow  of  a  di- 
lute intestinal  juice  takes  place.  This  appears  to  be  comparable 
to  the  paralytic  flow  of  saliva  and  pancreatic  juice. 

Thus,  while  the  influence  of  the  nervous  system  is  in  the 
case  of  the  submaxillary  gland  tolerably  clear,  in  the  case 
of  the  other  secretions  we  have  much  yet  to  learn,  and 
must  rest  rather  on  the  analogy  with  the  submaxillary  gland 
than  on  any  known  facts.  We  cannot,  however,  go  far 
wrong,  if  we  conclude  that  in  all  cases  secretion  is  essen- 
tially due  to  an  increase  in  the  activity  of  the  epithelium 
cells,  and  that  variations  in  the  blood-supply  have  a  secon- 
dary- etfect  only. 

It  must,  however,  be  borne  in  mind  that  substances  brought 
to  the  secreting  cell  by  the  blood  may  possibly  act  as  chemical 
stimuli  of  its  protoplasm,  just  as  certain  chemical  substances 
may  stimulate  a  muscular  fibre  to  contraction  in  the  absence  of 
all  nerves.  Thus,  any  substance,  such  as  a  therapeutic  drug, 
may  aftect  any  given  secretion,  in  various  wa3-s,  viz.,  (1)  by  di- 
lating the  bloodvessels  and  increasing  the  blood-suppl}',  (2)  by 
acting  as  a  direct  chemical  stimulus  on  the  protoplasm,  (3)  by 
exciting  secretion  in  the  cell  through  reflex  action  of  ihe  nervous 
mechanism  belonging  to  the  cell,  "(4)  by  acting  directly  on  the 
nervous  centre  of  that  mechanism.  We  shall  return  to  these 
questions  when  we  come  to  speak  of  the  secretion  of  urine. 

We  are  now  in  a  position  to  attack  the  second  problem. 
What  is  the  exact  pature  of  the  activity  which  is  thus  called 
forth  ? 

We  learn  from  the  researches  of  Heidenhain^  that  each 
secreting  cell  of  a  pancreas  of  an  animal  (dog)  which  has 
been  fasting  for  80  hours  or  more  consists  of  two  zones:  an 
inner  zone,  next  to  the  lumen  of  the  alveolus,  which  is 
studded  with  fine  granules,  and  a  small  outer  zone,  which  is 

^    Wien.  Sitznngsbericht,  1,  p.  77. 
2  Centrbt.  Med.  Wiss.,  1868,  p.  209. 
^  Pfliiger's  Archiv,  x  (1875),  p.  557. 


362    THE  TISSUES  and  xMechanisms  of  digestion. 

homogeneous  or  marked  with  delicate  striiL\  Carmine  stains 
tlie  outer  zone  easily,  the  inner  zone  with  diniculty.  'I'he 
nucleus,  more  or  less  irregular  in  shape,  is  placed  i)artly  iu 
the  one  and  partly  in  the  other  zone.  When,  however,  the 
pancreas  of  an  animal  in  full  digestion  (about  six  hours 
after  food  and  onwards)  is  examined,  the  outer  homogene- 
ous zone  is  found  to  be  much  wider,  the  granular  inner  zone 
being  correspondingly  narrower,  and  in  some  cases  actually 
disn})pearing.  The  whole  cell  is  smaller,  and  owing  to  the 
relatively  larger  size  of  the  outer  zone,  stains  well.  The 
nucleus  is  spherical  and  well  formed.  If  the  pancreas  be 
examined  at  the  end  of  digestion,  when  its  activity  has  once 
more  ceased,  and  it  has  entered  into  a  state  of  rest,  the 
outer  zone  is  again  found  to  be  nari-ow,  the  granular  inner 
zone  occup3'ing  the  greater  part  of  the  cell,  which  in  conse- 
quence stains  with  difticulty  ;  and  the  whole  cell  has  once 
more  become  larger.  There  seems  to  be  but  one  interpre- 
tation of  these  facts.  During  the  time  that  the  pancreas  is 
secreting  most  rapidly,  there  is  a  diminution  of  the  inner 
zone  ;  that  is  to  say,  the  inner  zone  furnishes  material  for 
the  secretion.  But  while  the  inner  zone  is  diminishing,  the 
outer  zone  is  increasing,  that  is  to  say,  the  outer  zone  is 
being  built  up  again  out  of  materials  brought  to  it  from  the 
blood,  though  not  to  such  an  extent  as  to  prevent  the  whole 
cell  from  becoming  smaller.  When  digestion  is  ended,  after 
the  pancreas  has  ceased  to  secrete,  the  inner  zone  again  en- 
larges, evidently  at  the  expense  of  the  outer  zone,  though 
the  latter  also  continues  to  increase,  causing  the  whole  cell 
to  become  bigger.  From  thence  till  the  next  meal  there 
occurs  a  partial  consumption  of  the  inner  zone,  so  that  the 
outer  zone  becomes  more  conspicuous  again,  though  the 
whole  cell  becomes  smaller.  Evidently  out  of  the  protoplasm 
of  the  cell,  which  is  itself  formed  at  the  expense  of  the 
blood,  the  granules  are  formed,  and  these  being  deposited 
towards  the  lumen  of  the  alveolus  distinguish  the  outer 
homogeneous  from  the  inner  granular  zone,  and  the  secre- 
tion is  produced  at  the  expense  of  the  granules. 

Kiihne  and  Sheridan  Lea,^  observing,  under  the  micro- 
scope, the  pancreas  of  the  living  rabbit,  have  been  able  to 
watch  the  actual  process  of  secretion  ;  and  their  results, 
while  they  extend,  in  the  main  corroi)orate  those  of  Ileiden- 
hain.     In  the  quiescent  pancreas  of  the  rabbit,  Fig.  109  A, 

1  Verhandl.  Naturhist.  Med.  Vereins,  Heidelberg,  Bd.  1  (1877),  Hft.  5. 


SECRETORY    CHANGES-  IN    PANCREAS. 


363 


the  cells  are  for  the  most  part  filled  with  grannies,  the  trans- 
parent onter  zone  being  redncerl  to  small  dimensions  ;  the 
outlines  of  the  individual  cells  are  very  indistinct,  with  the 
margins  of  the  alveoli  smooth  ;  the  lumen  of  the  alveolus  is 
obscure,  and  the  blood-suppl}'  is  scanty.  Upon  secretion 
being  set  up,  Fig.  109  B,  the  margins  of  the  active  alveoli 
become  indented  through  a  bulging  of  their  constituent 
cells,  the  outlines  of  which  now  become  distinct;  the  gran- 
ules retreat  towards  the  inner  zone,  bordering  on  the  cavity 
of  the  alveolus,  and  as  secretion  goes  on,  evidently  diminish 
in  number,  the  whole  cell  becoming  hyaline  and  transparent 
from  the  outer  border  inwards ;  at  the  same  time  the  blood- 


FlG.  109. 


-^^  a:  --^^ 

A  portion  of  the  Pancreas  of  the  Rabbit  (Kiihne  and  Sheridan  Lea),  A  at  rest,  B  in 
a  state  of  activity. 

a,  the  inner  granular  zone,  which  in  A  is  larcfer  and  more  closply  studded  with  fine 
granules  than  in  B,  in  wliich  the  granuli'S  are  fewer  and  coarser. 

b,  the  outer  transparent  zone,  small  in  A,  hirger  in  B,  and  in  the  hitter  marked 
with  faint  striae. 

c,  the  lumen,  very  obvious  in  B,  but  indistinct  in  A. 

(I,  an  indentation  at  tlie  junction  of  two  cells,  seen  in  B,  but  not  occurring  in  A. 


vessels  dilate  largely,  and  the  stream  of  blood  through  the 
capillaries  becomes  full  and  rapid. 

We  have  already  seen,  p.  oGo,  that  in  order  to  obtain  an 
actively  proteolytic  aqueous  pancreatic  extract,  the  aniuial 
must  be  killed  during  full  digestion.  This  statement  now 
requires  nit)dification. 

If  the  pancreas  of  an  animal,  even  in  full  digestion,  be 
treated,  ivhile  still  icarm  from  the  hody^  with  glycerin,  the 
glycerin  extract  is  inert,  or  nearly  so,  as  regards  proteid 
bodies.     If,  however,  the  same  pancreas  be  kept  for  twent}'- 


364     THE    TISSUES    AND    MECHANISMS    OF    DIGESTION. 

four  hours  bcforo  trt'jitiuo-  wltli  irlyeeriu,  tlic  clyccriu  extract 
riudily  digests  fibrin  and  other  proteids  in  the  presence  of 
an  alkali.  If  the  pancreas,  while  si  ill  warm,  he  rubbed  up 
in  a  mortar  for  a  few  minutes  with  dilute  acetic  acid,  and 
then  treated  with  glycerin  the  glycerin  extract  is  strongly 
proteolytic.  If  the  glycerin  exti'act  obtained  without  acid 
from  tiie  warm  pancreas,  and  theiefore  inert,  be  diluted 
largely  with  water,  and  kept  at  '.]^-)°  C.  for  some  time,  it  be- 
comes active.  If  treated  with  acidulated  instead  of  distilled 
-water,  its  activity,  as  judged  of  by  its  action  on  fibrin  in  the 
presence  of  sodium  carl)onate,  is  much  sooner  developed.  If 
tlie  inert  glycerin  extract  of  warm  pancreas  be  precipitated 
with  alcohol  in  excess,  the  precipitate,  inert  as  a  proteolytic 
ferment  when  fresh,  becomes  active  when  exposed  for  some 
time  in  an  aqueous  solution,  rapidly  so  when  treated  witli 
acidulated  water.  These  facts  show  that  a  pancreas  taken 
fresh  from  the  body, even  during  full  dlgefil'um^  contains  but 
little  ready-made  fcrmeut ^  though  there  is  present  in  it  a  body 
which,  by  some  kind  of  decomi)osition,  ry/»;e.s' 6/r//i  to  the  fer- 
ment. They  further  show  that  though  the  presence  of  an 
alkali  is  essential  to  proteolytic  action  of  the  actual  ferment, 
the  formation  of  the  ferment  out  of  the  body  in  (piestion  is 
favored  by  the  presence  of  an  acid.  To  this  body,  this 
mother  of  the  ferment,  Heidenhain  has  given  the  name  of 
zijmoijen}  It  has  not  at  present  been  satisfactorily  isolated. 
Hence,  in  judging  of  the  functional  activity  of  the  pan- 
creas under  various  circumstances,  we  must  look  to  not  the 
ready-made  ferment,  but  the  ferment-giving  zymogen.  And 
Heidenhain  has  made  the  important  observation  that  the 
amount  of  zymogen  in  a  pancreas  at  any  given  time  rises 
and  sinks  pari  pat^f^u  with  the  granular  inner  zone.  The 
wider  the  inner  zone  the  larger  the  amount,  the  narrower 
the  zone  the  smaller  the  amount  of  zymogen;  and  in  cases 
of  so-called  paralytic  secretions  from  old-established  fistulae, 
where  the  juice  is  wholly  inert  over  |)roteids,  the  inner  gran- 
ular zone  is  absent  from  the  cells.  Evidently  so  far  from  the 
proteolytic  ferment  being  simply  drained  oti'  from  the  blood, 
in  the  first  place  the  actual  ferment  is  formed  in  the  pancreas 
out  of  the  zymogen,  and  in  the  second  place  the  zymogen 
of  the  inner  granular  zone  is  formed  in  the  cell  itself  out  of 

^  Or  zymogen  may  be  reserved  a.s  a  generic  name  for  "  mother  of  fer- 
ment ;"  in  that  c;ise  the  particular  mother  of  the  pancreatic  proteolytic 
ferment  might  be  called  trypsinogen. 


ZYMOGEN.  365 

the  homogeneous  outer  zone.  We  have  in  fact  two  distinct 
processes  to  deal  with:  (1)  the  manufacture  of  zymogen; 
this  is  parfof  the  growth  or  nutrition  of  the  cell,  and  is  slow 
and  continued;  (2)  the  splitting  up  or  conversion  of  the 
zymogen  into  the  proteolytic  ferment;  this  is  the  real  act  of 
secreting,  and  is  intermittent  and  rapid  ;  this  is  the  form  of 
activity  which  can  he  called  forth  by  nervous  impulses,  the 
form  of  activit}^  which  is  comparable  to  a  muscular  contrac- 
tion. 

The  thought  at  once  suggests  itself  that  the  appearance  of  an 
acid  in  the  protoplasm  of  the  cell  under  circumstances  similar  to 
those  which  give  rise  to  the  acid  formed  during  muscular  con- 
traction, might  be  the  immediate  cause  of  the  zymogen  becoming 
converted  into  ferment. 

In  the  ease,  then,  of  the  proteolytic  ferment  of  the  pan- 
creas we  have  striking  proof  that  the  process  of  secretion, 
both  in  its  preparatory^  and  executive  stages,  is  a  laborious, 
active,  manufacturing  function  of  the  cell,  and  not  simply 
a  passive,  selective,  filtering  function.  How  far  this  is  also 
true  of  the  other  ferments  of  the  pancreas,  and  of  the  active 
constituents  of  the  other  digestive  juices,  cannot  at  present 
be  authoritatively  affirmed,  but  we  have,  both  in  the  case  of 
the  stomach  and  of  the  salivar}"  glands,  facts  pointing  very 
distinctly  in  that  direction. 

In  the  gastric  glands  of  an  animal  previous  to  taking  a 
meal,  the  central  (as  distinguislied  from  the  ovoid  or  "  pep- 
tic "J  cells  are  pale  and  finel}'  granular,  and  in  sections 
taken  from  glands  hardened  in  alcoliol,  do  not  stain  readily 
with  carmine  and  other  dyes.  During  the  early  stages  of 
gastric  digestion,  the  same  cells  are  found  somewiiat  swoUeti, 
but  turbid  and  more  coarsely  granular;  tliey  stain  much 
more  readily.  At  a  later  stage  they  become  smaller  and 
shrunken,  but  are  even  more  turbid  and  granular  than 
before,  and  stain  even  still  more  deeply.  This  is  true,  not 
only  of  the  central  cells  of  the  so-called  peptic  glands,  but 
also  of  the  cells  of  which  the  so-called  mucous  glands  of  the 
pyloric  end  of  the  stomach  are  built  up.  (The  ovoid  or 
peptic  cells  themselves  during  digestion  appear  swollen,  and 
project  more  on  the  outside  of  the  gland,  but  otherwise  ap- 
pear unchanged.)  Evidently,  during  digestion,  the  central 
cells  become  changed  in  nature   so  as  to  be  more  readily 

31 


366      THE    TISSUES    AND    MECHANISMS    OF    DIGESTION. 

stained  with  carmine  and  at  the  same  time   loaded  with  a 
more  closely  <»^ranular  material.^ 

In  the  glands  of  the  pylorus  there  is  seen  in  (he  lumen  also  of 
the  inland  a  i^ranular  material,  which,  since  it  makes  its  a))pear- 
ance  after  the  mechanical  stimulation  of  the  memhrane  of  an 
empty  stomach,  cannot,  when  it  occiu's  during  digestion,  be  re- 
garded as  simply  digested  food  abont  to  be  absorbed.  The 
granular  character  of  the  cells  themselves  therefore  must  also 
come  from  within,  and  cannot  be  due  to  material  absorbed  from 
the  cavity  of  the  stomach. 

It  will  be  observed  that  the  phenomena  of  the  gastric  cells  are 
son  ewhat  ditferent  from  those  of  the  pancreatic  cells.  In  the 
case  of  the  pancreatic  cell  it  is  the  part  of  the  cell  wdiich  contains 
the  granules  which  docs  not  stain  readily  ;  and  the  granules  make 
their  appearance  during  rest,  and  disappear  upon  stimulation. 
In  the  case  of  gastric  central  cells,  it  is  wdien  the  cell  becomes 
loaded  w^ith  granules  that  it  stains  most  deeply,  and  it  becomes 
loaded  with  granules  not  during  rest  but  during  stimulation,  or 
at  least  when  the  stomach  is  digesting.  The  observations  of 
Kuhne  and  Lea  show  that  in  the  pancreas  the  granules  are  actu- 
ally used  up  to  form  the  secretion.  If  in  the  gastric  cell  the 
granules  are  really  elements  of  the  secretion,  they  must  during 
active  digestion  be  formed  more  rapidly  than  they  are  used  up, 
and  must  cease  to  be  formed  as  the  work  ofdigestion  languishes. 

There  has  been  a  great  dispute  as  to  whether  the  pyloric  end 
of  the  stomach,  that  containing  the  so-called  mucous  glands 
only,  has  peptic  powers.  But  the  researches  of  Heidenhain'  have 
decided  the  question  in  the  affirmative.  This  observer  succeeded 
in  isolating  the  pylorus  from  the  rest  of  the  stomach  after  the 
manner  of  Thiry's  operation  on  the  small  intestine,  and  obtained 
from  the  isolated  portion  a  small  quantity  of  viscid  alkaline 
secretion,  which  when  treated  with  dilute  hydrochloric  acid  rap- 
idly digested  tibrin.  The  secretion  also,  without  the  addition  of 
acid,  rapidly  curdled  milk,  but  showed  no  amylolytic  action.  A 
reconciliation  of  some  of  the  previous  contradictory  statements 
may  perhaps  be  found  in  the  fact,^  that  while  the  glycerin  extract 
of  the  fresh  pylorus,  even  in  the  presence  of  free  hydrochloric 
acid,  is  inert,  care  being  taken  to  avoid  admixture  with  the  se- 
cretion of  the  cardiac  end,  an  acid  infusion  of  the  same  part 
rapidly  becomes  peptic.  This  would  seem  to  indicate  that  the 
pyloric  glands  are  free  from  actual  pepsin  but  contain  a  pepsin o- 


1  Heidenhain,  Archiv  f.  niicr.  Anat.,  vi  (1870),  p.  oG8.     Rollett,  Un- 
tersuch.  a.  d.  Inst.  f.  Physiol,  u.  Hist,  in  Graz,  Hft.  ii  (1871),  p.  143. 

2  Pfiuger's  Archiv,  xviii  (1878),  p.  169;  also  Kleruensievvicz,  Wien. 
Sitzungs-Bericht.  Bd.  71,  March,  LS75. 

^  Ebstein  and  Griit/ner,  PHiigei-'s  .\rehiv,  viii  (lS74),p.  122.     Griitz- 
ner,  Untensucli.  ii.  Bild.  n.  Ausschicd.  d.  Pepsin,  1875. 


SECRETION    OF    GASTRIC    JUICE.  367 


gen,  comparable  to  pancreatic  zymogen,  which  by  the  action  of 
an  acid  is  split  up  into  pepsin.  Apparentl}^  however,  pepsinogen 
differs  from  zymogen  in  being  insoluble  in  glycerin,  while  the 
latter  is,  as  we  have  seen,  freely  soluble  in  that  fluid.  This  point 
requires  to  be  more  fully  worked  out. 

We  may  therefore  v»'ith  good  reason  suppose  that  pepsin 
is  formed  by  the  direct  activity  of  the  gastric  cells  ;  and  in 
that  case  the  pepsin  which  is  present  in  blood/  in  muscle, 
and  in  urine,^  is  not  the  source  of  the  pepsin  in  the  gastric 
juice,  but  is  already-used  pepsin  reabsorbed  from  tiie  stom- 
ach and  intestine,  and  on  its  way  to  be  discharged  from  the 
body. 

The  formation  of  the  free  acid  of  the  gastric  jnice  is  very 
obscure.  It  seems  natural  to  suppose  that  it  arise  s  in  some 
way  from  the  decomposition  of  sodium  chloi'ide;  but  noth- 
ing delinite  can  at  present  be  stated  as  to  the  mechanism  of 
that  decomposition  ;  and  even  admitting  that  sodium  chlo- 
ride is  the  ultimate  source  of  the  chlorine  element  ofthe  acid, 
it  appears  more  likely  that  that  element  should  be  set  free 
in  the  stomach  by  the  decomposition  of  some  highly  com- 
plex and  unstable  chlorine  compound  previously  generated, 
than  that  it  should  arise  by  the  direct  si)litting  up  of  so 
stable  a  bod3'  ^^  sodium  chloride,  at  the  time  when  the  acid 
is  secreted,^  One  thing  however  seems  certain,  that  the  acid 
is  formed  only  at  the  surface  of  the  gastric  membrane. 

If  the  reaction  of  the  mucous  membrane  of  the  stomach  be 
tested  at  different  depths  from  the  surface,  as  in  the  long  tubular 
glands  of  a  bird,  it  will  be  seen  that  the  acidity  is  confined  to 
the  upper  portion,  indeed  to  the  mouths,  of  the  glands.  So  also 
when  potassium  ferrocyanide  and  an  iron  salt  are  injected  into 
the  veins,  a  blue  color  is  developed  only  on  the  surface  of  the 
mucous  membrane,  and  not  in  the  depths  of  the  gland,  showing 
that  an  acidity  sutiicient  to  allow  of  the  development  ofthe  blue 
is  present  only  at  the  surface. 

Heidenhain  has  made  the  suggestion  not  only  that  the  central 
cells  manufacture  pepsin  (or  pepsinogen),  (ancl  of  this  after  the 
proved  peptic  powers  of  the  pylorus  there  can  be  hardly  any 
doubt),  iDut  also  that  the  large  ovoid  (peptic)  cells  manufacture 

*  The  presence  of  pepsin  in  blood  is  one  reason  why  boi'ed  fibrin 
should  be  used  in  peptic  experiments  rather  than  raw.  The  boiling 
destroys  the  pepsin  clinginf?  to  the  tibrin. 

-  Briicke,  Moleschott's  Untersnch  ,  vi,  474. 

^  Cf.  Maly,  Liebig's  Annalen,  Bd.  17-3  (lcS74),  p.  227. 


368    THE  TISSUES  and  meciianiSxMS  of  digestion. 


the  acid  of  the  i^astric  juice.  Since  the  ovoid  cells  lie  chietly  in  the 
middle  portions  of  the  gland,  the  superficial  development  of  the 
aciil  rcMpiircs,  on  this  view,  some  special  explanation.  In  favor 
of  such  a  function  of  the  ''ovoid  "  cells  has  been  adduced  the 
curious  circumstance  that  in  the  frog  pepsin  is  largely  present  in 
the  lower  part  of  the  a'sophagus,  where  cells  altogether  like  the 
"  central  "  cells  «)f  the  gastric  glands  are  abundant,  whereas  the 
stomach  itself,  which  is  richly  supplied  with  "  ovoid"  or  peptic 
cells,  api)ears  to  secrete  an  acid  tkiid,  which  when  the  oesophagus 
is  ligatured  is  extremely  poor  in  pepsin.^ 

In  the  case  of  the  salivary  glands  the  phenomena,  to  a 
certain  extent,  differ  according  as  the  gland  is  a  '*  uhicous  " 
gland,  2.  e".,  one  containing  a  larger  or  smaller  nmni)er  of 
mucus-produciitg  cells,  and  secreting  a  more  or  less  viscid 
mucous  saliva,  or  a  ''  serous  "  gland,  i. 


r:,r:    ^^       .M 


W 


2) 

Section  of  a  "  Mucous"  Gland.    J,  in  a  state  of  rest  ;  B,  after  it  has  been  for  some 
time  actively  secreting. — After  Lavdow.sky. 

a,  demilune  cells,    c,  leucocytes  lying  in  the  inter-alveolar  spaces.    The  darker 
shading  in  both  figures  is  intended  to  indicate  the  amount  of  staining. 

no  such  mucns-prodncing  cells,  and  secreting  a  thin  limpid 
saliva  free  from  mucus.  The  submaxillary  gland  of  the  dog 
may  he  taken  as  the  type  of  mucous  ^glands.  If  a  section 
is  prepared  of  this  gland  when  at  rest,  i.e.,  when  it  has  not 
for  some  time  been  actively  secreting,  the  cells  of  the  alve- 
oli (Fig.  110)  are  found  not  to  stain  readily  with  carmine; 
and  this  lack  of  staining  appears  to  be  due  to  the  fact  that 

^  Swiecicki,  Pfliiger's  Archiv,  xiii  (1876),  p.  444,     Partsch,  Archiv  f. 
micros  Anat.,  xiv  (1877),  179. 


MUCOUS    AND    SEROUS    GLANDS.  369 

the  greater  part  of  tlie  protoplastn  of  the  cells  has  become 
converted  into  a  mucin-bearlng  substance,  only  a  small  por- 
tion of  unchanged  protoplasm,  easily  staining  with  carmine, 
remaining  round  the  nucleus.  In  addition  to  these  ''  mu- 
ciparous cells"  are  seen  a  number  of  smaller  half-moon- 
shaped  (demilune)  cells,  the  protoplasm  of  which  stains 
deeply  with  carmine.  These  half-moon  cells,  which  lie  out- 
side the  muciparous  cells,  between  them  and  the  basement 
membrane,  are  apparently  young  cells,  frequently  possess 
two  or  more  nuclei,  and  in  general  seem  to  be  in  a  stale  of 
active  growth  and  multiplication. 

When  similar  sections  are  prepared  from  a  gland  which 
has  been  thrown  into  long-continued  activity  by  stimulation 
of  the  chorda,'  the  muciparous  portion  of  the  alveolar  cells, 
that  portion  which  does  not  stain  rapidly,  is  found  to  have 
diminished,  and  the  protophismic  staining  portion  to  have 
increased  in  quantity  in  proportion  to  the  amount  of  stimu- 
lation (Fig.  110  B).  In  some  cases  no  mucii)arous  cells  can 
anywhere  be  seen  ;  all  the  cells  are  small,  all  are  alike  com- 
posed of  protoplasm,  and  all  stain  deeply.  It  has  been  dis- 
puted whether  a  mucii)arous  cell  simj:)ly  discharges  its 
nmcin,  the  rem(jval  of  the  mucin  being  followed  by  a  growth 
of  the  protoplasm  round  the  nucleus,  to  be  in  turn  followed 
by  a  new  development  of  mucin,  the  snme  cell  thus  forming 
and  discharging  mucin  again  and  again ;  or  whether  the 
whole  cell  goes  to  pieces  at  the  time  it  discliarges  the  mu- 
cus, its  place  being  taken  by  one  of  the  half-moon  cells, 
which  grows  up  rapidly  for  that  purpose.  In  all  probability 
both  events  occur,  at  least  after  prolonged  stimulation,  the 
simple  discharge  of  mucus  and  regeneration  of  the  cell 
being  analogous  to  what  takes  place  in  the  pancreas,  while 
tile  substitution  of  the  young  half-moon  cell,  in  place  of  the 
old  disintegrated  muciparous  cell,  is  something  special  to 
the  submaxillary  gland. 

In  the  case  of  a  ''serous"  gland  such  as  the  submax- 
illary of  the  rabbit,  no  very  marked  differences  in  micro- 
scopic appearance  can  be  recognized  even  after  long-con- 
tinued stimulation  of  the  chorda  tympani,  and  a  similar 
absence  of  structural  changes  seems  to  be  characteristic  of 
the  parotid  of  the  rabljit,  also  a  serous  gland,  even  when  a 
most  copious  secretion  has  been  called  forth  by  stimulation 
of   the  auriculotemporal.       When,    however,   the    cervical 

^    Cf,  Lavdowsky,  Archiv  f.  micros.  Anat.,  xiii  (1877),  p.  281. 


370     THE    TISSUES    AND    MECHANISMS    OF    DIGESTION. 


sympatlu'lic  is  sliiniilaUMl.  citluT  in  ihc  r:it)l)it  or  the  (lo<r, 
vcM'v  mtu'Ued  (.'luinge's  occur  \n  tlie  })aroli(l,  {illlioiii>;li  in  the 
(log  no  saliva  whatever  may  he  secreted  ;  and  tiiese  clianges 
are  (juite  similar  to  those  vvitnet-sed  in  the  central  cells  of 
the  gastric  glands.  During  rest  the  cells  of  the  parotid  as 
seen  in  sections  of  the  gland  hardened  in  alcohol  (  Fig.  1  I  I 
A),  are  pale,  ti'ansparent,  with  sparse  grannies,  staining  with 
diUicnlty,  and    the    nuclei    [)osscss    irregular  outlines   as   it* 


-r-"^,. 


A     ■■ 

Section  of  a  "  Serous"  Gland,  the  Parotid  of  the  Kabbit.    A,  at  rest, 
stimulation  of  the  cervical  synipathotic. — After  Heidp:xhaix. 


B,  after 


shrunken.  After  stimulation  of  the  sympathetic,  the  pro- 
toplasm of  the  cells  becomes  turbid,  and  laden  with  granules 
(Fig.  Ill  B),  and  stains  much  more  readily,  and  the  nuclei 
losing  their  irregular  outline  grow  round  and  larger,  with 
conspicuous  nucleoli,  the  whole  cell  at  the  same  time,  at 
least  after  prohniged  stimidation,  beccming  distinctly 
smaller.' 

Putting  all  the  above  facts  together  it  is  clear  that  in  the 
case  of  the  salivaiT  glands,  gastric  glands,  and  pancreas, 
and  presumably  in  the  case  of  all  secreting  glands,  the  se- 
cretion is  the  result  of  the  activity  of  the  protojilasm  of  the 
secreting  cell.  Where  mucin  is  an  important  element  of 
the  secretion  the  microscopic  changes  are  very  conspicuous. 
During  rest  the  protoi)las>m  of  the  cell  becomes  converted 
into  a  mucigenous  substance;  when  the  gland  is  excited  to 
activity  the  mucigenous  substance  gives  ris4  to  mucin,  which 
is  ejected  from  the  cell.  The  cell  is  either  thus  broken  up 
entirely  or  reduced  in  dimensions;  but  coincidently  a  re- 
juvenescence of  the  protoplasm,  either  of  the  remnant  of 
the  cell  itself  or  of  the  adjoining  demilune,  takes  place,  and 
the  old  cell  is  thus  replaced  by  a  new  cell  of  smaller  size, 
but  composed  of  fresh,  deeply  staining  protoplasm,  which  at 


'  Heidenhain,  Pfliiger's  Archiv,  xvii  (1878),  p.  1. 


THEORY    OF    SECRETION.  371 

first  is  native  niiditferentiated  protoplasm,  but  which  siibse- 
(piently  generates  out  of  itself  fresh  mucigenous  material. 
Where  the  secretion  does  not  contain  nuicus  the  changes 
are  less  gross  and  not  so  readily  recognizable,  but  we  have 
a  des-cending  series  from  the  mucous  salivary  gland,  through 
the  pancreas  and  gastric  gland  and  serous  gland  stimulated 
])y  the  sympathetic  to  the  serous  gland  stimulated  by  a 
cerebi-o-si)inal  nerve,  in  each  of  which  more  or  less  distinctly 
an  explosive  decomposition,  leading  to  a  discharge  of  the 
secreted  material,  is  accompanied  In' an  increased  growth  of 
protoi)lasm  whereby  the  supply- of  a  further  seci'etion  is  pro- 
vided for.  Jn  the  last  case,  the  serous  gland  stimulated  by 
means  of  a  cerebro-spinal  nerve,  the  destructive  and  con- 
structive metabolic  processes  a[)pear  to  be  so  exactly  ad- 
justed that  no  obvious  change  in  the  appearance  of  the  cells 
results.  It  must  be  left  for  future  inquiry  to  determine  the 
nature  of  the  various  granules,  which  make  their  appearance 
in  the  various  cases,  and  their  relation  to  the  ferments  or 
other  constituents  of  the  secretions. 

AVe  are  now  in  a  better  position  to  discuss  the  exact  nature  of 
the  changes  etlected  in  the  salivar}'  gland  by  stimulation  of  the 
chorda  tympani  (or  auriculo-tempural)  and  .sympathetic  nerves 
respectiveh'. 

Czermak-  was  the  first  to  point  out  that  in  the  dog  the  eflect 
of  chorda  stimulation  was  hindered  Ijv  a  concomitant  stimula- 
tion of  the  sj-mpathetic  ;  and  Kuhne'  observed  that  no  tiow  at 
all  took  place  when  both  nerves  were  simultaneously  stimulated 
with  minimum  currents,  i.  c,  with  currents  which  applied  to 
either  nerve  sej^.arately  were  just  sufficient  to  produce  an  ob- 
vious flow  ;  each  nerve,  in  lact,  seemed  to  be  the  antagonist  of 
the  other. 

But  Langley^  finds  that  in  the  cat  (in  which  animal,  contrary 
to  what  occurs  in  the  dog,  the  sympathetic  saliva  is  less  viscid 
than  the  chorda  saliva,  and  the  action  of  the  synipathetic  is  like 
the  chorda  paralyzed  by  atropin),  minimal  stimuli,  when  applied 
simultaneousK'  to  the  chorda  and  sympathetic  nerves,  are  not 
antagonistic  as  regards  secretion  ;  on  the  contrary,  the  amount 
of  secretion  following  simultaneous  stimulation  of  the  two  nerves 
is  at  least  equal  to  the  sum  of  the  amounts  of  separate  stimu- 
lation. 

Ludwig  and  Becker'  observed,  in  the  submaxillary  gland  of  the 
dog,  that  after  continued  stimulation  of  the  chorda  (i.  e.,  a  long 

^  Wien.  Sitzungsberichte,  xxv  (1857),  p.  3. 

2  Lehrb.,  p.  5  (1866). 

3  Journal  PhvsioL,  i  (1878),  p.  96. 
*  Zt.  I  rat.  Med.,  i,  278. 


372      THE    TISSUES    AND    MECHANISMS    OF    DIGESTION. 


series  of  stimulations  repeated  with  very  brief  intervals)  the  pcr- 
c'enta<::e  of  solids  in  the  saliva  very  considerably  diminished,  tiic 
k'ssi-ninir  bcini^  largely  conlinud  to  the  organic  matter,  and  the 
inorij;anic  salts  beini;  only  sliuhtly  allected.  Ileidcnhain'  con- 
lirmi'd  this  result,  and  extended  it  to  the  sympathetic  as  well; 
he  found,  in  fact,  that  Jifter  prolonged  stimulation  the  synipa- 
tlu'tic  saliva  became  watery.  He  also  observed  that  prolonged 
stimulation  of  the  chorda  or  sympathetic  diminished  the  ori^anic 
matter  in  the  saliva  produced  by  a  stimulation  of  the  sympa- 
thetic or  chorda  inunediately  foUowiUir.  These  facts  show  that 
there  is  in  the  salivary  cell  a  store  of  material  upon  which  both 
chorda  and  sympathetic  can  alike  draw,  material  which  may  ^ive 
rise  to  the  organic  constituents  of  either  chorda  or  symj)athetic 
saliva,  according  as  the  one  or  the  other  nerve  is  stinmlated  ; 
and,  further,  that  during  nerve-stimulation  the  supply  of  this 
material  does  not  keep  i)ace  with  its  consumi)tion. 

These  results  Heidenhain^  has  contirmed  and  extended  by  ad- 
ditional recent  observations.  Thus  he  tinds  that,  in  the  case  of 
the  submaxillary  and  parotid  of  the  dog,  the  rate  of  secretion 
when  the  cerebro-spinal  nerves  are  stimulated,  exhaustion  being 
avoided,  increases  up  to  a  maximum  with  increas^!  of  the  stimu- 
lation, and  that  the  percentage  of  saline  inattcrs  in  the  saliva 
increases  similarly  up  to  a  certain  maximum,  whatever  may 
have  been  the  condition  of  the  gland  before  the  beginning  of  the 
stimulation;  but  that  the  percentage  of  oryanic  matter,  though 
also  a  function  of  the  strength  of  the  stimulus,  is  dependent  on 
the  condition  of  the  gland,  increasing  with  the  stinmlus  if  the 
gland  had  been  previously  at  rest,  but  not  so  increasing  if  the 
gland  had  been  previously  thrown  into  a  state  of  jn'olonged  ac- 
tivity;  moreover,  so  long  as  the  gland  has  not  become  completely 
exhausted,  strong  stimulation  may  be  followed  by  a  j^eriod  of 
after-art  ion,  during  which  the  percentage  of  organic  matter  is 
once  more  increased.  In  other  words,  the  organic  constituents 
of  the  secretion  are  derived  from  the  store  of  material  laid  up  in 
the  cell,  which  store  is  comparatively  soon  exhausted,  and  re- 
quires time  and  nutritive  labor  for  its  restoration.  The  saline 
constituents,  on  the  other  hand,  seem  to  be  ejected  from  the 
gland  during  secretion  by  some  operation  of  a  more  simple,  and 
of  presumabl}'  a  more  physical  nature,  being  apparently  taken 
up  from  the  surrounding  lymph  and  merely  passed  through  the 
cell,  so  that  an  unlimited  quantity  may  be  got  rid  of  without  the 
loss  being  felt  by  the  gland-cell.  "^Ile,  moreover,  has  ascertained 
that,  in  the  parotid  of  the  dog,  stimulation  of  the  sympathetic, 
even  when  it  gives  rise  of  itself  to  no  secretion,  has  a  remark- 
able effect  on  the  constitution  of  the  secretion  produced  by  simul- 
taneous or  sequent  stimulation  of  the  cerebro-spinal  secretory 
fibres  ;  the  percentage  of  organic  constituents  of  the  saliva  se- 

'  Breslau.  Studien,  iv  (1868). 

2  Pfliiger's  Archiv,  xvii  (1878),  p.  1. 


THEORY    OF    SECRETION.  373 


creted  under  the  influence  of  stimulation  of  the  cerebro-spinal 
nerve  is  very  largely  increased  bv  a  previous  or  simultaneous 
stimulation  of  the  cervical  sympathetic.  In  the  parotid  of  the 
rabbit  (and  sometimes  in  the  parotid  of  the  dog)  stimulation  of 
the  sympathetic  does  produce  a  secretion  ;  and  since  the  saliva 
thus  secreted  is  markedly  richer  in  organic  matter  than  that 
secreted  under  stimulation  of  the  cerebro-spinal  nerve,  the  larger 
amount  of  organic  matter  which  is  observed  in  the  saliva  se- 
creted under  simultaneous  stimulation  of  both  nerves  as  com- 
pared with  the  amount  in  that  secreted  under  stimulation  of  the 
cerebro-spinal  nerve  alone,  might  be  explained  as  the  result  of 
mere  admixture  with  sympathetic  secretion.  No  such  explana- 
tion can  be  given  of  the  change  which  sympathetic  stimulation 
produces  in  Uie  character  of  the  cerebro-spinal  secretion,  when, 
as  is  generall}'  the  case  in  the  parotid  of  the  dog,  it  is  unable  by 
itself  to  give  rise  to  any  secretion.  And  in  all  cases  the  micro- 
scopic changes  in  the  parotid  gland  induced  by  sympathetic 
stimulation  are  very  pronounced,  while  those  resulting  from 
cerebro-spinal  stimulation  are  comparatively  slight.  The  inter- 
pretation which  Ileidenhain  puts  on  his  results  is  that  in  the  act 
of  secretion  of  saliva  there  are  at  least  two  processes  :  one  by 
which  the  stored-up  organic  material  of  the  cell  is  converted  into 
the  soluble  organic  constituents  of  the  secretion,  and  a  second 
b}'^  which  a  stream  of  saline-holding  fluid  passes  from  the  lymph 
s]3aces  around  the  alveolus  through  the  cell  into  the  lumen  of  the 
duct,  carrying  with  it  as  it  goes  the  organic  material  furnished 
by  the  flrst  process.  Both  these  processes,  he  suggests,  are  gov- 
erned b}-  distinct  fibres,  which  he  calls  respectively  trophic  fibres, 
viz.,  those  bringing  about  the  metabolism  of  the  cell-substance 
and  .vec/-e^or// fibres,  i.  e.,  those  giving  rise  to  the  flow  of  fluid  out- 
wards to  the  duct.  The  latter  ma}-  be  regarded  as  dominant  in 
those  nerves,  such  as  the  chorda  tympaniof  the  dog,  stimulation 
of  which  produces  a  copious  but  watery  solution  ;  the  former  in 
those,  such  as  the  cervical  sympathetic  o'l  the  same  animal,  stimu- 
lation of  which  produces  a  secretion  rich  in  organic  matter.  In 
other  words,  the  ciuantity  and  qualit}-  of  the  secretion  produced 
by  the  stimulation  of  any  nerve,  sympathetic  or  cerebro-spinal, 
will  depend  on  the  relative  amount  of  trophic  and  secretory 
fibres  i^resent  in  the  nerve.  This  view  of  Heidenhain"s  is  very 
acceptable  as  enabling  us  to  form  clearer  notions  of  the  complex 
act  of  secretion,  but  tt  obviously  leaves  much  yet  to  be  cleared  up. 
The  metabolic  action  of  the  trophic  fibres  is  fairly  comparable  to 
the  explosive  decomposition  n'hieh  is  the  basis  of  a  muscular  con- 
traction, but  the  hypothesis  of  a  purely  secretory  activity,  of  the 
starting  and  maintenance  of  a  rapid  flow  through  the  cell  inde- 
pendent of  physiological  changes  in  the  substance  of  the  proto- 
plasm, and  yec  directl}'  dependent  on  the  action  of  nerves,  lands 
us  in  considerable  ditficulties.  ^ 


'  Cf.  Hering,  Wien.  Sitzungsberiehte,  Bd.  Qio  (1872),  p.  S3. 
32 


374    THE  TISSUES  and  mechanisms  of  digestion. 

Relyiiiir  on  the  aiialooy  of  the  glands  just  studied,  we 
may  lairly  assume  that  the  secretion  of  even  such  a  complex 
fluid  as  the  !»ile  is  in  the  main  the  result  of  the  direct  meta- 
bolic activity  of  the  protoplasm  of  the  hepatic  ci3lls.  And 
this  view  is  suppr)rted  l)y  the  fact  that  after  extirpation  of 
the  liver,  no  accumulation  of  the  biliary  constituents  is  ob- 
served to  take  place  duriuir  the  few  hours  of  life  remainini^ 
to  the  animal  after  the  operation.  Still  the  great  co>n- 
plexity  of  the  secretion  introducos  several  very  important 
considerations.  In  the  first  place,  the  liver,  unlike  the 
other  digestive  glands,  has  a  double  supply  of  blood  ;  and 
vain  attempts  have  been  made  to  settle  by  direct  experi- 
ment the  question  whether  the  hepatic  artery  or  the  vena 
portre  is  the  more  closely  concerned  in  the  production  of 
bile.  Ligature  of  the  iiepatic  artery'  has  sometimes  had  no 
effect  on  the  secretion,  sometimes  has  interfered  with  it. 
Sudden  ligature  of  the  vena  portne  at  once  stojjs  the  flow  of 
bile  ;  but  gradual  obliteration  may  be  effected  without  either 
causing  death  or  even  interfering  with  the  secretion,  anasto- 
motic branches  forming  a  collateral  circidation  and  thus 
maintaining  an  eflicient  flow  of  blood  tlirough  the  liver. 
The  problem,  which  is  probaljly  a  barren  one,  cannot  be 
settled  in  this  way. 

In  the  second  place,  the  hepatic  cells  not  only  secrete 
bile,  but,  as  we  shall  see  later  on,  take  an  active  part  in  otiier 
operations  of  even  greater  importance.  The  consideration 
of  the  question  in  what  way  these  several  functions  of  the 
hepatic  cells  are  related  to  each  other  must  be  deferred  for 
the  present. 

In  the  third  place,  even  if  we  maintain  that  the  chief  con- 
stituents of  the  bile  are  manufactured  in  the  hepatic  cells, 
and  not  simply  drained  off  from  the  blood,  we  are  not  there- 
by precluded  from  admitting  that  the  hepatic  cells  may 
avail  themselves  of  certain  half-made  materials,  the  arrival 
of  wliich  in  the  blood  may,  so  to  speak,  lighten  their  labors, 
or  that  tliey  may  even  boldly  seize  upon  and  pass  off  as 
their  own  handiwork  any  wholly  manufactured  constituents 
which  may  be  offered  to  them.  Thus  we  have  already  seen 
reasons  for  thinking  that  the  bile-pigments  are  not  made  de 
7100O  in  the  hepatic  cells,  but  spring  from  hfiemoglobin,  the 
change  in  the  liver  being  simple  transformation.  So,  also, 
it  is  quite  possible,  though  not  proved,  that  much  if  not  all 
of  the  cholesterin  of  bile  is  merely  withdrawn  by  the  liver 
from  the  body  at  large.     And  even  with  the  central  compo- 


SECRETION    OF    BILE.  375 

nents  of  bile,  tlie  bile  salts,  we  know  that  in  the  case  of  tan- 
rocholic  acid,  taurin  is  normally  present  in  certain  tissues, 
and  that  in  the  case  of  glycocholic  acid,  glycin,  if  not  a 
normal  constituent  of  any  tissue,  is  present  in  the  liver, 
since  the  liver  can  convert  benzoic  into  hii)pnric  acid,  as  we 
sliall  see  in  a  succeeding  section  ;  so  that  the  formation  of 
these  bodies  by  tlie  hepatic  cells  may  be  limited  to  the  pro- 
duction of  cholalic  acid  and  its  conjugation  with  one  or  other 
of  the  al)ove  amido  acids.  Moreover,  as  a  matter  of  fact, 
we  find  that  the  flow  of  bile  from  a  biliary  fistula  is  much 
increased  by  the  injection  of  bile  into  the  small  intestines.^ 
This  experiment  renders  it  possil)le  that  some  of  the  bile, 
which  in  natural  digestion  is  poured  into  the  intestine,  is 
reabsorbed  and  carried  back  to  the  liver  to  do  duty  over 
again. 

Possibly,  however,  the  eflfect  may  be  explained  by  some  more 
indirect  action  of  the  bile  in  the  intestine. 

In  medical  practice  distinction  is  drawn  between  jaundice  by 
suppression  of  the  secreting  functions  of  the  liver  and  jaundice 
by  retention,  brought  about  by  an  obstruction  existing  in  some 
part  of  the  biliary  passages.  "^The  gravity  of  the  symptoms  in 
the  first  class  of  cases  shows  that  an  arrest  or  a  too  great  dimi- 
nution of  the  normal  functions  of  the  hepatic  cells  is  at  least 
accompanied  by  the  presence  in  the  blood  of  substances  injurious 
to  life  ;  but  how  far  the  presence  of  those  substancc^s  is  due  to  a 
failure  of  the  manufacture  of  bile  and  the  accunuilatiou  in  the 
system  of  the  materials  for  the  formation  of  bile,  or  to  a  failure 
of  other  functions  of  the  hepatic  cells,  must  be  regarded  as  at 
present  inidetermined.  The  presence  of  the  bile-pigment  in  this 
form  of  jaundice  would  seem  to  indicate  that  the  formation  of 
the  pigment,  i.  e.,  the  transformation  of  haemoglobin  into  bili- 
rubin, requires  but  little  labor  on  the  part  of  the  cell,  and  may 
be  carried  on  even  when  the  protoplasm  of  the  cell  is  higlih'  de- 
ranged. 

Seeing  the  great  solvent  power  of  both  gastric  and  pancreatic 
juice,  the  question  is  naturally  sugiiested,  AVhy  does  not  the 
stomach  digest  its'elf  V  After  death  the  stomach  is  frequently 
found  partially  digested,  viz.,  in  cases  where  death  has  takeii 
place  suddenly  on  a  full  stomach.  In  an  ordinary  death  the 
membrane  ceases  to  secrete  before  the  circulation  is  at  an  end. 
That  there  is  no  special  virtue  in  living  things  which  prevents 
their  being  digested  is  shown  by  the  facl;  that  the  legs  of  a  froa:, 
or  the  ear  of  a  rabbit,  introduced  into  a  gastric  fistula,  are  readily 
digested.     Pavy^  has  suggested  that  the  blood-current  keeps  up 


Schiff,  Pfliiger's  Arehiv,  iii  fl870),  p.  398. 
Proc.  Kov,  iSoc,  xii,  3S6,  559. 


37G     THE    TISSUES    AND    MECHANISMS    OF    DIGESTION. 


an  alkalinity  snllicient  to  ncntralize  the  acidity  of  the  jnicc  ;  and 
he  shows  by  experiment  that  tracts  of  tiie  gastric  membrane 
from  which  the  circulation  is  cut  olfare  digested.  J5ut  tracts  so 
cut  oil" soon  die  ;  they  lose  not  only  the  alkalinity  of  the  blood  but 
also  all  their  powers  ;  and  the  alkalinity  of  the  blood  will  not  ex- 
plain why  the  moutlis  of  the  glands,  which  are  acid,  are  not 
digested,  or  why  the  i)ancreatic  juice,  which  is  active  in  an  alka- 
line medium,  does  not  digest  the  i)rotei(ls  of  the  pancreas  itself, 
or  why  the  gastric  membrane  of  the  bloodless  actinozoon  or  hy- 
drozoon  does  not  digest  itself.  We  might  add,  it  does  not  explain 
why  the  amieba,  while  dissolving  the  protoplasm  of  the  swallowed 
diatom,  does  not  dissolve  its  own  i)r()toi)lasm.  We  cannot  answer 
this  question  at  all  at  present,  any  more  than  the;  similar  one, 
why  the  delicate  i)rotoplasm  of  the  amteba  resists  during  life  all 
osmosis,  while  a  tew  moments  after  it  is  dead,  osmotic  etiects 
become  abundantly  evident. 


Sec.  3.  The  Muscular  Mechanisms  of  Digestion. 

From  its  entrance  into  the  mouth  until  such  remnant  of 
it  as  is  undigested  leaves  the  hody,  the  food  is  continually 
subjected  to  movements  having  for  their  object  the  tritura- 
tion of  the  food  as  in  mastication,  or  its  more  complete  mix- 
ture with  the  digestive  juices,  or  its  forward  progress 
through  the  alimentary  canal.  These  various  movements 
may  briefly  be  considered  in  detail. 

Mastication. — Of  this  it  need  only  be  said  that  in  man  it 
consists  chiet]y  of  an  up  and  down  movement  of  the  lower 
jaw,  combined,  in  the  grinding  action  of  the  molar  teeth, 
with  a  certain  amount  of  lateral  and  fore  and  aft  movement. 
The  lower  jaw  is  raised  by  means  of  the  temporal,  massetei", 
and  internal  pterygoid  muscles.  The  slighter  etibrt  of 
depression  brings  into  action  chiefly  the  digasti'ic  muscle, 
though  the  mylo  hyoid  and  genio-hyoid  probably  share  in  the 
matter.  Contraction  of  the  external  pterygoids  pulls  for- 
wai'd  the  condyles,  and  thrusts  the  lower  teeth  in  front  of 
the  upper.  Contraction  of  the  pterygoids  on  one  side  will 
also  throw  the  teeth  on  to  the  opposite  side.  The  lower 
horizontally  placed  fibres  of  the  temporal  serve  to  retract 
the  jaw. 

During  mastication  the  food  is  moved  to  and  fro,  and 
rolled  about  by  the  movements  of  the  tongue.  These  are 
effected  by  the  muscles  of  that  organ  governed  by  the  hypo- 
glossal nerve. 


DEGLUTITION.  377 

The  act  of  mastication  is  a  voluntary  one.  ornided,  as  are 
so  many  voluntary  acts,  not  only  by  muscular  sense,  but 
also  by  contact  sensations.  The  motor  fibres  of  the  fifth 
cranial  nerve  convey  motor  impulses  from  the  brain  to  the 
muscles;  but  })aralysis  of  the  sensor}^  fibres  of  the  same 
nerve  renders  mastication  difficult  by  depriving  the  will  of 
the  aid  of  the  usual  sensation. 

Deglutition. — The  food  when  sufficiently  masticated  is,  b}^ 
tiie  ujovenients  of  the  tongue,  gathered  up  into  a  bolus  on 
the  middle  of  the  upper  surface  of  that  organ.  The  front 
of  the  tongue  being  raised — partly  by  its  intrinsic  muscles, 
and  })artly  by  the  styloglossus — the  bolus  is  thrust  back 
between  the  tongue  and  the  palate  through  the  anterior 
pillars  of  the  fauces  or  iathmus  fauciuni.  Immediately  be- 
fore it  arrives  there,  the  soft  palate  is  raised  by  the  levator 
palati,  and  so  brought  to  touch  the  posterior  wall  of  the 
pharynx,  which,  by  the  contraction  of  the  upper  margin  of 
the  superior  constrictor  of  the  pharynx,  bulges  somewhat 
forward.  The  elevation  of  the  soft  palate  causes  a  distinct 
rise  of  pressure  in  the  nasal  ciiambers;  this  can  be  shown 
by  intriKlucing  a  water  manometer  into  one  nostril,  and 
closing  the  other  just  previous  to  swallowing.  By  the  con- 
traction of  the  palato-pharyngeal  muscles  which  lie  in  the 
posterior  pillars  of  the  fauces,  the  curved  edges  of  those 
pillars  are  made  straight,  and  thus  tend  to  meet  in  the 
middle  line,  the  small  gap  between  them  being  filled  up  l)V 
the  uvula.  Through  these  mananivres,  the  entrance  into  the 
posterior  nares  is  blocked,  while  the  soft  palate  forms  a 
sloping  roof,  guiding  the  bolus  down  the  pharynx.  By  the 
contraction  of  the  stylo-pharyngeus  and  palato-pharyngeus. 
the  funnel-siiapefl  bag  of  the  pharynx  is  brought  up  to  meet 
the  descending  morsel,  very  much  as  a  glove  may  be  drawn 
up  over  the  finger. 

Meanwhile  in  the  larynx,  as  shown  by  the  laryngoscope, 
the  arytenoid  cartilages  and  vocal  cords  are  approximated, 
the  latter  being  also  raised,  so  that  they  come  very  near  to 
the  false  vocal  cords  ;  the  cushion  at  the  base  of  the  epiglottis 
covers  the  rima  glottidis,  while  the  epiglottis  itself  is 
depressed  over  the  larynx.  The  thyroid  cartilage  is  now, 
Ity  the  action  of  the  laryngeal  muscles,  suddenly  raised  up 
behind  the  hyoid  bone,  and  thus  assists  the  epiglottis  to 
cover  the  glottis.  This  movement  of  the  thyroid  can  easily 
be  felt  on   the  outside.     Thus,  both  the  entrance  into  the 


;>78      THE    TISSUES    AND    MECHANISMS    OF    DIGESTION. 

posterior  narcs  and  that  into  the  larynx  being  closed,  the 
impulse  given  to  the  bolus  by  the  tongue  can  have  no  otiier 
elieet  than  to  propel  it  beneatii  the  sloping  soft  palate,  over 
the  incline  lormed  b}''  the  root  of  the  tongue  and  tiie 
epiglottis,  into  tiie  grasp  of  the  constrictor  muscles  of  tlie 
jiharynx:  tlie  j)alato-ghs,si  or  coii,Hfricfo7'efi  is/hmi  faucium, 
which  lie  in  the  anteiior  pillars  of  the  fauces,  by  contract- 
ing, close  the  door  behind  the  food  which  has  passed  them. 
The  morsel  being  now  within  the  reach  of  the  consti'ictors 
of  the  phaiynx.  these  contract  in  sequence  from  above 
downwards,  and  thus  necessarily  thrust  the  food  into  the 
OL'sopliagus. 

Deglutition  tiierefoie,  though  a  continuous  act,  may  be 
regarded  as  divided  into  three  stages.  The  (irst  stage  is  the 
thrusiing  of  the  food  through  the  i^fhmua  faucium  ;  this 
being  a  voluntary  act,  may  be  either  of  long  or  short  dura- 
tion. The  second  stage  is  the  passage  through  the  ui)per 
part  of  the  pharynx.  Here  the  food  traverses  a  region  com- 
mon both  to  the  food  and  to  respiration,  and  in  consequence 
the  movement  is  as  rapid  as  possible.  The  third  stage  is 
the  descent  through  the  grasp  of  the  constrictors.  Here 
the  food  has  passed  the  respiratory  orifice,  and  in  conse- 
quence its   j)assage  may  again   become  comparatively  slow. 

The  first  stage  in  this  complicated  process  is  undoubtedly 
a  voluntary  action  ;  the  raising  of  the  soft  palate  and  the 
approximation  of  the  posterior  pillars  must  also  be  in  a 
measure  voluntary,  since  they  were  seen,  in  a  case  where 
the  pharynx  was  laid  bare  by  an  operation,  to  take  place 
before  the  food  had  touched  tliem  ;^  but  tiiey  may  take  place 
without  any  exercise  of  the  will  or  presence  of  conscious- 
ness, and  indeed  the  whole  part  of  the  act  of  deglutition 
which  follows  upon  the  pah^sing  of  the  food  through  the  an- 
terior pillars  of  the  fauces  must  be  regarded  as  a  reflex  act : 
though  some  of  the  earlier  component  movements  are,  as  it 
were,  on  the  borderland  between  the  voluntai-y  and  invol- 
untary kingdoms.  The  constricting  action  of  the  constric- 
tors on  the  other  hand  is  purely  reflex  ;  tlie  will  has  no 
power  whatever  over  it  ;  it  cannot  either  originate,  stop,  or 
modify  it. 

Deglutition  as  a  whole  is  a  reflex  act  and  cannot  take 
place  unless  some  stimulus  be  applied  to  tiie  mucous  mem- 
brane of   the   fauces.     When    we   voluntarily   bring   at)Out 

^  Biiicke,  Voi-lesiingen,  i,  p.  281. 


PERISTALTIC     ACTION.  379 

swallowing  movements  with  tlie  month  empty,  we  supply 
the  necessary  stimulus  by  forcing  with  the  tongue  a  small 
quantity  of  saliva  into  the  fauces,  or  by  touching  the  fauces 
with  the  tongue  itself. 

In  the  reflex  act  of  deglutition  the  afferent  impulses  orig- 
inated in  the  fauces  are  carried  up  chiefly  by  the  glosso- 
pharyngeal, but  also  by  branches  of  the  fifth,  and  by  the 
pharyngeal  branches  of  the  superior  laryngeal  division  of 
the  vagus.  The  efferent  impulses  descend  the  hyi)oglossal 
to  the  muscles  of  the  tongue,  and  pass  down  the  glosso- 
pharyngeal, the  vagus  through  the  pharyngeal  plexus,  tlie 
fifth  and  the  facial,  to  the  muscles  of  the  fauces  and  pharynx  : 
their  exact  paths  being  as  yet  not  fully  known,  and  proba- 
bly varying  in  different  animals.  The  laryngeal  muscles 
are  governed  by  the  laryngeal  branches  of  the  vagus. 

The  centre  of  the  reflex  act  lies  in  the  medulla  oblongata. 
Deglutition  can  be  excited,  by  tickling  the  fauces,  in  an 
animal  rendered  unconscious  i)y  removal  of  the  brain,  pro- 
vided the  medulla  be  left.  If  the  medulla  be  destroyed, 
deglutition  is  impossible.  The  centre  for  deglutition  lies 
liigher  up  than  that  of  respiration,  so  that  the  former  act  is 
fiequeutly  impaired  or  rendered  impossil>le  while  the  latter 
remains  untouclied.  It  is  probable  that,  as  is  tlie  case  in  so 
many  other  reflex  acts,  the  whole  movement  can  be  called 
forth  by  stimuli  affecting  the  centre  directly,  and  not  acting 
on  the  usual  afferent  nerves. 

As  each  successive  segment  of  the  pharyngeal  constric- 
tors contracts  in  sequence  from  above  downwanls,  the  bolus 
is  carried  down  into  tlie  upper  end  of  the  oesophagus.  Here 
it  is  sulnected  to  tlie  influence  of  a  peculiar  muscular  action 
known  as  ••peristaltic."  Since  this  kind  of  muscular  action 
is,  with  local  vaiiations,  characteristic  of  th.e  whole  alimen- 
tary canal  from  the  beginning  of  the  a?sophagus  to  the  end 
of  the  rectum,  it  will  be  of  advantage  to  disregard  the  sti'ict 
topographical  order  of  events,  and  to  consider,  first  of  all, 
the  movement  in  that  part  of  the  canal  where  it  is  compar- 
atively simple  in  nature,  and  has  been  best  studied,  viz.,  in 
the  small  intestine  ;  and  afterwards  to  deal  with  the  varia- 
tions occurring  in  particular  phices  and  under  special  cir- 
cumstances. 

Peristaltic  Action  of  the  Small  Intestine. — We  have  al- 
ready seen,  in  treating  of  unstriated  muscular  fibre  (p.  149), 
that  a  stimulus  applied   to   any  part  of  the  small  intestine 


380     THE    TISSUES    AND    MECHANISMS    OF    DIGESTION. 

gives  rise  to  a  circular  contraction,  or  contraction  of  the 
circular  muscular  coat,  which  travels  leiiijthways  as  a  wave 
alonu:  the  intestine,  and  also  to  a  longitudinal  contraction, 
or  contraction  of  ti»e  loni^itudinal  coat,  which  also  travels 
leuiJjtlnvays  as  a  wave  alonjr  the  intestine.  Since  the  circu- 
lar coat  is  much  tiiicker  than  the  longitudinal  one,  the  cir- 
cular wave  is  more  powerful  and  more  important  than  the 
longitudinal  one  ;  the  circular  coat  has  hy  far  the  greater 
share  in  proj^elling  the  food  along  the  intestine.  It  is  obvi- 
ous that  a  circuhir  contraction  travelling  down  tiie  intestine 
(and  in  the  natural  state  of  things  it  does  travel  downwards, 
and  not  both  upwards  and  downwar<ls)  must  drive  the  con- 
tents of  the  intestine  onwards  towards  the  c.Tcum.  And 
practically  when  the  intestines  are  watched  after  opening 
the  abdomen,  the  contents  are  seen  to  be  thus  thrust  on- 
ward by  the  contraction  of  the  circular  coat.  The  contrac- 
tions of  the  longitudinal  coat  appear  to  be  chiefly  of  use  in 
producing  peculinr  oscillating  movements  of  the  pendant 
loops  in  which  the  intestine  is  arranged.  The  rhythmic 
occurrence  of  these  circular  and  to-and-fro  movements, 
togetiier  with  the  passive  movements  caused  by  the  entrance 
of  the  fluid  contents  into  or  their  exit  from  the  various  loops, 
gives  rise  to  the  peculiar  writhing  of  the  intestines  which 
is  known  as  peristaltic  action. 

The  movements,  as  w-e  have  said,  take  place  from  above 
downwards,  and  a  wave  beiiinning  at  the  pylorus  may  be 
traced  a  long  way  down.  But  contractions  may,  and  in  all 
probability  occasionally  do,  begin  at  various  points  along 
the  length  of  the  intestine.  In  the  living  body  the  intes- 
tines have  periods  of  rest,  alternating  with  periods  of  activ- 
ity, the  occurrence  of  the  periods  depending  on  various  cir- 
cu  instances. 

With  regard  to  the  causation  of  the  peristaltic  move- 
ments of  tlie  intestine,  this  much  may  be  aflirmed.  They 
may  occur,  as  in  a  piece  of  intestine  cut  out  from  the  body, 
wholly  independently  of  the  central  nervous  system.  The 
only  nervous  elements  which  can  be  regarded  as  essential 
to  their  develo[mient  are  the  ganglia  of  Auerbacli  or  those 
of  Meissner  in  the  intestinal  walls. 


Though  peristaltic  movements  can  readily  be  excited  by  stim- 
uli, applied  either  to  the  outside,  or  more  especially  to  the  inside 
of  the  intestine,  they  are  probably  at  bottom  automatic.  The 
presence  of  food,  especially  of  food  in  motion,  may  at  times  act 


PERISTALTIC    ACTION.  381 


as  a  stimulus,  and  may  in  all  cases  be  a  condition  affectinp;  the 
nature  and  extent  of  the  movement,  but  cannot  be  regarded  as 
the  real  cause  of  the  action.  When  any  bod}-  is  introduced  into 
the  intestine,  a  contraction  at  first  occurs,  but  soon  passes  off"  as 
the  intestine  becomes  accustomed  to  the  presence  of  the  body. 
Tliere  is  no  reason  why  the  intestine  should  not  become  equally 
accustomed  to  the  presence  of  food  ;  and,  as  a  matter  of  fact, 
peristaltic  movements  are  often  aljsent  when  the  intestines  are 
full.  The  presence  of  food  bears  about  the  same  relation  to  the 
movements  of  the  intestine,  that  the  presence  of  blood  bears  to 
the  beat  of  the  heart.  Both  are  favoring  but  not  indispensable 
conditions ;  in  both  cases  the  action  can  go  on  without  them. 
We  may  add  that  just  as  the  tension  of  a  muscle  increases  up  to 
a  certain  extent  the  amount  of  its  contraction,  and  a  full  heart 
beats  more  strongl}"  than  an  empty  one,  so  distension  of  the  in- 
testine largely  increases  peristaltic  action.  Hence  in  cases  of 
obstruction  of  the  bowels,  the  movements  become  distressing  by 
their  violence. 

Among  the  chief  circumstances  affecting  peristaltic  ac- 
tion ma\'  be  mentioned  in  the  first  place  the  condition  of  the 
blood.  A  lack  of  oxygen  or  an  excess  of  carbonic  acid  in 
the  blood  excites  powerful  movements.  This  is  well  seen 
in  asphyxia,  and  the  post-mortem  peristaltic  movements 
witnessed  on  opening  a  recently  killed  animal,  are  probably 
due  to  the  deficiency  of  oxygen  or  the  accumulation  of  car- 
bonic acid  in  the  blood  and  tissues  of  the  intestinal  walls. 
Conversely,  saturation  of  the  blood  with  oxygen,  as  in  the 
peculiar  condition  known  as  a])noea  (see  chapter  of  Res[)l- 
ration),  tends  to  check  peristaltic  movements. 

Judging  from  the  analogy  of  the  respiratory  and  other  nerv- 
ous centres,  the  efl:ects  should  be  attributed  to  variations  in  the 
quantity  of  oxygen  rather  than  of  carbonic  acid  ;  this,  however, 
does  not  at  present  seem  clearly  proved. 

In  the  second  plrtce,  peristaltic  action  is  largely  influenced 
by  nervous  influences  passing  along  the  splanchnic  and 
vagus  nerves.  The  movements  will  go  on  after  section  of 
both  these  nerves;  but,  as  a  general  rule,  while  stimulation 
of  the  splanchnic  tends  to  check.^  that  of  the  vagus  tends 
to  excite  them.  It  is  probal)ly  tlirough  the  vagus  that 
peristaltic  movements  can  be  eflected  in  a  reflex  manner,  as 
in  that  increase  of  the  movements  of  the  intestine  in  conse- 


Pfliiger,  Die  Hemmungsnerven  des  Darms,  b 


oS2     THE    TISSUES    AND    MECllANISiMS    OF    DIGESTION. 


qiieiice  of  emotions,  which  has  given  rise  to  the  phrase  "ray 
bowels  yearned." 

It  is  generally  stated  that  sudden  stoppage  of  the  blood-eurrent 
excites" peristaltic  action,  the  explanation  given  bcnng  that,  as 
after  general  death,  there  is  an  accumulation  of  carbonic  acid 
and  a  lack  of  oxygen  in  the  intestinal  tissues.  A^an  Braam 
Ilouckgeest,'  however,  states,  on  the  contrary,  that  it  brings  the 
intestine  to  rest ;  and  Nasse'  found  that  the  injection  of  arterial 
blood,  at  a  hiuh  i)ressure,  caused  very  powerful  movements.  On 
the  other  hand,  exposure  to  air  has  been  considered  as  an  excit- 
ing cause  of  the  movements;  and  undoubtedly  a  very  large 
amount  of  movement  may  frequently  be  observed,  on  laying  open 
the  abdomen,  even  in  animials  whose  crculation  is  active.  Since, 
however,  the  movements  continue  when  the  body  is  immersed  in 
weak  sodium  chloride  solution  and  the  intestine  thereby  excluded 
from  direct  contact  with  air,  they  cannot  be  attributed  to  mere 
exposure.  If  the  splanchnic  nerve  be  stimulated  while  active 
movement  is  going  on,  the  intestine  is  undoubtedly  brought  to 
rest.  Since,  at  the  same  time  the  bloodvessels  of  the  intestine 
are  by  the  vaso-conslrictor  action  of  the  splanchnic  constricted, 
the  quiescence  of  the  intestine  ma}'  be  indirecth'  due  to  insufii- 
cient  blood -supply.-'  Ilouckgeest,  however,  denies  this,  on  the 
ground  that  when  by  exposure  to  the  air  the  bloodvessels  of  the 
hitestine  are  so  far  paralyzed  as  to  be  no  longer  constricted  by 
the  action  of  the  splanchnic,  quiescence  of  the  intestine  is  still 
observed  on  irritating  that  nerve.  The  splanchnic  thus  appears 
to  be  a  direct  inhibitory  nerve  as  regards  peristaltic  action,  while 
the  vagus  is  undoubtedly  an  adjuvant  or  accelerator  nerve.  It 
is  stated  that  after  section  of  the  splanchnics  peristaltic  move- 
ments are  more  active  and  more  readily  brought  about  by  stimu- 
lation of  the  vagus  than  when  the  splanchnics  are  entire.  Ac- 
cording to  Ludwig,'  however,  stimulation  of  the  splanchnic,  while 
it  stops  an  already-developed  peristaltic  action,  will  bring  on  the 
movement  when  brought  to  bear  on  an  intestine  previously  at 
rest. 

When  the  vagus  is  stimulated,  peristaltic  contraction  is  seen 
to  begin  at  the  pylorus  of  the  stomach  and  so  to  descend  along 
the  intestine.  It  has  been  stated  that  no  so-called  antiperistaltic 
action,  that  is,  a  wave  of  contraction  passing  upwards  instead  of 
downwards  along  the  intestine,  ever  occurs  naturally  in  the  in- 
testine, the  backward  dow  undoubtedly  seen  when  an  obstruction 
exists  being  explained  as  being  simply  due  to  a  central  return 
current.  When,  however,  the  duodenum  is  mechanically  stimu- 
lated both  a  peristaltic  and  an  antiperistaltic  wave  may  be  ob- 

1  Pfliiger's  Archiv,  vi  (1872),  p.  266. 
'^  Beitr.  z.  Physiol,  d.  Darmbewegungen,  1866. 
^  Basch,  Wien.  Sitzungsbericht,  Ixviii  (1873). 
*  Lehrb.,  Bd.,  ii,  p.  616. 


MOVEMENTS    OF    THE    (ESOPHAGUS.  383 


served,  the  former  passing  downward  and  ceasing  at  the  ileo-ciecal 
valve  if  not  before,  the  latter  passing  up  and  ceasing  at  the  py- 
lorus. And  when  in  the  exposed  intestines  a  wave,  as  occasion- 
ally hapi)ens,  begins  spontaneously  in  the  duodenum,  it  may 
sometimes  he  seen  to  pass  both  upwards  and  downwards.  It  is 
worthy  of  notice  that  stimulation  of  the  stiiall  intestine  is  said 
not  to  cause  movement  either  in  the  stomach  or  large  intestine, 
and  stimulation  of  the  large  causes  no  movement  of  the  small 
intestine,  the  ileocoecal  valve  and  the  pylorus  barring  the  prog- 
ress of  the  Avaves.^ 

Certain  drugs,  such  as  nieotin,  induce  strong  peristaltic  action  ; 
the  modus  operandi  of  these  and  of  the  more  specitic  purgative 
drugs  is  at  present  uncertain. 

Having  thus  studied  the  general  characters  of  peristaltic 
action  in  its  most  marked  form,  we  may  hrietly  consider  the 
same  movement  in  other  parts  of  the  alimentary  canal. 

Movements  of  the  (Esophagus. — The  descent  of  the  food 
along  tlie  cesoi)hagus  is  effected  by  a  peristaltic  contraction  of 
the  circular  and  longitudinal  coats,  resembling  in  its  general 
characters  that  of  the  intestine.  It  differs,  however,  in 
being  more  closely  dependent  on  the  central  nervous  system, 
and  may  in  fact  be  considered  as  being  in  large  measure  a 
reflex  act,  with  the  centre  in  the  medulla  oblongata,  both 
afferent  and  efferent  impulses  being  supplied  by  the  vagus. 
It  may  be  readily  excited  by  stimulating  the  central  end  of 
the  superior  laryngeal  nerve  ;  and  this  nerve,  since  it  is  con- 
nected l\y  its  pharyngeal  branch  both  with  the  mucous  mem- 
brane of  the  pharynx  and  with  the  lower  pharyngeal  con- 
strictor, may  serve  to  inaugurate  the  oesophageal  movement, 
by  carrying  aflerent  impulses  started  by  the  presence  of  food 
in  the  piiarynx  or  by  the  muscular  act  of  swallowing.  Sec- 
tion of  the  trunk  of  the  vagus  renders  difficult  the  passage 
of  food  along  the  a?sophagus,  and  stimulation  of  the  periph- 
eral stump  causes  esophageal  contractions.  Hence  the 
motor  tracts  of  the  reflex  act  are  to  l»e  souglit  for  in  the 
vagus  also.  The  force  of  this  movement  is  considerable  ; 
thus  Mosso'-  found  that  in  tiie  dog  a  ball  pulling  bj'  means 
of  a  jndley  against  a  weight  of  250  grams  was  readih'  carried 
down  from  the  pharN'nx  to  the  stomach. 

Mosso'  states  that  section  and  even  removal  of  portions  of  the 
oesophagus  do  not  prevent  the  progression  of  a  peristaltic  wave 

'  En,(jelraann,  Pfliiger's  Archiv,  iv  (1871),  p.  33. 

'  Moleschott's  Untersucli.,  xi  (1874),  p.  327.  ^  i^^^  f.[^^ 


384     THE    TISSUES    AND    MECHANISMS    OF    DKIESTION. 


from  tlu'  i)baryiix  to  the  stomach,  provided  the  retlcx  machinery 
of  tlie  meihdla  be  intact.  He  argues  in  consequence  that  the 
natural  movement  in  swallovvinijj  is  entirely  carried  on  by  the 
medulla  as  a  reflex  act.  Xevertheless  an  a'sophatxus  .accordiuix 
to  his  own  account  will  when  removed  from  the  bod}-,  and  theri'- 
fore  entirely  separated  from  any  extrinsic  nervous  niechanism, 
exhibit  jj^ood  peristaltic  movements.  The  extrinsic  central  mech- 
anism, therefore,  would  seem  only  to  be  useful  in  i)erfecting  a 
movement  which  in  its  absence  would  be  imperfect  and  ineffi- 
cient. 

Goltz'  has  shown  that  if,  in  a  urarized  frog,  tiuid  be  poured 
down  the  throat,  both  stomach  and  (jesoi)hagusvvill,  after  tlie  fu-st 
peristaltic  movements  carrying  down  the  first  portions  of  Huid 
have  passed  away,  remain  perfectly  quiescent  in  an  enormously 
distended  condition  (the  contraction  of  the  pylorus  preventing 
the  descent  of  the  tluid  into  the  duodenum)  so  long  as  the  me- 
dulla oblongata  and  vagi  are  intact.  Destruction  of  the  medulla 
or  section  of  the  vagi  gives  rise  to  the  development  of  abundant 
downward  and  upward  peristaltic  waves  of  contraction,  by  which 
the  stomach  becomes  wrinkled  and  the  top  of  the  (X'SO))hagus  closed  ; 
and  these  movements  last  as  long  as  the  irritability  of  the  organs 
continues.  During  the  quiescence  observed  with  intact  vagi  and 
medulla,  tem])orary  ])eristaltic  action  may  be  induced  by  direct 
irritation  of  tlie  vagus,  or  in  a  reliex  manner  through  the  n"iedulla, 
by  stimulation  of  the  skin  or  intestine.  Chauveau-and  Schiff"  also 
saw  occasional  movements  in  the  tesophagus  after  section  of  the 
vagus.  Goltz  interprets  his  result  by  supposing  that  the  move- 
ments are  primarily  caused  by  local  motor  centres  in  the  oesoph- 
agus and  stomach,  habitually  inhibited  by  the  action  of  a  centre 
in  the  medulla.  Hence  when  this  inhibition  is  removed  by  de- 
struction of  the  medulla  or  section  of  the  vagi,  the  energy  of  the 
local  centres  is  free  to  act.  Stimulation  of  the  skin  or  other  dis- 
tant spots  produces  movements  by  depressing  the  medullary  in- 
hibitory centre.  Stimulation  of '  the  vagus  probably  produces 
movements  by  directly  augmenting  the  local  centres. 

The  junction  of  the  oesophagus  with  the  stomach  remains 
in  a  more  or  less  permanent  condition  of  tonic  or  obscurely 
rhythmic  contraction,  more  particularly  when  the  stomach 
is  full  of  food,  and  thus  serves  as  a  sphincter  to  prevent  tlie 
return  of  food  from  the  stomacii  into  the  (esoj)hagus.  During 
the  passage  of  the  food  fi'om  the  a30S')phagus  into  the  stomach 
this  sphincter  becomes  relaxed,  probably  by  a  mechanism 
which  will  be  described  in  treating  of  vomitina:. 


1  Pfl user's  Arcliiv,  vi  (1872),  p.  616. 

2  Journal  de  Phvsiolo.£?ie,  v  (bS6.3),  p.  P>37. 

3  Lemons  siir  la  Physioloi^ie  de  Digestion,  p. 


i>/  / 


MOVEMENTS    OF    THE    STOMACH,  385 

Movements  of  the  Stomach. — These  are  at  bottom  peris- 
taltic in  nature,  thono;h  lai'geiy  modified  by  the  peculiar  ar- 
rangement of  the  gastric  muscular  fibres.  When  food  first 
enters  the  stomach,  the  movements  are  feeble  and  slight, 
but  as  digestion  goes  on  they  become  more  and  more  vigor- 
ous, giving  rise  to  a  sort  of  churning  within  the  stomach, 
the  food  travelling  from  the  cardiac  orifice  along  the  greater 
curvature  to  the  pylorus,  and  returning  by  the  lesser  curva- 
ture, while  at  the  same  time  subsidiary  currents  tend  to 
carry  the  food  which  has  been  passing  close  to  the  mucous 
membrane  towards  the  middle  or'the  stomach,  and  vice  versa. 
At  the  pyloric  end  strong  circular  contractions  are  set  up, 
by  which  portions  of  food,  more  especially  the  dissolved 
parts,  but  also'  small  solid  pieces,  are  carried  through  the 
relaxed  sphincter  into  the  duodenum.  As  digestion  pro- 
ceeds, more  and  more  material  leaves  the  stomach,  which  is 
thus  gradually  emptied,  the  last  portions  which  are  carried 
through  being  those  matters  which  are  least  digestible,  and 
foreign  bodies  which  happen  to  have  been  swallowed.  The 
presence  of  food  then  leads  to  the  development  of  obscurely 
peristaltic- rhythmic  movements,  the  stomach  when  empty 
lieing  contracted,  but  quiescent;  l)ut  evidently  it  is  not  the 
mere  mechanical  repletion  of  the  organ  which  is  the  cause 
of  the  movements,  since  the  stomach  is  fullest  at  the  begin- 
ning when  the  movements  are  slight,  and  becomes  empty 
as  the\'  grow  more  forcible.  The  one  thing  which  does  \\\- 
c\'Q2iSQ  i:ari  iiasf^u  with  the  movements  is  the  acidity,  which 
is  at  a  minimum  when  the  (generally  alkaline)  food  has  been 
swallowed,  and  increases  steadily  onwards.  It  has  not, 
however,  been  detinitel}'  shown  that  the  increasing  acidit}^ 
is  the  efficient  stimulus,  giving  rise  to  the  movements. 

The  nervous  mechanism  of  the  gastric  movements  is  very  per- 
plexing. Judging  from  the  analogy  of  the  intestine,  one  would 
imagine  that  they  originated  in  the  stomach  itself,  being  modified 
but  not  directly  caused  by  the  action  of  the  central  nervous  sys- 
tem. Spontaneous  movements,  however,  of  a  stomach,  whose 
nervous  connections  have  been  severed,  even  of  a  full  one,  are  at 
least  much  more  rare  than  those  seen  in  the  intestine  or  even  in 
the  oesophagus  ;  and  such  movements  as  are  occasioned  by  local 
mechanical  or  other  stimulation  are  limited  in  extent,  and  rarely 
put  on  all  the  characters  of  the  natural  complex  contractions. 
ISioce  there  are  abundant  ganglia  in  the  walls  of  the  stomach,  it 

^  Kiihne,  Lerhb.,  p.  53. 


38')      THE    TISSUES    AND    MECHANISMS    OF    DIGESTION. 


may  fairly  be  doubkMl  whotlicr  Ibc  automatic  movements  of  tlic 
excised  intestine  are  due  to  the  action  of  ganu;lia,  otherwise  why 
should  not  the  ganjjjlia  in  the  stomach  set  up  spontaneous  move- 
ments in  that  or^an  also  ?  For  if  iran^liaare  par  excellence  the 
oriians  of  automatic  actions  wc  should  expect  spontaneous  move- 
ments to  accom])any  their  presence. 

The  stomacl;  receives  its  nervous  supply  from  the  vagi  and  also 
from  the  solar  i^lexus,  with  which  the  splanchnics  are  connected. 
AVhen  the  vaiii  are  divided,  a  spasmodic  constriction  of  the  car- 
diac orilice  takes  place,  the  tonic  action  of  the  sphincter  is 
increased,  no  dilaticm  takes  place,  and  foxl  is  thus  prevented, 
for  a  time  at  least,  from  leavin";  the  cesophagus.  This  result  is 
in  harmony  with  the  observations  of  Goltzon  the  frog.  In  addi- 
tion the  natural  movements  of  the  stomach  itself  cease,  though 
the  introduction  of  food  after  section  of  the  vagi  is  said  to  cause 
some  amount  of  contraction.  They  may  be  induced  by  stimula- 
tion of  the  peripheral  stumps  of  the  vagi,  when  the  stomach  is 
full,  but  not  if  it  be  empty.  Neither  section  nor  stimulation  of 
the  splanchnics  or  of  the  branches  from  the  solar  plexus  iiroduce, 
it  is  said,  any  etTect  on  the  stomach  as  far  as  its  movements  are 
concerned.  Evidently  the  movements  of  the  stomach,  far  more 
than  those  of  the  intestine,  are  dependent  on  and  governed  by 
the  central  nervous  system,  but  the  exact  manner  in  which  they 
are  governed  and  the  pro])er  share  to  be  allotted  to  exciting  and 
inhibitory  mechanisms,  remain  yet  to  be  discovered.  The  sort 
of  tonic  contraction,  into  which  the  walls  of  the  stomach  fall 
when  its  cavity  is  empty,  does  not  occur  in  the  intestine  ;  and 
this  feature  probably  modifies  all  the  nervous  working  of  the  or- 
gan. Nor  do  we  know  the  exact  mechanism  by  w^hich  the 
pyloric  sphincter  is  used  to  strain  off  gradually  the  more  digested 
portions  of  the  food.  The  movements  of  even  a  full  stomach 
are  said  by  Busch^  to  cease  during  sleep. 

Movements  of  the  Large  Intestine.— These  are  fundament- 
ally the  same  as  those  of  the  small  intestine,  but  distinct  in 
so  far  as  the  latter  cease  at  the  ileo-cyecal  valve,  at  which 
spot  the  former  normally  begin. 

They  are  said,  however,  not  to  be  inhibited  by  stimulation  of 
the  splanchnics.'^ 

The  faeces  in  their  passage  through  the  colon  are  lorlged 
in  the  sacculi  during  the  pauses  between  the  peristaltic 
waves.  Arrived  at  the  sigmoid  flexure,  they  are  su|)ported 
b}'  the  bladder  and  the  sacrum,  so  that  they  do  not  press  on 
the  sphincter  ani. 

^  Yiroh.  Arcliiv,  xiv,  p.  16G. 
'  Pfliiger,  op.  cit. ;  Na.sse,  op.  cit. 


DEFECATION.  387 

Defecation. — Tliis  is  a  mixed  act,  being  superficially  the 
result  of  an  effort  of  the  will,  and  yet  carried  out  by  means 
of  an  involuntary  mechanism.  Part  of  the  voluntary  effort 
consists  in  producing  a  pressure-effect,  by  means  of  the 
abdominal  muscles.  These  are  contracted  forcibh'  as  in 
expiration,  but  the  glottis  being  closed,  and  the  escape  of 
air  from  the  lungs  prevented,  the  whole  force  of  the  pres- 
sure is  brought  to  bear  on  the  abdomen  itself,  and  so  drives 
the  contents  of  the  descending  colon  onward  into  the  rectum. 
The  sigmoid  flexure  is  by  its  position  sheltered  from  this 
pressure;  a  body  introduced  per  anum  into  the  empty  rec- 
tum is  not  affected  by  even  forcible  contractions  of  the 
abdominal  walls. 

The  anus  is  guarded  by  the  sphincter  ani,  which  is  habit- 
ually in  a  state  of  normal  tonic  contraction,  capable  of  being 
increased  or  diminished  by  a  stimulus  applied,  either  inter- 
nally or  externally,  to  the  anus.  The  tonic  conti'action  is 
in  part  at  least  due  to  the  action  of  a  nervous  centre  situated 
in  the  lumbar  spinal  cord.^  If  the  nervous  connection  of 
the  sphincter  with  the  spinal  cord  be  broken,  relaxation 
takes  place.  If  the  spinal  cord  be  dix'ided  in  the  dorsal 
region,  the  sphincter,  after  the  depressing  effect  of  the 
operation,  which  may  last  several  days,  has  passed  off,  still 
maintains  its  tonicitv,  showing  that  the  centre  is  not  placed 
higher  up  than  the  lumbar  region  of  the  cord.  The  increased 
or  ditninislied  contraction  following  on  local  stimulation  is 
probably  due  to  a  reflex  augmentation  or  inhibition  of  the 
action  of  this  centre.  The  centre  is  also  subject  to  influ- 
ences proceeding  from  higher  regions  of  the  cord,  and  from 
the  brain.  By  the  action  of  the  will,  by  emotions,  or  by 
other  nervous  events,  the  lumbar  sphincter  centre  ma}^  be 
Inhibited,  and  thus  the  sphincter  itself  relaxed  ;  or  aug- 
mented, and  thus  the  sphincter  tightened.  A  second  item 
therefore  of  the  voluntary  process  in  defecation  is  the  inhi- 
bition of  the  lumbAr  sphincter  centre,  and  consequent  relax- 
ation of  the  sphincter  muscle. 

According  to  Goltz,-  in  the  dog  after  division  of  the  dorsal 
cord,  and  consequent  separation  of  the  sphincter  centre  from  the 
cerebrum,  local  stimulation,  such  as  the  introduction  of  the  fin- 
ger, causes  not  a  steady  increase  or  decrease  of  the  action  of  the 
sphincter,  but  a  rhythmic  alternation  of  tightening  and  relaxing. 

^  Masuis,  Bull,  de  I'Acad.  R.  de  Belgique,  xxiv  (1867),  p.  312. 
^  Pfliiger's  Archiv,  viii  vl874j,  460. 


388      THE    TISSUES    AND    MECHANISMS    OF    DIGESTION. 


Tlio  iibst'iH'c  of  this  rliytbm  with  an  iutacl  cord  indicates  some 
obscure  action  ol"  the  ceroln\'il  centres  on  the  knnbar  centre. 
The  conversion  of  the  tonic  into  the  rhythmic  action  also  illus- 
trates the  close  relationship  between  these  two  kinds  of  move- 
ments. 

Thouizb  the  tonic  contraction  of  the  sphincter  seems  so  lar<j^ely 
dei)end('nt  (►n  the  lumbar  centres,  still  this  dependence  is  probably 
not  an  absolute  one.  In  the  case  of  a  mm  in  whom  as  the  re- 
sult of  injury  the  sacral  nerves  were  entirely  paralyzed,  and  the 
si)hincter  accordingly  had  no  nervous  connection  with  the  lumbar 
centre  (unless  there  were  a  roundabout  connection  by  means  of 
the  synii)athetic),  Gower'  observed  the  maintenance  of  a  certain 
amount  of  tonic  contraction  which  could  be  inhibited,  and  relax- 
ation induced,  by  stimulation  of  the  mucous  membrane  of  the 
rectum  and  anus.  As  in  the  case  of  the  arteries,  we  have  appar- 
ently to  deal  here  with  a  tonic  contraction  which  is  habitually 
dependent  on  a  spinal  centre,  but  which  may  nevertheless  exist 
without  the  action  of  that  centre. 

-Since  the  lumbar  centre  is  wholly  efficient  when  separated  from 
the  brain,  the  paralysis  of  the  sphincter  which  occurs  in  certain 
cereTjral  diseases  is  probably  due  to  inhibition  of  this  centre,  and 
not  to  paralysis  of  any  cerebral  centre. 

Thus  a  voluntary  contraction  of  the  abdominal  walls,  ac- 
companied by  a  relaxation  of  the  sphincter,  might  press  the 
contents  of  the  descending  colon  into  the  rectum  and  out 
at  the  anus.  Since,  however,  as  we  have  seen,  the  pressure 
of  the  abdominal  vvalls  is  warded  off'  the  sigmoid  flexure, 
such  a  mode  of  defecation  would  always  end  in  leaving  the 
sigmoid  flexure  full.  Hence  the  necessity  for  these  more 
or  less  voluntary  acts  being  accompanied  by  an  entirely 
involuntary  augmentation  of  the  peristaltic  action  of  the 
large  intestine  and  sigmoid  flexure.  Or,  rather,  to  describe 
matters  in  their  [proper  order,  defecation  takes  place  in  the 
following  manner:  The  sigmoid  flexure  and  large  intestine 
becoming  m<jre  and  more  full,  stronger  and  stronger  peris- 
taltic action  is  excited  in  their  walls.  By  this  means  the 
freces  are  driven  against  the  s[)hincter.  Through  a  voluntary 
act,  or  sometimes  at  least  by  a  simple  reflex  action,  the 
lumbar  sphincter  centre  is  inhibited  and  the  sphincter  re- 
laxed. At  the  same  time  the  contraction  of  the  abdominal 
muscles  presses  firmly  on  the  descending  colon,  and  thus 
the  contents  of  the  rectum  are  ejected. 

It  must,  however,  be  remembered  that,  while  in  appealing 
to  our  own  consciousness,  the  contraction  of  the  abdominal 

1  Proc.  Roy.  Soc,  xxvi  (1877),  p.  77. 


VOMITING.  889 

walls  and  the  relaxation  of  the  sphincter  seem  piireh'  vol- 
untar}'  efforts,  the  whole  act  of  defecation,  incliidini;-  both 
of  these  seenaingl^'  so  Toluntarv  components,  may  take  place 
in  the  absence  of  consciousness,  and,  indeed,  in  the  case  of 
Goltz's  dog,^  after  the  complete  severance  of  the  lumbar 
from  the  dorsal  cord.  In  such  cases  the  whole  act  must 
be  purely  reflex,  excited  b}'  the  presence  of  fieces  in  the 
rectum. 

Vomiting. — In  a  conscious  individual  this  act  is  preceded 
b}'  feelings  of  nausea,  during  which  a  copious  flow  of  saliva 
into  the  mouth  takes  place.  This  being  swallowed  carries 
down  with  it  a  certain  quantity  of  air,  the  presence  of  which 
in  the  stomach,  by  assisting  in  the  opening  of  the  cardiac 
sphincter,  subsequentlj'  facilitates  the  discharge  of  the  gas- 
tric contents.  Tlie  nausea  is  generally  succeeded  at  first 
b\^  ineffectual  retching,  in  which  a  deep  inspirator}'  effort  is 
made,  so  that  tiie  diaphragm  is  thrust  down  as  low  as  pos- 
sible against  tlie  stomach,  tiie  lower  ribs  being  at  the  same 
time  forcibly  drawn  in  ;  since  during  this  inspirator}^  effort 
the  glottis  is  kept  closed,  no  air  can  enter  into  the  lungs  ; 
but  some  is  drawn  into  tlie  pharynx,  and  thence  probably 
descends  by  a  swallowing  action  into  the  stomach.  In  ac- 
tual vomiting  this  inspiratory  effort  is  succeeded  by  a  sud- 
den violent  expiratory'  contraction  of  the  abdominal  walls, 
the  glottis  still  being  closed,  so  that  the  whole  force  of  the 
effort  is  spent,  as  in  defecation,  in  pressure  on  the  abdomi- 
nal contents.  The  stomach  is,  therefore,  forcibl}'  compressed 
from  without.  At  the  same  time,  or  rather  immediately 
before  tlie  expiratory-  effort,  l)y  a  contraction  of  its  longi- 
tudinal fibres  the  oesophagus  is  shortened,  and  the  cardiac 
orifice  of  the  stomach  brought  close  under  the  diaphragm, 
while  apparently  by  a  contraction  of  the  fibres  which  radiate 
from  the  end  of  the  oesophagus  over  the  stomach,  the  cardiac 
orifice,  which  is  normally  closed,  is  somewhat  suddenly 
dilated.  This  dilation  opens  a  wa}'  for  the  contents  of  the 
stomach,  which,  pressed  upon  by  the  contraction  of  the 
abdomen,  and  to  a  certain  but  probably  only  to  a  slight 
extent  by  the  contraction  of  the  gastric  walls,  are  driven 
forcibly  up  the  cesophagus,  their  passage  along  that  channel 
being  possibly  assisted  by  the  contraction  of  the  longitudi- 
nal muscles.     The  mouth  being  widely  open,  and  the  neck 

1  Op.  cit. 
33 


390     THE    TISSUES    AND    MECHANISMS    OF    DIGESTION. 

Stretched  to  afford  as  straight  a  course  as  possible,  the  vomit 
is  ejected  from  the  body.  At  tiiis  moiiieut  there  is  an  addi- 
tional expiratory  elFort  which  serves  to  prevent  the  vomit 
passing  into  the  larynx.  In  m  )st  cases,  too,  the  posterior 
pillars  of  the  fances  are  approximated,  in  order  to  close  the 
nasal  i)assage  against  the  ascending  stream.  This,  however, 
in  severe  vomiting  is  frequently  ineffectual. 

Thus  in  vomiting  there  are  two  distinct  acts,  the  dilation 
of  the  cardiac  orifice  and  the  extrinsic  i)ressure  of  the  ab- 
dominal walls  in  an  expiratory  effort.  Without  the  former 
the  latter,  even  when  distressingly  vigorous,  is  ineffectual. 
Without  the  latter,  as  in  urari  poisoning,  the  intrinsic  move- 
ments of  the  stomach  itself  are  rarely  sufficient  to  do  more 
than  eject  gas,  and,  it  may  be,  a  very  small  quantity  of  food 
or  fluid.  Pyrosis  or  waterbrash  is  probably  brought  about 
by  this  intrinsic  action  of  the  stomach. 

During  vomiting  the  i)ylorus  is  generally  closed,  so  that 
but  little  material  escapes  into  the  duodenum.  When  the 
gall-!)ladder  is  full,  a  copious  flow  of  bile  into  the  duodenum 
accompanies  the  act  of  vomiting.  Part  of  tiiis  ma}'  find  its 
way  into  the  stomach,  as  in  bilious  vomiting,  the  pylorus 
then  being  evidently  open. 

The  experiment  of  Magendie,  showing  that  vomiting  can  take 
place  when  a  simple  bladder  is  substituted  for  the  stomach,  is 
said  to  fail  unless  the  oesophageal  sphincter  be  removed  or  the 
dilating  mechanism  be  left  intact.  Schiff/  by  introducing  his 
finger  through  a  gastric  fistula,  was  able  to  ascertain  by  direct 
touch  both  the  normal  occlusion  of  the  cardiac  orifice,  broken 
only  during  the  descent  of  food,  and  its  sudden  dilation  just  pre- 
ceding the  expiratory  pressure  durins;  vomiting.  He  found  that 
when  the  muscular  fibres  radiating  from  the  oesophagus  over  the 
stomach  were  injured,  as  by  crushing  them  with  a  ligature  forci- 
bly applied  for  a  few  seconds,  the  constriction  of  the  cardiac 
orifice  remained  permanent ;  dilation  of  the  cardiac  orifice,  and 
in  consequence  vomiting,  became  impossible.  He,  therefore,  re- 
gards the  dilation  as  caused  by  the  active  contraction  of  these 
fibres,  and  not  as  due  to  inhibition  of  the  normally  contracted 
circular  fibres.  In  order  that  the  contraction  of  the  radiating 
fibres  should  cause  dilation,  their  ends  distal  from  the  oesophagus 
must  be  fixed.  This  is  provided  by  the  stomach  being  supported 
by  the  descent  of  tlie  diaphragm.  Tlie  support  afforded  to  the 
oesophagus  by  the  diaphragm  as  it  passes  through  that  muscle 
must  also  be  of  advantage,  and  the  longer  the  portion  of  oesoph- 
agus between  the  diaphragm  and  the  stomach,  the  greater  will 

1  Moleschott's  Untersuch.,  x  (1870),  p.  353. 


VOxMlTING.  391 


be  the  effect  of  the  radiating  muscles  in  pulling  down  the  oesoph- 
agus instead  of  dilating  its  orifice.  This  is  possibly  the  reason 
why  the  horse  and  other  herbivorous  animals  vomit  with  such 
difficult}'. 

The  nervous  mechanism  of  vomiting  is  complicated,  and 
in  many  aspects  obscure.  The  efferent  impulses  which  cause 
the  expiratory  effort  must  come  from  the  respiratory  centre 
in  the  medulla  :  with  these  we  shall  deal  in  speaking  of  respi- 
ration. The  dilation  of  the  cardiac  orifice  is  caused,  in  part 
at  least,  b}'  efferent  impulses  descending  the  vagi,  since  when 
these  are  cut  real  vomiting  with  discharge  of  the  gastric 
contents  is  diflicult,  through  want  of  readiness  in  the  dila- 
tion. Tlie  sympathetic  abdominal  nerves  coming  from  the 
coeliac  ganglia  and  the  splanchnic  nerves  seem  to  have  no 
share  in  the  matter.  The  efferent  impulses  wliich  cause  the 
flow  of  saliva  in  the  introductory  nausea  descend  the  facial 
along  the  chorda  tympani  branch.  These  various  impulses 
may  best  be  considered  as  starting  from  a  vomiting  centre 
in  the  medulla,  having  close  relations  with  the  respiratory 
centre.  This  centre  may  be  excited,  may  be  thrown  into 
action,  in  a  reflex  manner,  by  stimuli  applied  to  peripheral 
nerves,  as  when  vomiting  is  induced  by  ticlvling  the  fauces, 
or  by  irritation  of  the  gastric  membrane,  or  by  obstruction 
due  to  ligature,  hernia,  etc.,  of  the  intestine.  That  the  vom- 
iting in  the  last  instance  is  due  to  nervous  action,  and  not 
to  auy  regurgitation  of  the  intestinal  contents,  is  shown  by 
the  fact  tliat  it  will  take  place  when  the  intestine  is  perfectl}^ 
empty,  and  may  be  prevented  by  section  of  tlie  mesenteric 
nerves.  The  vomiting  attending  renal  and  biliary  calcuH  is 
apparently  also  reflex  in  origin.  The  centre,  however,  may 
be  affected  directly,  as  probably  in  the  cases  of  some  poisons, 
and  in  some  instances  of  vomiting  from  disease  of  the  me- 
dulla oblongata.  Lastly,  it  may  be  thrown  into  action  by 
impulses  reaching  it  from  parts  of  the  brain  higher  up  than 
itself,  as  in  cases  of  vomiting  produced  by  smells,  tastes, 
and  emotions,  and  by  the  memory  of  past  occasions,  and  in 
some  cases  of  vomiting  from  cerebral  disease. 

Man}-  emetics,  such  as  tartar  emetic,  appear  to  act  di- 
rectly on  the  centre,  since,  introduced  into  the  blood,  they 
will  produce  vomiting  even  when  a  bladder  is  substituted 
for  the  stomach.  Others  again,  such  as  mustard  and  water, 
act  in  a. reflex  manner  by  irritation  of  the  gastric  mucous 
membrane.     With  others,  again,  which  cause  vomiting  by 


392    THE  TISSUES  and  mechanisms  of  digestion. 


developing  a  nauseous  taste,  the  reflex  action  involves  parts 
of  tlie  brain  higher  than  the  centre  itself. 

Since  the  vagus  acts  as  an  efferent  nerve  in  causing  the  dila- 
tion of  the  cardiac  orifice  so  essential  to  the  act,  it  is  difficult  to 
eliminate  the  share  taken  by  the  vagus  as  an  afferent  nerve  car- 
rying up  impulses  from  the  stomach  to  the  vomiting  centre.  The 
remarkable  fact  that,  by  giving  tartar  emetic,  vomiting  may  in 
dogs  be  sometimes  induced,  even  after  secti(m  of  the  vagi,  shows 
that  the  dilation  of  the  cardiac  orifice,  though  normally  effected 
through  the  vagus,  may  be  carried  out  by  means  of  some  local 
mechanism,  and  that  the  emetic  may  also  stimulate  that  local 
mechanism  at  the  same  time  that  it  is  affecting  the  general 
centre. 


Sec.  4.  The  Changes  which  the  Food  undergoes  in 
the  Alimentary  Canal. 

Having  studied  the  properties  of  the  digestive  juices,  and 
the  various  mechanisms  by  means  of  which  the  food  is 
brought  under  their  influence,  we  have  now  to  consider 
what,  as  matters  of  fact,  are  the  actual  changes  wliieh  tiie 
food  does  undergo  in  passing  along  the  alimentary  canal, 
wliat  are  the  steps  by  which  the  food  is  converted  into 
fjcces. 

In  the  mouth  tlie  presence  of  the  food,  assisted  by  the 
movetnents  of  the  jaw.  causes,  as  we  have  seen,  a  flow  of 
saliva.  By  mastication,  and  by  the  addition  of  mucous 
saliva,  the  food  is  broken  into  small  pieces,  moistened,  and 
gathered  into  a  convenient  bolus  for  deglutition.  In  man 
some  of  the  starch  is,  even  during  tlie  short  stay  of  the  food 
in  the  mouth,  converted  into  sugar  ;  for  if  boiled  starch  free 
from  sugar  be  even  momentarily  held  in  the  moutli,  and  then 
ejected  into  water  (kept  boiling  to  destroy  the  feiment),  it 
will  be  found  to  contain  a  decided  amount  of  sugar.  In 
man}'  animals  no  such  change  takes  place.  The  viscid  saliva 
of  the  dog  serves  almost  solel>'  to  assist  in  deglutition  ;  and 
even  the  longer  stay  which  food  makes  in  the  mouth  of  the 
horse  is  insutlicient  to  produce  any  marked  conversion  of  the 
starch  it  may  contain.  During  the  rapid  transit  through 
the  oesophagus  no  appreciable  change  takes  place. 

In  the  stomach,  the  arrival  of  the  food,  the  reaction  of 
which  is  either  naturally  alkaline,  or  is  made  alkaline,  or  at 


CHANGES    OF    FOOD    IN    THE    STOMACH.  393 

least  is  reduced  in  acidity,  by  the  addition  of  saliva,  causes 
a  flow  of  gastric  juice.  This  already  commencing  while  the 
food  is  as  yet  in  the  mouth,  increases  as  the  food  accumu- 
lates in  the  stomach,  and  as,  by  the  churning  gastric  move- 
ments, unchanged  particles  are  continually  being  brought 
into  contact  with  the  raucous  membrane.  Moreover  (see  p. 
357),  the  absorption  of  the  earlier  digested  portions  gives 
rise  to  a  further  increase  of  secretion,  and  especiall}'  of  pep- 
sin. The  secretion  of  acid  appears  to  continue  at  a  fairly 
constant  rate  ;  and  consequently,  unless  neutralized  by  fresh 
alkaline  food,  the  reaction  of  the  gastric  contents  becomes 
more  and  more  distinctly  acid  as  digestion  proceeds.  The 
change  of  starch  into  sugar  is  lessened  or  perhaps  arrested. 
The  fats  themselves  remain  unchanged  ;  but,  through  the 
'conversion  of  proteids  into  peptone,  not  only  are  the  more 
distinctly  proteid  articles  of  food,  such  as  meat,  broken  up 
and  dissolved,  but  the  proteid  framework,  in  which  the 
starch  and  fats  are  frequently  imbedded,  is  loosened,  the 
starch-granules  are  set  free,  and  the  fats,  melted  for  the  most 
part  by  the  heat  of  the  stomach,  tend  to  run  together  in 
large  drops,  whicli  in  turn  are  more  or  less  apt  to  be  broken 
up  into  an  imperfect  emulsion.  The  collagenous  tissues  are 
dissolved  ;  and  hence  the  natural  bundles  of  meat  and  vege- 
tables fall  asunder;  the  muscular  fibre  splits  up  into  disks, 
and  the  protoplasm  is  dissolved  from  the  vegetable  cells. 
While  these  chaiiges  are  proceeding,  the  thick  turbid  grayish 
liquid  or  chyme,  formed  by  the  imperfectly  dissolved  food, 
is  from  time  to  time  ejected  through  the  pylorus,  accompa- 
nied by  even  large  morsels  of  solid  less-digested  matter. 
This  may  occur  within  a  few  minutes  of  food  having  been 
taken,  but  the  larger  escape  from  the  stomach  probably  does 
not  begin  till  from  one  to  two,  and  lasts  from  four  to  five 
hours  after  the  meal,  becoming  more  rapid  towards  the  end, 
such  pieces  as  most  resist  the  gastric  juice  being  the  last  to 
leave  the  stomach*. 

Busch^  saw^  in  the  case  of  a  duodenal  fistula,  portions  of  food 
pass  into  the  duodenum  within  fifteen  or  twenty  minutes  from 
the  beginning  of  the  meal.  Beaumont-  gives  a  ver}'  full  state- 
ment of  the  time  during  which  various  articles  of  food  remained 
in  the  stomach  of  Alexis  St.  Martin.  The  length  of  stay,  how- 
ever, of  the  same  substance  varied  very  much  under  various  cir- 

'  Virchow's  Archiv,  Bd.  14  (1858),  p.  140. 
^  Expos,  and  Obs.  on  Gastric  Juice,  1834. 


394     TOE    TISSUES    AND    MECHANISMS    OF    DIGESTION. 


c'umstances.  Moreover,  it  would  be  very  hazardous  to  make  a 
fistulous  stomach  the  canon  of  what  takes  place  in  a  healtliy 
organ.  In  animals  the  stay  of  the  food  in  the  stomach  is  very 
variable.  Ileidenhain'  found  food  in  the  stomach  of  dons  six- 
teen to  twenty-four  hours  after  a  meal,  and  it  is  well  known  the 
stomach  of  rabbits  are  never  empty  but  always  more  or  less  filled 
with  food. 

In  the  presence  of  liealthy  gastric  juice,  and  in  the  absence 
of  any  nervous  interference,  the  question  of  the  dio:estil)ility 
of  any  food  is  determined  chiefl}'  by  mechanical  conditions. 
The  more  finely  divided  the  material,  and  the  less  the 
proteid  constituents  are  sheltered  by  not  easily  soluble 
envelopes,  such  as  those  of  cellulose,  the  more  rapid  the 
solution.  So.  also,  pieces  of  hard  boiled  egg^  which  have  to 
be  gradually  dissolve  I  from  the  outside,  are  less  easily 
digested  than  the  more  friable  muscular  fibre,  the  repeated 
transverse  cleavage  of  which  increases  the  surface  exposed 
to  the  juice.  Unboiled  white  of  egg^  again,  unless  thor- 
oughly beaten  up  and  mixed  with  air,  is  less  digestible 
than  the  same  boiled.  The  unboiled  white  forms  a  viscid 
clotted  mass,  of  low  diffusibility,  into  whicli  the  juice  per- 
meates with  the  greatest  dirticulty.  And  so  with  other 
instances.  Beyond  this  mechauical  aspect  of  iiidigestibility, 
it  is  to  be  remembered  that  different  substances  may  differ- 
ently affect  the  gastric  membrane,  promoting  or  checking 
the  secretion  of  the  juice.  Hence  a  substance,  the  mass  of 
which  is  readily  dissolved  b}'  gastric  juice,  and  which  offers 
no  mechanical  obstacles  to  digestion,  may  yet  prove  indi- 
gestible by  so  affecting  the  gastric  membrane  through  some 
special  constituent  (or  possibly  in  other  ways)  as  to  inhibit 
the  secretion  of  the  juice. 

That  substances  can  be  absorbed  from  the  cavity  of  the 
stomach  into  the  circulation  is  proved  by  the  fact  that  food 
when  introduced  disappears  very  largel}'  from  the  stomach 
of  an  animal,  the  pylorus  of  which  has  been  ligatured.  But 
we  cannot  speak  with  certainty  as  to  what  extent  in  ordi- 
nary life  gastric  absorption  takes  place,  or  by  what  mechan- 
ism it  is  carried  out.  The  presumption  is,  that  the  diffusible 
sugars  and  peptone  pass  by  osmosis  direct  into  the  capilla- 
ries, and  so  into  the  gastric  veins.  The  filtrate  of  chyme 
taken  from  a  stomach  in  full  digestion  contains  parapeptonc, 

'  Pfluger's  Archiv,  xix  (1879),  p.  148. 


ric 
\r- 
or 


CHANGES    OF    FOOD    IN    THE    STOMACH.  395 

but  scarcely  ai\y  peptone.     From  this  it  ma}-  fairl}'  be  in- 
ferred that  the  peptone  has  been  absorbed. 

In  the  act  of  swallowing,  no  inconsiderable  quantity  of 
air  is  carried  dow^n  into  the  stomach,  entangled  in  the 
saliva,  or  in  the  food.  This  is  returned  in  eructations. 
When  the  gas  of  eructation  or  that  obtained  directly  from 
the  stomach  is  examined  it  is  found  to  consist  chiefly  of 
nitrogen  and  carbonic  acid,  the  oxygen  of  the  atniospheri' 
air  having  been  largely  absorbed.  In  most  cases  the  car 
bonic  acid  is  derived  by  simple  diffusion  from  the  blood,  o. 
from  the  tissues  of  the  stomach,  which  similarly  take  up  the 
oxygen.  In  many  cases  of  flatulenc}^,  however,  it  may  arise 
from  a  fermentative  decomposition  of  the  sugar  which  has 
been  taken  as  such  in  food,  or  which  has  been  produced 
from  the  starch. 

In  the  latter  case,  however,  hydrogen  ought  also  to  make  its 
appearance  ;  thus  C,jB[,,0;  =  2C.;li„0,,  (lactic  acid)  ==  C^H^Oj 
(butyric  acid)  +  2C0,,  +  H^,  whereas  hydrogen  has  only  been 
found  in  the  small  intestine.  In  the  dog,  Planer'  found  in  the 
stomach  after  a  meat  diet  a  small  amount  of  s^as  of  the  composi- 
tion CO  2.).20,  N  68.68,  O  6.12,  after  a  meal  of  bread,  CO,  32.91, 
K  66.30,  O  .79. 

The  enormous  quantity  of  gas  which  is  discharged  through  the 
mouth  in  'ases  of  hysterical  flatulency,  even  on  a  perfectly  empty 
stomach,  and  which  seems  to  consist  largely  of  carbonic  acid, 
presents  difliculties  in  the  way  of  explanation  ;  it  is  possible  that 
it  may  be  simply  diftused  from  the  blood. 

In  the  small  intestine  the  semi-digested  acid  food,  or 
chyme,  as  it  passes  over  the  biliary  orifice,  causes  gushes  of 
bile,  and  at  the  same  time,  as  we  have  seen  (p.  359),  the 
pancreatic  juice,  which  flowed  freeh'  into  the  intestine  at 
the  taking  of  the  meal,  is  secreted  again  with  renewed  vigor, 
when  the  gastric  digestion  is  completed.  These  two  alka- 
line fluids  tend  to  neutralize  the  acidit}'  of  the  chyme,  but 
the  contents  of  the  duodenum  do  not  become  distinctly 
alkaline  until  some  distance  from  the  pylorus  is  reached. 
Even  in  the  lower  part  of  the  ileum  the  chyme  may  be  acid ;'' 
possibly,  however,  in  such  cases  it  has  been  reacidified. 
The  conversion  of  starch  into  sugar,  which  ma}'  have  lan- 
guished in  the  stomach,  is  resumed  with  great  activity  by 

'    Wien.  Sitzungsberichte,  xlii,  p.  307. 

2  Losnitzer,  Henle,  and  Meissners  Bericht,  1864,  p.  2o0. 


31)G      THE    TISSUES    AND    MECHANISMS    OF    DIGESTION. 

llio  pancreatic  Juice,  though  portions  of  nndiocstcd  starch 
may  l)e  found  in  tlie  hirge  intestine  and  even  at  times  in  the 
fjuces. 

Tlie  pancreatic  juice,  as  we  have  seen,  emulsifies  Hits,  and 
also  splits  them  into  their  respective  fatty  acids  and  glyc- 
erin. The  fatty  acids  thns  set  free  become  converted  by- 
means  of  the  alkaline  contents  of  the  intestine  into  soaps  ; 
but  to  what  extent  sai)onification  thus  takes  place  is  not 
exactly  known.  Undoubtedly  soaps  have  to  a  small  extent 
been  found  both  in  portal  blood  and  in  the  thoraric  duct 
after  a  meal  ;  but  there  is  no  i)roof  that  any  large  quantity 
of  fat  is  introduced  in  tiiis  form  into  the  circidation.  On 
the  other  hand,  the  presence  of  neutral  fats,  both  in  portal 
blood,  and  especially  in  tlie  lacteals,  is  a  conspicuous  result 
of  the  digestion  of  fatty  matters  ;  and  in  all  probability 
saponification  in  the  intestine  is  a  subsidiary  process,  intend- 
ed rather  to  facilitate  the  emulsion  of  neutral  fats  than  to 
introduce  soaps  as  such  into  the  blood.  For  the  presence 
of  soluble  soa[)s  favors  the  emulsion  of  neutral  fats.  Thus 
a  rancid  fat,  i  e.,  a  fat  containing  a  certain  amount  of  free 
fatty  acid,  forms  an  emulsion  with  an  alkaline  fiuid  more 
readily  than  a  neutral  fat.  A  drop  of  rancid  oil  let  fall  on 
the  surface  of  an  alkaline  fluid,  such  as  a  solution  of  sodium 
carbonate  of  suitable  strength,  rapidly  fVn-ms  a  broad  ring 
of  emulsion,  and  tliat  even  without  tiie  least  agitation.  As 
saponification  takes  place  at  the  junction  of  the  oil  and  alka- 
line fluid,  currents  are  set  up,  by  which  globules  of  oil  are 
detached  from  the  main  drop  and  driven  out  in  a  centrifugal 
direction.  The  intensit3'  of  the  currents  and  the  consequent 
amount  of  emulsion  depend  on  the  concentration  of  the 
alkaline  medium  and  on  the  solul)ility  of  the  soaps  which 
are  formed  ;  hence  some  fats  sucli  as  cod-liver  oil  are  much 
more  easily-  emulsionized  in  this  way  tlian  others.  Xow  the 
bile  and  pancreatic  juice  supply  just  such  conditions  as  the 
above  for  emulsionizing  fats  :  they  both  together  aflfbrd  an 
alkaline  medium,  the  pancreatic  juice  supplies  an  adequate 
amount  of  free  fatty  acid,  and  the  bile  renders  duh^  soluble 
the  soaps  tiius  formed.  So  that  we  may  speak  of  the  emul- 
sion of  fats  in  the  small  intestine  as  being  carried  on  by 
both  bile  and  pancreatic  juice  •/  and  as  a  matter  of  fact  the 

•  Cf.  Brucke,  Wien.  Sitzungsberichte,  Bd.  61  (1870),  p.  362;  Steiner, 
Archiv  f.  Anat.  u.  Physiol.,  1874,  p.  286 ;  Gad,  ibid.,  1878,  p.  181  ; 
Quincke,  PHiiger's  Archiv,  xix,  1879,  p.  129. 


DIGESTION    OF    FATS.  397 

bile  and  pancreatic  juice  do  largely  emulsify  the  contents  of 
the  small  intestine,  so  that  the  grayish  turbid  ch^'me  is 
changed  into  a  creamy-looking  fluid,  which  has  been  some- 
times called  chyle.  It  is  advisable  however  to  reserve  this 
name  for  the  contents  of  the  lacteals. 

This  mutual  help  of  bile  and  pancreatic  juice  in  produc- 
ing an  emulsion,  explains  to  a  certain  extent  the  controversy 
wiiich  long  existed  between  those  who  maintained  that  the 
bile  and  those  who  maintained  that  the  pancreatic  juice  was 
necessary  for  the  digestion  and  absorption  of  fatty  food. 
That  the  pancreatic  juice  does  produce  in  the  intestine  such 
a  change  as  favors  the  transference  of  neutral  fals  from  the 
intestine  into  the  lacteals,  is  shown  by  the  fact  that  in  dis- 
eases affecting  the  pancreas,  much  fatty  food  frequently 
passes  through  the  intestine  undigested,  and  great  wasting 
ensues.  On  the  other  hand,  that  the  bile  is  of  use  in  the 
digestion  of  fat  is  shown  by  the  prevalence  of  fatt\'  stools 
incases  of  obstruction  of  the  bile-ducts;  and  though  the 
operation  of  ligaturing  the  bile-ducts,  and  leading  all  the 
bile  externally  through  a  biliary  fistula,  is  open  to  objection, 
since  it  so  exhausts  the  animal  as  indirectly  to  affect  diges- 
tion, still  the  results  of  Bidder  and  Schmidt,  in  which  the 
resorption  of  fat  was  distinctly  lessened  (the  quantity  of 
fat  in  the  lacteals  falling  from  8.2  to  .02  per  cent.)  by  the 
ligature  and  fistula,  obviously  point  to  the  same  conclusion. 
Thus  while  the  view  that  the  bile  alone,  or  the  view  that  the 
pancreatic  juice  alone,  is  the  agent  in  the  digestion  of  fat, 
is  contiadicted  by  facts,  the  conflicting  experiments  are 
reconciled  in  the  conclusion  that  both  help  towards  the 
same  end  ;  a  conclusion  which  is  in  harmony  with  the  prop- 
erties of  the  juices,  as  seen  when  studied  out  of  the  body, 
and  which  is  supported  by  the  observation  of  Busch.  in  a 
case  where  the  duodenum  opened  on  the  surface  by  a  fistula 
in  such  a  way  that  the  lower  part  of  the  intestine  could  be 
kept  free  from  the  contents  of  the  upper  part  containing  tlie 
bile  and  pancreatic*  juice.  Fats  introduced  into  the  lower 
part,  where  tiiey  could  not  be  acted  upon  either  by  the  bile 
or  by  the  pancreatic  juice,  were  but  slightly  digested.  The 
succus  entericus  may  have  a  slight  emulsifying  power,  but 
one  wholly  insufficient  to  meet  the  needs  of  the  economy. 

We  have  seen  that  bile,  when  added  to  a  digesting  mix- 
ture, first  precipitates  and  then  redissolves  the  parapeptone 
and  peptone,  the  pepsin  being  carried  down  with  them. 
The  object  of  this  precipitation  is  probably  to  render  inert 

34 


[VJS      THE    TISSUES    AND    MECHANISMS    OF    DIGESTION. 

tlic  i)0[)siii  and  tliiis  prevent  it  from  impairing  the  pancreatic 
trypsin,  as  well  as  periuips  to  hinder  the  too  rapid  passai^e 
of*  the  senii-di^ested  rnpiids  along  the  ititestine.  The  gran- 
ular material  whieii  is  t'onnd  lining  the  duodenum  is  i)ossibl3'' 
the  result  of  such  a  i)rccii)itation.  We  have  seen  that  bile, 
while  it  stops  gastiic  digestion,  favors  rather  than  hinders 
the  pancreatic  digestion  of  proteids.  Asa  matter  of  fact, 
since  the  contents  of  the  stomach  as  they  issue  from  the 
l)ylorus  consist  very  largely  of  undigested  proteids.  tiiese 
must  he  digested  by  the  pancreatic  juice  (with  or  without 
the  assistance  of  the  succus  entericus),  since  the  pe})sin  of 
the  gastric  juice  is  either  precipitated  by  the  bile,  or  ren- 
dered inert  by  the  increasing  alkalinity  of  the  intestinal 
contents.  To  what  stage  the  pancreatic  digestion  is  carried, 
whether  peptone  is  chietiy  formed,  and  when  formed  at  once 
absorbed,  or  to  what  extent  the  pancreatic  juice  in  the  body, 
as  out  of  the  body,  carries  on  its  work  in  the  more  destruc- 
tive form,  whereby  the  proteid  material  subjected  to  it  is 
broken  down  largely  into  leucin  and  tyrosin,  is  at  present 
not  exactly  known.  Leucin  and  tyrosin  are  found  in  the 
intestinal  contents,  and  are  therefore  formed  during  normal 
digestion,  but  whether  a  large  quantity  or  a  small  quantity 
of  the  proteid  material  of  food  is  thus  huri'ied  into  a  crys- 
talline form  cannot  be  definitely  stated.  Possibly  where 
large  quantities  of  })roteids  are  taken  at  a  meal,  the  excess 
is  at  once  got  rid  of  by  tliis  form  of  so-called  "  luxus  con- 
sumption ;"  and  possibh'  also,  in  the  intestine  as  in  the  lab- 
oratory, this  pancreatic  digestion  of  proteids  in  excess  is 
accompanied  by  a  considerable  development  of  bacteria  and 
other  organized  bodies,  which  create  trouble  by  inducing 
fermentative  changes  in  the  accompan3ing  saccharine  con- 
stituents of  the  chyme. 

That  fermentative  changes  do  occur  in  the  small  intestine  is  indi- 
cated by  the  fact  that  the  gas  present  there  does  contain  free  hy- 
drogen. Planer'  found  the  gas  from  tlie  small  intestine  of  a  dog 
fed  on  a  meat  diet  to  consist  of  CO^  40.1,  H  13.80,  X  45.52,  with 
only  a  trace  of  oxygen.  In  a  dog  fed  on  vegetable  diet  the  com- 
position of  the  gas  was  CO,  47.34,  II  48.09,  N  3.97.  Chyme  after 
removal  from  the  intestine  continues  at  the  temperature  of  the 
body  to  produce  carbonic  acid  and  hydroi^en  in  equal  volumes. 
As  was  stated  above  (j).  412),  during  l)utyric  acid  fermentation 
from  sugar,  carbonic  acid  and  hydrogen  are  evolved  in  equal  vol- 

'  Op.  cit. 


CHANGES    OF    FOOD    IN    THE    LARGE    INTESTINE.      399 


umes.  These  facts  su£rg'est  the  way  in  which  the  carbo-hydrate 
constituents  of  food  may  become  converted  into  fat,  for  by  this 
butyric  acid  fermentation  the  sugar  is  converted  into  a  member 
of  the  fatty  acid  series ;  and  it  is  at  least  within  the  bounds  of 
possibility  tliat,  by  fermentative  changes  of  some  sort  or  other, 
the  lower  members  of  the  series  may  be  raised  to  the  higher. 
But  did  butyric  acid  fermentations  occur  largely  in  the  intestine, 
we  should  expect  to  find  a  large  quantity  of  free  hydrogen  dis- 
charged from  the  system  b}-  the  bowel  or  lungs.  As  a  matter  of 
fact  it  is  discharged  in  small  quantities  only.  Hence,  unless  we 
suppose  that  the  nascent  hydrogen  is  used  up  in  some  contempo- 
raneous processes  of  reduction,  we  must  regard  butyric  acid  fer- 
mentation as  slight  and  unimportant.  Indeed,  the  quantity  of 
gas  on  which  Planer  worked  was  small.  It  is  probable,  however, 
that  by  fermentative  changes  a  considerable  quantity  of  sugar  is 
converted  into  lactic  acid,  since  this  acid  is  found  in  increasing 
quantities  as  the  food  descends  the  intestine. 

Thus  during  its  transit  througli  the  small  intestine,  by 
the  action  of  the  bile  and  pancreatic  juice,  assisted  possibly 
to  some  extent  by  the  succns  entericus,  the  proteids  are 
largely  dissolved  and  converted  into  peptone  and  other  prod- 
ucts, the  starcl]  is  changed  into  sugar,  the  sugar  possibly 
being  in  part  further  converted  into  lactic  acid,  and  the  fats 
are  largely  emulsified,  and  to  some  extent  saponified.  These 
products,  as  tiiey  are  formed,  pass  into  either  tlie  lacteals  or 
the  portal  bloodvessels,  so  that  the  contents  of  the  small 
intestine,  by  the  time  they  reach  the  ileo-c.^cal  valve,  are 
largely  but  1)}'  no  means  wholly  deprived  of  their  nulritious 
constituents.  As  far  as  water  is  concerned,  the  secretion 
into  the  small  intestine  is  about  equal  to  the  ahsoiption  from 
it,  so  that  tlie  intestinal  contents  at  the  end  of  the  ileum, 
thouojh  much  more  broken  up,  are  about  as  fluid  as  in  the 
duodenum. 

In  the  large  intestine  the  contents  become  once  more  dis- 
tinctly acid.  This,,  iiowever,  is  not  caused  by  any  acid  se- 
cretion from  the  mucous  membrane  ;  the  reaction  of  the 
intestinal  walls  in  the  large  as  in  the  small  intestine  is  alka- 
line. It  must,  therel'ore,  arise  from  acid  fermentations  going 
on  in  the  contents  themselves;  as,  indeed,  is  shown  by  the 
composition  of  the  gases  which  make  their  appearance  in 
this  portion  of  the  alimentary  canal.  In  carnivora  the  con- 
tents of  the  caecum  are  said   to  be  alkaline,^  and  naturally 

^  Bernard,  Liquides  de  I'Organisme. 


40O      THE    TISSUES    AND    MECHANISMS    OF    DIGESTION. 


till'  ainoinit  of  rcrmentation  will  depend  largely  on  liie  na- 
ture of  the  food. 

Ru!:;e'  found  the  2;as  of  the  large  intestine,  collected  per  amim^ 
to  have  the  following  composition  : 


Mix.Ml  ,liot. 

Leg. 

iininous  diet. 

Meat  diet. 

CO,,     . 

40.54 

21.05 

8.45 

N,"     .        .        . 

,     17.50 

18.9(3 

64.41 

CII„     . 

.     11).77 

55.9-t 

20.45 

H,         .        .        . 

22. '22 

5.03 

.69 

SH2,  a  trace  only, 

Of  the  particular  changes  which  take  place  in  the  large 
intestine  we  have  no  definite  knowledge;  but  it  is  exceed- 
ingly i)r()l)al)le  that  in  the  voluminous  cnecum  of  the  herbi- 
vora,  a  large  amount  of  digestion  of  a  peculiar  kind  goes 
on.  We  know  that  in  herbivora  a  considerable  quantity  of 
cellulose  disappears  in  passing  through  the  canal,  and  even 
in  man  some  is  probal)ly  digested.  We  are  driven  to  sup- 
pose that  this  cellulose  digestion  is  carried  on  in  the  large 
intestine,  though  we  know  nothing  of  the  nature  of  the 
agency  by  which  it  is  effected.  The  other  digestive  changes 
are  probably  of  a  fermentative  kind. 

Be  this  as  it  may,  whether  digestion,  properly  so  called, 
is  all  but  complete  at  the  ileo-cKcal  valve,  or  whether  im- 
portant changes  still  await  the  chyme  in  the  large  intestine, 
the  chief  characteristic  of  the  work  done  in  the  colon  is  ab- 
sorption. By  the  abstraction  of  all  the  soluble  constituents, 
and  especially  by  the  withdrawal  of  water,  the  liquid  chyme 
becomes,  as  it  approaches  the  rectum,  converted  into  the 
firm  solid  fasces,  and  the  color  shifts  from  the  bright  orange, 
which  the  gray  chyme  gradually  assumes  after  admixture 
with  bile,  into  a  darker  and  dirtier  brown. 

In  the  faeces  there  are  found  in  the  first  j^lace  the  indigest- 
ible an<l  undigested  constituents  of  the  meal ;  shreds  of  elastic 
tissue,  hairs  and  other  corneous  elements,  much  cellulose 
and  chlorophyll  from  vegetable,  and  some  connective  tissue 
from  animal  food,  fragments  of  disintegrated  muscular  fibre, 
fat-cells,  and  not  unfrequently  undigested  starch-corpuscles. 
The  amount  of  each  must  of  course  vary  very  largely,  ac- 
cording to  the  nature  of  the  food  and  the  digestive  powers, 

^  Wien.  Sitzungsberichte,  1862,  p.  729. 


ABSORPTION    OF    THE    PRODUCTS    OF    DIGESTION.      401 

temporary  or  permanent,  of  the  individual.  In  the  sec- 
ond place,  to  these  must  be  added  substances  not  intro- 
duced as  food,  but  arising  as  part  of,  or  as  products  of.  the 
digestive  secretions.  The  faeces  contain  a  ferment  similar 
to  pepsin,  and  an  amylolytic  ferment  similar  to  that  of  saliva 
or  pancreatic  juice.  They  also  contain  mucus  in  variable 
amount,  sometimes  albumin,  cholesterin,  hydrobilirubin, 
butyric  and  other  fatty  acids,  lime  and  magnesia  soaps, 
excretin  (a  non-nitrogenous  crystalline  body,  containing 
sulphur,  obtained  by  Marcet),  and  salts,  especially  those  of 
magnesia.  Cholalic  acid  (and  dyslysin)  are  found  in  very 
small  quantities  onl>',  thus  indicating  that  the  l>ile-salts 
have  been  in  part  at  least  destroyed  (they  may  have  been 
in  part  reabsorbed,  see  p.  375),  the  less  stable  tauro- 
cholic  acid  (of  the  dog)  disappearing  more  readiW  than  the 
glycocholic  acid  (of  the  cow).  The  fact  that  the  faces 
become  "  clay -colored  "  when  the  bile  is  cut  off' from  the  intes- 
tine, shows  that  the  bile-pigment  is  at  least  the  mother  of 
the  faecal  pigment;  and  tiie  special  pigment,  which  has  been 
isolated  and  called  stercobilin,^  is  said  to  be  identical  with 
urobilin,  i.  e.,  with  hydrobilirubin.  We  have  already  seen 
that  during  artificial  pancreatic  digestion,  a  distinctly  fffical 
odor  due  to  the  presence  of  indol  is  generated  ;  and  the  fact 
that  the  presence  of  bacteria,  or  other  similar  organism,  is 
essential  to  the  production  of  this  body,  does  not  preclude 
the  possibility  of  it,  with  its  derivatives,  being  the  chief 
cause  of  the  natural  odor  of  fteces,  for  undoubtedly  bacteria 
may  exist  throughout  the  whole  length  of  the  intestinal 
canal.  At  the  same  time  it  is  quite  possible,  if  not  probable, 
that  specific  odoriferous  substances  may  be  secreted  directly 
from  the  intestinal  wall,  especially  from  that  of  the  large 
intestine. 

Brieger-  finds  in  human  excrement  a  small  quantity  only  of 
indol,  but  a  considerable  quantity  of  a  similar  body,  which  he 
calls  s'katol^  possessing  an  intense  fecal  odor. 

Sec.  5.    Absorption  of  the  Products  of  Digestion. 

AVe  have  seen  that  absorption  does,  or  at  least  may,  take 
place  from  the  stomach.     We  have  also  stated  that  a  large 

^  Vaulair  and  Masius,  Centrbt.  f.  med.  Wiss.,  1871,  No.  24.  JafFe, 
ibid.,  Xo.  31. 

»  Ber.  deatsch.  Chem.  Gesellsch.,x  (1877),  p.  1027. 


402      THE    TISSUES    AND    MECHANISMS    OF    DIGESTION. 


absorption,  especially   of    water,  occurs    along   the  whole 
large  intestine. 

Absorption  from  the  large  intestine  after  injectiou  per  anum., 
or  through  a  fistula,  has  been  observed  not  only  in  the  case  of 
soluljle  iH'ptone  and  sugar,  but  also  in  that  of  starch,  white  of 
egg,  and  casein  ;  but  the  exact  changes  undergone  by  the  latter 
previous  to  absorption  are  unknown.^ 

Nevertheless  the  largest  and  most  important  part  of  the 
digested  material  passes  away  from  the  canal,  during  the 
transit  of  food  along  the  small  intestine,  partly  into  the 
lacteals,  partly  into  tlie  portal  vessels. 

Digestion  being,  broadly  speaking,  the  conversion  of  non- 
dilfusible  proteids  and  starch  into  highly  diffusible  peptone 
and  sugar,  and  the  emulsifying,  or  division  into  minute 
particles,  of  various  fats,  it  is  natural  to  suppose  that  the 
diffusible  peptone  and  sugar  pass  by  osmosis  into  the  blood- 
vessels, and  that  the  emulsified  fats  pass  into  the  lacteals. 
That  a  large  part  of  the  fat  which  enters  the  body  from  the 
intestine  does  pass  through  the  lacteals,  there  can  be  no 
doubt;  and  there  can  be  but  little  doubt  that  a  considerable 
quantity  of  peptone  and  sugar  does  pass  into  the  portal* 
blood.  But  we  are  unable  to  say  at  present  how  far  the  fat 
in  its  diflicult  passage  into  the  lacteals  is  accompanied  by 
soluble  peptone  or  by  less  diffusible  forms  of  proteids  arising 
as  subsidiary  products  of  proteol3'tic  digestion  or  b\'  carbo- 
hydrate products. 

Characters  of  Chyle.— In  a  fasting  animal  the  contents  of 
the  thoracic  duct  are  clear  and  transparent;  siiortly  after  a 
meal  they  become  milky  and  opaque,  the  change  being 
entirely  due  to  a  difference  in  the  quantity  of  the  fluid 
brought  to  the  duct  by  1  he  lacteals,  that  fluid  also  being,  as 
seen  by  inspection  of  the  mesentery,  transparent  during 
fasting,  and  becoming  milky  and  opaque  after  a  meal,  espe- 
cially after  one  containing  much  fat.  The  contents  of  tiie 
thoracic  duct  therefore  after  a  meal  may  be  taken  as  illus- 
trative of  the  nature  of  the  chyle  present  in  the  lacteals, 
though  strictly  speaking  the  chyle  of  the  thoracic  duct  is 
mixed  with  lymph  coming  from  the  intestines  and  from  the 
rest  of  the  bodv.     During  fasting  the  contents  of  the  lacteals 

1  Bauer,  Zeitschft.  f.  Biol.,  v,  536. 


CUYLE.  403 


agree  in  their  general  character  with  l^'mph  obtained  from 
other  structures. 

The  contents  of  the  thoracic  duct  may  be  obtained  by  laying 
bare  the  junction  of  the  subclavian  and  jugular  veins  and  intro- 
ducing a  canula  into  the  duct  as  it  enters  into  the  venous 
system  at  that  point.  The  operation  is  not  unattended  with 
difficulties. 

Chyle  obtained  from  tlie  thoracic  duct,  after  a  meal,  is  a 
wliite-looking  fluid,  which  after  its  escape  coagulates,  forming 
a  not  ver}^  tirm  clot.  The  nature  of  the  coagulation  seems 
to  be  exactly  the  same  as  that  of  the  blood.  The  surface  of 
the  clot  after  exposure  to  air  becomes  pink,  even  though  no 
blood  be  artificially  mixed  with  the  chyle  dui'ing  tlie  opera- 
tion; the  color  is  due  to  immature  red  corpuscles  proper  to 
the  chyle.  Examined  microscopically,  the  coagulated  chyle 
consists  of  fibrin,  a  large  number  of  white  corpuscles,  a 
small  number  of  developing  red  corpuscles,  an  abundance  of 
oil-globules  of  various  sizes  but  all  small,  and  a  quantity  of 
fatty  granules,  too  minute  to  be  i-ecognized  under  the 
microscope  as  fatty  in  nature,  forming  the  so-called 
"  molecular  basis."  Each  oil  globule  is  invested  with  an 
albuminous  envelope;  this  may  be  dissolved  Iw  the  aid  of 
alkalies,  whereupon  the  globules  run  together.  The  fibiin 
and  white  corpuscles  are  very  scanty  (and  the  red  corpuscles 
entirely'  absent)  in  lymph  or  chyle  taken  from  peripheral 
vessels  ;  but  they  increase  in  quantity  as  the  lymph  passes 
through  the  lymphatic  glands. 

The  composition  of  chyle  varies  considerably,  not  oidy  in 
different  animals  but  in  the  same  animal  at  difl^'ereut  times. 
The  average  percentage  of  solids  may  perhaps  be  put  down 
as  about  9,  that  of  proteid  material  as  al)Out  4  or  5,  and  that 
of  fat  as  about  3  or  4,  the  remainder  being  extractives  and 
salts.  The  fats  occur  chiefly  in  the  form  of  neutral  fats, 
though  some  soap's  or  fatty  acids  are  present. 

The  percentages  of  solid  matters  vary  in  the  different  anah'ses 
from  3  to  11,  of  proteids  from  2  to  7,  ot  fats  from  less  than  1  to 
4  ;'  but  Zawilski-  finds  that  in  dogs  after  a  meal  rich  in  fat,  the 
percentage  of  ftit  in  the  chyle  may  vary  from  14.6  to  0.-25.  The 
proteids  consist  chiefly  of  serum-albumin,  with  a  globulin  or 

1  Cf.  Hensen,  Pfliiger's  Archiv,  x  (1875),  p.  94. 
-  Ludwig's  Arbeiten,  187G,  p.  147. 


404      THE    TISSUES    AND    MECHANISMS    OF    DIGESTION. 


alkali-albiiiDin  in-eci)Vit:iMe  by  acids,  and  a  variable  but  small 
quantity  of  lil)rin,  Anionu  tbeextraftive.s  luivi'  been  found  sugar, 
urea,  and  leucin  ;  ebolcsterin  is  also  frequently  present  in  con- 
siderable (juantity.  Since  tbesc  extractives  are  found  in  lymph 
as  well  as  chyle  they  cannot  be  reujarded  as  derived  exchisively 
from  the  intestinal  contents.  The  amount  of  peptone  is  very 
small  indeed.  Tbe  gas  which  can  be  extracted  from  chyle  or 
lymph  consists  almost  entirely  of  carbonic  acid,  there  being  only 
a  small  quantity  of  nitrogen,  and  no  satisfactory  evidence  of  the 
presence  of  any  free  oxygen  at  all.  Ilammarsten'  obtained  from 
the  100  vols,  of  lymph  of  the  dog  about  1.5  (1.17)-' vols,  nitrogen, 
and  about  53  (40.30)  vols,  carbonic  acid.  The  ash  is  remarkable 
for  tbe  abundance  of  sodium  chloride  and  the  scantiness  of  phos- 
phates. Iron  is  present  in  greater  quantity  than  can  be  ac- 
counted for  by  the  presence  of  red  corpuscles. 

Tiie  nature  of  the  fat  is  supposed  to  vary  with  tbat  of  the 
food,  but  this  has  not  been  conclusively  shown. 

The  lymidi  taken  fiom  the  duct  during  fasting  differs 
chiefly  from  that  taken  after  a  meal,  in  the  much  smaller 
quantity  of  fat,  the  microscope  showing  white  corpuscles 
with  very  few  oil-gloitules,  and  in  the  almost  entire  absence 
of  the  molecular  basis.  Lympii  in  fact  is,  broadly  s[)eaking, 
blood  mi)nis  its  red  corpuscles,  and  chyle  is  lynipli  7:»/<(.s  a 
very  large  (piantity  of  minutely  divided  neuti'al  fat. 

It  has  been  calculated  that  a  quantity  equal  to  that  of  the 
M'hole  blood  may  pass  through  the  thoracic  duct  in  twenty- 
four  hours,  and  of  this  it  is  supposed  that  about  half  comes 
from  food  through  the  lacteals  and  the  remainder  from  the 
body  nt  large;  but  these  calculations  are  based  on  uncer- 
tain data. 

Entrance  of  the  Chyle  into  the  Lacteals. — The  lacteal 
begins  as  a  club-shaped  (or  bifurcate)  lympliatic  space  lying 
in  the  centre  of  the  villus,  and  connected  with  the  smaller 
lymphatic  spaces  of  the  adenoid  tissue  around  it;  it  opens 
below  into  the  submucous  lymphatic  plexus  from  which  the 
lacteal  vessels  spring.  The  adenoid  tissue  of  tiie  surround- 
ing crypts  of  Lieberkiihn  is  by  its  lymphatic  spaces  con- 
nected with  the  same  lymphatic  plexus.  That  the  finely 
divided  fat  does  pass  from  the  intestine,  through  the  epi- 

'   Ludwig's  Arbeiten,  1871,  p.  121. 

^  The  larger  figures  are  the  nieasiirements  obtained  at  0°  C.  and  a  pres- 
sure of  760  mm.  mercury,  the  smaller  figures  in  parentheses  the  measure- 
ments according  to  the  prevalent  German  method  at  0°  C.  and  1  meter 
of  mercury  pressure. 


CHYLE.  405 


thelial  envelope  of  the  villus,  into  the  adenoid  tissue,  and  so 
into  the  lacteal  chamber,  is  certain,  but  much  discussion  has 
arisen  as  to  the  exact  mechanism  of  the  transit.  The  pas- 
sage is  probably-  assisted  by  tlie  movements  of  the  intestine, 
though  even  in  the  contractions  of  strong  peristaltic  move- 
ments the  pressure  within  the  intestine  is  never  ver^^  great. 
Of  more  obvious  use  is  the  contraction  of  the  villus  itself. 
The  longitudinal  muscular  fibre-cells,  in  contracting,  pull 
down  the  villus  on  itself;  the  contents  of  the  lacteal  chamber 
are  thus  forced  into  the  underlying  lymphatic  plexus.  When 
the  fibre-cells  relax,  the  empty  lacteal  ciiamber  is  expanded; 
the  chyle  cannot  flow  back  from  the  lymphatic  channels  by- 
reason  of  the  valves  present  in  them,  and  in  consequence 
the  lacteal  chamber  is  filled  from  the  substance  of  the  villus, 
and  thus  the  entrance  into  the  villus  of  material  from  the 
intestine  is  facilitated.  The  villus  in  fact  acts  as  a  kind  of 
muscular  suction-pump. 

Merunowicz'  finds  the  flow  of  lymph  increased  by  muscarin 
poisoning,  and  attributes  the  increase  of  flow  to  the  coincident 
increase  of  the  peristaltic  movements  of  the  intestine. 

After  a  meal  the  epithelium  cells  of  the  villus  are  found  crowded 
with  fat.  Since  the  striation  of  the  hyaline  border  of  the  cells 
is  not  due  to  pores,  as  was  once  thought,  the  particles  must  have 
entered  into  the  cells  very  much  as  foreign  particles  enter  the 
body  of  an  amoeba.  The  epithelium  may  in  fact  be  said  to  eat 
the  fat.  Since  the  (frequently)  branched  and  protoplasmic  base 
of  the  cell  is  in  intimate  connection  with  the  spaces  of  the  ade- 
noid tissue  of  the  villus,  the  fat  could  more  readily  pass  from  the 
cell  in  this  direction  than  from  the  intestine  into  the  cell.  There 
would  thus  be  a  stream  of  fatty  particles  through  the  cell  from 
without  inwards,  a  stream  in  the  causation  of  which  the  cell  took 
an  active  part.  In  fact,  under  this  view,  absorption  by  the  cell 
might  be  regarded  as  a  sort  of  inverted  secretion,  the  cell  taking 
much  material  from  the  chyme  and  secreting  it,  with  little  or  no 
change,  into  the  villus.  The  observations  of  Watney^  have  led 
him  to  believe  the  fat  passes  not  through  but  between  the  epithe- 
lium cells,  being  taken  up  by  the  inter-epithelium  processes  of  the 
peculiar  epitheloid  cells,  described  by  Jiim  as  forming  a  contin- 
uous protoplasmic  reticulum,  the  epithelium  cells  themselves 
therefore  having  no  active  share  in  absorption.  It  is  ditflcult  on 
this  view%  however,  to  explain  the  almost  unanimous  opinion  of 
previous  observers,  that  the  fat  ma}^  be  seen  in  the  substance  of 
the  cell  itself,  though  Watney  argues  that  particles  of  fat  adher- 
ing to  the  outside  of  the  cell  have  been  erroneously  supposed  to 
be  really  \Vithin  the  cells. 

1  Ludwig's  Arbeiten,  1876,  p.  117.         2  p^ii.  Trans.,  1870,  p.  451. 


40G     THE    TISSUES    AND    MECHANISMS    OF    DIGESTION. 

Movements  of  the  Chyle. — Ilaviiiir  rc^ached  the  lymphatic 
cliaiiiiels  the  onward  [)r()gress  of  the  chyle  is  determined  hy 
a   vaiiety   of   circumstances.     Putting   aside   the   pumping 
action  of  the  villi,  the   satne   events  whicii  cause  the  move- 
ment of  the  lymph   generally  also   further  the  flow  of  the 
ciiyle  ;  and  these  are  briefly  as   follows.     In   tiie  flrst  place, 
the  widespread   presence  of  valves  in  the  lymphatic  vessels 
causes  every  pressure  exerted  on  the   tissues  in  which  they 
lie  to  assist  in  the  propulsion  forward  of  the  lymph.     Hence 
all  muscular   movements  increase   the  flow.     If  a  canula  be 
inserted  in  one  of  the  larger  lymphatic  trunks  of  the  limb 
of  a  dog,  the   discharge  of  lymph  from  the  canula  will  be 
more  distinctly  increased  by  movements,  even  passive  move- 
ments, of  the  limb  than   by  anything  else.     In  addition  to 
the  valves  along  the  course  of  the  vessels,  the   eral)ouche- 
ment  of  the  thoracic  duct  into  the  venous  system  is  guarded 
by  a  valve,  so  that  every  escape  of  lymph  or  chyle  from  the 
duct  into  the  veins  becomes  itself  a  lielp  to  the  flow.     In  the 
second  place,  considering  the  whole  hmphatic  system  as  a 
set  of  branching  tubes  passing  from  the  extra-vascular  re- 
gions just  outside  the   small  arteries,  veins  and  capillaries, 
to  the  large  venous  trunks,  it  is  obvious  that  tlie  mean  pres- 
sure of  the  blood  in  the  subclavian  vein,  at  its  junction  with 
the  jugular,  must  be  considerably  less  than  that  of  the  lymph 
in  the  lymphatic  spaces  around  the  small  bloodvessels,  even 
though  the  pressure  in  the  tissues  outside  the  small  blood- 
vessels is  distinctly  less  than  that  of  the   blood  within  the 
same  vessels.     In   other  words,  there   is   a  distinct   fall   of 
pressure  in    passing   from  the  beginning  to  the  end  of  the 
lymphatics;   this  of  course  would   alone  cause  a  continuous 
flow.     Further,  this  flow,  caused  by  the  lowness  of  the  mean 
venous  pressure  at  the  subclavian,  will  be   assisted  at  every 
respirator}'  movement,  since  at   every  inspiration  the  pres- 
sure in  the  venous  trunks  becomes  negative,  and  thus  l^'mph 
will  be  sucked  in  from  the  thoracic  duct,  while  the  increase 
of  pressure  in  the  great  veins  during  expiration  is  warded 
off  from  the  duct  by  the  valve  at  its  opening.     In  the  third 
place,  the  flow  may  be  increased  by  rhythmical  contractions 
of  the   muscular  walls  of  the   lym[)hatics  themselves  ;   but 
this  is  doubtful,  since  it  is   not  clear  whether  the  rhythmic 
variations  seen  by  Heller^  in  the  mesentery  of  the  guinea-pig 
were  active  or  simply  passive,  i.  e.,  caused  b}"  the  rhythmic 

'  Cbt.  Med.  Wiss.,  1869,  p.  545. 


MOVEMENTS    OF    CHYLE    AND    LYMPH.  407 

peristaltic  action  of  the  intestine,  eacli  contraction  of  the 
intestine  filling  the  lymph-channels  more  full}-.  Lastly,  it 
is  quite  open  for  us  to  suppose  that  just  as  osmosis  may 
give  rise  to  increased  pressure  on  one  side  of  a  diffusion 
septum,  so  the  diffusion  of  substances  from  the  intestines  into 
the  lacteals,or  from  the  tissues  into  tlie  lymphatics,  may  be 
itself  one  of  the  causes  of  the  flow  of  lymph.  We  have  at 
least,  under  all  circumstances,  one  or  otiier  of  these  causes 
at  work  promoting  a  continual  flow  from  the  lymphatic  roots 
to  the  great  veins.  We  have  no  ver}-  satisfactory  evidence 
that  the  flow  of  lymph  is  in  an}'  way  directh-  governed  by 
the  nervous  S3stem. 

In  frogs  and  some  other  animals  the  centripetal  flow  of  lymph 
from  the  limbs  is  assisted  by  rhythmically  pulsating  muscular 
13'mph-hearts. 

The  observations  of  Paschutin'  and  Emniinghaus-  failed  to 
show  any  direct  connection  between  the  nervous  system  and  the 
lymph-flow.  Section  of  the  sciatic,  leading  to  arterial  dilation 
and  consequent  increased  pressure  in  the  capillaries  and  small 
veins,  had  ver}^  little  eflect,  whereas  ligature  of  the  veins  led  to 
a  very  marked  inx'rease.  Active  movements  of  the  limb,  caused 
by  stimulation  of  the  sciatic,  produced  no  greater  flow  than  did 
passive  movements.  Goltz'^  has  recorded  an  interesting  observa- 
tion, bearing  on  the  influence  of  the  nervous  system  on  absorp- 
tion. Of  two  frogs  placed  under  the  influence  "^of  nrari  so  as  to 
do  away  with  muscular  movements  and  the  action  of  the  lymph- 
hearts,  the  brain  and  spinal  cord  of  one  are  destro3'ed,  but  in 
the  other  are  left  intact.  Both  animals  are  suspended  by  the 
lower  jaw  ;  chloride  of  sodium  solution  (.75  per  cent.)  is  poured 
into  the  dorsal  lymphatic  sacs  of  both  ;  and  in  both  the  aorta 
is  cut  across.  In  the  one  where  the  nervous  system  is  intact, 
absorption  from  the  lymphatic  sac  takes  place  copious!}',  and  the 
heart  pumps  out  large  quantities  of  fluid  by  the  aorta.  In  the 
other,  absorption  does  not  occur ;  the  heart,  though  beating,  re- 
mains empt}',  and  the  skin  becomes  dry.  The  result  however 
shows  rather  the  influence  of  the  nervous  system  in  maintaining 
the  tonicity/  of  the  bloodvessels  and  keeping'^up  the  connection  of 
the  heart  with  the  peripheral  vessels,  than  any  distinct  connec- 
tion between  absorption  proper  and  the  nervous  system.  When 
the  nervous  SN'stem  is  destroyed,  dilation  of  the  splanchnic  vas- 
cular area  causes  all  the  blood  to  remain  stagnant  in  the  portal 
vessels,  so  that  little  or  none  reaches  the  heart,  and  with  the 
enfeebled  circulation  the  absorption  from  the  lymphatic  sac  is 

'  Lndwig's  Arbeiten,  1872,  p.  197. 

"  Ibid.,  1873,  p.  51. 

3  Pfiiiger's  Archiv,  v  (1872),  p.  53. 


408      THE    TISSUES    AND    MECHANISMS    OF    DIGESTION. 


sliglit.  So  loiii;  as  the  nervous  system  is  still  intact  this  stagna- 
tion does  not  occur,  the  blood  reaches  the  heart,  and  with  the 
more  vigorous  circulation  absori)tion  from  the  lynii)hatic  sac 
goes  on  rapidly.  As  the  blood  is  i)umped  away  its  place  is  re- 
newed by  the  lymph,  sui)pli(d  by  the  lluid  in  the  sac,  and  thus 
the  heart  may  be  made  I'or  a  long  time  to  i)ump  away  the  tluid 
poured  into  the  sac.  Still,  though  we  caiuiot  prove  any  direct 
connection  between  the  nervous  system  and  absorption,  the  phe- 
nomena of  disease  render  such  a  connection  at  least  probable. 

The  Couri<e  taken  hij  the  Seceral  Froducta  of  Digestion. 

The  digested  contents  of  the  intestine  pass  into  the  blood 
either  directly  by  the  portal  system  (Fig.  112)  or  indirectly 


[Fig.  112. 


Diagram  sbowin* 


the  larger  Vessels  concerned  in  the  so-called  PorJal  Circulation 
or  System.— After  Marshall. 


FATS.  409 


The  trunk,  or  body,  is  supposed  to  he  divided  down  the  middle  line,  so  as  to  show' 
the  cavity  of  the  thorax  or  chest  above  the  arched  diaphragm,  and  that  of  the  abdo- 
men below  it.  In  the  abdomen,  I  is  the  liver  ;  s,  the  stomach  ;  d,  a  section  of  the 
duodenum  and  pancreas;  f,  the  small  intestine  ;  co,  a  part  of  the  colon  ;  r,  the  rec- 
tum ;  m,  the  lower  end  of  the  spleen,  and  k,  the  right  kidney.  The  blood  of  all  these 
parts  is  supplied  through  arteries  which  are  branches  of  the  abdominal  aorta,  marked 
a.  From  the  rectum,  r,  and  the  kidney,  k,  the  blood  is  returned  by  vein**,  which 
end  in  the  great  ascending  vein,  named  the  ascending  vena  cava,  marked  c,  which 
conveys  the  venous  blood  directly  through  the  diaphragm,  and  into  the  right  side 
of  the  heart,  o.  But  the  bh)od  from  the  stomach,  s;  spleen,  to;  duodenum  and  pan- 
creas, d ;  small  intestine,  i;  and  large  intestine,  co  (excepting  the  rectum,  ?-\  is  col- 
lected by  venous  biauciies,  which  end  in  a  large  venous  trunk,  named  the  vena 
portte,  or  portal  vein,  p,  by  which  this  venous  blood  is  conveyed  to  and  distributed 
by  branches  through  the  liver.  From  this  organ  it  is  collected  by  other  veins,  which 
unite  to  form  hepatic  veins,  h,  which  then  join  the  ascending  vena  cava,  c,  and  so 
reach  the  right  side  of  the  heart.] 

by  means  of  the  lymphatics.  It  cannot  be  a  matter  of  in- 
difference which  course  is  taken  by  the  particular  digestive 
products;  for  in  the  latter  case,  tliej^  pass  into  the  general 
blood-current  with  only  such  changes  as  the}'  may  undergo 
in  the  lymphatic  system,  wliile  in  the  foruier  they  are  sub- 
jected to  the  powerful  influences  of  the  liver  before  they  find 
their  way  to  the  right  side  of  the  heart.  What  those  influ- 
ences are  we  shall  study  in  a  future  chapter. 

Fats. — As  we  have  seen,  a  special  mechanism  is  provided 
for  the  passage  of  I'ats  into  the  lacteals.  On  the  otiier  hand, 
it  is  ditiicult  to  suppose  that  solid  particles  of  fat  can  pass 
into  the  interior  of  the  blood  capillaries.  So  that  we  are 
led  a  ijriori  to  tlie  view  that  the  whole  of  the  fat  takes  the 
course  of  the  lacteals.  But  we  cannot  say  that  this  is  defi- 
nitel}'  proved.  On  the  contrary-,  a  deficit  is  observed  when 
the  quantity  of  fat  disap[)earing  after  a  meal  from  the  ali- 
mentary canal  is  compared  with  that  flowing  into  the  tho- 
racic duct ;  and  if  it  he  true,  as  stated,  that  the  blood  of  the 
portal  vein  contains  (Uiiing  digestion  more  fat  than  the 
general  venous  blood,  some  of  this  deficit  ma}^  be  explained 
by  the  fat  passing  into  the  blood  capillaries,  difficult  as  that 
passage  may  appear.  The  portal  blood,  moreover,  during 
digestion  contains  a  small  but  appreciable  quantity  of  soaps. 

Zawilski^  finds  that  in  a  dog  after  a  meal  rich  in  fat  the  stream 
of  fat  from  the  thoracic  duct  into  the  venous  svstem  becomes 


Ludwig's  Arbeiten,  1876,  p.  14'J 


410      THE    TISSUES    AND    MECHANISMS    OF    DIGESTION. 

rapid  at  about  the  second  hour,  but  does  not  n>ach  its  maximum 
till  after  the  liflh  hour.  This  it  maintains  till  al)out  the  twen- 
tieth hour,  afh-r  which  it  sinks  till  about  the  thirtieth  hour,  at 
which  time,  and  not  before,  has  all  the  fat  of  the  food  disappeared 
from  the  alimentary  canal.  In  dogs  wei.uhini;  about  14  or  15 
kilos,  and  fed  with  a  meal  containing  150  grm.  fat,  the  maximum 
discharge  of  fat  from  the  thoracic  duct  into  the  venous  system 
was  about  lUO  mgrm.  a  minute.  When  the  total  amount  of  fat 
passing  through  the  thoracic  duct  was  compared  with  the  total 
amount  of  fat  which  had  disappeared  from  the  alimentary  canal, 
it  was  found  that  about  one-half  of  the  fjit  could  not  be  tlms  ac- 
counted for.  This  missing  quantity  could  not  be  considered  as 
the  portion  still  in  transHu  on  its  way  from  the  intestines  to  the 
mouth  of  the  thoracic  duct,  since  it  was  quite  as  marked  when 
the  experiment  was  carried  on  until  the  percentage  of  fat  in  the 
chyle  had  sunk  to  its  lowest  limit.  Some  fat,  therefore,  and  in- 
deed a  large  quantity,  must  have  either  passed  into  the  portal 
blood  or  have  been  removed  from  the  lymphatic  vessels  on  its 
course  between  the  villi  of  the  intestine  and  the  thoracic  duct,  or 
have  been  disposed  of  in  some  other  unknown  way.  The  fat 
thus  entering  the  blood  either  directly  or  indirectly  is  rapidly  got 
rid  of  in  some  way  or  other,  for  the  percentage  of  ftit  in  the  blood 
of  a  dog  after  a  meal  rich  in  fat,  did  not,  at  the  lapse  of  20  hours 
from  the  swallowing  of  the  food,  differ  materially  whether  the 
fat  had  been  during  the  whole  time  shut  off  from  the  blood  by 
being  allowed  to  flow  out  of  a  canula  placed  in  the  thoracic 
duett  or  had  been  allowed  to  pass  into  the  venous  system  in  the 
usual  way. 

Proteids. — The  question  as  to  the  course  taken  by  the  di- 
gested proteids  is  complicated  by  the  insufficiency  of  our 
knowledge  concerning  the  exact  stages  to  which  the  diges- 
tion of  proteids  is  naturally  carried  in  the  alimentary  canal. 
If  we  take  it  for  granted  that  the  proteids  taken  as  food  are 
reduced  at  least  to  the  condition  of  soluble  and  diffusible 
j)eptone,  it  seems  easy  to  suppose  that  the  proteids  of  food 
pass  by  diffusion  as  peptone  into  the  portal  capillaries, 
though  even  under  this  view  it  is  open  for  us  to  imagine  that 
all  the  peptone  which  })asses  through  the  epithelium  of  a 
villus  is  not  intercepted  by  the  blood  capillaries,  but  that 
some  reaches  and  is  absorbed  I\v  the  more  centrally  i)laced 
lacteal.  On  the  other  hand,  while  it  is  difficult  to  imagine 
how  proteids  can  pass  through  the  walls  of  the  cai)illaries 
in  any  other  form  than  that  of  diffusible  peptone,  the  normal 
passage  of  the  natural  proteids  of  the  blood  being  exactly 
in  the  opposite  direction,  from  the  interior  of  the  capillaries 
into  the  extravascular  elements  of  the  tissues,  still  it  is  open 


ABSORPTION    OF    PROTEIDS.  411 

for  us  to  ask  the  question,  If  solid  particles  of  fat  can  pass 
from  the  interior  of  the  alimentary-  canal  into  the  lacteals, 
wh}'  should  not  various  forms  of  proteids  pass  in  the  same 
way  into  the  lacteals,  either  in  solution  or  even  as  solid  par- 
ticles ? 

Br'dcke'  observed  that  after  a  meal  of  milk,  the  contents  of  the 
villus  after  death  were  loaded  with  a  granular  deposit  of  proteid 
nature,  and  of  an  acid  reaction.  He  infers  from  this,  that  to- 
gether with  the  iat  there  passes  into  the  villus  a  quantity  of  the 
proteid  material  of  food  in  the  form  of  alkali-albumin,  precipi- 
table  by  weak  acids ;  and  argues  from  this  and  other  facts  that 
a  considerable  quantity  of  the  proteids  of  food  thus  obtains  en- 
trance into  the  blood  without  sutfering  the  change  into  peptone. 

It  would  thus  seem  possible  for  some  of  the  proteids  to 
pass  into  tiie  lacteals,  and  so  into  the  system  in  a  less  di- 
gested form  tiian  peptone  ;  and  it  is  further  possible  that  the 
proteids  thus  entering  into  the  system  in  different  forms 
may  play  different  parts  in  the  nutritive  labors  of  the 
economy. 

But  in  all  these  considerations  the  fact  must  he  borne  in 
mind  that  the  intestinal  walls  undouhtedlv  possess  a  selec- 
tive power  of  absorption,  which  overrides  the  laws  of  diffu- 
sion and  solubility.  This  is  shown,  for  instance,  by  the 
results  of  Tappeiner,^  who  found  that  the  fairly  soluble 
and  diffusible  salts,  sodium  taurocholate  and  glycocholate, 
were  not  absorbed  by  the  duodenum  and  upper  jejunum 
even  at  a  time  when  fat  was  being  rapidly  aliSorl)ed  in  those 
regions,  but  did  disappear  in  the  ileum  or  lower  jejunum, 
the  glycocholate  apparently  being  absorbed  by  both  the 
ileum  and  lower  jejunum,  while  the  taurocholate  passed  away 
in  the  ileum  alone. 

We  cannot  judge,  therefore,  of  the  course  taken  by  the 
proteids,  or  of  the  form  in  which  they  are  absorbed,  by  de- 
ductions based  on  solubility  and  diffusion.  The  problems 
we  are  discussing  can  only  be  satisfactorily  settled  by  direct 
experiment.  And  here  we  meet  wiih  dithculties.  If  all 
proteids  are  converted  into  peptone,  and  so  pass  into  the 
lacteals  or  into  the  Idood  capillaries,  we  might  expect  to  find 
a  quantity  of  })e|>tone  in  the  chyle,  or  in  portal  blood,  or  in 
both  after  a  proteid  meal.     But  neither  in  the  portal  Idood, 

^   Wien.  Sitzungsberichte,  xxxvii,  lix. 

^  Wien.  SitznngsbericlUe,  Bd.  77,  Ap.  1878, 


412      THE    TISSUES    AND    MECHANISMS    OF    DIGESTION. 

nor  in  the  chyle,  nor  in  tiie  general  blood  (liirinij  digestion, 
is  there  any  apprecialjle  qnantity  of  peptone.  Of  conrse  the 
quantity  of  peptone  passing  into  the  portal  blood  at  any 
moment  might  be  small,  and  yet  a  considerable  quantity 
might  so  pass  during  the  hours  of  digestion.  We  may  sup- 
pose moreover  that  that  which  does  pass  is  immediately 
converted,  possibly  by  some  ferment  action,  into  one  or 
other  of  tiie  natural  i)rotoids  of  the  blood,  or  otherwise  dis- 
posed of;  and  Plosz  and  (xyergyai^  have  shown  that  peptone 
injected  carefully  into  a  vein  disappears  from  the  blood, 
though  little  or  even  none  passes  out  by  the  kidney.  Hence 
the  failure  to  find  peptone  in  the  blood  (and  the  same  may 
be  said  of  the  chyle)  does  not  dis[)rove  the  view  which  seems 
to  follow  legitimately  from  the  results  of  artificial  digestion, 
that  proteid  food  is  converted  into  peptone  before  i)assing 
from  tlie  alimentary  canal  into  the  system  ;  and  we  know 
that  artificially  formed  peptone  is  available  for  nutrition  ; 
for  Plosz'^  and  Plosz  and  Gyergyai'  found  that  dogs  fed  on 
peptone  and  non-nitrogenous  food  actuall}'  put  on  flesh  and 
gained  weight.^ 

On  the  other  hand,  that  the  proteids  pass  by  the  portal 
blood  (and  if  so,  probably  in  tlie  form  of  peptone)  is  indi- 
cated by  the  experiments  of  Schmidt-Miilheim,^  who  finds 
that  wiien  the  chyle  is  entirely  prevented  from  entering  the 
blood,  not  only  are  proteids  absorbed,  but  that  they  are-  so 
metai)olized  in  the  l»ody  that  the  quantity  of  urea  which  in 
consequence  makes  its  ap[>earance  in  the  urine  is  the  same 
as  vviien  the  chyle  flows  into  the  venous  system  as  usual. 
Except,  therefore,  on  the  very  improbable  view  that  pro- 
teids absorbed  into  the  lacteals  of  the  villi  escape  from  the 
lymphatic  system  before  they  reach  the  thoracic  duct,  we 
must  infer  that  they  are  absorbed  by  the  blood  capillaries. 

Sugar. — With  regard  to  the  path  taken  by  the  sugar,  the 
careful  inquiries  of  v.  Mering'''  show  that  the  percentage  of 
sugar,  both  in  chyle  and  in  general  blood,  is  fairly  constant, 
being  to  no  marked  extent  increased  by  even  amylaceous 
meals ;  but  that  a  meal  of  sugar  or  starch  does  temporarily 


'  Pfliiger's  Archiv,  x  (1875),  36. 

2  Ibid.,  ix  (1874),  325.  s  Op.  cit. 

*  Cf.  Adamkiewicz,  Die  ISatur  nnd  der  Niihrwerth  des  Peptons,  1877. 

5  Archiv  f.  Anat.  u.  Phvsiol.,  1877,  p.  549. 

«  Ibid.,  p.  379. 


ABSORPTION    BY    DIFFUSION.  413 

increase  the  quantit}^  of  sugar  in  the  portal  blood.  From 
this  we  may  infer  that  such  portions  of  the  sugar  of  the 
intestinal  contents  as  are  absorbed  as  sugar  pass  exclusively 
by  the  portal  vein.  But  it  must  be  remembered  that  at 
present  we  have  no  accurate  information  as  to  how  large  a 
proportion  of  the  sugar  resulting  from  a  meal  passes  in  this 
way  unchanged  until  it  reaches  the  liver,  and  how  much 
undergoes  the  lactic  acid  or  analogous  fermentation.  Xor 
do  we  know  as  yet  how  much  of  the  starch  taken  as  food  is 
removed  from  the  alimentary  canal  in  the  form,  not  of  sugar 
but  of  dextrin. 

When  a  solution  of  sugar  is  injected  into  an  empty  isolated  loop 
of  intestine  a  large  quantity  disappears,  without  the  contents  of 
the  loop  becoming  acid.^  In  such  a  case  it  may  fairly  be  inferred 
that  the  sugar  is  directly  absorbed  without  undergoing  any 
change.  And  where  sugar  is  introduced  in  large  quantities  into 
the  alimentary  canal  the  percentage  of  sugar  in  the  blood  may 
be  temporarih'  increased  ;  to  such  an  extent  indeed  that  sugar 
may  appear  in  the  urine.-'  But  neither  of  these  facts  prove  that 
the  sugar  of  an  ordinary-  meal,  passing  as  it  does  along  the  in- 
testine with  the  other  portions  of  the  food  and  products  of  diges- 
tion, and  appearing  as  it  does  in  most  cases  in  comparatively 
small  quantities  at  a  time,  owing  to  the  more  or  less  gradual  con- 
version of  the  starch  of  the  meal,  is  similarly  absorbed  nn- 
changed  ;  while,  in  order  that  the  marked  acidity  of  the  c(mtents 
of  the  lower  intestine  should  be  kept  up,  a  considerable  quantity 
of  sugar  must  sutler  lactic  acid  fermentation,  if  the  acidity  be  due 
as  stated  to  lactic  acid. 

To  sum  up,  the  evidence  is  distinctly  in  favor  of  the  fats 
passing  largely  by  the  chyle,  and  of  the  proteids  and  sugar 
passing  largely  by  the  portal  vein;  but  there  still  remains 
mucii  doul)t  as  to  the  course  and  fate  of  a  not  inconsiderable 
portion  of  the  fat,  and  the  question  as  to  the  exact  form  in 
which  proteids  and  carbohydrates  leave  the  alimentar\'  canal, 
cannot  be  answered- in  a  perfectl}'  definite  manner. 

Absorption  by  Diffusion. — It  is  evident,  from  the  discus- 
sion just  concluded,  that  simple  ditfusion  is  far  from  ex- 
plaining the  whole  transit  of  the  digested  food  from  the 
intestine  into  the  blood.  Nevertheless,  it  must  not  be  sup- 
posed that  the  great  and  general  property  of  ditlusion  does 

'  Funke,  Lehrb.,  6th  Aiifl.,  i,  p.  235. 

^  C.  Schmidt  uud  v.  Becker,  quoted  in  Funke,  op.  cit.,  p.  236. 

35 


414      THE    TISSUES    AND    MECHANISMS    OF    DIGESTION. 

not  make  itself  felt  in  the  process  of  absorption,  however 
nuu'li  it  may,  in  the  case  of  various  snhstances,  be  subordi- 
nated and  hekl  in  clieck  by  more  potent  influences.  Thus 
the  passaije  of  water  from  tiie  alimentary  cavity  into  the 
blood,  or  from  the  blood  into  the  alimentary  cavity,  and  the 
behavior  of  various  inorganic  salts,  when  taken  as  food  or 
medicine,  illustrate  very  clearly  the  influence  of  osmosis. 
When  the  intestine  contains  a  large  quantity  of  watery 
matter  the  surplus  water  passes  by  diffusion  into  the  blood, 
just  as  it  [)asses  through  the  membrane  of  a  dialyzer,  with 
blood  or  serous  fluid  on  the  one  side  and  water  on  the  other. 
When  an  albuminous  fluid  of  the  specific  gravity  of  bhjod- 
serum  is  exposed  in  a  dialyzer  to  water  about  200  parts  of 
^vater  i)ass  through  the  membrane  of  the  dialyzer  from  the 
water  into  the  all)uminous  fluid  for  every  one  part  of  albu- 
min which  passes  from  the  fluid  into  the  water.  Moreover, 
in  the  living  body  the  blood  in  the  mesenteric  capillary,  thus 
diluted  by  diffusion  from  the  intestinal  contents,  is  con- 
tinually being  replaced  by  fresh  blood  concentrated  by  its 
passage  through  the  skin,  lung,  or  kidney.  By  tiie  help  of 
the  circulation  an  almost  unlimited  quantity  of  water  can 
be  absorbed  from  the  alimentary  canal. 

It  is  a  matter  of  common  experience  that  such  inorganic 
and  organic  salts  as  are  readily  diffusible,  pass  with  great 
rapidity  into  the  blood  (and  thus  into  the  urine)  when  taken 
by  the  mouth ;  and  the  rapidity  with  which  they  are  ab- 
sorbed is  in  large  measure  proportionate  to  their  difl'usibility. 
Of  course,  coincident  with  this  passage  of  the  salt  from  the 
intestine  into  the  blood,  there  is  a  proportionate  current  of 
water  in  the  contrary  direction  from  the  blood  into  the  in- 
testi!ie  ;  but  this,  though  opposed  to,  is,  under  ordinary 
circumstances,  too  small  to  diminish  to  any  serious  extent 
the  passage  of  water  from  the  intestine  into  the  blood,  of 
whicli  we  spoke  just  now,  as  caused  by  the  osmotic  influence 
of  the  albuminous  constituents  of  the  blood.  But,  under 
certain  circumstances,  the  former  may  overcome  the  latter. 
Thus,  when  a  concentrated  solution  of  a  highly  diffusible 
salt,  such  as  magnesium  sulphate,  is  introduced  into  the  ali- 
mentary canal,  the  flow  of  water  from  the  blood  into  the 
intestine  accompanying  the  osmotic  transit  of  the  salt  from 
the  intestine  into  the  blood,  is  so  great  as  largely  to  exceed 
tiie  current  in  the  contrary  direction  ;  and  the  intestine  be- 
comes filled  with  water  at  the  expanse  of  the  blood.  This 
is  probably  the  cause  of  the  purgative  action  of  large  doses 


DIGESTION.  415 

of  many  saline  mattei-vS.  And  even  tlie  purgative  action  of 
more  dilute  solutions  ma^'  he  explained  in  the  same  way, 
since  in  the  case  of  some  salts  at  least  the  transit  of  water 
as  compared  with  the  transit  of  the  salt  is  relatively  more 
rapid  with  very  dilute  solutions  than  with  more  concentrated 
solutions.  Salts  such  as  these,  which,  when  introduced  into 
the  intestine,  produce  diarrh(jea,  bring  about  a  contrary  con- 
dition when  injected  directly  into  the  blood;  and  magnesium 
sulphate,  with  its  higher  endosmotic  equivalent,  is  more 
purgative  in  its  action  than  sodium  chloride  with  its  lower 
equivalent. 

Our  knowledge  of  the  physiology  of  digestion  is  the  accumu- 
lated gain  of  many  labors,  some  dating  back  from  very  old  times. 
To  Reaumur.  Spallanzani,  Tiedemann  and  Gmelin,  Eberle  (who 
first  obtained  artificial  digestion  with  gastric  mucus  and  an  acid), 
Prout,  Sch\Yann  (who  first  introduced  the  idea  of  pepsin ^^  though 
Wasmann  first  obtained  it  in  a  comparatively  pure  state),  Ber- 
zelius  and  other  chemists,  we  owe  much.  The  observations  of 
Dr.  Beaumont,'-  carried  on  by  means  of  the  accidental  gastric 
fistula  of  Alexis  St.  Martin,  not  only  added  largely  to  our  posi- 
tive knowledge,  but  were  also  of  great  indirect  use  as  indicating 
a  method  of  "investigation  which  has  since  proved  so  fruitful. 
The  labors  of  Bidder  and  Schmidt'  and  Frerichs*  were  of  great 
value.  The  publication  of  Bernard's  work  on  pancreatic  juice'' 
marked  a  distinct  step  in  advance  •,  but  of  far  greater  importance 
was  the  same  illustrious  physiologist's  discovery  of  the  vaso-motor 
action  of  the  sympathetic,  see  p.  2(3(3,  followed  up  as  that  was  by 
Ludwig's  demonstration^  of  the  secretor}-  activity  of  the  chorda 
tympani,  and  enlarged,  as  this  has  been  in  turn,  as  well  by  the 
labors  of  Ludwig  and  his  school,  as  by  those  of  Bernard,  Eck- 
hard,  Wittich,  Heidenhain  and  others.  To  the  importance  of 
Heidenhain's  later  observations  we  have  called  attention  in  the 
text.  The  proofs  offered  by  Corvisart,^  and  amplified  by  Kuhne,* 
of  the  proteolytic  action  of  the  pancreatic  juice  opened  out  a  line 
of  inquiry  of  great  importance,  which  is  as  yet  far  from  being 
exhausted. 


1  Muller's  Archiv,  1836,  p.  90. 

^  Exps.  and  Obs.  on  the  Gastric  Juice  and  Phvs.  of  Digestion,  Boston, 
U.  S.,  1834. 

^  Die  Verdauungssafte,  etc.,  1852. 

**  Art.  "  Verdauung,"  Wagner's  Handworterbucli,  1S4G. 

^  Mem.  sur  1.  Pancreas,  1856. 

^  Zt.  f.  rat.  Med.,  X.  F.,  i,  p.  255,  1851. 

''  Sur  une  Function  peu  connue  du  Pancreas,  1857. 

^  Vircliow's  Archiv,  xxxix  (1867),  p.  130. 


410       TISSUES    AND    MECUANISMS    OF    RESPIRATION. 

CHAPTER  IT. 

TITE  TISSUES  AXDMECIIAXISMS  OF  RESPIRATION". 

[^Phymological  Anatomy  of  the  Trachea  and  Lungs. 

The  trachea  is  a  meinhiauo-cartilaijiiions  cvHndrical  tube, 
soinewliat  ttattened  posteriorly.  It  is  alioiit  four  and  a  lialf 
inches  long,  ahoiii  Ihree-loiirLlis  of  an  inch  in  diameter.  It 
is  composed  of  an  external  (ibrous  and  an  internal  mncous 
coat.  Tiie  fil)rons  coat  consi^^ts  of  several  layers  which  are 
composed  of  elastic  and  non-elastic  fibrous  tissue,  a  circular 
and  longitudinal  layer  of  unstriated  muscular  tissue,  and 
about  twenty  impei'fect  cartilaginous  rings,  which  are  placed 
|)arallel  with  each  other  and  partially  enciicle  the  tube.  The 
rings  are  imperfect  posterioily,  wheie  the  tube  is  completed 
by  a  tibio  musculiir  membrane.  The  mucous  coat  consists  of 
a  basement  membrane  which  is  covered  b\'  a  layer  of  ciliated 
columnar  epithelium.  On  the  surface  of  this  membrane  can 
be  seen  numerous  orifices,  which  are  the  apertures  of  the 
ducts  leading  from  the  tracheal  mucous  glands.  These 
glands  are  of  the  racemose  and  follicular  varieties,  and  are 
most  abundant  in  the  posterior  portions  of  the  trachea. 

The  lungs  ai-e  bilateral  organs,  situated  within  the  thoracic 
cavity.  When  the  chest  is  oi)ened  they  are  seen  to  occupy 
but  a  portion  of  the  space,  or  in  other  words  are  colla[)sed. 
This  is  not  the  case  in  the  unopened  chest,  where  the  lungs 
are  partially  expanded  and  in  contact  wiih  the  chest-walls. 

The  lungs  are  divided  into  lobes,  which  are  subdivided  into 
lobules,  and  are  composed  of  a  pai^enchynia^  and  a  ><erouH  and 
i^uhf^fj^ovs  coat.  The  serous  coat  is  a  continuation  of  the  intra- 
thoracic lining,  and  forms  the  pulmonary  or  visceral  layer  of 
the  pleura.  The  subserous  coat  is  composed  of  an  areolar 
tissue  containing  a  very  large  amount  of  elastic  fibres. 
This  coat  envelops  the  lungs  and  sends  numerous  prolon- 
gations or  trabeculae  into  the  pulmonary  substance.  The 
jyarenchyma  of  the  lungs  is  made  up  of  the  lol)ules,  which 
are  bound  together  by  a  fibro-elastic  tissue,  which  also 
forms  a  nidus  for  the  ramifications  of  the  bloodvessels,  lym- 
phatics, and  nerves.  This  fibro-elastic  tissue  plays  an  im- 
portant part  in  expiration  :  in  inspiration  the  fibres  are  put 
on  the  stretch,  and  in  their  return  to  their  normal  condition, 
contract,  and  thus  assist  in  expelling  the  air. 

The  trachea  is  connected  above  with  the  larynx  ;  below, 


ANATOMY  OF  THE  TRACHEA  AND  LUNGS.   417 

it  divides  into  two  branches,  which  are  the  right  and  left 
bronchial  tubes.  The  right  is  larger,  shorter,  and  placed 
more  iiorizontal  than  the  left.  The  reason  of  the  larger  size 
of  the  right  is  obviousl^y  due  to  the  greater  capacity  of  the 
right  lung.  These  primary  bronchial  tubes  undergo  sub- 
division through  numerous  gradations  of  smaller  tubes 
until  the  ultimate  divisions,  or  olceolar  pasHogea^  are 
reached.  The  coats  of  the  bronchial  tubes  become  more 
delicate  in  structure  as  the  tubes  are  diminished  in  size.  The 
layer  of  cartilaginous  I'ings,  which  is  seen  in  the  trachea,  is 


Fig.  11.3. 


Part  of  a  Transverse  Section  of  a  Bronchial  Tube  from  the  IMg,  magnified  240  di- 
ameters, rt,  external  fibrous  layer ;  6,  muscular  layer;  c,  internal  fibrous  layer;  d, 
epithelial  layer;  /,  one  of  the  surrounding  alveoli. 

continued  in  the  larger  bronchi,  but  the  rings  soon  become 
replaced  b}^  irregular  cartilaginous  plates,  which  them- 
selves disappear  when  the  size  of  the  bronchi  have  reached 
a  diameter  of  about  2  mm.  The  mucous  glands  disappear 
consentaneously  with  the  disappearance  of  the  cartilaginous 
plates.  The  muscular  fibres  are  in  the  form  of  a  contin- 
uous transverse  layer.  Tiie  fibrous  and  muscular  tissues  are 
continued  into  the  smallest  bronchi. 

The  mucous  membrane  is  also  continuous  with  that  of  the 
trachea,  and  is  lined  with  ciliated  columnar  epithelium. 

The  smallest  bronchi  terminate  in  subdivisions,  called  the 
alveola?'  pannages.     (Figs.  114  and  115.)     Each  of  these  pas- 


418      TISSUES    AND    MECHANISMS    OF    RESPIRATION. 


sages  sul)divide  through  several  <rrailalions,  and  ultimately 
terminate  in  cpeeal  processes,  winch  gradually  become  ex- 
panded towards  tlieir  cjecal  extremities,  and  present  an  ap- 
pearance similar  to  that  of  the  expanded  part  of  a  funnel, 
iience  they  have 


been  called  the  infandibula.     The  interior 


Fig.  114.— System  of  Alveolar  Passages  and  lulunuibulu  irom  the  Margin  of  the 
Liiug  of  a  Monkey  (Cercopethecus)  injected  with  mercury,  magnified  10  diameters, 
a,  Terminal  bronchial  twig;  6,  b,  infundibiila;  c,  c,  alveolar  passages. 

Fig.  115. — Two  small  groups  of  air-cells,  or  injundibula,  a,  a,  with  air-cells,  b,  b,  and 
the  alveolar  passages,  c,  c,  with  which  the  air-cells  communicate.  From  a  newborn 
child.— After  Kolliker. 

of  each  infundibulum  is  marked  by  fifteen  or  twenty  incom- 
plete cells,  which  are  termed  alveoli  or  air-ceMn.  Tliese  cells 
average  about  0.25  mm.  in  diameter.  Their  walls  consist 
of  a  delicate  basement  membrane,  which  is  lined  by  a  layer 
of  pavement  epithelium.  This  membrane  forms  by  its  redu- 
plications the  incomplete  septa  between  the  air-cells.  The 
space  in  the  interior  of  an  infundibulum  is  termed  an  inter- 
cellular pannage. 

Each  lobule  or  infundibulum  is  composed  of  an  ultimate 
alveolar  passage,  with  its  terminal  alveoli,  and  of  nerves, 
bloodvessels,  and  lymphatics;  all  of  which  are  bound  to- 
gether by  fibro-elastic  tissue. 

The  capillaries  (Fig.  lUi)  form  a  plexus  between  the 
cells,  which  is  remarkable  for  its  density.  The  diameters 
of  the  intercapillary  spaces  are  often  less  than  the  diame- 
ters of  the  vessels.  These  capillaries  are  so  arranged  in 
the  intercellular  tissue  that  both  sides  of  the  vessels  are  in 
contact  with  the  walls  of  contitjuous  cells. 


RESPIRATION. 


419 


The  cartilaf!;inons  rings  of  the  trachea  and  laro:er  bronchi 
keep  them  continually  open.  The  smaller  bronchi,  in  which 
these    cartilages   are   absent,   are   capal)le  of  considerable 


Capillary  Network  of  the  Piiliuonary  Bloodvessels  in  the  Human  Lung. 

expansion  and  contraction  by  virtue  of  their  elastic  and 
muscular  tissues.  The  nerves  of  the  lungs  are  derived  from 
the  pneumogastric  and  sympathetic.  Blood  is  conveyed 
through  the  pubnonary  artery  to  the  lungs,  where  it  is  arte- 
rialized,  and  then  returned  tlirough  the  pulmonary  veins  to 
the  heart.  The  lungs  receive  blood  for  their  nutrition, 
principall}',  through  the  bronchial  arteries.] 

We  have  already  seen  (Introduction,  p.  16)  that  one  par- 
ticular item  of  the  body's  income,  viz.,  oxygen,  is  peculiarly 
associated  with  one  particular  item  of  the  body's  waste,  viz., 
carbonic  acid,  the  means  which  are  applied  for  the  introduc- 
tion of  the  former  being  also  used  for  the  getting  rid  of  the 
latter.  Both  are  gases,  and  in  consequence  the  ingress  of 
the  one  as  well  as  the  egress  of  the  other  is  far  more  de- 
pendent on  the  sim})le  physical  process  of  diffusion  than  on 
any  active  vital  processes  carried  on  b}"  means  of  tissues. 
Oxygen  passes  from  the  air  into  the  blood  mainly  b^'  diffu- 
sion, and.  mainly  by  diffusion  also  from  the  blood  into  the 
tissue ;  in  the  same  way  carbonic  acid  passes  mainly  by 
diffusion  from  the  tissues  into  the  blood,  and  from  the  blood 


420      TISSUES    AND    MECHANISMS    OF    RESPIRATION. 

into  the  air.  Whereas,  as  we  have  seen,  in  the  secretion  of 
tlie  digestive  Jnices  the  epithelium-cell  plays  an  all-import- 
ant part,  in  respiration  the  entrance  of  oxygen  from  the 
lungs  into  the  blood,  and  from  the  blood  into  the  tissue,  and 
the  passage  of  carbonic  acid  in  the  contrary  direction  are 
effected,  if  at  all,  in  a  wholly  subordinate  manner,  by  the 
l)ehavior  of  the  pulmonary,  or  of  the  capillary  epithelium. 
What  we  have  to  deal  with  in  respiration  then  is  not  so 
much  the  vital  a(;tivitics  of  any  particular  tissue,  as  the 
various  mechanisms  by  which  a  rapid  interchange  between 
tile  air  and  the  blood  is  effected,  the  means  by  which  the 
blood  is  enal)led  to  carry  oxygen  and  carbonic  acid  to  and 
from  the  tissues,  and  the  manner  in  which  tlie  several  tissues 
take  oxygen  from  and  give  carbonic  acid  up  to  the  blood. 
We  have  reasons  for  thinking  that  oxygen  can  be  taken  into 
the  blood,  not  only  from  the  lungs,  but  also  from  the  skin, 
and,  as  we  have  seen,  occasionally  from  the  alimentary  canal 
also  ;  and  carbonic  acid  certainly  passes  away  from  the  skin, 
and  through  the  various  secretions,  as  well  as  by  the  lungs. 
Still  the  lungs  are  so  eminently  tiie  channel  of  the  inter- 
change of  gases  between  the  body  and  the  air,  that  in  deal- 
ing at  the  present  with  respiration,  we  shall  confine  ourselves 
entirely  to  pulmonary  respiiation,  leaving  the  consideration 
of  the  subsidiary  respiratory  processes  till  we  come  to  study 
the  secretions  of  which  thej-  respectively  form  part. 

Sec.  1.   The  Mechanics  of  Pulmonary  Respiration. 

The  lungs  are  placed,  in  a  semi-distended  state,  in  the 
air-tight  thorax,  the  cavity  of  which  they,  together  with  the 
heart,  great  bloodvessels,  and  other  organs,  completely  fill. 
By  the  contraction  of  certain  muscles  the  cavity  of  the 
thorax  is  enlarged  ;  in  consequence  the  pressure  of  the  air 
within  the  lungs  becomes  less  than  that  of  the  air  outside 
the  body,  and  this  difference  of  pressure  causes  a  rush  of 
air  through  the  trachea  into  the  lungs  until  an  equilibrium 
of  pressure  is  established  between  the  air  inside  and  that 
outside  the  lungs.  This  constitutes  inspiration.  Upon  the 
relaxation  of  the  inspiratory  muscles  (the  muscles  whose 
contraction  has  brought  about  the  thoracic  expansion),  the 
elasticity  of  the  cliest-walls  and  lungs,  aided,  perhaps,  to 
some  extent  by  the  contraction  of  certain  muscles,  causes 
the  chest  to  return  to  its  original  size;  in  consequence  of 
this  the  pressure  within  the  lungs  now  becomes  greater  than 


INSPIRATION    AND    EXPIRATION.  421 

that  outside,  and  thus  air  rushes  out  of  tlie  trachea  until 
equilibrium  is  once  more  estaV)lished.  This  constitutes  ex- 
piration ;  the  inspiratory  and  expiratory  act  together  form- 
ing a  respiration.  The  fresh  air  introduced  into  the  upper 
part  of  the  puhnonary  passages  by  the  inspiratory  move- 
ment contains  more  oxygen  and  less  carbonic  acid  than  the 
old  air  previously  present  in  the  lungs.  By  diffusion  tlie 
new  or  tidal  air,  as  it  is  frequently  called,  gives  up  its  oxy- 
gen to.  and  takes  carbonic  acid  from,  the  old  or  i<tationary 
air,  as  it  has  been  called,  and  thus  when  it  leaves  the  chest 
in  expiration  has  been  the  means  of  both  introducing  oxy- 
gen into  the  chest  and  of  removing  carbonic  acid  from  it. 
In  this  waj^,  by  the  ebb  and  flow  of  the  tidal  air,  and  by 
diffusion  between  it  and  the  stationary  air,  the  air  in  the 
lungs  is  being  constantly  renewed  through  the  alternate  ex- 
pansion and  contraction  of  the  chest. 

In  ordinar}^  respiration,  the  expansion  of  the  chest  never 
reaches  its  maximum  ;  by  more  forcible  muscular  contrac- 
tion, by  what  is  called  labored  inspiration,  an  additional 
thoracic  expansion  can  be  brought  about,  leading  to  the  in- 
rush of  a  certain  additional  quantity  of  air  before  equilib- 
rium is  established.  This  additional  quantity  is  often  spoken 
of  as  complemental  air.  In  the  same  way,  in  ordiuarj'  res- 
piration, the  contraction  of  the  chest  never  reaches  its 
maximum..  By  calling  into  use  additional  muscles,  b}'  a 
labored  expiration,  an  additional  quantity  of  air,  the  so- 
called  re>ieri:e  or  supplemental  air.  may  be  driven  out.  But 
even  after  the  most  forcil)le  expiration,  a  considerable 
quantity  of  air,  the  reaidital  air,  still  remains  in  the  lungs. 
The  natural  condition  of  the  lungs  in  the  chest  is  in  fact  one 
of  partial  distension.  The  elastic  pulmonary  tissue  is  al- 
ways to  a  certain  extent  on  the  stretch  ;  it  is  always,  so  to 
speak,  striving  to  pull  asunder  the  pulmonary  from  the 
parietal  pleura  ;  but  this  it  cannot  do,  because  the  air  can 
have  no  access  to  the  pleural  cavity.  When,  however,  the 
chest  ceases  to  be  air-tight,  when  by  a  puncture  of  the  chest- 
wall  or  diaphragm,  air  is  introduced  into  the  pleural  cham- 
ber, the  elasticity  of  the  lungs  pulls  the  pulmonary  away 
from  the  parietal  pleura,  and  the  lungs  collapse,  driving  out 
by  the  windpipe  a  considerable  quantity  of  the  residual  air. 
Even  then,  however,  the  lungs  are  not  completely  emptied, 
some  air  still  remainiug  in  the  air-cells  and  passages.  It 
need  hardly  be  added  that  when  the  pleura  is  punctured, 
and  air  can  g^m  free  admittance  from  the  exterior  into  the 

36 


422       TISSUES    AND    xMECUANISMS    OF    RESPIRATION. 

jileurjil  chauiher,  the  efrcct  of  the  rCvSpii-atory  movements  is 
fsitiiply  to  drive  air  in  and  out  of  that  chaml)er,  instead  of 
in  and  out  of  the  hmg.  Tiiere  is  inconsequence  no  renewal 
of  tlie  air  vvitliin  the  kings  under  those  circumstances. 

In  man  the  pressure  exerted  by  the  elasticity  of  the  lun(;s  alone 
amounts  to  about  5  mm.  of  mercury.  This  is  estimated  by  tying 
a  manometer  into  the  windpipe  of  a  dead  sul)ject  and  observing 
the  rise  of  mercury  whicli  takes  place  when  the  chest-walls  are 
l)unctured.  If  the  chest  be  f<jrcibly  distended  beforehand,  a 
much  larger  rise  of  the  mercury,  amounting  to  30  nmi.  in  the 
case  of  a  distension  corresponding  to  a  very  forcible  inspiration, 
is  observed.  In  the  living  body  this  mechanical  elastic  force  of 
the  lungs  is  assisted  by  the  contraction  of  the  plain  muscular 
fibres  of  the  bronchi  ;  the  pressure  however  which  can  be  exerted 
b\'  these  probably  does  not  exceed  1  or  2  mm. 

When  a  manometer  is  introduced  into  a  lateral  opening  of  the 
windpipe  of  an  animal,  the  mercury  will  fall,  indicating  a  nega- 
tive i)ressure  as  it  is  called,  during  inspiration,  and  rise,  indicat- 
ing a  i)ositive  pressure,  during  expiration,  the  former  or  negative 
pressure  amounting  to  about  3  mm.,  and  the  latter  or  positive 
pressure  to  2  mm.  of  mercury.  When  a  manometer  is  fitted  with 
air-tight  closure  into  the  mouth,  or  better,  in  order  to  avoid  the 
suction  action  of  the  mouth,  into  one  nostril,  the  other  nostril 
and  the  mouth  being  closed,  and  efibrts  of  inspiration  and  expi- 
ration are  made,  the  mercury  falls  or  undergoes  negative  pressure 
with  inspiration,  and  rises,  or  undergoes  positive  pressure  during 
expiration.  Donders  found  in  this  way  that  the  negative  pres- 
sure of  a  strong  inspiratory  efibrt  varied  from  30  to  74  mm., 
while  the  positive  pressure  of  a  strong  expiration  varied  from  62 
to  lOO  mm. 

The  total  amount  of  air  wdiich  can  be  given  out  b}'  the 
most  forcible  expiration  following  upon  a  most  forcible  in- 
spiration, that  is,  the  sum  of  the  complemental,  tidal  and 
reserve  airs,  was  called  bv  Hutciiinson  ^  the  vital  capacity  ;" 
"  extreme  differential  capacity  "  is  a  better  phrase.  It  may 
be  measured  by  a  modification  of  a  gas-meter  called  a  spir- 
ometer. The  medium  vital  capacity  may  be  put  down  at 
3-4000  cc.  (200  to  250  cubic  inches;. 

Independent  of  other"  causes  of  variation,  Hutchinson  found 
the  vital  capacity  to  be  decidedly  dependent  on  stature,  the  taller 
persons  having  the  greater  capacity. 

Of  the  whole  measure  of  vital  capacity,  about  500  cc.  (30 
c.  inch)  may  be  put   down   as  the  average   amount  of  tidal 


RHYTHiM    OF    RESPIRATION. 


423 


air,  llie  remainder  being  nearly  equally  divided  between  tlie 
complemental  and  reserve  airs.  The  quantity  left  in  the 
lungs  after  the  deepest  expiration  amounts  to  about  1400- 
2000  cc. 

Since  the  respiratory  movements  are  so  easily  affected  by  vari- 
ous circumstances,  the  simple  fact  of  attention  being  directed  to 
the  breathing  being  sufficient  to  cause  modifications,  both  of  the 
rate  and  depth  of  the  respiration,  it  becomes  very  difficult  to  fix 
the  volume  of  an  average  breath.  Thus  various  authors  have 
given  figures  varying  from  53  cc.  to  792  cc.  The  statement 
made  above  is  that  given  by  Yierordt  as  the  mean  of  observa- 
tions varying  from  177  to  699  cc. 

The  Rhythm  of  Respiration. — If  the  movements  of  the 
column  of  tidal  air,  or  the   movements   of  expansion   and 


Fig.  ir 


Tracing  of  Thoracic  Respiratory  Movenients  obtained  by  means  of  Marey's  Pneu- 
mograph.   (To  be  read  from  left  to  right.) 

A  whole  respiratory  phase  is  comprised  between  a  and  a  ;  inspiration,  during  wliich 
the  lever  descends,  extending  irom  n  to  b,  and  expiration  from  b  to  a.  The  uudiihi- 
tions  at  c  are  caused  by  the  heart's  beat. 

contraction,  or  the  fall  and  rise  of  the  diaphragm,  lie  regis- 
tered, some  such  curve  as  that  represented  in  Fig.  117  is 
obtained. 


The  movements  of  the  column  of  air  may  be  recorded  by  in- 
troducing a  T  piece  into  the  trachea,  one  cross  piece  being  left 
open  or  connected  with  a  piece  of  india-rubber  tubing  open  at 
the  end,  and  the  other  connected  with  a  Marey's  tambour  or  with 
a  receiver,  which  in  turn  is  connected  with  a  tambour,  Fig.  118. 
The  movements  of  the  column  of  air  in  the  trachea  are  trans- 
mitted to  the  tambour,  the  consequent  expansions  and  contrac- 


i24      TISSUES    AND    MECHANISMS    OF    RESPIR\T10N. 


iiiiilililllii 


mm 


RHYTUM    OF    RESPIRATION.  425 


The  recording  apparatus  shown  is  the  ordinary  cylinder  recording  apparatus  The 
cylindiT  A  covered  with  >nioktd  paper  is  by  means  of  the  friction-plate  B  put  into 
revolution  by  the  spring  clock-work  in  C  regulated  by  Foucault's  regulator  D.  By 
means  of  the  screw  E,  the  cylinder  can  be  raised  or  lowered,  and  by  means  of  the 
sscrew  F  its  speed  may  be  increased  or  diminished. 

The  tracheotomy  tube  t  fixed  in  the  trachea  of  an  animal  is  connected  by  india- 
rubber  tubing  a  with  a  glass  T  piece  inserted  into  the  large  jar  G.  From  the  other 
end  of  the  T  piece  proceeds  a  second  piece  of  tubing  b,  the  end  of  which  can  be 
either  closed  or  partially  obs.tructtd  at  pleasure  by  means  of  the  screw  clamp  c. 
From  the  jar  proceeds  a  third  piece  of  tubing  d,  connected  with  a  Marey's  tambour 
in  (see  Fig.  63,  p.  208),  the  lever  of  which  I  writes  on  the  recording  surface.  When 
the  tube  h  is  open  the  animal  breathes  freely  through  this,  and  the  movements  in 
the  air  of  G  and  consequently-in  the  tambour  are  slight.  On  closing  the  clamp  c, 
tl>e  animal  breathes  only  the  air  contained  in  the  jar,  and  the  movements  of  the 
lever  of  the  tambour  become  consequently  much  more  marked. 

IVlow  the  lever  is  seen  a  small  time-marker  n  connected  with  an  electro-magnet, 
the  current  through  which  coming  from  a  battery  by  the  wires  x  and  y  is  made  and 
broken  by  a  clock-work  or  metronome. 

tions  of  which  are  traDsmitted  by  means  of  a  lever  resting  on  it 
to  the  recording  drum.  The  movements  of  the  chest-walls  may 
be  recorded  by  means  of  the  recording  stethometer  of  Burdon- 
Sanderson.^  This  consists  of  a  rectangular  framework  con- 
structed of  tAvo  rigid  parallel  bars  joined  at  right  angles  to  a 
cross  piece.  The  free  ends  of  the  bars,  the  distance  "between 
which  can  be  regulated  at  pleasure,  are  armed,  the  one  with  a 
tambour,  the  other  simply  with  an  ivory  button.  The  tambour 
also  bears  on  the  metal  phite  of  its  membrane  (Fig.  63,  m' ,  p. 
208)  a  small  ivory  button  (in  place  of  the  lever  shown  in  Figs. 
63  and  118).  When  it  is  desired  to  record  the  changes  occurring 
in  any  diameter  of  the  chest,  e.  f/.,  an  autero-posterior  diameter 
from  a  point  in  the  sternum  to  a  point  in  the  back,  the  instru- 
ment is  made  to  encircle  the  chest  somewhat  after  the  fashion  of 
a  pair  of  callipers,  the  ivory  button  at  one  free  end  being  placed 
on  the  spine  of  a  vertebra  behind  and  the  tambour  at  the  other 
on  the  sternum  in  front  in  the  line  of  the  diameter  which  is  be- 
ing studied.  The  distance  between  the  free  ends  of  the  instru- 
ment being  carefully  adjusted  so  that  the  button  of  the  tambour 
presses  slightly  on  the  sterniun,  any  variations  in  the  length  of 
the  diameter  in  question  will,  since  the  framework  of  the  tam- 
bour is  immobile,  give  rise  to  variations  of  pressure  Avithin  the 
tambour.  These  variations  of  the  ''receiving"  tambour  as  it 
is  called  are  conve^-ed  by  a  tlexible  tube  containing  air  to  a  sec- 
ond or  "recording  "  tambour  similar  to  that  shown  in  Figs.  63 
and  118,  the  IcA^er  of  which  records  the  variations  on  a  travelling 
surface.  For  the  pm-pose  of  measuring  the  extent  of  the  move- 
ments the  instrument  must  be  experimentally  graduated.  In 
Marey's  pneumograph,  a  long  elastic  chamber  is  used  as  a  pec- 
toral girdle.     AVhen  the  chest  expands,  the  girdle  is  elongated, 


Hdb.  Phys.  Lab.,  p.  291. 


426      TISSUES    AND    MECHANISMS    OF    RESPIRATION. 


and  the  air  within  it  rareliod,  and  the  lever  of  the  tambour  con- 
nected with  it  depressed  ;  and  conversely,  when  the  chest  con- 
tracts, the  lever  is  elevated.  The  pneunio^raph  of  Fick  is  some- 
what similar.  The  movements  of  the  dia|)hragm  may  be  regis- 
tered by  means  of  a  needle,  which  is  thrust  throujj;!!  the  sternum 
so  as  to  rest  on  the  diai)hragm,  the  head  of  the  needle  being  con- 
nected with  a  lever.' 

It  is  seen  tliat  in  Fig.  117  ins|)irati()n  begins  somewhat  sud- 
denly and  advances  ra|)idly,  tliat  expiration  succeeds  inspi- 
ration immetliately,  advancing  at  first  rai)idly,])ut  afterwards 
more  and  more  shjwly.  Such  pauses  as  aie  seen  occur  be- 
tween the  end  of  expiration  and  the  beginning  of  inspira- 
tion. In  normal  breathing,  hardly  any  pause  is  observed 
between  the  extreme  end  of  expiration  and  the  beginning 
of  inspiration,  but  in  cases  where  the  respiration  becomes 
infrequent,  pauses  of  considerable  length  may  be  observed. 

In  what  may  be  considered  as  normal  breathing,  the  res- 
piratory act  is  repeated  about  IT  times  a  nnnute;  and  the 
duration  of  the  inspiration  as  comi)ared  with  that  of  the 
expiration  (and  sucii  pause  as  may  exist)  is  about  as  ten  to 
twelve. 

The  rate  of  the  respiratory  rhythm  varies  very  largely,  and  in 
this  as  in  the  volume  it  is  veryditficult  to  fix  a  satisfactory  aver- 
age. While  Hutchinson  places  it  at  20  a  minute,  Vierordt  puts 
it  at  11.1),  and  Funke  at  13.5.  The  frequency  is  greater  in  chil- 
dren than  in  adults,  but  rises  again  somewhat  after  30  years  of 
age.  Quetelet  gives  the  rate  of  respiration  of  new-born  infants 
at  44  ;  from  1  to  5  years,  20  ;  from  2.")  to  30, 16  ;  from  30  to  50, 18.1 
per  minute.  The  rate  is  influenced  by  the  position  of  the  body, 
being  quicker  in  standing  than  in  lying,  and  in  lying  than  in 
sitting.  Muscular  exertion  and  emotional  conditions  atfect  it 
deeply.  In  fact,  almost  every  event  which  occurs  in  the  body 
may  influence  it.  We  shall  have  to  consider  in  detail  hereafter 
the  manner  in  which  this  influence  is  brought  to  bear. 

When  the  ordinary  respiratory  movements  prove  insuffi- 
cient to  effect  the  necessary  changes  in  the  blood,  their 
rhythm  and  character  become  changed.  Normal  respiration 
gives  place  to  labored  respiration,  and  this  in  turn  to  dysp- 
noea, which,  uidess  some  restorative  event  occurs,  terminates 
in  asphyxia.  These  abnormal  conditions  we  shall  study 
more  full}-  hereafter. 

1  See  Hdb.  Physiol.  Laborat.,  p.  295. 


MOVEMENTS    OF    INSPIRATION.  427 


The  Respiratory  Movements. 

When  the  movements  of  the  chest  dnring  normal  breath- 
ing are  watched,  it  is  seen  that  dnring  respiration  an  en- 
largement talves  place  in  tlie  antero-posterior  diameter,  the 
sternum  being  thrown  forwards,  and  at  the  same  time  mov- 
ing upward.  The  lateral  width  of  the  chest  is  also  increased. 
The  vertical  increase  of  the  cavity  is  not  so  obvious  from 
the  outside,  though  wlien  the  movements  of  the  diaphragm 
are  watched  by  means  of  an  inserted  needle,  the  upper  sur- 
face of  that  organ  is  seen  to  descend  at  each  inspiration,  the 
anterior  walls  of  the  abdomen  bulging  out  at  the  same  time. 
In  the  female  human  subject,  the  movement  of  the  upper  part 
of  the  chest  is  very  conspicuous,  the  breast  rising  and  fall- 
ing with  every  respiration  ;  in  the  male,  however,  the  move- 
ments are  almost  entirely  contined  to  tiie  lower  part  of  the 
chest.  In  labored  respiration  all  parts  of  tlie  cliest  are  alter- 
nately expanded  and  contracted,  the  breast  rising  and  fall- 
ing as  well  in  tiie  male  as  in  the  female.  We  have  now  to 
consider  these  several  movements  in  greater  detail,  and  to 
study  the  means  b}'  which  they  are  carried  out. 

Inspiration. — There  are  two  chief  means  by  wliich  the 
chest  is  enlarged  in  normal  respiration,  viz.,  the  descent  of 
the  diaphragm  and  the  elevation  of  the  ribs.  The  former 
causes  that  movement  in  the  lower  part  of  the  chest  and  al>- 
domen  so  characteristic  of  male  breathing,  which  is  called 
diaphragmatic  ;  tbe  latter  causes  the  movement  of  the  upper 
chest  characteristic  of  female  breathing,  which  is  called 
costal.  These  two  main  factors  are  assisted  by  less  impor- 
tant and  subsidiary  events. 

The  descent  of  the  diai)hragm  is  etfected  by  means  of  the 
contraction  of  its  muscular  fibres.  When  at  rest  the  dia- 
phragm presents  a  convex  surface  to  the  thorax;  when  con- 
tracted it  becomes  much  flatter,  and  in  consequence  the 
level  of  the  chest-floor  is  lowered,  the  vertical  diameter  of 
the  chest  being  proportionately  enlarged.  (Fig.  119.)  In  de- 
scending, tlie  diaphragm  presses  on  the  abdominal  viscera, 
and  so  causes  a  projection  of  the  flaccid  abdominal  walls. 
From  its  attachments  to  the  sternum  and  the  false  ribs,  the 
diaphragm,  while  contracting,  naturally  tends  to  pull  the 
sternum  and  the  upper  false  ribs  downwards  and  inwards, 
and  the  lower  false  ribs  upwards  and  inwards,  towards  the 
lumbar  spine.     In  normal  breathing  this  tendency'  produces 


428       TISSUES    AND    MECHANISMS    OF    RESPIRATION, 


little  effect,  being  counteracted  by  the  accompanying  general 
costal  elevation,  and  by  certain  special  muscles  to  be  men- 


[FiG.  119. 


Apparatus  constructed  by  Donders  to  show  the  Mechanism  of  the  Diaphragm  in 
Respiration. 

1.  a  bottle  having  tliree  openings:  2,  is  closed  by  a  rubber  membrane,  which  may 
be  elevated  or  depressed  at  will;  4,  is  closed  with  a  cork,  having  a  tube  running 
through  its  centre,  and  having  attached  on  the  end  inside  of  the  bottle  the  trachea 
(5)  connected  with  a  cat's  or  rabbit's  lungs  (6);  the  third  opening  (7)  communicates 
by  a  glass  tube  (a)  with  the  air,  and  by  a  branch  (b)  with  a  manometer  (8;.  If  the 
rubber  diaphragm  be  elevated,  the  lungs  will  be  in  a  collapsed  state  ;  if  now  the  dia- 
phragm be  pulled  down  by  the  weight  (3)  the  air  in  the  bottle  will  become  ranfied.and 
the  weight  of  the  atmosphere  will  force  air  through  the  tube  (4)  into  the  lungs.  If  at 
the  same  time  the  finger  is  placed  over  the  opening,  a,  the  rarelication  of  the  air  in 
the  bottle  will  cause  the  liquid  in  the  manometer  to  be  drawn  towards  it,  as  is  seen  in 
c  and  d.  This  movement  of  the  liquid  in  the  manometer  towards  the  rarefied  air  of 
the  apparatus  is  analogous  to  tiie  negative  venous  pressure  which  occurs  in  the 
body  at  each  inspiration.] 


MOVEMENTS    OF    INSPIRATION. 


429 


tioiied  presently.  In  forced  inspiration,  however,  and  espe- 
cially where  there  is  any  obstruction  to  the  entrance  of  air 
into  the  lungs,  the  lower  ribs  ma\'  be  so  much  drawn  in  by 
the  contraction  of  the  diaphragm,  tliat  the  girth  of  the  trunk 
at  this  point  is  obviously  diminished. 

The  elevation  of  the  ribs  is  a  much  more  complex  matter 
than  the  descent  of  the  diaphragm.  If  we  examine  any  one 
rib,  such  as  the  fifth,  and  ol)serve  that  while  it  moves  freely 
on  its  vertebral  articulation,  it  descends  when  in  the  position 
of  rest  in  an  oblique  direction  from  the  spine  to  the  ster- 
num, it  is  obvious  that  \Nhen  the  rib  is  raised,  its  sternal 
attaciiraent  must  not  only  be  carried  upward  but  also  thrown 
forwards.  (Fig.  120.)  The  rib  may,  in  fact,  be  regarded 
as  a  radius,  moving  on  the  vertel)ral  articulation  as  a  centre, 
and  causing  the  sternal  attachment  to  descril  e  an  arc  of  a 

[Fig.  120.] 


circle  in  the  vertical  plane  of  the  body  ;  as  the  rib  is  carried 
upwards  from  an  oblique  to  a  more  horizontal  position,  the 
sternal  attachment  must  of  necessity  be  carried  farther 
away  in  front  of  -the  spine.  Since  all  the  ribs  have  a  down- 
ward slanting  direction,  they  must  all  tend,  when  raised 
towards  the  horizontal  position,  to  thrust  tlie  sternum  for- 
ward, sonje  more  than  others  according  to  their  slope  and 
length.  Tiie  elasticity  of  tlie  sternum  and  costal  caitilages, 
*ogetiier  with  the  articulation  of  tiie  sternum  to  the  clavicle 
above,  permit  the  front  surface  of  the  chest  to  be  thus  thrust 


430      TISSUES    AND    MECHANISMS    OF    RESPIRATION. 


forwards  as  well  as  upwards,  when  the  ribs  are  raised.  By 
this  action  tlie  anteroposterior  diameter  of  tlie  chest  is  en- 
larged. 

According  to  A.  Kansome,^  the  forward  movement  in  inspira- 
tion, especially  of  the  upper  ribs,  is  so  great  that  it  can  only  be 
accounted  for  l^y  an  expiratory  bending  in  and  inspiratory  straight- 
ening of  the  ribs. 

Since  the  ribs  form  arches  wliich  increase  in  their  sweep 
as  one  proceeds  from  the  first  downwards  as  far  at  least  as 
tiie  seventh,  it  is  evident  that  when  a  lower  rib  such  as  the 
fifth  is  elevated  so  as  to  occupy  or  to  approach  towards  the 
position  of  the  one  above  it,  the  chest  at  that  level  will  be- 
come wider  from  side  to  side,  in  proportion  as  the  fifth  arch 
is  wider  than  the  fourth.  Thus  the  elevation  of  the  rib  in- 
creases not  onl}'  the  antero-posterior  but  also  the  transverse 
diameter  of  the  c'.iest.  Further,  on  account  of  the  resist- 
ance of  the  sternum,  the  angles  between  the  ribs  and  their 
cartilages  are,  in  the  elevation  of  the  ribs,  somewhat  opened 
out,  and  thus  also  the  transverse  as  well  as  the  antero-pos- 
terior diameter  somewliat  increased.  In  several  ways,  then, 
the  elevation  of  the  ribs  enlarges  the  dimensions  of  the  chest. 

The  ribs  are  raised  l)y  the  contraction  of  certain  muscles. 
Of  these  tlie  external  intercostals  are  the  most  important. 
Even  in  the  case  of  two  isolated  ribs,  such  as  the  fifth  and 
sixth,  the  contraction  of  the  external  intercostal  muscle  of 
the  intervening  space  raises  the  two  ribs,  thus  bringing 
them  towards  the  position  in  which  the  fibres  of  tiie  mut?cle 
have  the  shortest  length,  viz.,  the  horizontal  one.  This 
elevating  action  is  further  favored  by  tlie  fact  that  the  first 
rib  is  less  movable  than  the  second,  and  so  affords  a  com- 
paratively fixed  base  for  the  action  of  the  muscles  between 
the  two,  the  second  in  turn  supporting  the  third,  and  so  on, 
while  the  scaleni  muscles  in  addition  serve  to  render  fixed, 
or  to  raise,  the  first  two  ribs.  So  that,  iu  normal  respira- 
tion, the  act  begins  probably  by  a  contraction  of  the  scaleni. 
The  first  two  ribs  being  thus  fixed,  the  contraction  of  the 
series  of  external  intercostal  muscles  acts  to  the  greatest 
advantage. 

While  the  elevating,  i.e.^  inspirator}^  action  of  the  external 
intercostals  is  admitted  by  all  autliors,  the  function  of  the 
internal  intercostals  has  been  much  disputed. 

^  On  Stethometry,  1876,  p.  96. 


MOVEMENTS    OF    INSPIRATION. 


431 


TTaller  may  be  regarded  as  the  leader  of  those  who  regard  the 
internal  intercostals  as  inspiratory,  while  Plamberger  was  the 
first  who  successfuly  advocated  the  perhajis  more  commonly 
adopted  view  that,  while  those  parts  of  tliem  which  lie  between 
the  sternal  cartilages  act  like  the  external  intercostals  as  eleva- 
tors, /.  e.,  as  inspiratory  in  function,  those  parts  which  lie  be- 
tween the  osseous  ribs  act  as  depressors,  i.e.,  as  expiratory  in 
function . 

In  the  well-known  model  invented  by  Bernoulli  and  adopted 
b}^  Hamberger,  consisting  of  two  rigid  bars,  representing  the 
ribs,  moving  vertically  by  means  of  their  articulations  with  an 
npright  representing  the  spine,  and  connected  at  their  free  ends 
b}'  a  piece  representing  the  sternum,  it  is  undoubtedl}^  true  that 


[Fig.  121. 
B 


a  and  b  represent  cross-bars,  articulating  on  the  vertical  bar  c;  x,  y,  and  ic,  z  are  two 
rubl)er  bands,  which  represent  respectively  the  external  and  internal  interco.stal 
muscles.  Diagram  A  represents  the  muscles  in  a  state  of  rest.  If,  now,  the  baud  x 
and  y  were  free  to  contract,  it  is  obvious  that,  in  order  to  attain  their  shortest  lengtli, 
it  would  assume  a  position  as  in  diagram  C.  If,  now,  the  baud  w  and  z  were  free 
to  movo,  the  converse  would  take  place  of  what  was  seen  when  .r  and  y  became 
shortened.     Thus,  in  diagram  B,  the  cross-bars  are  depressed. 

The  bands  x  and  y  represent  the  external  intercostal  muscles,  which,  by  contract- 
ing, elevate  the  ribs.  The  bands  w  and  z  represent  the  internal  intercostals,  whicii, 
by  contracting,  depress  the  ribs.] 


stretched  elastic  bands  attached  to  the  bars  in  such  a  way  as  to 
represent  respectively  the  external  and  internal  intercostals,  viz., 
sloping  in  the  one  case  downwards  and  forwards,  and  in  the  other 
downwards  and  backwards,  do,  on  being  left  free  to  contract, 
in  the  former  case  elevate  and  in  the  latter  depress  the  ribs 
(Fig.  1-21).  Such  a  model,  however,  does  not  fairly  represent 
the  natural  conditions  of  the  ribs,  which  are  not  straight  and 
rigid,  but  peculiarly  curved  and  of  varying  elasticity,  capable, 
moreover,  of  rotation  on  their  own  axis,  and  having  their  move- 
ments determined  by  the  characters  of  their  vertebral  articula- 


432      TISSUES    AND    MECHANISMS    OP    RESPIRATION. 


tions.  On  the  other  hand,  not  only  do  the  direction  and  attach- 
ments of  the  internal  intercostals  between  the  sternal  cartilai>es 
suggest  an  elevating  inspiratory  action,  but  the  absence  of  the 
exteinal  muscles  in  front  and  the  internal  behind  seems  to  point 
to  both  sets  of  muscles  acting  towards  the  same  end.  The  me- 
chanical conditions,  however,  are  in  the  case  of  these  muscles  so 
complex  that  a  deduction  of  their  actions  from  simple  mechanical 
principles,  or  from  the  direction  of  the  fibres,  must  be  exceedingly 
difficult  and  dangerous.  Newell-Martin  and  Hartwell'  have 
shown,  by  an  ingenious  experiment,  that  in  the  cat  and  the  dog 
the  internal  intercostals,  along  their  whole  length,  contract,  even 
in  the  early  stages  of  dyspnoea,  alternateh/  with  the  diaphragm, 
and  are  therefore  to  be  regarded  as  expiratory  in  function. 

Next  in  importance  to  the  external  intercostals  come  the 
levatores  costanim.  whicli,  tlioiigh  small  muscles,  are  able, 
from  the  nearness  of  their  costal  insertions  to  the  fulcrum, 
to  produce  consi(lerai)le  movement  of  the  sternal  ends  of 
the  ribs.  The  external  intercostals  and  the  levatores  cos- 
tarum,  with  the  scaleni,  may  fairly  be  said  to  be  the  elevators 
of  the  ribs,  i.e.,  the  cliief  muscles  of  costal  inspiration  in 
normal  breathing. 

Additional  space  in  the  transverse  diameter  is  afforded  prob- 
ably by  the  rotation  of  the  ribs  on  an  antero-posterior  axis  ;  but 
this  movement  is  quite  subsidiary  and  unimportant.  When  the 
chest  is  at  rest,  the  ribs  are  somewhat  inclined  with  their  lower 
borders  directed  inwards  as  well  as  downwards.  When  they  are 
drawn  up  by  the  action  of  the  intercostal  muscles,  their  lower 
borders  are  everted.  Thus  their  flat  sides  are  presented  to  the 
thoracic  cavity,  which  is  thereby  slightly  increased  in  width. 

Labored  Inspiration. — AVhen  respiration  becomes  labored 
other  muscles  are  brought  into  play.  The  scaleni  are  strongly 
contracted,  so  as  to  raise,  or  at  least  give  a  very  fixed  support 
to  the  first  and  second  ril>s.  In  the  same  way  the  terrains 
posticuii  superior,  which  descends  from  the  fixed  spine  in  the 
lower  cervical  and  ui)pcr  dorsal  regions  to  the  second,  third, 
fourth,  and  fifth  ribs,  by  its  contractions  raises  those  ribs. 
In  labored  breathing  a  function  of  the  lower  false  ribs,  not 
very  noticeable  in  easy  breathing,  c^mes  into  play.  They 
are  depressed,  retracted,  and  fixed,  thereby  giving  increased 
support  to  the  diaphragm,  and  directing  the  whole  energies 
of  that  muscle  to  the  vertical  enlaigement  of  the  chest.  In 
this   way  the  se.rratus  poiiticiis  wjerior^  which   passes  up- 


1  Journ.  Physiol.,  ii  (1879),  p.  24. 


EXPIRATION.  433 

vcRVi}  from  the  lumbar  ai>onenrosis  to  tlie  last  four  ribs,  by 
depressing  and  fixintr  those  ril)S  becomes  an  adjuvant  inspi- 
ratorv  muscle.  The  quadrolui^  lumbnrum  and  lower  portions 
of  the  ,<acro-lumb  ills  may  have  a  similar  function. 

All  these  muscles  may  come  into  action  even  in  breathing;, 
which,  deeper  than  usual,  can  hardly  perhaps  be  called 
labored.  When,  however,  tlie  need  for  2:reater  inspiratory 
efforts  becomes  urgent,  all  the  muscles  which  can,  from  any 
fixed  point,  act  in  enlarging  the  chest,  come  into  play.  Thus 
the  arms  and  shoulder  being  fixed,  the  ^erratus  magnus 
])assing  from  the  scapula  to  the  middle  of  the  first  eight  or 
nine  ribs,  the  pectoralia  minor  passing  from  the  coracoid  to 
tlie  front  parts  of  the  third,  fourth,  and  fifth  ribs,  the  pec- 
torolis  major  passing  from  the  humerus  to  tlie  costal  car- 
tilages, from  the  second  to  the  sixth,  and  that  portion  of 
the  Iatissimii-<  dor^^i  which  passes  from  the  humerus  to  the 
last  three  ribs,  all  serve  to  elevate  the  ribs  and  thus  to 
enlarge  the  chest.  The  sterno-mastoid  and  other  muscles 
I)assing  from  the  iieck  to  the  sternum  are  also  called  into 
action.  In  fact,  every  muscle  which  bv  its  contraction  can 
either  elevate  the  ribs  or  contribute  to  the  fixed  support  of 
muscles  which  do  elevate  the  ribs,  such  as  tiie  trapezius, 
levator  anguli  scapuh^  and  rhomboidei,  by  fixing  the  scapula, 
may,  in  the  inspiratory  efforts  which  accompany  dyspnoea, 
be  brought  into  play. 

Expiration. — In  normal  easy  breathing,  expiration  is  in 
the  main  a  simple  effect  of  elastic  reaction.  By  the  inspi- 
ratory effort  the  elastic  tissue  of  the  lungs  is  put  on  the 
stretch  ;  so  long  as  the  ins{)iratory  muscles  continue  con- 
tracting, the  tissue  rem.ains  stretched,  but  directly  those 
muscles  relax,  the  elasticity  of  the  lungs  comes  into  play 
and  drives  out  a  portion  of  the  air  contained  in  them. 
Similarly  the  elastic  sternum  and  costal  cartilages  are,  by 
the  elevation  of  the  ril>s,  put  on  the  stretch  ;  they  are  driven 
into  a  position  which  is  unnatural  to  them.  When  the  inter- 
costal and  other'  elevator  muscles  cease  to  contract,  the 
elasticity  of  the  sternum  and  costal  cartilages  causes  them 
to  return  to  their  previous  po^^ition,  thus  depressing  the  ribs, 
and  diminishing  the  dimensions  of  the  chest.  When  the 
diaphragm  descends,  in  pushing  down  the  al)dominal  viscera, 
it  puts  the  abdominal  walls  on  the  stretch  ;  and  hence,  when 
at  the  end  of  inspiration  the  diaphragm  relaxes,  the  ab- 
dominal walls  return  to  their  place,  and  by  pressing  on  the 


434      TISSUES    AND    MECHANISMS    OF    RESPIRATION. 

abdominal  viscera,  push  the  diaphragm  up  again  into  its 
position  of  rest.  Expiration  then  is,  in  the  main,  simple 
elastic  reaction  ;  hut  it  is  obvious  that  since  external  work 
has  been  eflected  V)y  the  respiratory  act,  viz.,  the  movement 
of  the  column  of  air,  the  reaction  of  expiration  must  fall 
short  of  the  action  of  inspiration  ;  there  must  be  some, 
though  it  may  be  a  very  slight,  additional  expenditure  of 
energy  to  bring  the  chest  completely  to  its  former  condition. 
This  is,  as  we  have  seen,  supposed  by  many  to  be  afforded 
by  the  internal  intercostals  acting  as  depressors  of  the  ril)s. 
If  these  do  not  act  in  this  way,  we  may  sui)pose  that  the 
elastic  return  of  the  abdominal  walls  is  accompanied  and 
ae^sisted  by  a  contraction  of  the  abdominal  muscles.  The 
triangularis  sterui,  the  effect  of  whose  contraction  is  to  pull 
down  the  costal  cartilages,  may  also  be  regarded  as  an  ex[)i- 
ratory  muj^cle. 

Wiien  expiration  becomes  labored,  the  abdominal  muscles 
become  important  expiratory  agents.  B3'  pressing  on  the 
contents  of  the  abdomen,  they  thrust  them  and  the  dia- 
phragm u[)  into  the  cliest,  the  vertical  diameter  of  which  is 
thereby  lessened,  and  by  pulling  down  the  sternum  and  the 
middle  and  lower  ribs  they  lessen  also  the  cavity  of  the  chest 
in  its  anteroposterior  and  transveise  diameters.  They  are, 
in  fact,  the  chief  expiratory  muscles,  though  they  are  doubt- 
less assisted  by  the  serratus  posticus  inferior  and  portions 
of  the  sacro-lumbalis,  since  when  the  diaphragm  is  not  con- 
tracting, the  dei)ression  of  the  lower  ribs  which  the  contrac- 
tion of  these  muscles  causes,  serves  only  to  narrow  the 
chest.  As  expiration  becomes  more  and  more  forced,  every 
muscle  in  the  body  which  can  either  by  contracting  depress 
the  ribs,  or  press  on  the  abdominal  viscera,  or  afford  fixed 
support  to  muscles  having  those  actions,  is  called  into  play. 

Facial  and  Laryngeal  Respiration.— The  thoracic  respiratory 
movements  are  accompanied  by  associated  respiratory  movements 
of  other  parts  of  the  body,  more  particularly  of  the  face  and  of 
the  glottis. 

In  normal  healthy  respiration  the  current  of  air  which  passes 
in  and  out  of  the  lungs,  travels,  not  through  the  mouth,  but 
through  the  nose,  viz.,  chietiy  through  the  lower  nasal  meatus. 
The  ingoing  air,  by  exposure  to  the  vascular  mucous  membrane 
of  the  narrow  and  winding  nasal  passages,  is  more  eflficiently 
warmed  than  it  would  be  if  it  passed  through  the  mouth  ;  and 
at  the  same  time  the  mouth  is  thereby  protected  from  the  desic- 
cating effect  of  the  continual  inroad  of  comparatively  dry  air. 


CHANGES    OF    THE    AIR.  435 


During  each  inspiratory  effort  the  nostrils  are  expanded,  proba- 
bly b}'  the  action  of  the  dilatores  naris,  and  thus  the  entrance  of 
air  facihtated.  The  return  to  their  previous  condition  during 
expiration  is  effected  by  the  elasticity  of  the  nasal  cartilages,  as- 
sisted, perhaps,  by  the  compressores  naris.  This  movement  of 
the  nostrils,  perceptible  in  many  people,  even  during  tranquil 
breathing,  becomes  very  obvious  in  labored  respiration. 

Whenlhe  mouth  is  closed,  the  soft  palate,  which  is  held  some- 
what tense,  is  swayed  by  the  respiratory  current,  but  entirely  in 
a  passive  manner,  and  it  is  not  until  the  larynx  is  reached  by  the 
ingoing  air  that  any  active  movements  are  met  with.  "When  the 
larynx  is  examined  witli  the  laryngoscope,  it  is  frequently  seen 
that,  while  during  inspiration  the  glottis  is  widel}-  open,  with 
each  expiration  the  arytenoid  cartilages  approach  each  other  so 
as  to  narrow  the  glottis,  the  cartilages  of  Santorini  projecting 
inwards  at  the  same  time.  Thus,  synchronous  with  the  respi- 
ratory expansion  and  contraction  of  the  chest,  and  the  respiratory 
elevation  and  depression  of  the  ahe  nasi,  there  is  a  rhythmic 
widening  and  narrowing  of  the  glottis.  Like  the  movements  of 
the  nostril,  this  respiratory  action  of  the  glottis  is  much  more 
evident  in  labored  than  in  tranquil  breathing.  Indeed,  in  the 
latter  case  it  is  frequently  absent.  The  manner  in  which  this 
rhythmic  opening  and  narrowing  is  effected  Avill  be  described 
when  we  come  to  study  the  production  of  the  voice.  AVhether 
there  exists  a  rhythmic  contraction  and  expansion  of  the  trachea 
and  bronchial  passages  effected  by  means  of  the  plain  muscular 
tissue  of  those  organs  and  synchronous  with  the  respiratory 
movements  of  the  chest,  is  uncertain.^ 


Sec.  2.    Changes  of  the  Air  in  Respiration. 

During  its  sta}^  in  the  lungs,  or  rather  during  its  stay  in 
the  bronchial  passages,  the  tidal  air  (by  means  of  diffusion 
chiefly)  effects  exchanges  with  the  stationary  air  ;  incon- 
sequence the  expired  air  difters  from  inspired  air  in  several 
important  particulars. 

1.  The  temperature  of  expired  air  is  variable,  but  under 
ordinary  circumstances  is  higher  than  that  of  the  inspired 
air.  At  an  average  temperature  of  the  atmospliere,  for 
instance  at  about  20^  C,  the  temi)erature  of  expired  air  is, 
in  the  mouth  33.9^,  in  the  nose  35.3^.  When  the  external 
temperature  is  low,  that  of  the  expired  air  sinks  somewhat, 
l>ut  not  to  any  great  extent,  thus  at  —6.3°  C.  it  is  29.8°  C. 
When  the  external  temperature  is  high,  the  expired  air  may 

1  Cf.  Horvath,  Pfluger's  Archiv,  xiii  (1876),  p.  508. 


436       TISSUES    AND    MECHANISMS    OP    RESPIRATION. 

become  cooler  than  tlie  inspired,  thus  at  41.9^  it  was  found 
by  Yalentiu  to  be  88.1^.  The  exact  temperature  in  fact 
depends  on  tlie  relative  temperatures  of  the  blood  and  in- 
spired air,  and  on  the  depth  and  rate  of  breathing. 

2.  Tlie  expired  air  is  loaded  with  aqueous  vapor.  The 
point  of  saturation  of  any  gas,  that  is,  the  utmost  quantity 
of  water  which  any  given  volume  of  gas  can  take  up  as 
aqueous  vapor,  varies  with  the  temperature,  being  higher 
with  the  higher  temperature.  For  its  own  temperature  ex- 
pired air  is  according  to  most  observers  saturated  with 
aqueous  vapor.  According  to  Edward  Smith  it  is,  when 
fasting,  only  half  saturated. 

3.  When  the  total  quantity  of  tidal  air\  given  out  at  any 
expiration  is  compared  with  that  taken  in  at  the  correspond- 
ing inspiration,  it  is  found  that,  both  being  dried  and  meas- 
ured at  tlie  same  pressure,  the  expired  air  is  less  in  volume 
than  the  inspired  air,  the  difference  amounting  to  about 
j\yth  or  g'^th  of  the  volume  of  the  latter.  Hence,  when  an 
animal  is  made  to  breathe  in  a  confined  space,  the  atmos- 
phere is  absolutely  diminished,  as  was  observed  so  long  ago 
as  lf)74  by  MaN^ow.  The  approximate  equivalence  in  vol- 
ume between  inspired  and  expired  air  arises  from  the  fact 
that  the  volume  of  any  given  quantity  of  carbonic  acid  is 
equal  to  the  volume  of  the  oxygen  consumed  to  produce 
it;  the  slight  falling  sliort  of  the  expired  air  is  due  to  the 
circumstance  that  all  the  ox\^gen  inspired  does  not  reappear 
in  the  carbonic  acid  expired,  some  having  formed  other 
combinations. 

4.  The  expired  air  contains  about  4  or  5  per  cent,  less 
oxygen,  and  about  4  per  cent,  more  carbonic  acid  than  the 
inspired  air,  the  quantity  of  nitrogen  suffering  but  little 
change.     Thus 

Oxygen.       Nitrofren.      Carbonic  acid. 

Inspired  air  contains      20.81        79.15  .04 

Expired     "         "  16.033      79.557  4.380 

The  quantity  of  nitrogen  in  the  expired  air  is  sometimes 
found  to  be  greater,  as  in  the  table  above,  but  sometimes 
less,  than  tliat  of  the  inspired  air. 

W.  Edwards  thought  that  nitrogen  was  absorbed  in  cold,  and 
thrown  out  in  warm  weather.     W.  Mliller  observed  that  in  an 


CHANGES    OF    THE    AIR.  437 


atmosphere  consisting  entirely  of  nitrogen,  an  absorption,  and  in 
one  devoid  of  nitrogen  or  containing  little  nitrogen,  an  escape  of 
nitrogen  took  place  ;  a  result  which  appears  probable. 

In  a  single  breath  the  air  is  richer  in  carbonic  acid  (and  poorer 
in  oxygen)  at  the  end  than  at  the  beginning.  Hence  the  longer 
the  breath  is  held,  the  greater  the  pause  between  inspiration  and 
expiration,  the  higher  the  percentage  of  carbonic  acid  in  the  ex- 
pired air.  Thus  Becher  found  that  by  increasing  the  pause  from 
0  to  100  seconds,  the  percentage  was  raised  from  3.6  to  7.5.  The 
•rate  of  increase  however  continually  diminishes,  being  greatest 
at  the  beginning  of  the  period. 

When  the  rate  of  breathing  remains  the  same,  by  increasing 
the  depth  of  the  breathing  the  percentage  of  carbonic  acid  in  each 
breath  is  lowered,  but  the  total  quantity  of  carbonic  acid  expired 
in  a  given  time  is  increased.  Similarl}-,  when  the  depth  of  breath 
remains  the  same,  by  quickening  the  rate  the  percentage  of  car- 
bonic acid  in  each  breath  is  lowered,  but  the  quantity  expired  in 
a  given  time  is  increased. 

The  variations  in  both  the  consumption  of  oxygen  and  produc- 
tion of  carbonic  acid,  due  to  variations  in  pressure,  will  be  con- 
sidered in  connection  with  the  respiratory  changes  of  blood. 

Taking,  as  we  have  done,  at  500  cc.  the  amount  of  tidal 
air  passing  in  and  out  of  the  chest  of  an  average  man,  such 
a  person  will  expire  about  22  cc.  of  carbonic  acid  at  each 
breath  ;  this,  reckoning  the  rate  of  breathing  at  17  a  minute, 
would  give  over  500  liters  of  carbonic  acid  for  the  day's 
production.  By  actual  experiment,  however,  Pettenkofer 
and  Yoit,  of  whose  researches  we  shall  have  to  speak  here- 
after, determined  the  total  daily  excretion  of  carbonic  acid 
in  an  average  man  to  be  800  grams,  i.  e..  rather  more  than 
400  liters  (406),  containing  218.1  grams  carbon,  and  581.9 
grams  oxygen,  the  oxygen  actually  consumed  at  the  same 
time  being  about  700  grams.  This  amount  represents  the 
gases  given  out  and  taken  in,  not  b}^  the  lungs  only,  but  by 
the  whole  body  ;  but  tlie  amount  of  carbonic  acid  given  out 
b}''  the  skin  is,  as  we  shall  see,  very  slight  (10  grams  or  even 
less),  so  that  800  grams  may  be  taken  as  the  average  produc- 
tion of  carbonic  acid  by  an  average  man.  The  quantity 
however,  both  of  Oxygen  consumed  and  of  carbonic  acid 
given  out,  is  subject  to  very  wide  variations  ;  thus  in  Petten- 
kofer and  Yoit's  observations,  the  daily  quantity  of  carbonic 
acid  varied  from  686  to  1285  grams,  and  that  of  the  oxygen 
from  594  to  1072  grams.  These  variations  and  their  causes 
will  be  discussed  when  we  come  to  deal  with  the  problems 
of  nutrition. 

37 


438       TISSUE?    AND    MECHAKISMS    OF    RESPIRATION. 


The  quantity  of  carbonic  acid  produced  and  oxygen  consumed 
increases  in  man  from  birth  up  to  about  thirty  years  and  after 
that  diminishes.  In  the  female  the  quantity,  always  less  than 
that  of  man,  increases  up  to  puberty,  remains  during  the  men- 
strual life  at  a  standstill,  and  after  the  climacteric  declines. 

5.  Besides  carbonic  acid,  expired  air  contains  various 
impurities,  many  of  an  unknown  nature,  and  all  in  small 
amounts.  Ammonia  has  been  detected  in  expired  air,  even, 
in  that  taken  directly  from  tiie  trachea,  in  which  case  its 
presence  could  not  be  due  to  decomposing  food  lingering  in 
the  mouth.  According  to  Lossen,  the  amount  given  olf  in 
ordinary  respiration  in  24  hours  is  .014  gram.  When  the 
expired  air  is  condensed  by  being  conveyed  into  a  cooled 
receiver,  the  aqueous  product  is  found  to  contain  organic 
matter,  and  rapidly  to  putref}^  The  organic  substances 
thus  shown  to  he  present  in  the  expired  air  are  the  cause  in 
part  of  the  odor  of  breath.  It  is  probable  that  many  of 
them  are  of  a  poisonous  nature  ;  for  an  atmosphere  contain- 
ing simply  ]  per  cent,  of  carbonic  acid  (with  a  correspond- 
ing diminution  of  oxygen)  has  very  little  etfect  on  the 
animal  economy,  whereas  an  atmosphere  in  which  the  car- 
bonic acid  has  been  raised  to  1  per  cent,  by  breathing,  is 
highly  injurious.  In  fact,  air  rendered  so  far  impure  by 
breathing  tliat  the  carbonic  acid  amounts  to  .08  per  cent,  is 
distinctly  unwholesome,  not  so  much  on  account  of  the 
carbonic  acid  as  of  the  accompanying  impurities.  Since 
these  impurities  are  of  unknown  nature  and  cannot  be  esti- 
mated, the  easily  determined  carbonic  acid  is  usually  taken 
as  the  measure  of  their  presence.  We  have  seen  that  the 
average  man  loads,  at  each  breath,  500  cc.  of  air  with  car- 
bonic acid  to  tlie  extent  of  4  percent.  He  will  accordingly 
at  each  breath  load  2  liters  to  the  extent  of  1  per  cent. ;  and 
in  one  hour,  if  he  breathe  17  times  a  minute,  will  load 
rather  more  than  2000  liters  to  the  same  extent.  At  the 
very  least  then  a  man  ought  to  be  supplied  with  this  quan- 
tity of  air  hourly  ;  and  if  the  air  is  to  be  kept  fairly  whole- 
some, that  is  with  the  carbonic  acid  reduced  to  .1  per  cent., 
he  should  have  ten  times  as  much. 

Sec.  3.    The  Respiratory  Changes  in  the  Blood. 

While  the  air,  in  passing  in  and  out  of  the  lungs,  is  thus 
robbed  of  a  portion  of  its  ox3'gen,  and  loaded  with  a  cer- 
tain quantity  of  carbonic  acid,  the  blood,  as  it  streams  along 


CHANGES    IN    THE    BLOOD.  439 

the  pulmonary  capillaries,  undergoes  important  correlative 
changes.  As  it  leaves  the  right  ventricle  it  is  venous  blood 
of  a  dark-purple  or  maroon  color;  when  it  falls  into  the 
left  auricle,  it  is  arterial  blocni  of  a  bright-scarlet  hue.  In 
passing  through  the  capillaries  of  the  body,  from  the  left  to 
the  right  side  of  the  heart,  it  is  again  changed  from  the 
arterial  to  the  venous  condition.  We  have  to  inquire,  What 
are  the  essential  differences  between  arterial  and  venous 
blood  :  b}'  what  means  is  the  venous  blood  changed  into 
arterial  in  the  lungs,  and  the  arterial  into  venous  in  the  rest 
of  the  body;  and  what  relations  do  these  changes  in  the 
blood  bear  to  the  changes  in  the  air  which  we  have  already 
studied  ? 

The  facts,  that  venous  blood  at  once  becomes  arterial  on 
being  exposed  to  or  shaken  up  with  air  or  oxygen,  and  that 
arterial  blood  becomes  venous  when  kept  for  some  little 
time  in  a  closed  vessel,  or  when  subuiitted  to  a  current  of 
some  inditlerent  gas,  such  as  nitrogen  or  hydrogen,  prepare 
us  for  the  statement  that  the  fundamental  diflerence  be- 
tween venous  and  arterial  blood  is  in  the  relative  proportion 
of  the  oxygen  and  carbonic  acid  gases  contained  in  each. 
From  both  a  certain  quantity  of  gas  can  be  extracted  b}' 
means  which  do  not  otherwise  materially  alter  the  constitu- 
tion of  the  blood  ;  and  this  gas,  when  obtained  from  arterial 
blood,  is  found  to  contain  more  oxygen  and  less  carbonic 
acid  than  that  obtained  from  venous  blood.  This  is  the  real 
differential  character  of  the  two  bloods  ;  all  other  differ- 
ences are  either,  as  we  shall  see  to  be  the  case  with  the  color, 
dependent  on  this,  or  are  unimportant  and  fluctuating. 

If  the  quantit}'  of  gas  which  can  be  extracted  b}'  the  mer- 
curial air-pump  from  100  vols,  of  blood  be  measured  at  0° 
C,  and  a  pressure  of  760  mm.,  it  is  found  to  amount,  in 
round  numbers,  to  60  vols.^ 

The  vacuum  produced  by  the  ordinary  mechanical  air-pump  is 
insufficient  to  extract  all  the  gas  from  blood.  Hence  it  becomes 
necessary  to  use  either  a  large  Torricellian  vacuum  or  a  Sprengel's 
pump.  In  the  former  (Fig.  122)  case  tw^o  large  globes  of  glass, 
one  fixed  and  the  other  movable,  are  connected  by  a  flexible 
tube  ;  the  fixed  globe  is  made  to  communicate  by  means  of  air- 
tight stopcocks  alternately  with  a  receiver  containing  the  blood, 
and  with  a  receiver  to  collect  the  gas.  When  the  movable  globe 
filled  with  mercury  is  raised  above  the  fixed  one,  the  mercury 

^  Or,  at  a  pressure  of  1  meter,  about  50  vols. 


440       TISSUES    AND    MECHANISMS    OF    RESPIRATION. 


from  the  former  runs  into  and  completely  fills  the  latter,  the  air 
previously  present  being  driven  out.     After  adjusting  the  cocks, 


Diagrammatic  Iliustra  ion  of  Ludwig's  Mercurial  Gas  Pump, 

A  and  B  are  two  glass  globes,  connected  by  strong  india-rubber  tubes,  a  and  b, 
with  two  similar  glass  globes.  A'  and  B'.  A  is  further  connected  by  means  of  the 
stopcock  c  with  the  rt-ceiver  C  containing  the  blood  (or  other  fluid)  to  be  analyzed, 
and  Bby  means  of  the  stopcock  d  and  the  tube  e  with  the  receiver  D  for  receiving 
the  gases.  A  and  B  are  also  connected  with  each  other  by  means  of  the  stopcocks 
/and  g,  the  latter  being  so  arranged  that  B  also  communicates  with  B'  by  the  pas- 


OXYGEN    IN    THE    BLOOD.  441 


?age  </'.  A'  ard  B'  being  full  of  mercury  and  the  cocks  fc,  /,  g,  and  d  being  open,  but 
c  and  g'  closed,  on  raiding  A'  by  means  of  the  pulley*  p  the  mercury  of  A'  fills  A, 
driving  out  the  air  contained  in  it,  into  B,  and  so  out  through  e.  Winn  the  mercury 
has  risen  above  g,f  is  closed,  and  g'  being  opened,  B'  is  in  turn  raised  till  B  is  com- 
pletely filled  with  mercury,  all  the  air  previouslj'  in  it  being  driven  out  through  e. 
Upon  closing  tf,  and  lowering  B',  the  whole  of  the  tnercury  in  B  falls  in  B' and  a 
vacuum  consequently  is  established  iu  B.  On  closing^',  but  opening  g,  /,  and  k  and 
lowering  A',  a  vacuuui  is  similarly  established  in  A  and  in  the  junction  between  A 
and  B.  If  the  cock  c  be  now  opened  the  gases  of  the  blood  in  C  escape  into  the 
vacuum  of  A  and  B.  By  raising  A',  after  the  cl  isure  of  e,  and  opening  of  cf,  the  gases 
so  set  free  are  driven  from  A  into  B,  and  by  the  raising  of  B'  from  B,  through  e  into 
the  receiver  I>,  standing  over  mercury. 

the  movable  globe  is  then  depressed  thirt3'  inches  below  the  fixed 
one,  iu  which  the  consequent  fall  of  the  mercur3'  produces  an 
ahnost  complete  vacuum.  By  turning  the  proper  cock  this 
vacuum  is  put  into  connection  with  the  receiver  containing  the 
blood,  which  thereupon  becomes  proportionatel}'  exhausted.  By 
again  adjusting  the  cocks,  and  once  more  elevating  the  movable 
globe,  the  gas  thus  extracted  is  driven  out  of  the  fixed  globe  into 
a  receiver.  The  vacuum  is  then  once  more  astablished,  and 
the  operation  repeated  as  long  as  gas  continues  to  be  given  ofl:' 
from  the  blood.  This  form  of  pump,  introduced  by  Ludwig,  or 
a  modification  of  it,  with  dr3ing  apparatus,  emplo^'ed  bv  Pfluger, 
is  the  one  which  has  been  hitherto  most  extensiveh'  used  ;  but  a 
Sprengel's  pump  is  preferred  b}-  some. 

The  average  composition  of  this  gas  is  in  the  two  kinds 
of  blood  as  follows  : 

From  100  vols.  may  be  obtained 

Of  oxygen.  Of  carbonic  acid.     Of  nitrogen. 

Of  arterial  blood,  20  (16)"  vols.  39  (30)  vols.     1  to  2  vols. 

Of  venous  blood,     8  to  12  (0  to  10)  vols.  46  (35)  vols.     1  to  2  vols. 
All  measured  at  760  mm.  and  0-  C.^ 

It  will  be  convenient  to  consider  the  relations  of  each  of 
these  gases  separatelv. 

The  Relation^'  of  Oxygen  in  the  Blood. 

When  a  liquid  such  as  water  is  exposed  to  an  atmosphere 
containing  a  gas  such  as  ox3'gen,  some  of  the  oxj^gen  will 
be  dissolved  in  the  water,  that  is  to  say,  will  be  absorbed 

^  The  numbers  in  parentheses  represent  in  round  numbers  the  same 
amounts  measured,  according  to  the  present  German  method,  at  a  pres- 
sure of  1  meter. 


442      TISSUES    ANL»    MECHANISMS    OF    RESPIRATION. 

from  the  atmosphere.  The  qnantit}^  which  is  so  absorbed 
will  depend  on  the  quantity  of  oxygen  whieii  is  in  the 
atinospliere  above ;  that  is  to  say,  on  tlie  pressure  of  the 
oxygen  ;  the  greater  the  pressure  of  the  oxygen  the  larger 
the  amount  which  will  be  absor'Ded.  If,  on  the  other  hand, 
water  already  containing  a  good  deal  of  oxygen  dissolved 
in  it,  be  exposed  to  an  atmosphere  containing  little  or  no 
oxygen,  the  oxygen  will  escape  from  the  water  into  the 
atmosphere.  Tlse  oxygen  in  fact  which  is  dissolved  in  the 
water  is  in  a  state  of  tension,  the  degree  of  tension  depend- 
ing on  the  quantity  dissolved  ;  and  when  water  containing 
oxygen  dissolved  in  it  is  exposed  to  any  atmosphere,  the 
point  whether  the  oxygen  escapes  from  the  water  into  the 
atmosphere,  or  passes  from  the  atmos[)liere  into  the  water, 
depends  on  whether  the  tension  of  the  oxygen  in  the  water 
is  greater  or  less  than  the  pressure  of  the  oxygen  in  the 
atmosphere.  Hence,  when  water  is  exposed  to  oxygen,  the 
oxygen  either  escai)es  or  is  al)sorbed  until  equilibrium  is 
eslahlished  between  the  pressure  of  the  oxygen  in  the 
atmosphere  above  and  the  tension  of  the  ox\  gen  in  the 
water  below.  This  residt  is,  as  far  as  mere  absorption  and 
escape  are  concerned,  quite  independent  of  what  other 
gases  are  present  in  the  water  or  in  the  atmosphere.  Sup- 
pose a  half  liter  of  water  were  lying  at  the  bottom  of  a  two- 
liter  flask,  and  that  the  atmosphere  in  the  flask  above  the 
water  was  one-third  oxygen  ;  it  would  make  no  ditterence,  as 
far  as  the  absorption  of  oxygen  by  the  water  was  concerned, 
wiiether  the  remaining  two  thirds  of  the  atmosphere  was  car- 
bonic acid,  or  nitrogen,  or  hydrogen,  or  whether  the  space 
above  the  water  was  a  vacuum  filled  to  one-third  with  pure 
oxygen.  Hence  it  is  said  that  the  absorption  of  any  gas 
depends  on  the  pai-tial  presaiwe  of  that  gas  in  the  atmos- 
phere to  which  the  liquicl  is  exposed.  This  is  true  not  only 
of  oxygen  and  water,  but  of  all  gases  and  liquids  which  do 
not  enter  into  chemical  combination  with  each  other.  Dif- 
ferent liquids  will  of  course  absorb  different  gases  with  differ- 
ing readiness, but  wiili  the  same  gas  and  the  same  liquid  the 
amount  absorbed  will  depend  directly  on  the  i)artial  pressure 
of  the  gas.  U  should  be  added  that  the  piocess  is  much 
influenced  by  temperature.  Hence,  to  state  the  matter 
generally,  the  absorption  of  any  gas  by  any  liquid  will  de- 
pend on  the  nature  of  the  gas,  the  nature  of  the  liquid,  the 
pressure  of  the  gas,  and  the  temperature  at  which  both 
stand. 


HyEMOGLOBIN.  443 

Now  it  might  be  supposed,  and  indeed  was  once  sup- 
posed, that  the  oxygen  in  the  blood  was  simply  dissolved 
by  the  blood.  If  this  were  so,  then  the  amount  of  oxygen 
present  in  an}-  given  quantity  of  blood  exposed  to  any 
given  atmosphere,  ought  to  rise  and  fall  steadily  and  regu- 
larl}'  as  the  partial  pressure  of  oxygen  in  that  atmosphere  is 
increased  or  diminished.  But  this  is  found  not  to  be  the 
case.  If  we  expose  blood  containing  little  or  no  oxygen  to 
a  succession  of  atmospheres  containing  increasing  quantities 
of  oxygen,  we  find  that  at  first  there  is  a  very  rapid  absorp- 
tion of  the  available  ox3'gen,  and  then  this  somewhat  sud- 
denly ceases  or  becomes  very  small ;  and  if,  on  the  other 
hand,  we  submit  arterial  blood  to  successively  diminishing 
pressures,  we  find  that  for  a  long  time  very  little  is  given 
off,  and  then  suddenly  the  escape  becomes  ver}^  rapid.  The 
absorption  of  oxygen  by  blood  does  not  follow  the  general 
law  of  absorption  according  to  pressure.  The  phenomena, 
on  the  other  hand,  suggest  the  idea  that  the  oxygen  in  the 
blood  is  in  some  particular  combination  with  a  substance  or 
some  substances  present  in  the  blood,  the  combination  being 
of  such  a  kind  that  dissociation  readily  occurs  at  certain 
pressures  and  certain  temperatures.  What  is  that  sub- 
stance or  w^hat  are  those  substances? 

If  serum,  free  from  red  corpuscles,  be  used  in  such  ab- 
sorption experiments,  it  is  found  that  as  compared  with  the 
entire  blood,  very  little  oxygen  is  absorbed,  about  as  much 
as  would  be  absorbed  by  the  same  quantity  of  water  ;  but 
such  as  is  absorbed  does  follow  the  law  of  pressures.  In 
natural  arterial  blood  the  quantity  of  oxygen  which  can  be 
obtained  from  serum  is  exceedingly  small ;  it  does  not 
amount  to  half  a  volume  in  one  hundred  volumes  of  the  en- 
tire blood  to  which  the  serum  belonged.  It  is  evident  that 
the  oxygen  which  is  present  in  blood  is  in  some  way  or 
other  pecnliarly  connected  with  the  red  corpuscles.  Xow 
the  distinguishing  feature  of  the  red  corpuscles  is  the  pres- 
ence of  h^emogloltin.  We  have  already  seen  (p.  49 j  that 
this  constitutes  90- per  cent,  of  the  dried  red  corpuscles. 
There  can  be  a  priori  little  doubt  that  this  must  be  the 
substance  with  which  the  oxygen  is  associated  ;  and  to  the 
properties  of  this  body  we  must,  therefore,  direct  our  atten- 
tion. 

Hsemoglobin  ;  its  Propei^ties  and  Derivatives. 

When  separated  from  the  other  constituents  of  the  serum, 
haemoglobin  appears  as   a  substance,  either  amorphous  or 


444      TISSUES    AND    MECHANISMS    OF    RESPIRATION. 


HiEMOGLOBIN.  445 


The  first  spectrum  of  oxyhceinoglobin  is  that  of  an  exceedingly  dilute  solution. 
That  of  a  solution  intfiinediate  between  the  first  and  second  spectra  would  resemble 
in  the  intensity  of  its  absorption-bands  the  spectrum  given  as  that  of  carbonic  oxide 
haemoglobin. 

ciystalline,   readily  soluble   in   water  (especialh'   in    warm 
water)  and  in  serum. 

Since  it  is  soluble  in  serum,  and  since  tbe  identity  of  the  crys- 
tals observed  occasionally  within  the  corpuscles  with  those  ob- 
tained ill  other  ways  shows  that  the  haemoglobin,  as  it  exists  ia 
the  corpuscle,  is  the  same  thing  as  that  which  is  artificially  pre- 
pared from  blood,  it  is  evident  that  some  peculiar  relationship 
between  the  stroma  and  the  haemoglobin  must,  in  natural  blood, 
keep  the  latter  from  being  dissolved  by  the  serum.  Hence,  in 
preparing  htemoglobin,  it  is  necessary  first  of  all  to  break  up  the 
corpuscles.  This  may  be  done  by  the  addition  of  chloroform  or 
of  bile-salts,  or  by  repeatedly  freezing  and  thawing.  It  is  also 
of  advantage  previously  to  remove  the  alkaline  serum,  so  as  to 
operate  only  on  the  red  corpuscles.  The  corpuscles  being  thus 
broken  up,  an  aqueous  solution  of  hcemoglol»in  is  the  result.  The 
alkalinity  of  the  solution,  when  present,  being  reduced  by  the 
cautious  addition  of  dilute  acetic  acid,  and  the  solvent  power  of 
the  aqueous  medium  being  diminished  by  the  addition  of  one- 
fourth  its  bulk  of  alcohol,  the  mixture,  set  aside  in  a  tempera- 
ture of  0-  C.  still  further  to  reduce  the  solubility  of  the  haemo- 
globin, readily  crystallizes,  Avhen  the  blood  used  is  that  of  the 
dog,  cat,  horse,  rat,  guinea-pig,  etc.  The  crystals  may  be  sepa- 
rated by  filtration,  r^dissolved  in  water  and  recrystallized. 

Haemoglobin  from  the  blood  of  the  rat,  guinea-pig,  squir- 
rel, hedge-hog.  horse,  cat,  dog,  goose,  and  some  other  ani- 
mals, crystallizes  readily,  the  crystals  being  generally 
slender  four-sided  prisms,  belonging  to  the  rhoml)ic  system, 
and  often  appearing  quite  acicular.  The  crystals  from  the 
blood  of  the  guinea-pig  are  octahedral,  but  also  belong  to 
the  rhombic  system  ;  those  of  the  squirrel  are  six-sided 
plates.  (^Figs.  124,  125,  and  126.)  The  blood  of  the  ox, 
sheep,  ral»bit,  pig,  and  man,  crystallizes  with  ditlicultj'. 
Why  these  differences  exist  is  not  known  ;  but  the  compo- 
sition, and  the  anlount  of  water  of  crystallization,  A^ary 
somewhat  in  the  crystals  obtained  from  different  animals. 
In  tbe  dog,  the  percentage  composition  of  the  crystals  is, 
according  to  Hoppe-Seyler,'  C  53  85,  H  7.82,  N*^  16.17,  O 
21.84,  S  0.39,  Fe  .43,  with  3  to  4  per  cent,  of  water  of.  cry s- 

^  Untersiich.,  iii  (1868),  p.  370. 
38 


446      TISSUES    AND    MECHANISMS    OF    RESPIRATION. 

tallization.  It  will  thus  be  seen  that  hnemoo^lohin  contains 
iron,  in  addition  to  the  other  elements  iisuall}'  present  in 
proteid  substances. 

[Fig.  124. 


<-Jl^  I       <^-A 


Tetrahfdral,  liuiii  Bluod  of  the  Pig.] 

The  crystals,  when  seen  under  the  microscope,  have  the 
same  bri"fht-scarlet  color  as  arterial  blood  has  to  the  naked 


[Fig.  125. 


Hexagonal  Crystals,  from  Blood  of  Scjuiriel.    On  ihese  six-!-ided  plates,  prismatic 
ciystals,  grouped  in  a  stellate  manner,  not  uufrequently  occur. — After  Funke.] 

eye;  when  seen   in   a  mass   they  naturally  appear   darker. 
An  aqueous  solution  of  hiemoglobin,  obtained  by  dissolving 


HAEMOGLOBIN.  447 

purified  crystals  in  distilled  water,  has  also  the  same  bright 
arterial  color.  A  tolerably  dilute  solution  placed  before  the 
spectroscope  is  found  to  alisorb  certain  rays  of  ligiit  in  a 
peculiar  and  characteristic  manner.  A  portion  of  the  red 
end  of  the  spectrum  is  absorbed,  as  is  also  a  much  larger 
portion  of  the  blue  end  ;  but  what  is  most  strikinii;  is  the 
presence  of  two  stronojly  marked  absorption  bands,  lying 
between  the  solar  lines  D  and  E.  (See  Fig.  123.)  Of  these 
the  one  «,  towards  tlie  red  side,  is  the  thinnest  but  the  most 
intense,  and  in  extremely  dilute  solutions  is  the  only  one 

Fig.  126. 


■"^^^LV. 


Prismatic,  from  Human  Bluad.] 

visible;  its  middle  lies  at  some  little  distance  to  the  blue 
side  of  D.  The  other,  /5,  much  broader,  lies  a  little  to  the 
red  side  of  E,  its  blue-ward  edge,  even  in  moderately  dilute 
solutions,  coming  close  up  to  that  line.  Each  band  is  thickest 
in  the  middle,  and  gradunlly  thins  away  at  the  edges.  These 
two  absorption  bands  are  extremely  characteristic  of  a  so- 
lution of  h{i3moglobin.  Even  in  very  dilute  solutions  both 
l)ands  are  visible  (they  may  be  seen  in  a  thickness  of  1  cm. 
in  a  solution  containing  1  gram  of  haemoglobin  in  10  liters 
of  water),  and  that  when  scarcely  any  of  the  extreme  red 
end,  and  very  little  of  the  blue  end,  is  cut  off.  They  then 
appear  not  only  faint  but  narrow.  As  the  strength  of  the 
solution  is  increased,  the  bands  broaden,  and  become  more 
intense ;  at  the  same  time  both  the  red  end,  and  still  more 


448       TISSUES    AND    MECHANISMS    OF    RESPIRATION. 

the  blue  end,  of  tlie  whole  spectrum,  are  encroaclied  upon. 
This  may  ijo  on  until  the  two  absorption  liands  l)ecome  fused 
togetiier  into  one  broad  band.  The  onl^-  rays  of  W^j^ht  which 
then  pass  through  the  hienioglobin  solution  are  those  in  tlie 
green  between  tlie  united  i)ands  and  the  general  absorption 
at  the  blue  end,  and  those  in  the  red  between  the  band  and 
the  general  absorption  at  the  red  end.  (See  Fig.  123.)  If 
tlie  solution  be  still  further  increased  in  strength,  the  interval 
on  the  blue  side  of  the  band  becomes  absorbed  also,  so  that 
the  only  rays  which  pass  through  are  the  red  rays  lying  to 
the  red  side  of  D  ;  these  are  the  last  to  disappear,  and  hence- 
the  natural  red  color  of  the  solution  as  seen  b3'  transmitted 
light.  Exactly  the  same  appearances  are  seen  when  crystals 
of  luTBraoglobin  are  examined  with  a  microspectroscope. 
They  are  also  seen  when  arterial  blood  itself  (diluted  with 
saline  solutions  so  that  the  corpuscles  remain  in  as  natural 
condition  as  possible)  is  examined  with  the  spectroscope,  as 
well  as  when  a  drop  of  blood,  which  from  the  necessary  ex- 
posure to  air  is  always  arterial,  is  examined  with  the  micro- 
spcctroscope.  In  fact,  the  spectrum  of  luemoglobin  is  the 
spectrum  of  normal  arterial  blood. 

When  crystals  of  h;emoglobin,  prepared  in  the  way  de- 
scribed above,  are  subjected  to  the  vacuum  of  the  mercurial 
air-pump,  they  give  off  a  certain  quantity  of  oxygen,  and 
at  the  same  time  they  change  in  color.  The  quantity  of 
oxygen  given  off  is  delinite,  1  gram  of  the  crystals  giving 
off'  1.76^  ccm.  of  oxygen."  In  other  words,  the  crystals  of 
luemoglobin  over  and  above  the  oxygen  which  enters  inti- 
mately into  their  composition  (and  which  alone  is  given  in 
the  elementary  composition  stated  on  p.  44.5),  contain  another 
quantity  of  oxygen,  which  is  in  loose  combination  only,  and 
which  may  be  dissociated  from  them  by  establishing  a  suf- 
ficiently low  pressure.  The  change  of  color  which  ensues 
when  this  loosely  comi)ined  oxygen  is  removed  is  charac- 
teristic ;  the  crystals  become  darker  and  more  of  a  purple 
hue,  and  at  the  same  time  dichroic,  so  that  while  the  thin 
edges  appear  green,  the  thicker  ridges  are  purple. 

An  ordinary  solution  of  hiemoglobin,  like  the  crystals 
from  which  it  is  formed,  contains  a  definite  quantity  of  oxy- 
gen in  a  similarly  peculiar  loose  combination  ;  this  oxygen 
it  also  gives  up  at  a  sufficiently  low  pressure,  becoming  at 

^  Or,  1.34  measured  at  a  pressure  of  1  meter. 

2  Cf.  Hufner,  Zt.  f.  Physiol.  Chera.,  i  (1877),  p.  317. 


HEMOGLOBIN.  449 

the  same  time  of  a  purplish  hue.  This  loosely  combined 
oxygen  may  also  be  removed  by  passino-  a  stream  of  hydro- 
gen or  other  inditterent  gas  througii  the  solution,  whereby 
dissociation  is  effected.  It  may  also  be  got  rid  of  by  the 
nse  of  reducing  agents.  Thus,  if  a  few  drops  of  ammonium 
sulpiiide  or  of  an  alkaline  solution  of  ferrous  sulphate,  kept 
from  precipitation  by  the  presence  of  tartaric  acid,'  be 
added  to  a  solution  of  haemoglobin,  or  even  to  an  unpiirified 
solution  of  blood-corpuscles  such  as  is  afforded  by  the 
washings  from  a  blood  clot,  the  oxygen  in  loose  combina- 
tion with  the  haimoolobin  is  immediately  seized  upon  by  the 
reducing  agent.  This  may  be  recognized  at  once,  without 
submitting  the  fluid  to  the  air-pump,  by  a  characteristic 
change  of  color ;  from  a  bright-scarlet  the  solution  becomes 
of  a  purplish-claret  color,  when  seen  in  any  thickness,  but 
green  when  sufficiently  thin  ;  the  color  of  tlie  reduced  solu- 
tion is  exactly  like  that  of  the  crystals  from  which  the  loose 
ox3'gen  has  been  removed  by  the  air-pump. 

Examined  by  the  spectroscope,  this  reduced  solution,  or 
solution  of  reduced  haemoglobin  as  we  may  now  call  it,  off^ers 
a  spectrum  (Fig.  128)  entirely  different  from  that  of  the 
unreduced  solution.  The  two  absorption  bands  have  disap- 
peared, and  in  their  place  is  seen  a  single,  much  broader, 
but  at  the  same  time  much  fainter  band  a,  whose  middle 
occupies  a  position  about  midway  between  the  two  absorp- 
tion bands  of  the  unreduced  solution,  thougii  the  red-ward 
edge  of  the  band  shades  away  rather  farther  towards  the 
red  than  does  the  other  edge  towards  the  blue.  At  the  same 
time  the  general  absorption  of  the  spectrum  is  diff'erent  from 
that  of  the  unreduced  solution  ;  less  of  the  blue  end  is 
absorbed.  Even  when  the  solutions  become  tolerably  con- 
centrated, many  of  the  bluish-green  rays  to  the  blue  side  of 
the  single  band  still  pass  through.  Hence  the  difference  in 
color  between  hicmoglobin  wiiich  retains  the  loosely  com- 
bined oxygen,-  and  haemoglobin  which  has  lost  its  oxygen 
and  become  reduced.  In  tolerably  concentrated  solutions, 
or  tolerably  thick,  layers,  the  foi'mer  lets  through  the  red 
and  the  orange-yellow  iays,the  latter  the  red  and  bluish-green 
rays.     Accordingly,  the  one  appears  scarlet,  the  other  pur- 

'  Stokes,  Proc.  Koy.  Soc,  xiii  (1864),  p.  355. 

2  For  brevity's  sake  we  may  call  the  haemoglobin  containing  oxygen 
in  loose  combination,  oxi/hcemoglobin,  and  the  ha-moglobin  from  which 
this  loosely  combined  oxygen  has  been  removed,  reduced  haemoglobin  or 
simply  hemoglobin. 


450      TISSUES    AND    MECHANISMS    OF    RESPIRATION. 

pie.  In  dilute  solutions,  or  in  a  thin  lajer,  the  reduced 
luiemoglobin  lets  through  so  mucii  of  the  green  rays  that 
they  preponderate  over  the  red,  and  the  resulting  impression 
is  one  of  green.  Jn  the  unreduced  haemoglobin  or  oxy- 
hsemoglobin,  the  potent  3'ellow  which  is  blocl^ed  out  in  the 
reduced  lijiemoglohin  makes  itself  felt,  so  that  a  very  thin 
layer  of  hsemoglobin,  as  in  a  single  corpuscle  seen  under  tiie 
microscope,  appears  yellow  rather  than  red. 

When  the  haemoglobin  solution  (or  crystal)  whfbh  has  lost 
its  oxygen  by  the  action  either  of  the  air-pump  or  of  a  re- 
ducing agent  or  by  the  passage  of  an  indifl'erent  gas,  is 
exposed  to  air  containing  oxygen,  an  absorpti(m  of  ox3gen 
at  once  takes  place.  If  sudicient  oxygen  be  present,  the 
whole  of  the  lit«moglobin  seizes  upon  its  complement,  each 
gram  taking  up  in  combination  1.76  ( 1.34)  c.cm.  of  ox3gen  ; 
if  there  be  an  insufficient  quantity  of  oxygen,  a  part  only 
of  the  liremoglobin  gets  its  allowance  and  the  remainder 
continues  reduced.  If  the  amount  of  oxygen  be  sutlicient, 
the  solution  (or  crystal),  as  it  takes  up  the  oxygen,  regains 
its  bright-scarlet  color,  and  its  characteristic  absorption 
spectrum,  the  single  band  being  replaced  by  the  two.  Tluis 
if  a  solution  of  oxyhsemoglobin  in  a  test-tube  after  being 
reduced  by  the  ferrous  salt,  and  showing  the  purple  color 
and  the  single  band,  be  shaken  up  with  air, the  bright-scar- 
let color  at  once  returns,  and  when  the  fluid  is  placed  before 
the  spectroscope,  it  is  seen  that  the  single  faint  broad  band 
of  the  reduced  hamoglobin  has  w-holly  disappeared,  and  that 
in  its  place  are  the  two  sharp  thinner  bands  of  the  oxyhaemo- 
globin.  If  left  to  stand  in  the  test-tube  the  quantity  of 
reducing  agent  still  present  is  generally  sufficient  again  to 
rob  the  haemoglobin  of  the  oxygen  thus  newly  acquired,  and 
soon  the  scarlet  hue  fades  back  again  into  the  purple,  the 
two  bands  giving  place  to  the  one.  Another  shake  and 
exposure  to  air  will  however  again  bring  back  the  scarlet 
hue  and  the  two  bands  ;  and  once  more  these  may  disappear. 
In  fact,  a  few  drops  of  the  reducing  fluid  will  allow  this  game 
of  taking  oxygen  from  the  air  and  giving  it  up  to  the  re- 
ducer to  be  played  over  and  over  again,  and  at  each  turn  of 
the  game  the  color  shifts  from  scarlet  to  purple,  and  from 
purple  to  scarlet,  while  the  two  bands  exchange  for  the  one, 
and  the  one  for  the  two. 

Color  of  Venous  and  Arterial  Blood. — Evidently  we  liave 
in  these  properties  of  haemoglobin  an  explanation  of  at  least 


HEMOGLOBIN.  451 

one-balf  of  the  crreat  respiratory  process,  aiul  they  teach  us 
the  meaning  of  the  change  of  color  which  takes  place  when 
venous  blood  becomes  arterial  or  arterinl  venous.  In  venous 
Mood,  as  it  issues  from  the  riglit  ventricle,  the  oxygen  pres- 
ent is  insufficient  to  satisfy  the  wliole  of  the  haemoglobin  of 
the  red  corpuscles  ;  much  reduced  hjemoglohin  is  present, 
hence  the  purple  color  of  venous  blood. 

When  ordinary  venous  blood,  diluted  without  access  of  oxygen, 
is  brought  before  the  spectroscope,  the  two  bands  of  oxyh^emo- 
globin  are  seen.  This  is  explained  by  the  fact  that  in  a  mixture 
of  oxyhasnioglobin  and  (reduced)  haemoglobin,  the  two  sharp 
bands  of  the  former  are  always  much  more  readily  seen  than  the 
much  fainter  band  of  the  latter.  Xow  in  ordinar\'  venous  blood 
there  is  always  some  loose  ox3-gen,  removable  by  diminished 
pressure  or  otherwise  ;  there  is  always  some,  indeed  a  consider- 
able quantity,  of  oxy haemoglobin  as  well  as  (reduced)  haemoglo- 
bin. It  is  only  in  the  last  stages  of  asphyxia  that  all  the  loose 
oxygen  of  tbe'blood  disappears  ;  and  then  the  tAvo  bands  of  the 
oxyhaemoglobin  vanish  too.  So  distinct  are  the  two  bands  of 
even  a  sn^all  quantity  of  oxyhaemoglobin  in  the  midst  of  a 
large  quantity  of  haemoglobin  that  a  sohition  of  (completely 
reduced)  haemoglobin  may  be  used  as  a  test  for  the  presence  of 
oxygen.^ 

As  the  blood  passes  through  tlie  capillaries  of  the  lungs, 
this  reduced  hiemoglobin  takes  from  the  pulmonary  air  its 
complement  of  oxygen,  all  or  nearl3'  all  the  h?emoglol)in  of 
the  red  corpuscles  becomes  oxy  haemoglobin,  and  the  purple 
color  forthwith  shifts  into  scarlet. 

The  haemoglobin  of  arterial  blood  is  saturated  or  nearly  satu- 
rated with  oxygen.  By  increasing  the  pressure  of  the  oxygen,  an 
additional  quantity  ma}'  be  driven  into  the  blood,  but  this  is 
etfected  b}-  simple  absorption.  The  quantity  so  added  is  extremely 
small  compared  with  the  total  quantity  combined  with  the  hremo- 
globin,  but  its  physiological  importance  is  increased  by  its  being 
present  at  a  high  tension. 

Passing  from  tjie  left  ventricle  to  the  capillaries,  some 
of  the  oxyhiiemoglobin  gives  up  its  oxygen  to  the  tissues, 
l^ecomes  reduced  haemoglobin,  and  the  blood  in  consequence 
becomes  once  more  venous,  with  a  purj)le  hue.  Thus  the 
red  corpuscles,  by  virtue  of  their  haemoglobin,  are  emphati- 
cally oxygen  carriers.     Undergoing  no  intrinsic  change  in 

'  Hoppe-Seyler,  Zt.  f.  Physiol.  Chem.,  i  (1877),  p.  121. 


452      TISSUES    AND    MECHANISxMS    OF    RESPIRATION. 

itself,  the  luemoglohin  combines  in  tlie  lnn2;s  with  oxygen, 
which  it  cai'i'ies  to  the  tissues  ;  these,  more  greedy  of  oxygen 
than  itself,  rob  it  of  its  cliarge,  and  the  reduced  luTemoglobin 
hurries  back  to  the  bings  in  the  venous  blood  for  another 
portion.  The  change  from  venous  to  arterial  blood  is  then 
in  part  (for  as  we  shall  see  tliere  are  other  events  as  well)  a 
peculiar  combination  of  hiemoglobin  with  oxygen,  while  the 
change  from  arterial  to  venous  is,  in  part  also,  a  reduction 
of  oxyhfemoglobin  ;  and  the  difference  of  color  between 
venous  and  arterial  blood  depends  almost  entirely  on  the 
fa<'.t  that  the  reduced  hcTinoglobin  of  tlie  former  is  of  purple 
color,  while  the  oxyha?mogiobin  of  the  latter  is  of  a  scarlet 
color. 

There  maj^  be  other  causes  of  the  change  of  color,  but  these  are 
wholly  subsidiary  and  unimportant.  When  a  corpuscle  swells, 
its  refractive  power  is  diminished,  and  in  consequence  the  number 
of  rays  which  pass  into  and  are  absorbed  by  it  are  increased  at 
the  expense  of  those  reflected  from  its  surface  ;  anything,  there- 
fore, which  swells  the  corpuscles,  such  as  the  additicm  of  water, 
tends  to  darken  blood,  and  anything,  such  as  a  concentrated  sa- 
line solution,  which  causes  the  corpuscles  to  shrink,  tends  to 
brighten  blood.  Carbonic  acid  has  apparently  some  influence 
in  swelling  the  corpuscles,  and  therefore  may  aid  in  darkening 
the  venous  blood. 

We  have  spoken  of  the  combination  of  hremoglobin  with 
oxygen  as  being  a  peculiar  one.  The  peculiarit\'  consists 
in  the  facts  that  the  oxygen  may  be  associated  and  disso- 
ciated, without  any  general  disturbance  of  the  molecule  of 
haemoglobin,  and  that  dissociation  may  be  brought  about 
ver}'  readily.  H.emoglobin  combines  in  a  wholh'  similar  man- 
ner with  other  gases.  If  carbonic  oxide  be  passed  through  a 
solution  of  haemoglobin,  a  change  of  color  takes  place,  a 
peculiar  bluish  tinge  making  its  appearance.  At  the  same 
time  the  spectrum  is  altered  ;  two  bands  are  still  visible,  but 
on  accurate  measurement  it  is  seen  that  they  are  placed  more 
towards  the  blue  end  than  are  the  otherwise  similar  bands  of 
oxyha?moglobin.  (See  Fig.  123.)  When  a  known  quantity 
of  carl)()nic  oxide  gas  is  sent  through  a  haemoglobin  solution, 
it  will  be  found  on  examination  tiiat  a  certain  amount  of  the 
gas  has  been  retained,  an  equal  volume  of  oxygen  appearing 
in  its  place  in  the  gas  whicii  issues  from  the  solution.  If  the 
solution  so  treated  be  crystallized,  the  crystals  will  have  the 
sauie  characteristic  color,  and  give  the  same  absorption  spec- 
trum as  the  solution;  when  subjected  to  the  action  of  tiie  mcr- 


HiEMOGLOBIN.  453 


cnrial  pump,  they  will  oive  olT  a  definite  quantity  of  carbonic 
oxide, 1  gram  of  the  crystals  afford  ing  1.7B  (I  34)  c.cm.  of  the 
gas.  In  fact  hfemogloitin  combines  loosely  with  carbonic 
oxide  just  as  it  does  with  oxygen  ;  but  its  attinit^'  with  the 
former  is  greater  than  witli  tlie  latter.  While  carbonic  oxide 
readily  turns  out  oxygen,  oxygen  cannot  so  readily  turn  out 
carbonic  oxide.  Indeed,  carbonic  oxide  has  been  used  as  a 
means  of  driving  out  and  measuring  the  quantity  of  oxygen 
present  in  any  given  blood.  This  property  of  carbonic  oxide 
explains  its  poisonous  nature.  When  the  gas  is  breathed, 
the  reduced  and  the  unreduced  hpemoglobin  of  the  venous 
blood  unite  with  the  carbonic  oxide,  and  hence  the  peculiar 
bright  cherry-red  color  ol)servable  in  the  blood  and  tissues 
in  cases  of  poisoning  l)y  this  gas.  Tlie  carbonic  oxide 
haimoglobin,  however,  is  of  no  use  in  respiration  ;  it  is  not 
an  oxygen-carrier,  nay  more,  it  will  not  readily,  though  it 
does  so  slowly  and  eventuall}',  give  up  its  carbonic  oxide 
for  oxygen,  when  the  gas  no  longer  enters  the  chest  and 
pure  air  is  supplied.  The  organism  is  killed  by  suffocation, 
by  want  of  oxygen,  in  spite  of  tiie  blood  not  assuming  any 
dark  venous  color.  As  Bernard  phrased  it,  the  corpuscles 
are  paralyzed. 

Haemoglobin  similarly  forms  a  compound,  having  n  chai'acter- 
istic  spectrum  with  nitric  oxide,  more  stable  than  that  with  car- 
bonic oxide,  1  gram  of  hjemoglobin  uniting  with  1.7(3  (h34)  c.cm. 
of  the  gas.  In  all  these  compounds,  in  fact,  the  same  volume  of 
gas  unites  with  the  san:ie  quantity  of  the  substance,  and  all  three 
compounds  are  isomorphous.  Com]")()unds  also  exist  between 
haemoglobin  and  hydroc3'anic  acid.  Nitrous  oxide  reduces  haemo- 
globin. 

Haemoglobin  is  a  so-called  ozme-carrier.  If  to  a  mixture  of 
ozonized  turpentine  (turpentine  kept  for  some  time)  and  tincture  of 
guaiacum.  a  drop  of  blood  or  haemaglobin  solution  be  added,  the 
turpentine  at  once  oxidizes  the  guaiacum  and  produces  a  blue 
color  ;  this,  before  the  addition  of  the  hasmoglobin,  it  is  unable  to. 
[If  to  such  a  mixture  oi  ozonized  turpentine  tincture  of  guai- 
acum and  blood,  either  quinine,  nitrite  of  amyl-  or  nitrite  of  po- 
tassium be  added,  it  will  be  found  that  the  ozoniziuij;  power  is 
diminished  by  the  action  of  these  drugs  on  the  haemoglobin.] 
If  a  drop  of  tincture  of  guaiacum  (the  experiment  fails  with 
many  specimens  of  tincture)  be  spread  out  and  allowed  to  dry  on 
a  piece  of  white  tiltering-pai>er,  and  a  drop  of  blood  or  haemo- 
globin solution  be  placed  on  it,  a  blue  ring  is  developed.  This 
was  held  by  A.  Schmidt  to  indicate  that  the  oxygen  in  combina- 
tion with  hremoglobin  was  in  an  active,  or  ozonic  condition. 
Since,  however,  the  experiment  fails  when  glass  or  even  smooth 


454      TISSUES    AND    xM  ECU  AN  ISMS    OF    RESPIRATION. 


paper  is  used  instead  of  filterins^-paper,  it  is  more  than  probable 
that  the  result  is  caused  b}^  a  decomposition  of  the  heemoglobin 
due  to  the  porous  nature  of  the  paper.  ^ 

Although  a  crystalline  body,  hjemoglobin  ditfuses  with 
great  ditliculty.  This  arises  from  the  fact  that  it  is  in  part 
a  proteid  body;  it  consists  of  a  colorless  proteid,  associated 
with  a  colored  compound  named  hdematin.  All  tlie  iron 
belonging  to  the  hcTmoglobin  is  in  reality  attached  to  the 
hgematin.  A  solution  of  haemoglobin,  when  heated,  coagu- 
lates, the  exact  degree  at  which  the  coagulation  takes  place 
depending  on  the  amount  of  dilution  ;  at  the  same  time  it 
turns  brown  from  the  setting  free  of  the  hgematin.  If  a 
strong  solution  of  haemoglobin  be  treated  with  acetic  (or 
other)  acid,  the  same  brown  color,  from  the  appearance  of 
hsematin,  is  observed.  The  proteid  constituent,  however, 
is  not  coagulated,  but  by  the  action  of  the  acid  passes  into 
the  state  of  acid-albumin.  On  adding  ether  to  tiie  mixture, 
and  shaking,  the  lunematiii  rises  into  the  supernatant  ether, 
which  it  coh)rs  a  daik  red,  and  which,  examined  with  the 
spectroscope,  is  found  to  possess  a  well-marked  spectrum, 
tlie  spectrum  of  the  so-called  acid  hdematin  of  Stokes  (Fig. 
123).  The  proteid  in  the  water  l)elow  the  ether  api)ears  in  a 
coagulated  form.  In  a  somewhat  sinr.ilar  manner  alkalies 
split  up  luiemoglobin  into  a  proteid  constituent  and  luematin. 
The  exact  nature  of  tiie  proteid  constituent  has  not  as  yet 
been  clearly  determined  ;  it  was  sui)po8ed  to  be  globulin, 
hence  the  name  hsematoglobulin  contracted  into  haemoglobin. 
The  proteid  which  is  precipitated  when  a  solution  of  haemo- 
globin is  exposed  to  the  air,  though  belonging  to  the  glob- 
ulin family,  has  characters  of  its  own.  It  has  been  named 
by  Preyer"^  globin.  It  is  free  from  asii.  Haematin,  when 
separated  from  its  proteid  fellow  and  purified,  appears  as  a 
dark-brown  amorphous  powder,  or  as  a  scaly  mass  with 
a  metallic  lustre,  having  the  prol)able  composition  of 
€3.^,  Hg^,  N^,  Fe,  O..  It  is  readily  soluble  in  dilute  alkaline 
solutions,  and  then  gives  a  characteristic  spectrum  (Fig. 
123). 

An  interesting  feature  in  haematin  is  that  its  aR-alme  solution 
is  capable  of  being  reduced  by  reducing  agents,  the  spectrum 
changing  at  the  same  time,  and  that  the  reduced  solution  will, 

1  Pfliio-er,  Pfliiger's  Archiv,  x  (1875),  p.  2.52. 

2  Die  JBlut-Krystalle,  1871. 


OXYGEN  IN  THE  BLOOD.  4o5 


like  the  hsemotrlobin,  take  up  oxyoen  again  on  being  brought 
into  contact  with  air  or  oxygen  This  would  seem  to  indicate 
that  the  oxygen-holding  power  of  haemoglobin  is  connected  ex- 
clusively with  its  luematin  constituent.  By  the  action  of  strong 
sulphuric  acid  ha?matin  ma}^  be  robbed  ( f  all  its  iron.  It  still 
retains  the  feature  of  possessing  color,  the  solution  of  iron-free 
hfematin  being  a  dark  rich  brownish-red  ;  but  is  no  longer  ca- 
pable of  combining  loosely  with  oxygen.  This  indicates  that  the 
iron  is  in  some  way  associated  with  the  peculiar  respiratory 
funct  ons  of  hremoglobin  ;  though  it  is  obviously  an  error  to 
suppose,  as  was  once  supposed,  that  the  change  from  venous  to 
arterial  blood  consists  essentially  in  a  change  from  a  ferrous  to  a 
ferric  salt. 

Though  not  erystallizable  itself,  haematin  forms  with  hy- 
drochloric acid  a  compound,  occurring  in  minute  rhombic 
crystals,  the  so-called  haimin  crystals. 

The  spectrum  of  hsematin  in  an  alkaline  solution  (Fig.  123) 
gives  one  broad  band  to  the  red  side  of  the  lineD.  The  blue  end 
of  the  spectrum  suffers  much  absorption  ;  and  since  the  charac- 
teristic single  band  is  faint,  and  only  seen  in  concentrated  solu- 
tions, the  whole  ai^jK^arance  of  the  spectrum  of  hfematin  is  far 
less  striking  than  that  of  hfemoglobin.  The  solutions  are  dichroic, 
of  a  reddis^h-brow^i  in  a  thick,  and  of  an  olive-green  in  a  thin 
layer.  The  spectrum  of  reduced  hfematin  is  marked  by  two  faint 
bands  to  the  blue  side  of  the  single  band  of  the  unreduced  hfem- 
atin  ;  there  is  at  the  same  time  less  absorption  of  the  blue  end. 
The  spectrum  of  the  so-called  acid-ha?matin,  i.  e.,  of  hsematin 
prepared,  as  spoken  of  above,  by  treatment  with  acetic  acid  and 
ether,  is  marked  by  a  very  characteristic  and  easily  seen  band,  o, 
in  the  red,  to  the  blue  side  of  C  (Fig.  12:)),  the  other  bands  {  i,  },  f) 
shoAvn  in  the  figure  being  less  easily  seen.  This  so-called  hsem- 
atin band  readily  appears  when  haemoglobin  is  acted  upon  by- 
weak  acids,  and  hence  is  seen  when  carbonic  acid  is  passed  for 
some  time  through  haemoglobin  A  wholly  similar  band,  how- 
ever, makes  its  appearance  when  blood  is  acted  upon  for  some 
time  by  ammonium  sulphide,  or  when  blood  is  allowed  to  stand 
for  any  length  of  time,  or  after  the  action  of  weak  alkalies  ;  in 
these  cases  it  is  supposed  to  indicate  the  existence  of  a  hypotheti- 
cal bod}',  methfemoglobin,  an  intermediate  stage  which  haemo- 
globin is  supposed  to  pass  through  on  its  way  to  be  split  up  into 
heematin  and  the  proteid  body.  When  hrematin  or  luemoglobin 
is  dissolved  in  concentrated  sulphuric  acid  a  spectrum  is  ob- 
tained, on  diluting  with  the  acid,  resembling  but  in  some  points 
differing  from  that  of  acid  haematin  as  given  in  Fig.  128.  The 
iron-free  hsematin,  obtained  by  precipitating  with  a  large  quan- 
tit}^  of  water  the  solution  of  hsematin  or  hgemoglobin  in  concen- 
trated sulphuric  acid,  also  gives  in  ammoniacal  and  in  acetic 


466      TISSUES    AND    MECHANISMS    OF    RESPIRATION. 


acid  solutions  spectra  differing  in  minor  points  only  from  the 
same  spectrum.  Preyer'  believes  that  Stokes's  acid  h?ematin,  i.  e,, 
the  substance  in  solution  in  the  ether  added  to  blood  treated 
with  acetic  acid,  is  in  reality  iron-free  hrematin,  or,  as  he  prefers 
to  call  it,  lup/inatoin.  H}?ematin  also  forms  a  special  compound 
with  a  characteristic  spectrum,  when  acted  on  by  potassium 
cyanide.  Hoppe-Seyler,^  l)y  treating  reduced  haemoglobin  with 
acids  or  alkalies,  in  the  total  absence  of  oxygen,  obtained  a  color- 
ing body,  with  a  characteristic  spectrum,  to  which  he  gave  the 
name  of  hsemochromogen,  regarding  it  as  the  substance,  forming 
part  of  luemoglobin,  which  by  oxidation  passes  into  h?ematiu. 

In  conclusion,  the  condition  of  oxygen  in  the  blood  is  as 
follows  :  Of  the  wliole  quantity  of  oxygen  in  the  blood, 
only  a  minute  fraction  is  simply  absorbed  or  dissolved,  ac- 
cording to  the  law  of  pressures  (the  Henry-Dalton  law). 
The  great  mass  is  in  a  state  of  combination  with  the  haemo- 
globin, the  connection  being  of  such  a  kind  that  while  the 
hannoglobin  readily  combines  with  the  oxygen  of  the  air  to 
which  it  is  exposed,  dissociation  readily  occurs  at  low  pres- 
sures, or  in  the  presence  of  indirterent  gases,  or  by  the 
action  of  sul)Stances  having  a  greater  afTinity  for  oxygen 
than  has  h?pmoglobin  itself.  Tiie  difference  between  venous 
and  arterial  blood,  as  far  as  oxygen  is  concerned,  is  that 
while  in  tiie  latter  there  is  an  insignificant  quantity  of  re- 
duced iiaemoglobin,  in  the  former  tiiere  is  a  great  deal ;  and 
the  characteristic  colors  of  venous  and  arterial  blood  are  in 
the  main  due  to  the  fact  that  tiie  color  of  reduced  haemo- 
globin is  purple,  while  that  of  oxyhiiemoglobin  is  scarlet. 


I'he  IleJations  of  the  Carbonic  Acid  in  the  Blood. 

The  presence  of  carl)onic  acid  in  the  blood  appears  to  be 
determined  by  conditions  more  complex  in  tiieir  nature  and 
at  present  not  so  well  understood  as  those  which  determine 
the  presence  of  oxygen.  The  carbonic  acid  is  not  simply 
dissolved  in  the  blood  ;  its  absorption  by  blood  does  not 
follow  tiie  law  of  pressures.  It  exists  in  association  witii 
some  sul)stance  or  sul)stances  in  the  blood,  and  its  escape 
from  the  blood  is  a  process  of  dissociation.  We  cann<)t, 
however,  speak  of  it  as  being  associated  like  the  oxygen  vvitii 
the  haimoglobin  of  the  red  corpuscles.     So  far  from  the  red 

'  Die  Blm-Krvstalle  (1871),  p.  181. 
2  Untersuch.,  iv  (1871],  540. 


CARBOLIC  ACID  IN  THE  BLOOD.        457 

corpuscles  containing,  as  is  the  case  witli  the  ox3'gen.  the 
great  mass  of  the  carbonic  acid,  tlie  quantity  of  this  gas 
which  is  present  in  a  vohime  of  serum  is  actually  greater 
than  that  which  is  present  in  an  equal  vohime  of  blood,  2.  e., 
an  equal  volume  of  mixed  corpuscles  and  serum. 

Wlien  serum  is  sul>jected  to  the  mercurial  vacuum,  by  far 
the  greater  part  of  the  carbonic  acid  is  given  otf;  but  a 
small  additional  quantity  (2  to  5  vols,  per  cent)  may  be  ex- 
tracted by  tlie  subsequent  addition  of  an  acid.  This  latter 
portion  may  be  spoken  of  as  "fixed"  carbonic  acid  in  dis- 
tinction to  the  larger  '•  loose  "  portion  wiiich  is  given  off  to 
the  vacuum.  Wlien,  iiowever,  tlie  whole  blood  is  subjected 
to  tlie  vacuum  all  the  carbonic  acid  is  given  otf,  so  that 
when  sernm  is  mixed  witii  corpuscles  all  the  carbonic  acid 
may  be  spoken  of  as  ''  loose;"  and  according  to  Fredericq/ 
the  excess  of  carbonic  acid  in  serum  over  that  present  in 
entire  blood,  corresponds  to  tlie  fixed  jiortion  in  serum 
which  has  to  be  driven  off  by  an  acid.  Moreover,  though 
the  quantity  of  carbonic  acid  in  blood  is  less  than  that  in 
an  equal  volume  of  serum,  the  ten.^ion  of  the  carbonic  acid 
in  blood  is  greater  than  in  serum. 

Putting  these  facts  together  it  seems  probable  that  the 
carbonic  acid  exists  associated  with  some  sulistance  or 
substances  in  the  serum,  but  that  the  condition  of  its  asso- 
ciati(m  (and  therefore  of  its  dissociation)  are  determined  by 
the  action  of  some  substance  or  substances  present  in  the 
corpuscles.  It  is  further  probable  that  the  association  of 
the  carl)onic  acid  in  the  serum  is  with  sodium  as  sodium 
bicarbonate,  and  it  is  even  possible  that  the  haemoglobin  of 
the  corpuscles  plays  a  [lart  in  promoting  the  dissociation  of 
the  sodium  bicarbonate,  or  even  the  cari)onate,  and  thus 
keeping  up  the  carbonic  acid  tension  of  the  entire  blood. 
But  further  investigations  are  necessary  before  the  matter 
can  be  said  to  have  been  placed  on  wholly  satisfactoiy  foot- 
ing. 

Gaule'  puts  forward  the  view  that  a  constituent  of  the  red  cor- 
puscles (probably  the  haemoglobin)  possesses  an  athnity  for  so- 
dium carbonate,  and  by  continually  withdraw-ing  this  from  the 
serum,  promotes  the  dissociation  of  the  bicarbonate  and  the  set- 
ting free  of  carbonic  acid.  He  further  suggests  that  so  long  as 
the  tension  of  the  carbonic  acid  in  the  serum  is  low,  the  hgemo- 

1  Conipt.  Kend.,  t.  84  (1877),  p.  661,  t.  85  (1878),  p.  29. 
=  Archiv  f.  Antit.  u.  Phys.,  1878,  Phys.  Abth.,  p.  469. 


458       TISSUES    AND    MECHANISMS    OF    RESPIRATION. 


globin  is  able  to  split  up  even  the  simple  carbonate,  iinitinoj  witli 
the  sodium,  and  setting  free  carbonic  acid.  As  tlie  tension  in 
the  serum  increases,  however,  he  supposes  this  process  to  be 
reversed,  and  thus,  by  a  constant  action  and  reaction  of  haemo- 
globin and  sodium  carbonate,  the  tension  of  carbonic  acid  in  the 
blood  is  kept  constant.' 


The  Relations  of  tJie  Nitrogen  in  the  Blood. 

The  small  quantity  of  this  gas  which  is  present  in  both 
arterial  and  venous  blood  seems  to  exist  partly  in  a  state 
of  simple  solution,  partly  in  some  loose  chemicnl  combina- 
tion, but  the  conditions  of  the  association  are  unknown. 


Sec.  4.    The  Respiratory  Changes  in  the  Lungs. 

The  Entrance  of  Oxygen. — We  have  already  seen  that  the 
blood  in  passing  through  the  lungs  takes  up  a  certain  vari- 
able quantity  (from  8  to  12  per  cent,  vols.)  of  oxygen.  We 
have  further  seen  that  the  quantity  so  taken  up,  putting 
aside  the  insignificant  fraction  simply  absorbed,  enters  into 
direct  but  loose  combination  with  the  luTemoglolnn.  We 
have  also  seen  that  at  low  pressures  the  oxygen  is  disso- 
ciated from  the  hremoglobin  and  set  free,  but  not  at  high 
pressures.  If  the  tension  of  the  oxygen  in  the  lungs  is 
higher  than  the  tension  of  the  oxygen  in  the  venous  blood 
of  the  pulmonary  artery,  there  will  be  no  difficulty  in  the 
reduced  hjemoglobin  of  that  blood  taking  up  oxygen  ;  and 
this  may  go  on  until  the  haemogh:)bin  of  the  blood  in  the  pul- 
monary' capillaries  is  all  converted  into  oxylisemoglobin,  or 
until  tlie  oxygen  tension  in  the  blood  is  increased  so  as  to 
be  equal  to  that  of  the  air  in  the  lungs.  Now  the  oxygen  in 
the  expired  air  amounts  to  about  IB  per  cent.,  having  lost 
4  or  5  per  cent,  in  tlie  lungs.  Of  course  the  air  at  tlie  bot- 
tom of  the  lungs  will  contain  still  less  oxygen.  How  much 
less  we  do  not  exactly  know,  but  we  may  probably  put  the 
limit  of  reduction  at  10  per  cent.  We  may  say,  then,  that 
the  tension  of  the  oxygen  in  the  pulmonary  air-cells  is  at 
least  10  per  cent.,  or  to  measure  it  in  millimeters  of  mer- 
cury, since  the  pressure  of  the  one  entire  atmosphere  is  TOO 
mm.,  y'^th  of  that  will  amount  to  7fi  mm. 

Now  the  tension  of  oxygen   in  the   arterial   blood  of  the 

>  Cf.  however  Bert,  Conip.  Rend.,  t.  87  (1878),  p.  628. 


THE    CHANGES    IN    THE    LUNGS.  459 


dogi  amoniits  to  3.Q  per  cent,  (varving  from  5.6  to  2.8),  or 
about  30  mm.  of  mercury.  That  is  to  say,  the  arterial  blood 
of  the  dog  exposed  to  an  atmosphere  containing  3.9  per 
cent,  of  oxygen  neither  gives  olf  nor  takes  up  any  oxygen. 
The  tension  of  the  oxygen  in  the  average  venous  blood  of 
tlie  dog  amounts  to  2.9  per  cent,  (varying  from  4.6  to  1.4).^ 
Both  these  numbers  are  far  below  10  per  cent.,  in  fact  we 
may  suppose  the  percentage  of  oxygen  in  the  pulmonary 
alveoli  to  be  less  than  half  the  amount  stated  above,  and 
see  no  dilRculty  in  ordinary  venous  blood  taking  up  oxygen 
while  passing  through  the  lungs.  But  what  takes  place 
wlien  the  tension  of  the  oxygen  in  the  air  is  lowered,  as 
when  the  windpipe  is  obstructed,  and  asphyxia  sets  in  ?  It 
has  been  ascertained  that  in  the  dog,  in  the  last  breath  given 
out  in  such  an  asphyxia,  the  expired  air  has  an  oxygen  ten- 
sion of  2.3  per  cent ,  and  when  the  heart  ceases  to  beat,  the 
oxygen  of  the  pulmonary  air  sinks  to  .403  per  cent.  These 
tensions  are  of  course  lower  than  that  of  ordinary  venous 
blood,  but  in  asphyxia  tlie  blood  is  no  longer  ordinary  venous 
blood  ;  instead  of  containing  a  comparatively  small  amount, 
it  contains  a  large  and  gradually  increasing  amount,  of  re- 
duced haemoglobin.  And  as  the  reduced  haemoglobin  in- 
creases in  amount,  the  oxygen  tension  of  the  venous  blood 
decreases  ;  it  thus  keeps  below  that  of  the  air  in  the  lungs  ; 
and  hence  even  the  last  traces  of  oxygen  in  the  lungs  are 
taken  up  by  the  blood,  and  carried  away  to  the  tissues. 
Even  with  the  last  heart's  beat,  when  the  oxygen  in  the 
lungs  has  sunk  to  .403  per  cent.,  the  bands  of  oxyhiiemoglo- 
bin  may  still  for  a  moment  be  detected  in  the  blood  of  the 
left  side  of  the  liearL.^ 

The  Exit  of  Carbonic  Acid. — It  seems  natural  to  suppose 
that  the  carbonic  acid  would  escape  by  diffusion  from  the 
blood  of  the  alveolar  capillaries  into  the  air  of  the  alveoli. 
But  in  order  that  diffusion  should  thus  take  place,  the  car- 
bonic acid  tension  of  the  air  in  the  pulmonary  alveoli  must 
always  be  less  than  that  of  the  venous  blood  of  the  pulmo- 
nary artery,  and  indeed  ought  not  to  exceed  that  of  the 
blood  of  the  pulmonary  vein.  There  are,  however,  many 
practical  difficulties   in  the  way  of  an  exact  determination 

^  Strassbiirg,  Pfluo:er's  Archiv,  vi  (1872),  p.  65, 

2  Wolfi'berg,  Pfiiiger's  Archiv,  iv  (1871),  465,  vi  (1872),  23. 

^  Stroganow,  Pfliiger's  Archiv,  xii  (1876),  p.  18. 


460      TISSUES    AND    MECHANISMS    OF    RESPIRATION. 

of  the  carbonic  acid  tension  of*  the  pnlmonarv  alveoli  (for 
though  it  must  be  greater  than  tliat  of  the  expired  air,  it  is 
difficult  to  say  how  much  gieater),  and  of  the  carbonic  acid 
tension  of  tlie  blood  at  the  same  time,  so  as  to  be  in  a  posi- 
tion to  compare  the  one  with  the  other.  Hence  though  the 
balance  of  evidence  is  in  favor  of  the  escape  of  carbonic 
acid  being  simply  a  process  of  diffusion,  and  against  it  be- 
ing effected  by  i\ny  si)ecial  action  taking  place  in  the  alveoli, 
the  matter  can  hardly  be  said  at  present  to  be  satisfactorily 
cleared  up. 

An  experiment  distinctly  in  favor  of  the  process  being  simply 
one  of  diffusion  has  been  brought  forward  by  Wolllberg.^  Tiiis 
observer  introduced  into  the  bronchus  of  the  lung  of  a  dog  a 
catheter,  round  which  \vas  arranged  a  small  bag,  by  the  inflation 
of  which  the  bronchus,  whenever  desired,  could  be  completely 
blocked  up.  Thus,  without  any  disturbance  of  the  general 
breathing,  and  therefore  without  any  change  in  the  normal  pro- 
])()rtions  of  the  gases  of  the  blood,  he  was  able  to  stop  the  ingress 
of  fresh  air  into  a  limited  portion  of  the  lung.  The  blood  pass- 
ing through  the  alvef)lar  capillaries  of  this  limited  portion  would 
naturally  possess  the  same  carbonic  acid  tension  as  the  rest  of  the 
venous  blood  flowing  through  the  pulmonary  artery,  a  tension 
which,  though  varying  slightly  from  moment  to  moment,  would 
maintain  a  normal  average.  On  the  supposition  that  carbonic 
acid  passes  sim])ly  by  diffusion  from  the  pulmonary  blood  into 
the  air  of  the  alveoli,  because  the  carbonic  acid  tensicm  of  the 
latter  is  normally  lower  than  that  of  the  former,  one  would  ex- 
pect to  find  that  the  air  in  the  occluded  portion  of  the  lung  would 
continue  to  take  up  carbonic  acid  until  an  equilibrium  was  estab- 
lished between  it  and  the  carbonic  acid  tension  of  the  venous 
blood,  and  consequently  that  if  after  an  occlusion,  say  of  some 
minutes  (by  which  time  the  equilibrium  might  fairly  be  assumed 
to  have  been  established),  the  carbonic  acid  tension  of  the  air  of 
the  occluded  portion  were  determined,  it  would  be  found  to  be 
equal  to,  and  not  more  than  equal  to,  the  carbonic  acid  tension 
of  the  venous  blood  of  the  pulmonary  artery.  And  this  w^as  the 
result  at  which  WollTberg  arrived;  he  found  that  the  carbonic 
acid  of  the  o(;cluded  air  and  of  the  venous  blood  of  the  right 
side  of  the  heart  were  Just  about  equal  ;  allowing  for  errors  of 
observation,  the  tension  of  each  was  about  3.5  per  cent. 

The  carbonic  acid  tension  of  the  venous  blood  as  determined 
by  Wolff  berg  was  decidedly  low.  Strassburg^  makes  it  (for  the 
dog)  5.4  per  cent.  ;  and  the  assumption  that  the  limit  of  the  car- 
bonic acid  tension  in  the  pulmonary  alveoli  is  only  .3.5  per  cent, 
necessitates  that  the  carbonic  acid  in  the  expired  air  of  the  dog 

'  Wolff  berg,  op.  cit.  ^  Op.  cit. 


THE    CHANGES    IN    THE    LUNGS.  461 


is  less  than  this,  much  less  in  fact,  than  that  in  the  expired  air 
of  man.  Moreover  in  the  normal  condition  of  the  lung  when 
the  venous  blood  is  becoming  arterial  (which  of  course  was  not 
the  case  in  the  occluded  lung),  the  continuance  of  diti'usion  de- 
pends on  the  carbonic  acid  tension  of  the  alveoli  having  for  its 
limits  the  degree  of  carbonic  acid,  not  of  the  venous  but  of  the 
arterial  blood,  and  this  Wolti'berg  puts  as  low  as  2.8  per  cent. 
Consequently  the  expired  air  (of  the  dog)  ought  to  contain  less 
than  2.8  per  cent,  of  carbonic  acid,  a  result  which  does  not  agree 
with  those  of  other  observers. 

The  belief  that  some  local  action  in  the  pulmonar}^  alveoli 
temporarily  raised  the  carbonic  acid  tension  of  tlie  blood,  as  it 
passed  through  the  alveolar  capillaries,  above  that  of  the  venous 
blood  tlowing  along  the  trunk  of  the  pulmonary  artery,  was  orig- 
inally based  on  Becher's  conclusion  (see  ante,  p.  437j  that  in  man 
at  least  the  carbonic  acid  tension  of  the  pulmonary  alveoli  is  as 
high  as  7.5  or  8  per  cent.,  a  degree  of  tension  which  had  not  been 
found  by  experiment  to  exist  in  the  normal  venous  blood  of  any 
animal.  Becher's  results  however  are  clearly  invalidated  by  the 
consideration  that  in  holding  his  breath  he  necessarily  increased 
beyond  the  normal  the  carbonic  acid  tension  of  his  blood  ;  and 
he  of  course  did  not  determine  the  gases  of  his  own  blood. 
Hence  though  AVolff  berg's  results  seem  to  require  repetition  they 
probably  give  a  more  correct  view  of  the  matter. 

On  the  supposition  that  the  carbonic  acid  tension  of  the  pul- 
monary alveoli  is  reall}-  higher  than  that  of  the  venous  blood,  and 
that,  therefore,  some  additional  process  is  necessar}^  to  promote 
the  escape  of  the  carbonic  acid,  it  has  been  suggested  that  the  act 
of  absorption  of  oxygen  by  the  haemoglobin  in  some  way  or  other 
raises  temporarih^  at  the  same  time  the  carbonic  acid  tension  of 
the  blood,  ex  gr.^  brings  about  an  exaggeration  of  that  function 
of  the  corpuscles  of  which  we  have  alread}"  spoken  on  p.  457.  In 
support  of  this  it  is  stated  that  the  carbonic  acid  tension  of  ve- 
nous blood  is  greater  when  determined  by  the  agitation  of  the 
blood  with  air  containing  oxygen  than  when  air  free  from  oxygen 
is  used.  And  it  might  be  urged  against  Wolffberg's  result  that 
in  the  occluded  portion  of  the  lung  the  absorption  of  ox3'gen  after 
awhile  did  not  take  place,  as  usual,  and  that  in  consequence  the 
limit  of  carbonic  acid  tension  in  the  occluded  portion  is  not  a 
measure  of  that  of  the  normal  lung. 

It  has  also  been  suggested  that  Uie  escape  of  carbonic  acid  is 
effected  by  a  direct  activity  of  the  pulmonary  epithelium,  that 
the  cells  of  the  alveoli  actively  excrete,  in  fact,  carbonic  acid. 
The  arguments  in  favor  of  this  view  are  based  on  the  experiments 
of  J.  J.  Muller,'  who  found  that  more  carbonic  acid  was  given  otf 
when  venous  blood  was  driven  through  the  pulmonary  artery, 

'   Ludwig's  Arbeiten,  1869,  p.  37. 
39 


462      TISSUES    AND    MECHANISMS    OF    RESPIRATION. 


and  so  expired  to  air  in  a  normal  manner  throuirli  the  walls  of 
the  alveoli  of  a  living  lung,  than  when  it  was  simpl}^  agitated 
with  air. 

Sec.  5.  The  Respiratory  Changes  in  the  Tissues. 

In  passing  through  the  several  tissues  the  arterial  blood 
becomes  once  more  venous.  A  considerable  quantity  of  the 
oxyhemoglobin  becomes  reduced,  and  a  quantity  of  car- 
bonic acid  passes  from  the  tissues  into  the  blood.  The 
amount  of  change  varies  in  the  various  tissues,  and  in  the 
same  tissue  may  vary  at  different  times.  Thus  in  a  gland 
at  rest,  as  we  have  seen,  the  venous  blood  is  dark,  showing 
the  presence  of  a  large  quantity  of  reduced  haemoglobin  ; 
when  the  gland  is  active,  tiie  venous  blood  in  its  color,  and 
in  the  amount  of  haemoglobin  which  it  contains,  resembles 
closely  arterial  blood.  The  blood,  therefore,  which  issues 
from  a  gland  at  rest  is  more  ''  venous  "  than  that  from  an 
active  gland,  though  the  total  quantity  of  carbonic  acid 
formed  in  a  given  time  may  be  greater  in  the  latter.  The 
l)lood,  on  the  other  hand,  which  comes  from  a  contracting 
muscle,  is  not  only  richer  in  carbonic  acid,  but  also,  though 
not  to  a  corresponding  amount,  poorer  in  oxygen  than  the 
blood  which  flows  from  a  muscle  at  rest. 

In  all  these  cases  the  great  question  which  comes  up  for 
our  consideration  is  this:  Does  the  oxygen  pass  from  the 
blood  into  tlie  tissues,  and  does  the  oxidation  take  place  in 
the  tissues,  giving  rise  to  carbonic  acid,  which  passes  in  turn 
away  from  the  tissues  into  the  blood?  or  do  certain  oxidiza- 
ble  reducing  substances  pass  from  the  tissues  into  the  blood, 
and  there  become  oxidized  into  carbonic  acid  and  other 
products,  so  that  the  chief  oxidation  takes  place  in  the 
blood  itself? 

There  are,  it  is  true,  reducing  oxidizable  substances  in 
the  blood,  but  these  are  small  in  amount,  and  the  quantity 
of  carbonic  acid  to  which  they  give  rise  when  the  blood  con- 
taining them  is  agitated  with  air  or  oxygen,  is  so  small  as 
scared}'  to  exceed  the  errors  of  observation. 

The  conclusion  of  Estor  and  St.  Pierre,  that  the  oxygen  di- 
minishes even  in  the  great  arteries  from  the  heart  outwards,  has 
been  shown  by  Pfl/iger  to  be  based  on  erroneous  analyses. 

On  the  other  hand,  it  will  be  remembered  that  in  speak- 
ing of  muscle,  we   drew  attention  to  the   fact  that  a  frog's 


THE    CHANGES    IN    THE    TISSUES.  463 

muscle  removed  from  the  body  Tand  the  same  is  true  of 
muscles  of  other  animals;  contained  no  free  oxygen  what- 
ever; none  coukl  be  obtained  from  it  by  the  mercurial  air- 
pump.  Yet  such  a  muscle  will  not  only  when  at  rest  go  on 
producing  and  discharging  a  certain  quantity,  but  also  when 
it  contracts  evolve  a  very  considerable  quantity  of  carbonic 
acid.  Moreover  tliis  discharge  of  carbonic  acid  will  go  on 
for  a  certain  time  in  muscles  under  circumstances  in  which 
it  is  impossible  for  them  to  obtain  oxygen  from  without. 
Oxygen,  it  is  true,  is  necessary  for  the  life  of  the  muscle  ; 
when  venous  instead  of  arterial  blood  is  sent  through  the 
bloodvessels  of  a  muscle,  the  irrital)ility  speedilj'  disappears, 
and  unless  fresh  oxygen  be  administered  the  muscle  soon 
dies.  The  muscle  may,  however,  during  the  interval  in 
which  irritability  is  still  retained  after  the  supply  of  oxygen 
has  been  cut  off',  continue  to  contract  vigorously.  The  pres- 
ence of  oxygen,  though  necessary  for  the  maintenance  of 
irratability,  is  not  necessary  for  the  manifestatioii  of  that 
irritability,  is  not  necessary  for  that  explosive  decomposi- 
tion which  develops  a  contraction.  A  frog's  muscle  will 
continue  to  contract  and  to  produce  carbonic  acid  in  an  at- 
mosphere of  hydrogen  or  nitrogen,  that  is  in  the  total  ab- 
sence of  free  oxygen  both  from  itself  and  from  the  medium 
in  which  it  is  placed.  And  a  considerable  quantity  of  car- 
bonic acid  may  be  set  free  from  living  muscle  by  simply  ex- 
posing it  to  the  temperature  of  boiling  water, ^  the  quantity 
being  largely  diminished  if  the  muscle  be  thrown  immedi- 
ately before  into  a  violent  tetanus. 

Thus  on  the  one  hand  the  muscle  seems  to  have  the  prop- 
erty of  taking  up  and  fixing  in  some  way  or  other  the  oxygen 
to  which  it  is  exposed,  of  converting  it  into  intra-molecular 
oxygen,  in  which  condition  it  cannot  be  removed  by  simple 
diminished  pressure,  so  that  the  tension  of  ox^-gen  in  the 
muscular  substance  may  be  considered  as  always  nil;  while 
on  the  other  hand  the  muscular  substance  is  alwa^'s  under- 
going a  decomposition  of  such  a  kind  that  carbonic  acid  is 
set  free,  sometimes,  as  when  the  muscle  is  at  rest,  in  small, 
sometimes,  as  during  a  contraction,  in  large  quantities.  But 
if  the  oxygen  tension  of  the  muscular  tissue  be  thus  always 
nil,  the  ox3'gen  of  the  blood-corpuscles,  in  which  it  is  at  a 
comparatively  high  tension,  will  be  always  passing  over, 
through  the  plasma,  through  the  capillary  walls,  the  hmph 


Stintzing,  Pfliiger's  Archiv,  xviii  (1878),  p.  388. 


464      TISSUES    AND    MECHANISMS    OF    RESPIKATION. 

spaces  and  the  sareoleinma,  into  the  muscuhvr  substance, 
and  as  soon  as  it  arrives  tliere  will  be  hidden  away  as  intra- 
niolecniar  oxygen,  leaving  the  oxygen  tension  of  the  muscu- 
lar sulistance  once  more  nil.  Conversely',  the  carbonic  acid 
produced  by  tiie  decomposition  of  the  muscular  substance 
will  tend  to  raise  the  carbonic  acid  tension  of  the  muscle 
until  it  exceeds  tiiat  of  tiie  blood  ;  whereupon  it  will  pass 
from  the  muscle  into  tiie  blood,  its  place  in  the  muscular 
substance  being  supplied  by  freshly  generated  carbonic 
acid.  There  will  always,  in  fact,  be  a  stream  of  ox3'gen 
from  the  blood  to  tiie  muf^cle  and  of  carbonic  acid  from  the 
muscle  to  the  blood.  Tiie  respiration  of  the  muscle  then 
does  not  consist  in  throwing  into  the  blood  oxidizable  sub- 
stances there  to  be  oxidized  into  carbonic  acid  and  other 
matters  ;  but  it  does  consist  in  the  assumption  of  oxygen  as 
intra-molecular  oxygen,  in  the  building  up  by  help  of  that 
oxygen  of  explosive  decomposal»le  substances,  and  in  the 
occurrence  of  decompositions  whereby  carbonic  acid  and 
other  matters  are  discharged  first  into  the  substance  of  the 
muscle  and  subsequently  into  the  blood.  We  cannot  as  yet 
trace  out  the  steps  taken  b}-  the  oxygen  from  the  moment 
it  slips  into  its  intra-molecular  position  to  the  moment  when 
it  issues  united  with  cari)on  as  carbonic  acid.  Tiie  whole 
mystery  of  life  lies  hidden  in  the  story  of  that  progress,  and 
for  the  present  we  must  be  content  with  simply  knowing  tiie 
beginning  and  the  end. 

Our  knowledge  of  the  respiratory-  changes  in  muscle  is 
more  complete  than  in  the  case  of  any  other  tissue ;  but  we 
have  no  reason  to  suppose  the  phenomena  of  muscle  are 
exceptional.  On  the  contrary,  all  the  available  evidence 
goes  to  show  that  in  all  tissues  the  oxidation  takes  place  in 
the  tissue,  and  not  in  the  adjoining  blood.  It  is  a  remark- 
able fact,  that  lymph,  serous  flui(is,  bile,  urine,  and  milk*^ 
contain  a  mere  trace  of  free  or  loosely  combined  oxygen, 
and  saliva  or  pancreatic  juice  a  very  small  quantity  only 
(about  .5  per  cent),  while  tlie  tension  of  carbonic  acid  in 
peritoneal  fluid  is  as  high  as  (i  per  cent.,  and  in  bile  and 
urine  is  still  higher.  Tiie  tension  of  carbonic  acid  in  lymph, 
while  higher  than  that  of  arterial  blood,  is  lower  than  that 
of  the  general  venous  blood  ;  but  this  probably  is  due  to  the 
fact  that  the   lymph  in   its  passage   onwards   is  largel}'  ex- 

1  Pflii^er,  Pflu^^er's  Archiv,  i  (1868),  p.  686;  ii  (1869),  p.  156.  Hoppe- 
Seyler,  Zt.  f.  Physiol.  Chem.,  i  (1877),  p.  137. 


THE    CHANGES    IN    THE    TISSUES.  465 

posed  to  arterial  blood  in  the  connective  tissues  and  in  the 
lymphatic  glands,  where  the  production  of  carbonic  acid  is 
slight  as  compared  to  that  going  on  in  muscles.  Strassburg* 
has  attempted  to  determine  the  tension  of  carbonic  acid  in 
the  intestinal  walls;  the  experiment  is  perhaps  open  to  objec- 
tion, but  the  result  is  worth  recording  ;  he  found  the  tension 
to  l)e  7.7  percent.,  i.  e.,  higher  than  that  of  the  venous  blood 
examined  at  the  same  time.  All  these  facts  point  to  the 
conclusion  that  it  is  the  tissues,  and  not  the  blood,  which 
become  primarily  loaded  with  carbonic  acid,  the  latter  sim- 
ply receiving  the  gns  from  the  foriQer  by  diffusion,  except 
the  (probably)  small  quantity  which  results  from  the  meta- 
bolism of  the  blood  corpuscles;  and  that  the  oxygen  which 
passes  from  tlie  blood  into  the  tissues  is  at  once  taken  up  in 
some  combination,  so  that  it  is  no  longer  removable  by  di- 
minished tension. 

As  a  matter  of  fact^  Oertmann-'  has  shown  that  if  in  a  frog 
the  wdiole  blood  of  the  body  be  replaced  by  normal  saline  soln- 
tion,  the  total  metabolism  of  tlie  body  is,  for  some  tiuie,  un- 
changed. The  saline  medium  is  able,  owing  to  the  low  rate  of 
metabolism,  and  large  I'espiratory  surface  of  the  animal,  to  sup- 
ply the  tissues  with  all  the  oxygen  they  need,  and  to  remove  all 
the  carbonic  acid  they  produce.  It  is  difficult  to  believe  that,  in 
such  an  experiment,  the  oxidation  took  place  in  the  saline  solu- 
tion itself  while  circulating  in  the  bloodvessels  and  tissue-spaces 
of  the  animal. 

We  may  add,  that  the  oxidative  power  which  the  blood 
itself  removed  from  the  body  is  able  to  exert  on  substances 
which  are  undoubtedly  oxidized  in  the  body  is  so  small  that 
it  may  be  neglected  in  the  present  considerations.  If  grape- 
sugar  be  added  to  blood,  or  to  a  solution  of  hemoglobin, 
the  mixture  may  be  kept  for  a  long  time  at  the  temperature 
of  the  body  without  undergoing  oxidation.^ 


Almost  the  only  indication,  and  that  an  indirect  one,  that 
blood  is  capable  of  oxidizing  sugar  is  to  be  found  in  thefact.^  that 
wdien  the  sugar  in  shed  blood  is  quantitatively  determined,  the 

'  Pfliiger's  Archiv,  vi  (1872),  p.  65. 

2  Pfliiger's  Archiv,  xv  (1877),  p.  881. 

3  Hoppe-Sevier,  Untersuch.,  i  (1866),  p.  136.  See  also  Pfliiger's  Ar- 
chiv, vii  11873),  p.  399. 

1  Bernard,  Lcfons  sur  le  Diabete,  1877.  Pavy,  Proc.  Key.  Soc,  xxvi 
(1877),  p.  346. 


466       TISSUES    AND    MECHANISMS    OF    RESPIRATION. 

amount  is  greatest  when  the  blood  is  examined  immediately  on 
leaving  the  bloodvessels,  and  diminishes  afterwards.  Schenie- 
metjewski'  found  that  sodium  lactate  injected  into  the  veins  in- 
creased the  respiratory  interchange  ;  but  that  the  increase  was 
not  due  to  the  direct  combustion  of  the  salt  in  the  blood  seems 
to  be  indicated  by  the  fact  that  no  oxidation  of  the  salt  took 
place  when  it  was  simply  exposed  to  the  action  of  shed  blood  ; 
moreover  the  injection  of  sugar  did  not  even  increase  the  respir- 
atory interchange. 

Even  within  the  body  a  slight  excess  of  sugar  in  the  blood 
over  a  certain  percentage  wholly  escapes  oxidation,  and  is 
discharged  unchanged.  Many  easily  oxidized  substances, 
such  as  pyrogallic  acid,  pass  largely  through  the  blood  of  a 
living  body  without  being  oxidized.  The  organic  acids, 
such  as  citric,  even  in  combination  with  alkaline  bases,  are 
only  partially  oxidized  ;  when  administered  as  acids,  and 
not  as  salts,  they  are  hardly  oxidized  at  all.  It  is  of  course 
quite  possible  that  the  changes  which  the  blood  undergoes 
when  shed  might  interfere  with  its  oxidative  action,  and 
hence  the  fact  that  shed  blood  has  little  or  no  oxidizing 
power,  is  not  a  satisfactory  proof  that  the  unclianged  blood 
within  the  living  vessels  ma}'  not  have  such  a  power.  But 
did  oxidation  take  place  largely  in  the  blood  itself,  one  would 
expect  even  highly  diffusii)ie  substances  to  be  oxidized  in 
their  transit ;  whereas  if  we  suppose  the  oxidation  to  take 
place  in  the  tissues,  it  becomes  intelligible  wh}^  such  diffusi- 
ble substances  as  those  which  the  tissues  in  general  refuse 
to  take  up  largel}^  should  readily  pass  unchanged  from  the 
blood  through  the  secreting  organs. 

We  have  seen  that  in  muscle  the  production  of  carbonic 
acid  is  not  directly  dependent  on  the  consumption  of  oxy- 
gen. The  muscle  produces  carbonic  acid  in  an  atmosphere 
of  hydrogen.  What  is  true  of  muscle  is  true  also  of  other 
tissues  and  of  the  body  at  large.  Spallanzani  and  W.  Ed- 
wards showed  long  ago  that  animals  might  continue  to 
breathe  out  carbonic  acid  in  an  atmosphere  of  nitrogen  or 
b^'drogen ;  and  recently  Pfliiger-'  has  shown,  by  a  remark- 
able exi)eriment,  tiiat  a  frog  kept  at  a  low  temperature  will 
live  for  several  hours,  and  continue  to  produce  carbonic 
acid,  in  an  atmospiiere  absolutely  free  from  oxygen.  The 
carbonic   acid   produced  during   this  period  was   made  by 

1  Liidwig's  Arbeiten,  1868,  p.  114. 

2  PHiigers  Archiv,  x  (1875),  p.  251. 


THE    CHANGES    IN    THE    TISSUES.  467 

help  of  the  oxygen  inspired  in  the  hours  anterior  to  the 
commencement  of  the  experiment.  The  oxygen  then  ab- 
sorbed was  stowed  away  from  the  ha2mogk)bin  into  the 
tissues,  it  was  made  use  of  to  build  up  the  explosive  com- 
pounds, whose  explosions  later  on  gave  rise  to  the  carbonic 
acid  ;  or,  to  adopt  Pfliiger's  simile,  the  oxygen  helps  to 
wind  up  the  vital  clock  ;  but  once  wound  up,  the  clock  will 
go  on  for  a  period  without  further  winding.  The  frog  will 
continue  to  live,  to  move,  to  produce  carbonic  acid  for  a 
while  without  any  fresh  oxygen,  as  we  know  of  old  it  will 
without  any  fresh  food;  it  will  continue  to  do  so  till  the 
explosive  compounds  wiiich  the  oxygen  built  up  are  ex- 
hausted; it  will  go  on  till  the  vital  clock  has  run  down. 

To  sura  up,  then,  the  results  of  respiration  in  its  chemical 
aspects.  As  the  blood  passes  through  the  lungs,  the  low 
oxygen  tension  of  the  venous  blood  permits  the  entrance  of 
oxygen  from  the  air  of  the  pulmonary  alveolus,  through  the 
thinalveolar  wall,  through  the  thin  capillary  sheath,  through 
the  thin  layer  of  blood-plasma  to  the  red  corpuscle,  and  the 
reduced  haemoglobin  of  the  venous  blood  becomes  whoU}', 
or  all  but  wholly,  oxyha^moglobin.  Hurried  to  the  tissues, 
the  oxygen,  at  a  convparatively  high  tension  in  the  arterial 
blood,  passes  largely  into  them.  In  the  tissues  the  oxygen 
tension  is  always  kept  at  an  exceedingl}'  low  pitch  by  the  fact 
that  they,  in  some  wa}'  at  present  unknown  to  us,  pack  away 
at  every  moment  into  some  stalile  combination  each  mole- 
cule of  oxygen  which  they  receive  from  the  blood.  With 
much  but  not  all  of  its  oxyha^moglobin  reduced,  the  blood 
passes  on  as  venous  blood.  How  much  hnemoglobin  is 
reduced  will  dppend  on  the  activity  of  the  tissue  itself.  The 
quantity  of  ha?moglobin  in  the  blood  is  the  measure  of  limit 
of  the  oxidizing  power  of  the  body  at  large  ;  but  within  that 
limit  tlie  amount  of  oxidation  is  determined  by  the  tissue, 
and  by  the  tissue  alone. 

Though  the  quantity  of  carbonic  acid  expired  (p.  437)  may  be 
temporarily  increaseil  ])y  an  increase  of  the  respiratory  m')ve- 
ments,  this,  according  to  Pflliger,  is  to  be  regarded  as  the  result 
of  increased  ventilation  rather  than  of  increase(i  metabolic  pro- 
duction. This  physiologist'  has  brought  forward  strong  evidence 
in  favor  of  the  view  urged  by  him,  that  neither  the  extent  of  the 
respiratory  movements  nor  the  velocity  of  the  How  of  blood  are 

'  Pfliiger's  Arch iv,  vi  (1872),  p.  43;  x  (1875),  p.  251;  xiv  (1877), 
p.  1.    Finkler,  ibid.,  x,  p.  368.    Finkler  and  Oertiuann,  ibid.,  xiv,  p.  38. 


4t)8       TISSUES     AND    MECHANISMS    OF    RESPIRATION. 


to  be  refjarded  as  prime  factors  determining  the  amount  of  gen- 
eral metabolism.  It  is,  according  to  him,  tlie  quicker  metabolism 
which  determines  the  more  active  circulation  and  the  more  vig- 
orous respiration  ;  not  vice  versa. 

We  cannot  trace  the  oxygen  through  its  sojourn  in  the 
tissue.  We  only  know  that  sooner  or  later  it  comes  back 
combined  in  carbonic  acid  (and  other  matters  not  now  under 
consideration).  Owing  to  the  continual  production  of  car- 
bonic acid,  the  tension  of  that  gas  in  the  extravascular  ele- 
ments of  the  tissue  is  always  higher  than  that  of  the  blood ; 
the  gas  accordingly  passes  from  tlie  tissue  into  the  blood,  and 
the  venous  blood  passes  on  not  onl3'  with  its  haemoglobin 
reduced,  i.  e.^  with  its  oxygen  tension  decreased,  but  also 
with  its  carbonic  acid  tension  increased.  Arrived  at  the 
lungs,  the  l^lood  finds  tlie  pulmonary  air  at  a  lower  carbonic 
acid  tension  than  itself.  The  gas  accordingly  streams 
through  the  thin  vascular  and  alveolar  walls,  till  the  tension 
without  the  bloodvessel  is  equal  to  the  tension  within. 
Thus  the  air  of  the  pulmonary  alveoli,  having  given  up 
ox3-gen  to  the  blood  and  taken  up  carbonic  acid  from  the 
blood,  having  a  higher  carbonic  acid  tension  and  a  lower 
oxygen  tension  than  the  tidal  air  in  the  bronchial  passages, 
mixes  rapidly  with  tliis  by  diffusion.  The  mixture  is  further 
assisted  by  ascending  and  descending  currents;  and  the 
tidal  air  issues  from  the  chest  at  the  breathing  out  poorer 
in  oxygen  and  richer  in  carbonic  acid  than  the  tidal  air 
which  entered  at  the  breathino-  in. 


Sec.  6.    The  Nervous  Mechanism  of  Respiration. 

Breathing  is  an  involuntary  act.  Though  the  diaphragjn 
and  all  the  other  muscles  emi>lo3ed  in  respiration  are  volun- 
tary muscles,  i.  ^.,  muscles  which  can  be  called  into  action 
by  a  direct  effort  of  the  will,  and  though  respiration  may  be 
modified  within  very  wide  limits  b^'  the  will,  yet  we  habitu- 
ally breathe  without  the  intervention  of  the  will ;  the  normal 
breathing  may  continue,  not  onh^  in  the  absence  of  con- 
sciousness, but  even  after  the  removal  of  all  the  parts  of  the 
brain  above  the  medulla  oblongata. 

We  have  ahead >'  seen  how  complicated  is  even  a  simple 
respirator}'  act.  A  very  large  number  of  muscles  are  called 
into  play.  Many  of  these  are  very  far  apart  from  each 
other,  such  as  the  diaphragm  and  the  nasal   muscles;  yet 


NERVOUS    MECHANISM.  4G9 

they  act  in  hnrmonioiis  sequence  in  point  of  time.  If  tlie 
lower  intercostal  nuiscles  contracted  liefoi-e  the  scakni.  or  if 
the  diaj^hragra  contracted  while  the  other  chest  muscles 
Avere  enjoying  an  interval  of  rest,  the  satisfactory  entrance 
and  exit  of  air  would  be  impossible.  Tliese  muscles,  more- 
over, are  co-ordinated  also  in  respect  of  the  amount  of  their 
several  contractions;  a  gentle  and  ordinary  contraction  of 
the  diaphragm  is  accompanied  by  gentle  and  ordinary*  con- 
tractions of  the  intei  costals.  and  tliese  are  prv.^ceded  by 
gentle  and  ordinary  contractions  of  the  scaleni.  A  forcible 
contraction  of  the  scaleni,  followed  i)y  simply  a  gentle  con- 
traction of  the  intercostals,  would  hinder  rather  tlian  assist 
inspiration.  Further,  the  wdiole  complex  inspiratory  eflbrt 
is  often  followed  by  a  less  marked  but  still  complex  expi- 
ratory action.  It  is  impossible  that  all  these  so  carefully 
co-ordinated  muscular  contractions  should  be  brought  about 
in  any  other  way  than  by  co-ordinate  nervous  impulses  de- 
scending along  efferent  nerves  from  a  co-ordinating  centre. 
By  experiment  we  find  this  to  be  the  case. 

When  in  a  rai)bit  the  trunk  of  a  phrenic  nerve  is  cut,  the 
diaphragm  on  that  side  remains  motionless,  and  respiration 
goes  on  without  it.  When  both  nerves  are  cut,  the  whole 
diaphragm  remains  quiescen.t,  though  the  respiration  be- 
comes excessively-  labored. 

The  occasional  slight  rhythmic  movements  of  the  diaphragm 
observed  by  Brown-Sequard,  after  section  of  the  phrenic,  interest- 
ing from  another  point  of  view,  do  not  militate  against  the  above 
statement. 

When  an  intercostal  nerve  is  cut  no  active  resjjiratory 
movement  is  seen  in  that  space,  and  when  the  spinal  cord  is 
divided  below  the  origin  of  the  seventh  cervical  spinal  nerve, 
costal  respiration  ceases,  though  the  diaphragm  continues 
to  act,  and  that  with  increased  vigor.  When  the  cord  is 
divided  just  below  the  medulla,  all  thoracic  movements 
cease,  but  the  resj)iratory  actions  of  the  nosirils  and  glottis 
still  continue.  The'se,  however,  disappear  when  the  facial 
and  recurrent  laryngeal  are  divided.  We  have  already 
stated  that  after  removal  of  the  brain  above  the  medulla, 
respiration  still  continues  very  much  as  usual,  the  modifica- 
tions which  ensue  from  loss  of  the  brain  being  unessential. 
Hence,  putting  all  these  facts  together,  it  is  clear  that  in 
respiration,  co-ordinated  impulses  do,  as  we  suggested,  de- 

40 


470       TISSUES    AND    MECHANISMS    OF    RESPIRATION. 

scend  from  tlie  medulla  along:  the  several  efferent  nerves. 
The  proof  is  com()leted  by  the  fact  that  the  removal  or 
injury  of  the  medulla  alone  at  once  stops  all  respiratory 
movements,  even  though  every  muscle  and  every  nerve  con- 
cerned be  left  intact.  Nay  more,  if  only  a  small  portion  of 
the  medulla,  a  tract  whose  limits  are  not  as  yet  exactly  fixed, 
but  which  lies  below  the  vaso-motor  centre,  between  it  and 
the  calamus  scriplorius^  be  removed  or  injured,  respiration 
ceases  forever,  though  every  other  part  of  the  body  be  left 
intact.^  When  this  spot  is  excised  or  injured,  breathing  at 
once  ceases,  and  since  the  inhibitory  vagus  centre  is  gener- 
ally at  the  same  time  stimulated,  and  the  heart's  beat  ar- 
rested, death  ensues  instantaneously.  Hence  this  portion 
of  the  nervous  system  was  called  by  Flourens  the  vital  knot, 
or  uanglion  of  life,  nnp.iid  vital.  We  shall  speak  of  it  as  the 
respiratory  centre.  The  nature  of  this  centre  must  be  ex- 
ceedingly complex  ;  for  while  even  in  ordinar}"  respiration 
it  gives  rise  to  a  whole  group  of  co-ordinate  nervous  im- 
pulses of  inspiration,  followed  in  due  sequence  b}'  a  smaller 
but  still  co-ordinate  group  of  expiratory  impulses,  in  labored 
respiration  fresh  and  larger  impulses  are  generated,  though 
still  in  co-ordination  with  the  normal  ones,  the  expiratory 
events  being  especially  augmented  ;  and  in  the  more  ex- 
treme cases  of  dyspnoea  and  asph3'xia  impulses  overflow,  so 
to  speak,  from  it  in  all  directions,  though  only  gradually 
losing  their  co-ordination,  until  almost  ever}^  muscle  in  the 
bodv  is  thrown  into  contractions. 

The  first  question  we  have  to  consider  is  :  Are  we  to  re- 
gard the  rhythmic  action  of  this  respiratory  centre  as  due 
e.'^sentially  to  ciianges  taking  place  in  itself,  or  as  due  to 
afferent  nervous  impulses  or  other  stimuli  which  affect  it  in 
a  rhythmic  manner  from  without?  In  other  wTjrds  :  Is  the 
action  of  the  centre  automatic  or  purely  reflex  ?  We  know 
that  the  centre  may  be  influenced  by  impulses  proceeding 
from  without,  and  that  the  breathing  may  be  affected  by  the 
action  of  the  will,  or  b}'  an  emotion,  or  b}'  a  dash  of  cold 
water  on  the  skin,  or  in  a  hundred  other  ways;  but  the  fact 
that  the  action  of  the  centre  may  be  thus  modified  from 
without,  is  no  proof  that  the  continuance  of  its  activity  is 
dependent  on  extrinsic  causes. 

'  Strieker,  Wien.  Sitzungsbericht,  Bd.  75  (1877),  p.  8,  has  seen  in  dogs 
poisoned  by  antiarin,  respiratory  eflfbrts  after  division  of  the  medulla 
oblongata. 


NERVOUS    MECHANISM.  471 

In  attemptino-  to  decide  this  question  we  naturally  turn 
to  the  pneumogastric  as  being  the  nerve  most  likely  to  serve 
as  the  channel  of  afferent  impulses  setting  in  action  the 
respiratoi-y  centre.  If  both  vasi  be  divided,  respiration 
still  continues  though  in  a  modified  form.  This  proves  dis- 
tinctly that  afferent  impulses  ascending  those  nerves  are 
not  the  efUcient  cause  of  the  resi)iratory  movements.  We 
have  seen  that  when  the  spinal  cord  is  divided  below  the 
medulla,  the  facial  and  laryngeal  movements  still  continue. 
This  proves  that  the  respiratory  centre  is  still  in  action, 
though  its  activity  is  unal)le  to  manifest  itself  in  any  thoracic 
movement.  But  when  the  cord  is  thus  divided  the  respi- 
ratory centre  is  cut  off  from  all  sensory  impulses,  save  those 
which  may  pass  into  it  from  the  cranial  nerves;  and  the 
division  of  these  cranial  nerves  in  no  way  destroys  respira- 
tion. Hence  it  is  clear  that  the  resi)iratory  impulses  pro- 
ceeding from  the  respiratory  centre  are  not  simply  afferent 
impulses  reaching  the  centre  along  afferent  nerves,  and 
transformed  by  reflex  action  in  that  centre.  They  evidently 
start  de  novo  from  the  centre  itself,  however  much  their 
characters  may  be  affected  by  afferent  impulses  reaching 
that  centre  at  the  time  of  their  being  generated.  The  action 
of  the  centre  is  automatic,  not  simply  reflex. 

Among  the  afferent  impulses  which  affect  the  automatic 
action  of  the  centre,  the  most  im[)ortant  are  those  which 
ascend  along  the  vagi.  If  one  vagus  be  divided,  the  respi- 
ration becomes  slower;  if  both  be  divided,  it  becomes  very 
slow,  the  pauses  between  expiration  and  inspiration  lieing 
excessively  prolonged.  The  character  of  the  respiratory 
movement  too  is  markedly  changed,  each  respiration  is 
fuller  and  deeper,  so  much  so  that  what  is  lost  in  rate  is 
gained  in  extent,  the  amount  of  carbonic  acid  produced  and 
oxygen  consumed  in  a  given  period  remaining  after  division 
of  the  nerves  about  the  same  as  when  they  were  intact.  It 
is  evident  from  this,  in  the  first  place,  that  during  life 
afferent  impulses  are  continually  ascending  the  vagi  and 
modifying  the  action  of  the  respiratory  centre,  and  in  the 
second  [)lace.  that  the  modihcation  bears  simply  on  the  dis- 
tribution in  time  of  the  efferent  respiratory  impulses,  and 
not  at  all  on  the  amount  to  which  they  are  generated.  These 
afferent  impulses  are  proliably  started  in  the  lungs  by  the 
condition  of  the  blood  in  the  pulmonary  capillaries  acting  as 
a  stimulus  to  the  peripheral  endings  of  the  nerves,  though 


472       TISSUES    AND    MECHANISMS    OF    RESPIRATION. 


possibly  tlie  altered   air  in  the  air  cells  may  also  act  as  a 
stinuilus  on  the  nerve  endings. 

It  has  been  suggested  that  the  mere  movements  of  expansion 
and  contrnction  may  also  serve  as  a  stimulus.  According  to 
Hering  and  Breuer/  when  air  is  mechanically  driven  into  the 
chest,  an  expiratory  movement  follows,  and  when  air  is  drawn 
out,  an  inspiratory  ;  and  this  not  only  with  atmospheric  air  but 
with  indifferent  gases,  such  as  nitrogen  ;  when  both  vagi  are  cut, 
these  effects  do  not  appear.  They  infer  from  this  that  the  mere 
mechanical  expansion  of  the  lungs  transmits  along  the  vagus  an 
impulse  tending  to  inhibit  inspiration  and  to  generate  an  expira- 
tion, and  the  mechanical  contraction  of  the  lungs  an  impulse 
tending  to  inhibit  expiration  and  to  generate  an  insi)iration. 
Hence,  according  to  them  the  very  expansion  of  the  lungs,  which 
is  the  natural  effect  of  an  inspiration,  tends  of  itself  to  cut  short 
that  inspiration  and  to  inaugurate  the  sequent  expiration,  and 
similarly  the  contraction  of  an  expiration  promotes  the  following 
inspiration.  They  speak  in  fact  of  the  lungs  as  being  so  far  self- 
regulating.  This  view,  however,  though  very  interesting,  can 
perhaps  hardly  at  present  be  regarded  asproved.^ 

Wlien  the  central  stum})  of  one  of  the  divided  vagi  is 
stimnlnted  with  a  gentle  interrupted  cnrrent,  tlie  respira- 
tion, which  from  the  division  of  the  nerves  had  become  slow, 
is  quickened  again  ;  and  with  care,  by  a  proper  ai)i)lication 
of  the  slimulns,  the  normal  respiratory  rhythm  may  i\>r  a 
time  be  restored.  Upon  the  cessation  of  the  stimulus,  the 
slower  rhythm  returns.  If  the  current  be  increased  in 
strength,  the  rliythm  may  in  some  cases  be  so  accelerated 
that  at  last  the  diaphragm  is  brought  into  a  condition  of 
prolonged  tetanus,  and  a  standstill  of  respiration  in  an  ex- 
treme inspiratory  phase  is  the  result. 

Jf  the  central  end  of  the  sui)erior  laryngeal  brancii  of  the 
vagus  be  stimulated,  wlietiier  the  main  trunk  of  the  nerve 
be  severed  or  not,  a  slov\ing  of  the  respiration  takes  place, 
and  this  may  I'V  proper  stimulation  be  carried  so  far  that 
a  c(miplete  standstill  of  resjiiration  in  the  phase  of  rest  is 
brought  about,  i.  e..  the  respiratory  ap[)aratus  remains  in 
the  condition  which  obtains  at  tiie  close  of  an  ordinary  ex- 
piration, the  diaphragm  being  completely  relaxed.  In  other 
words,  the  superior  laryngeal  nerve  contains  fibres,  the 
stimulation  of  whicli  produces  afferent  im[)ulses  whose  effect 

^  Wien.  8itznngsl)ericht,  Nov.  5,  1868. 

2  Guttuuuin,  Dii  Bois-Keymond's  Archiv,  1875,  p.  500. 


NERVOUS    MECHANISM.  473 

is  to  inhiiiit  the  action  of  the  respiratoiy  centre;  wliile  the 
main  trunk  of  the  vagus  contains  fil)res,  the  stimulation  of 
which  produces  afferent  impulses  whose  effect  is  to  accel- 
erate or  augment  the  action  of  tlie  respiratory  centre.  lu 
some  cases  stimulation  of  the  main  trunk  of  tlie  vagus  also 
causes  a  slowing  or  even  standstill  of  the  respiration  espe- 
cially when  the  nerve  has  become  exhausted  liy  previous 
stimulation.  We  may,  for  the  present  at  least,  exijhiin  these 
results  by  supposing  that  while  the  superior  laryngeal  con- 
tains only  inhil)itory  fibres,  the  main  trunk  of  the  vagus 
contains  both  accelerating  and  inhil)itory  fibres,  the  former, 
however,  greatly  prei)onderating.  Wliile,  from  the  results 
of  simple  section  of  the  main  trunk,  it  is  clear  tiiat  the  ac- 
celerating fibres* are  continually  at  work,  it  is  not  so  clear 
that  the  inhibitory  fiiu-es  are  always  in  action,  since  section 
even  of  l)oth  superior  laryngeals  does  not  necessarily  quicken 
respiration. 

The  statement  made  above,  if  not  wholly  satisfactor}',  has  at 
least  the  merit  of  reconciling  conflicting  statements.  For  a  long 
time  a  controversy  was  carried  on  between  those  authors  who 
maintained  that  stimulation  of  the  central  end  of  the  vagus, 
when  the  nerve  was  divided  in  the  neck,  brought  about  a  tetanic 
contraction  of  the  diaphragm  and  so  had  an  inspiratory  eftect, 
and  those  wlio  observed  a  complete  relaxation  to  follow  upon 
stimulation,  and  so  regarded  the  efiect  as  expiratory.  We  are 
indebted  to  Eosenthab  for  pointing  out  the  contrast  between  the 
action  of  the  main  trunk  of  the  vagus  and  that  of  the  superior 
laryngeal  branch  ;  and  the  view  just  put  forward  in  the  text  is 
in  the  main  that  of  Kosenthal,  except  that  he  denies  the  exist- 
ence, admitted  by  most  other  observers,-  of  any  inhibitory  fibres 
in  tlie  main  trunk.  We  further  owe  to  Kosenthal  a  consistent 
theory  of  the  manner  in  which  the  vagus  acts  on  the  respiratory 
centre.  According  to  him  we  ma\'  regard  the  respiratorv  centre  as 
the  seat  of  two  conflicting  forces,  one  tending  to  generate  respira- 
tory impulses  and  the  other  oftering  resistance  to  the  generation 
of  these  impulses,  the  one  and  the  other  alternately  gaining  the 
victory  and  thus  leading  to  a  rhythmic  discharge.  The  afterentim- 
pulses  passing  upward  along  the  main  trunks  of  the  va.iii  are  fur- 
ther to  be  looked  upon  as  actinii  not  on  the  generation  of  impulses 
but  on  the  resistance  oflered  by  the  centre,  diminishing  that  resist- 
ance in  proportion  to  their  intensity.  Hence  when  the  vagi  are 
divided,  the  central  resistance  is  increased,  owing  to  the  abseni-e 
of  the  usual  aflerent  impulses  tending  to  diminish  that  resist- 

^  Die  Athembewegnngen,  1862,  and  Du  Bois-Revraond's  Archiv,  1864, 
p.  456  ;  1865,  p.  191 ;  1870,  p.  423. 

^  Cf.  Biu-kart,  Pfliiger's  Archiv,  xvi  (1878),  p.  427. 


474       TISSUES    AND    MECHANISMS    OF    RESPIRATION. 


ance  ;  in  consequence,  the  respiratory  impulses  take  a  lon^ertime 
in  gatliering  head  sufficient  to  overcome  the  increased  resistance, 
and  therefore  are  less  frequent,  though  the  discharge,  when  it 
docs  occur,  is  proportionately  more  forcible.  .Stimulation  of  the 
divided  vagi  on  Ihe  other  hand,  by  increasing  the  afierent  im- 
pulses and  so  diminishing  the  central  resistance,  renders  the  dis- 
charge more  frequent.  The  impulses  which  ascend  to  the  me- 
dulla along  the  superior  laryngeal  branches  may  in  like  manner 
be  regarded  as  increasing  the  central  resistance,  and  thus  as  in- 
hibitory of  the  respiratory  discharge. 

It  is  obvious  that  this  theory,  though  constructed  cliiefly  with 
the  view  of  explaining  inspiratory  impulses  and  their  inhibition, 
must,  in  order  to  be  satisfoctory," also  include  the  consideration 
of  distinctly  expiratory  impulses  ;  for  in  labored  respiration  we 
must,  in  some  way  or  other,  admit  the  existence  of  specitic  ex- 
piratory impulses,  and,  if  Hering  and  Breuer*s  view  be  correct, 
the  vngus  must  tiven  in  ordinary  breathing  be  the  channel  of 
stimuli  which  excite  expiratory  impulses.  Many  writers  regard 
the  standstill  which  is  produced  by  stimulation  of  the  superior 
laryngeal  nerve  as  an  expiratory  eftect,  and  indeed  frequently 
speak'of  it  as  an  ''expiratory  standstill."  But  it  is  obvious  that 
distinction  ought  to  be  made  between  a  state  of  things  in  which 
there  is  a  complete  absence  of  all  respiratory  muscular  activity, 
and  in  which  the  chest  remains  in  a  condition  of  passive  rest, 
and  one  in  which  the  chest  is  maintained  in  a  lixed  condition  by 
the  continued  contraction  of  certain  expiratory  muscles ;  it  is 
the  latter  which  is  the  true  expiratory  standstill,  the  antithesis 
of  the  inspiratory  standstill,  in  which  the  diaphragm  remains  in 
tetanic  contraction.  The  inhibition  of  inspiratory  impulses  is, 
however,  the  natural  precursor  of  expiratory  impulses,  and  it 
would  seem  tiiat  the  same  impulses  which  bring  about  a  stand- 
still of  inspiration  may,  when  increased  in  strength,  give  rise  to 
movements  of  a  distinctly  expiratory  character.  Thus  stimula- 
tion of  tlie  superior  laryngeal  branch,  when  carried  beyond  the 
strength  nece^sar}-  to  inhibit  inspiration,  may  give  rise  to  con- 
traction of  the  al)dominal  muscles  indicative  of  expiratory  efforts. 
We  may,  therefore,  complete  the  hypothesis  of  the  respiratory 
centre  by  supposing  it  to  consist  of  an  inspiratory  part  and  an 
expiratory  ])art,  so  disposed  in  reference  to  each  other  that  the 
impulses  which  tend  to  excite  the  one  part  tend  at  the  same  time 
to  inhibit  the  other  part,  and  vice  verm,  the  expiratory  tract, 
however,  being  less  irritable  than  the  inspiratory  tract,  so  that 
the  latter  is  thrown  into  action  first,  and  the  former  comes  into 
l)lay  to  any  very  appreciable  effect  only  when  comparatively 
strong  stimuU  are  brought  to  bear  upon  it.^ 

Stimulation  of  the  central  end  of  the  inferior  recurrent  laryn- 
geal is  said  to  have  an  inhibitory  effect  like  that  of  the  superior 
laryngeal,  but  much  slighter.^ 

'  Eosenthal,  Automat.  Nerven-Centn,  1875. 
'^  Rosenthal,  op.  cit. 


NERVOUS    MECHANISM.  475 

Tliis  double  or  alternate  respiratory  aetion  of  the  vagi 
may  be  taken  as  in  a  general  way  illustrative  of  the  manner 
in  which  other  afferent  nerves  and  various  parts  of  the  cere- 
brum are  enabled  to  influence  respiration,  this  or  that  arter- 
ent  impulse,  started  by  a  stimulus  applied  to  the  skin  or 
elsewhere,  or  by  an  emotion  and  the  like,  playing,  accord- 
ing to  circumstances,  now  an  inhibitory,  now  an  accelerat- 
ing part.  As  we  know  from  daily  experience,  of  all  the 
apsychical  nervous  centres,  the  respiratoiy  centre  is  the  one 
which  is  most  frequently  and  most  deeply  affected  by  nervous 
impulses  from  various  quaiters. 

According  to  Langendorff,^  weak  stimulation  of  any  sensory 
nerve  produces  acceleration,  strong  stimulation  inhibition,  or 
slowing  of  respiration.  It  is  absurd  to  suppose  that  ever}-  sen- 
sory nerve  contains  distinct  accelerating  and  inhibitory  tibres 
connected  with  the  respiratory  centre.  "  And  the  exisfence  of 
tico  classes  of  respirdtori/  Jibres  in  the  vagus  or  its  branches  must 
be  regarded  in  the  same  provisional  sense  as  the  existence  of  dis- 
tinct vaso-dilator  and  vaso-constrictor  fibres. 

The  one  thing,  however,  which,  above  others,  affects  the 
respiratory  centre,  is  the  condition  of  the  blood  in  respect 
to  its  respiratory  changes;  the  more  venous  (less  arterial) 
the  blood,  the  greater  is  the  activity  of  the  respiiatoiy 
centre.  When,  b}-  reason  either  of  any  hindrance  to  the 
entrance  of  air  into  the  chest,  or  of  a  greater  respiiatory 
activity  of  the  tissues,  as  during  musculrr  exertion,  tiie 
blood  becomes  less  ailerial,  more  venous,  i.  e.,  with  a  smaller 
charge  of  oxyhfemoglobin,  and  more  heavily  laden  with  cai- 
bonic  acid,  the  respiration  from  being  ncrmal  becon;es 
laliored.  This  effect  of  deficient  arterialization  of  blood  is 
very  different  from  that  of  section  of  the  vagi  ;  it  is  no  mere 
chai'ge  in  the  distribution  of  impulses;  the  breathing  is 
quicker  as  well  as  deeper  ;  there  is  an  increase  of  the  sum 
of  efferent  im})ulses  proceeding  from  the  centie,  and  the 
expiratory  impulses,  which  in  normal  respiration  are  veiy 
slight,  acquire  a  pronounced  importance.  As  the  blood 
becomes,  in  cases  of  obstruction,  less  and  less  arterial, 
more  and  more  venous,  the  discharge  from  the  respiratory 
centre  becomes  more  and  more  vehement,  and  instead  of 
confining  itself  to  the  usual  tracts,  and  passing  down  to  the 
ordinary  respiratory  muscles,  overflows   into   other  tracts, 

^  Mitth.  a.  d.  Konigsberger,  Physiol.  Lab.,  1878,  p.  33. 


476       TISSUES    AND    MECHANISMS    OF    RESPIRATION. 

puts  into  action  otlier  mnscles,  until  there  is,  perhaps, 
hardly  a  muscle  in  the  body  which  is  not  made  to  feel  its 
effects.  And  this  discliaroe  may,  as  we  shall  see  in  speak- 
ing of  asphyxia,  continue  till  the  nervous  energy  of  the 
respiratory  centre  is  completely  exhausted.  The  effect  of 
venous  blood,  then,  is  to  augment  these  natural  exi)losive 
decompositions  of  the  nerve-cells  of  the  respiratory  centre 
which  give  rise  to  respiratory  impulses  ;  it  increases  their 
amount,  and  also  quickens  their  rhythm.  The  latter  change, 
however,  is  always  much  less  marked  than  the  former,  the 
respiiation  in  dyspnoBa  being  much  more  dee[)ened  than 
hurried,  and  the  several  respiratory  acts  are  never  so  much 
hastened  as  to  catch  each  other  up,  and  so  to  produce  an 
inspiratory  tetanus  like  that  resulting  from  stimulation  of 
the  vagus.  On  the  contrary,  especially  as  exhaustion  begins 
to  set  in,  the  rhythm  becomes  slower  out  of  proportion  to 
the  weakening  of  the  individual  movements. 

There  seem  to  be  two  distinct  kinds  of  dyspnoea.  In  one  with 
increased  depth  the  rhythm  is  not  proportionately  quickened  or 
may  even  be  diminished.  Thus  in  the  dyspnoea  caused  by  sec- 
tion of  the  phrenic  nerves,  the  rhythm  falls  notably.'  In  the 
other,  which  may  be  called  the  asthmatic  type,  the  rhythm  is 
hurried,  wdiile  the  depth  of  each  breath  is  not  increased  but,  in 
many  cases  at  least,  diminished. 

On  the  other  hand,  the  blood  may  be  made  not  more  but 
less  venous  than  usual.  This  condition  may  be  brought 
a!)out  i»y  an  animal  Iteing  made  to  inspire  oxygen,  or  to 
breathe  for  a  time  more  rapidly  and  more  forcibly  than  the 
needs  of  the  economy  require.  If  in  a  rabbit  artificial  res- 
piration is  carried  on  very  vigoi-ously  for  awhile,  and  then 
suddenly  stoi)ped,  the  animal  does  not  immediately  begin 
to  breathe.  For  a  variable  period  no  respii'ation  takes  phtce 
at  all,  and  when  it  does  begin  occurs  gently  and  normally, 
only  pissing  into  dyspnoea  if  the  animal  is  una!)le  to  breathe 
of  itself,  and  then  quite  gradually.  Evidently  during  this 
period  the  respiratory  centre  is  in  a  state  of  complete  rest, 
no  explosions  are  taking  place,  no  respiratory  imj)ulses  are 
being  generated,  and  the  quiet  transition  from  this  condition 
to  that  of  normal  respiration  shows  that  the  subsequent 
generation  of  impulses  is  attended  liy  no  gi-eat  disturbance. 
The  cause  of  this  state  of  tilings,  which  is  known  as  that  of 

^   Purkinje,  quoted  by  Hering  and  Breuer,  op.  cit. 


NERVOUS    xMECHANISM.  477 


apnnra.  is  to  be  soiislit  for  in  the  condition  of  the  blood. 
By  the  increased  vij^or  of  the  artificial  respiratory  move- 
ments the  hjiemoijlobin  of  the  arterinl  blood,  whicli  is  natn- 
rally  not  qnite  saturated,  becomes  ahuost  completely  so.  and 
the  dissolved  oxygen  is  increased,  its  tension  being  laricely 
augmented.  Respiration  is  arrested  because  the  blood  is 
more  highly  arterialized  than  usual.  Thus  we  have  in  ap- 
nrea  the  converse  to  dyspnoea ;  and  both  states  point  to  the 
same  conclusion,  that  the  activity  of  the  respiratory  centre 
is  dependent  on  the  condition  of  the  blood,  being  aug- 
mented when  the  blood  is  less  arterial  and  more  venous, 
being  depressed  when  it  is  more  arterial  and  less  venous 
than  usual. 

The  question  now  arises,  Does  this  condition  of  the  blood 
affect  the  respiratory  centre  directly,  or  does  it  produce  its 
effect  by  stimulating  the  peripheral  ends  of  afferent  nerves 
in  various  parts  of  tiie  body,  and,  by  the  creation  there  of 
afferent  impulses,  indirectly  modify  the  action  of  the  centre  ? 
Without  denying  the  possibilit}-  that  the  latter  mode  of  ac- 
tion may  help  in  the  matter,  as  regards  not  onl}'  the  vagi, 
but  all  afferent  nerves,  it  is  clear  from  the  following  reasons 
that  the  main  eflfect  is  produced  by  the  direct  action  of  the 
blood  on  the  respiratory  centre  itself.  If  the  spinal  cord 
be  divided  below  the  medulla  oblongata,  and  both  vagi  be 
cut,  want  of  proper  aeration  of  the  blood  still  produces  an 
increased  activity  of  the  respiratory  centre,  as  shown  by 
the  increased  vigor  of  the  facial  respiratory  movement.^. 
If  the  supply  of  blood  be  cut  off"  from  the  medulla  by  liga- 
ture of  the  bloodvessels  of  the  neck,  dysi)noea  is  produced, 
though  the  operation  produces  no  change  in  the  blood  gen- 
erally, but  sirai)ly  affects  the  respiratory  condition  of  the 
medulla  itself,  by  cutting  off"  its  blood-supply,  the  immediate 
result  of  which  is  an  accumulation  of  carbonic  acid  and  a 
paucity  of  available  oxygen  in  the  protoplasm  of  the  nerve- 
cells  in  that  region.  If  the  blood  in  the  carotid  artery  in 
an  animal  be  warmed  above  the  normal,  dyspn(L\a  is  at  once 
produced.  The  over-warm  blood  hurries  on  the  activity  of 
the  nerve-cells  of  the  respiratory  centre,  so  that  the  normal 
supply  of  blood  is  insufficient  for  their  needs.  The  condi- 
tion of  the  blood  then  affects  respiration  by  acting  directly 
on  the  I'espiratory  centre  itself. 

Deficient  aeration  produces  two  effects  in  blood  :  it  di- 
minishes the  oxygen,  and  increases  the  carbonic  acid.  Do 
both  of  these  changes  affect  the  respiratory  centre,  or  only 


478      TISSUES    AND    MECHANISMS    OF    RESPIRATION. 

one,  and  if  so,  wliich  ?  Wlien  an  animal  is  made  to  breathe 
an  atmosphere  containing  nitrogen  only,  the  exit  of  car- 
bonic acid  by  diffusion  is  not  affected,  and  the  blood,  as  is 
proved  by  actual  analysis,  contains  no  excess  of  carbonic 
acid.'  Yet  all  the  phenomena  of  dyspncjea  are  present.  In 
this  case  these  can  only  be  attributed  to  the  deficienc}^  of 
oxygen.  On  the  other  hand,  if  an  animal  be  made  to 
breathe  an  atmospliere  rich  in  carbonic  acid,  but  at  the 
same  time  containing  an  abundance  of  oxygen,  tliough  the 
breathing  becomes  markedly  deeper  and  also  somewliat 
more  frequent,  there  is  no  culmination  in  a  convulsive 
asphyxia,  even  when  the  quantity  of  carbonic  acid  in  the 
blood,  as  shown  by  direct  analysis,  is  very  largely  increased.'^ 
On  the  contrary  the  increase  in  the  res})iratorv  movements 
after  awhile  passes  off",  the  animal  becoming  unconscious, 
and  appearing  to  be  suffering  rather  from  a  narcotic  poison 
than  from  simple  dyspnoea.  It  does  not  seem  certain  that 
the  increased  respiratory  movements  seen  at  first  are  the 
direct  result  of  the  action  of  the  carbonic  acid  on  the  re- 
spiratory centre  ;  it  is  possible  that  the  carbonic  acid  may 
affect  the  respirator3'  centre  in  an  indirect  way,  by  stimu- 
lating the  respir;vtor3'  passages,  or  by  its  action  on  higher 
paits  of  the  brain  ;  and  in  all  cases  there  is  a  marked  con- 
trast between  the  slow  develojjment  and  evanescent  charac- 
ter of  the  hype'rpnoea  of  carbonic  acid  poisoning,  and  the 
rapid  onset  and  speedy  culmination  in  convulsions  and 
death  of  the  dyspnwa  due  to  the  absence  of  oxygen.  There 
can  in  fact  be  no  doubt  that  the  action  of  deficiently  arte- 
rialized  blood  on  the  respiratory  centre,  as  manifested  in  an 
augmentation  of  the  respiratory  ex[)losions,  is  due  })rimarily 
to  a  want  of  oxygen,  and  in  a  secondar}-  manner  only  to  an 
excess  of  carbonic  acid. 

[The  action  of  drugs  upon  tlie  respiratory  centres  and 
peripheral  pulmonic  vagi  nerves,  is  both  physiologically  and 
therapeutically  of  consideraV)le  interest.  Thus  it  has  been 
found  that  ammonia  stimulates  the  respiratory  centres  ;  bella- 
donna fiist  stimulates,  afterwards  pai'alyzes  (?)  them ;  and 
salicylic  acid  in  small  doses  stimulates  and  in  large  doses 
paralyzes  the  centres  Apomorphia  stimulates  the  peripheral 
nerves,  and  in  labbits  the  centres  also.  Aconite,  hydrocy- 
anic acid,  opium,  caffein,  ether,  chloral,  nitrite  of  amyl,  vera- 
tria,  and  many  other  drugs  paralyze  the  centres.] 

1  Pfliiger,  Pfliiger's  Archiv,  i  (1868),  p.  61. 

2  Dohmen,I^ntersuch.  a.  d.  Physiol.  Lab.  in  Bonn,  1865.  Pfliiger,  op.  cit. 


EFFECTS    ON    CIRCULATION.  479 


Cheyne-Stokes  Respiration. — A  remarkable  abnormal  rbytbm 
of  respiration,  first  observed  byCbeyne'  bnt  afterwards  more  fully 
studied  by  Stokes"  and  bence  called  by  tbeir  combined  names,  oc- 
curs in  certain  patliological  cases.  The  respiratory  movements 
gradually  decrease  both  in  extent  and  rapidity  until  they  cease 
altogether,  and  a  condition  of  apncea,  lasting  it  may  be  for  sev- 
eral seconds,  ensues.  This  is  followed  b}'  a  feeble  respiration, 
succeeded  in  turn  by  a  somewhat  stronger  one,  and  thus  the 
respiration  returns  gradually  to  the  normal,  or  may  even  rise  to 
hyperpnoea  or  slight  dyspnoea,  after  which  it  again  declines  in  a 
similar  manner.  A  secondary  rhythm  of  respiration  is  thus  de- 
veloped, periods  of  normal  or  slightl}' dyspnceic  respiration  alter- 
nating by  gradual  transitions  with  periods  of  apnoea.  The  cause 
of  the  phenomena  is  not  tboroughl}-  understood.  Stokes  con- 
nected it  with  a  fiitty  condition  of  the  heart,  but  it  has  been  met 
with  in  various  maladies.  SchitP  observed  it  as  the  result  of 
compression  of  the  medulla  oblongata  ;  and  closeh'  similar  phe- 
nomena have  been  observed  during  sleep,  under  perfectly  normal 
conditions.^  It  presents  a  striking  analog}-  with  the  ''groups" 
of  heart-beats  so  frequently  seen  in  the  frog's  ventricle  placed 
under  abnormal  circumstances. 


Sec.  7.    The  Effects  of  Respiration  on  the 
Circulation. 

We  have  seen,  while  treating  of  the  circulation,  that  the 
blood-pressure  curves  are  marked  by  undulations,  wliicii, 
since  their  rliythm  is  synchronous  with  that  of  the  respira- 
tory movements,  are  evident!}^  in  some  wa^'  connected  with 
respiration.  An  analysis  of  these  undulations  shows  tliat 
their  causation  is  complex  ;  several  events  apparently  ma^^ 
combine  to  bring  them  about. 

When  the  brain  of  a  living  mammal  is  exposed  by  the 
removal  of  the  skull,  a  rhythmic  rise  and  fall  of  the  cerebral 
mass,  a  pulsation  of  the  l)rain,  quite  distinct  from  the  move- 
ments caused  by  the  pulse  in  the  arteries  of  tlie  brain,  is 
observed  ;  and  upon  examination  it  will  be  found  that  tliese 
movements  are  synchronous  witii  the  respiratory  move- 
ments, the  brain  rising  up  during  expiration  and  sinking 
during  inspiration.  Tliey  disappear  when  the  arteries 
going  to  the  brain  are  ligatured,  or  when  the  venous  sinuses 

1  Dublin  Hospital  Reports,  ii  (1816),  p.  21. 

2  See  Diseases  of  Heart,  etc.,  1854,  p.  324. 

3  Lehrb.,  1858,  p.  324. 

*  Cf.  Mosso,  Arch.  Anat.  u.  Phys.,  1878,  Phys.  Abth.,  p.  441. 


480      TISSUES    AND    MECHANISMS    OF    RESPIRATION. 

of  the  dura  mater  are  laid  open  so  as  to  admit  of  a  free 
escape  of  the  venous  blood.  They  evidently  arise  from  the 
ex|)iratory  movements  in  some  way  hindering  and  the 
insi)iratoiv  movements  assisting  the  return  of  hlood  from 
the  brain.  We  have  already  (p.  189)  stated  that  during 
inspiration  the  pressure  of  blood  in  the  great  veins  may 
become  negative,  i.  ^.,  sink  below  the  pressure  of  the  atmos- 
phere; and  a  puncture  of  one  of  these  veins  may  cause  im- 
mediate death  by  air  being  actually  drawn  into  the  vein 
and  thus  into  the  heart  during  an  inspiratory  movement. 
When  the  veins  of  an  animal  are  laid  bare  in  the  neck  and 
watched,  the  so-called  piilauH  venosua  may  be  oliserved  in 
them,  that  is,  they  swell  up  during  expiration  and  dimiiiish 
again  during  inspiration.  And  indeed  a  little  consideration 
will  show  that  the  expansion  and  contraction  of  the  chest 
must  have  a  decided  effect  on  the  flow  of  blood  through  the 
thoracic  portion  of,  and  thus  indirectly  through  the  whole 
of  the  vascular  system. 

The  heart  and  great  bloodvessels  aie.  like  the  lungs, 
placed  in  the  air-tight  thoracic  cavity,  and  are  sulyect  like 
the  lungs  to  the  pumping  action  of  the  respiratory  move- 
ments. Were  the  lungs  entirely  absent  from  the  chest,  the 
whole  force  of  the  expansion  of  the  thorax  in  inspiration 
would  be  directed  to  drawing  blood  from  the  extra  thoracic 
vessels  towards  the  heart,  and  conversely  the  effect  of  the 
contraction  of  the  thorax  in  expii-ation  would  be  to  drive  the 
blood  hack  again  from  the  heart  towards  the  extra-thoracic 
vessels.  In  the  presence  of  the  lungs  however  the  free  en- 
trance of  air  into  the  interior  of  the  chest  tends  to  maintain 
the  pressure  around  the  heart  and  great  vessels  within 
the  tliorax  equal  to  the  ordinary  atmosi)heric  pressure  on 
the  vessels  of  the  rest  of  the  body  outside  the  thorax  ;  but 
it  is  unai)le  completel}'  to  equalize  the  two  pressures.  Did 
the  air  enter  as  freely  into  the  lungs  as  it  does  into  tiie 
pleural  cavities  when  wide  openings  are  made  in  the  thoracic 
walls,  the  respiratory  movements  would  have  very  little 
effect  indeed  on  the  flow  of  blood  to  and  from  the  heart, 
just  as  under  similar  circumstances  (p.  422)  they  would  be 
ineffectual  in  promoting  the  entrance  and  exit  of  air  to  and 
from  the  lungs.  But  the  air  does  not  pass  into  the  pulmon- 
ary alveoli  as  freely  as  it  would  do  into  a  j^leural  cavity 
through  an  opening  in  the  thoracic  wall.  Before  the  in- 
spired air  can  fill  a  pulmonary  alveolus,  the  walls  of  the 
alveolus  have  to  be  distended  at  the  expen.se  of  the  pressure 


EFFECTS    ON    CIRCULATION.  481 

tchi'ch  caiL'^e:-^  /he  inspired  air  fo  enter.  Part  of  tlie  atmos- 
pheric pressure  in  fact  vvliieh  causes  the  entrance  of  the  air 
into  the  lung  is  spent  in  overcoming  the  elasticity  of  the 
pulmonary  passages  and  cells.  Consequently,  any  structure 
lying  within  the  thorax  hut  outside  the  lungs,  is  never,  even 
at  the  conclusion  of  an  inspiration  when  the  lungs  are  filled 
with  air,  subject  to  a  pressure  as  great  as  that  of  the  atmos- 
j)here.  The  pressure  on  such  a  structure  ahva3S  falls  short 
of  the  pressure  of  the  atmosphere  by  the  amount  of  pressure 
necessary  to  counterbalance  the  elasticity  of  the  pulmonary 
passages  and  cells.  And  since  the  fraction  of  the  atmos- 
•  pheric  pressure  which  is  thus  spent  in  distending  the  lungs 
increases  as  the  lungs  become  more  and  more  stretched,  it 
follows  that  the  fuller  the  inspiration  the  greater  is  the  dif- 
ference between  the  pressure  on  structures  outside  the 
lungs  but  within  the  thorax  and  the  ordinary  pressure  of 
the  atmosphere.  Now  we  have  seen  (p.  422)  that  the  pres- 
sure necessary  to  counterbalance  tiie  elasticity  of  the  lungs, 
when  they  are  completely  at  rest  (in  the  i)ause  between  ex- 
piration and  inspiration)  is  in  man  about  5  to  7  mm.  of 
mercury,  and  that  when  the  lungs  are  fully  distended,  as  at 
the  end  of  a  forcible  inspiration,  tlie  pressure  rises  to  as 
much  as  30  mm.  of  mercury.  Hence  at  tho  height  of  a 
forcible  inspiration  the  pressure  exerted  on  the  heart  and 
great  vessels  within  the  thorax  is  30  mm.  less  than  the 
ordinary  atmospheric  pressure  of  7fiO  mm.,  and  even  when 
the  chest  is  completely  at  rest,  at  the  end  of  an  expiration, 
the  pressure  on  the  heart  and  great  vessels  is  slightly  (by 
about  5  mm.  mercury)  below  that  of  the  atmosphere. 

During  an  inspiration  then  the  pressure  around  the  heart 
and  great  bloodvessels  becomes  considerably  less  than  that 
of  the  atmcsphere  on  the  vessels  outside  the  thorax.  Dur- 
ing expiration  this  i)ressure  returns  towards  that  of  the 
atmosphere,  bnt  in  ordinary  breathing  never  quite  reaches 
it.  It  is  only  in  forcible  expiration  that  the  pressure  on  the 
thoracic  vascular  organs  exceeds  that  of  the  atmosphere. 
But  if  during  inspir-ation  the  pressure  bearing  on  the  right 
auricle  and  the  venae  cava?  becomes  less  than  tiie  pressure 
which  is  bearing  on  the  jugular,  suliclavian,  and  other  veins 
outside  the  thorax,  this  must  result  in  an  increased  flow 
from  the  latter  into  the  former.  Hence,  during  each  inspi- 
ration a  lai'ger  quantity  of  blood  enters  the  right  side  of  the 
heai't.  This  [)robably  leads  to  a  stronger  stroke  of  the  heart, 
and  at  all  events  causes  a  larger  quantity  to  be  ejected  by 


482      TISSUES    AND    MECHANISMS    OF    RESPIRATION. 

the  right  ventricle  ;  this  causes  a  larger  quantity  to  escape 
from  the  left  ventricle,  and  thus  more  blood  is  thrown  into 
the  aorta,  and  the  arterial  tension  proportionately  increased. 
During  expiration  the  converse  takes  |)lace.  The  pressure 
on  the  intra-thoracic  bloodvessels  returns  to  the  normal,  the 
flow  of  blood  from  the  veins  outside  the  thorax  into  the 
venjB  cavre  and  riglit  auricle  is  no  longer  assisted,  and  in 
consequence  less  blood  passes  through  the  heart  into  the 
aorta,  and  arterial  tension  falls  again.  During  forced  ex- 
piration, the  intra-thoracic  pressure  may  be  so  great  as  to 
afford  a  distinct  ol)stacle  to  the  flow  from  the  veins  into  the 
heart. 

The  effect  of  the  respiratory  movements  on  the  arteries  is 
naturall}'  different  from  that  on  the  veins.  During  inspira- 
tion the  diminution  of  pressure  in  the  thorax  around  the 
aortic  arch  tends  to  draw  the  blood  from  tiie  arteries  outside 
the  thorax  back  to  the  arch  of  the  aorta,  or  in  other  words, 
tends  to  check  the  onward  flow  of  blood.  At  the  same  time, 
and  this  is  the  point  to  which  we  wish  to  call  attention,  the 
aortic  arch  itself  tends  to  expand  ;  in  consequence  the  pres- 
sure of  blood  within  it,  i.  e.,  the  arterial  tension,  tends  to 
diminish.  During  expiration,  the  increase  of  pressure  out- 
side the  aortic  arch  of  course  tends  to  increase  also  the 
blood-pressure  wdthin  it,  acting  in  fact  just  in  the  same  way 
as  if  the  coats  of  the  aorta  themselves  contracted.  Thus, 
as  far  as  arterial  blood-pressure  is  concerned,  the  effects  of 
the  respiratory  movements  on  the  great  veins  and  great  ar- 
teries respectively,  are  antagonistic  to  each  other  ;  the  effect 
on  the  veins  being  to  increase  arterial  tension  during  inspi- 
ration and  to  diminish  it  during  expiration,  while  the  eflect 
on  the  arteries  is  to  diminish  arterial  tension  during  inspira- 
tion and  to  increase  it  during  expiration.  But  we  should 
naturally  expect  the  effect  on  the  thin-walled  veins  to  be 
greater  than  that  on  the  stout  thick-walled  arteries,  so  that 
the  total  effect  of  inspiration  woukl  be  to  increase,  and  the 
total  effect  of  expiration  to  diminish,  arterial  tension. 

These  facts  seem  at  first  sight  to  afford  a  ready  explana- 
tion of  the  respiratory  undulations  of  the  blood  pressure 
curve  ;  the  rise  of  pressure  in  each  undulation  might  be  sup- 
posed to  be  due  to  the  inspiratory,  the  fall  to  the  expiratory 
movement.  Wiien,  how^ever,  the  respiratory  undulations  of 
the  blood-pressure  curve  are  compared  carefully  with  the 
variations  of  intrathoracic  pressure,  it  is  seen  that  neither 
the  rise  nor  the  fall  of  the  former  are  exactly  synchronous 


EFFECTS    ON    CIRCULATION. 


483 


with  cither  diminution  or  increase  of  the  latter.  Fig.  127 
shows  two  tracings  from  a  dog  talven  at  the  same  time,  one, 
o,  being  the  ordinary  l>lood-pressnre  curve  from  the  carotid, 
and  the  other,  />,  re[)resenting  the  condition  of  tlie  intra- 
thoracic pressure  as  obtained  by  carefuU}'  bringing  a  man- 
ometer into  connection  with  the  pleural  cavitv.  On  com- 
paring the  two  curves,  it  is  evident  that  neither  tlie  maximum 
nor  tlie  minimum  of  arterial  pressure  coincides  exactly 
either  with  ins))iration  or  with  expiration.  At  the  beginning 
of  inspiration  (i)  the  arterial  pressure  is  seen  to  be  falling  ; 
it  soon,  however,  begins  to  rise,  but   does   not  reach  the 


Fig. 127 


Comparison  of  Blood-Pressure  curve  with  curve  of  Intra-thoracic  Pressure. 
(To  be  read  from  left  to  right.) 

a  is  the  blood-pressure  curve,  with  its  respiratory  undulations,  the  slower  beats  on 
the  descent  being  very  marked,  b  is  the  curve  of  intra-thoracic  pressure  obtained 
by  connecting  one  limb  of  a  manometer  with  the  pleural  cavity.  Inspiration  begins 
at  i,  expiration  at  e.  The  intra-thoracic  pressure  rises  very  rapidly  after  the  cessa- 
tion of  the  inspiratory  effort,  and  then  slowly  fails  as  the  air  issues  from  the  chest; 
at  the  beginning  of  the  inspiratory  effort  the  fall  becomes  more  rapid. 


maximum  until  some  time  after  expiration  (e)  has  begun  ; 
the  fall  continues  during  the  remainder  of  expiration,  and 
passes  on  into  the  succeeding  inspiration.  In  order  to 
reconcile  tiie  facts  represented  b}^  tliese  curves  with  the 
meclianical  explana'tion  given  above,  we  must  suppose  that 
the  beneficial  effects  of  tiie  inspiratory  movement  in  the 
larger  supply  of  blood  brought  to  the  heart,  take  some  time 
to  develop  themselves,  and  last  beyond  tlie  movement  itself. 
Bat  there  are  phenomena  which  show  that  in  the  produc- 
tion of  the  respiratory  undulation  other  influences  besides 
those  just  discussed  are  at  work. 


484      TISSUES    AND    MECHANISMS    OF    RESPIRATION. 

Wlien.  as  for  instance  in  an  nnimal  nnder  nrari,  artificial 
is  substituted  for  natural  respiration,  undulations  of  tlie 
blood-piessure  curve  are  observed  (Fig.  128,  1),  similar  in 
character  to,  thougii  less  in  extent  than,  those  seen  under 
natural  conditions.  Ts^ow  in  artificial  respiration,  the  me- 
chanical conditions,  nnder  whicii  the  thoracic  viscera  are 
placed  as  regards  })ressure,  are  the  exact  opposite  of  those 
existing  during  natural  respiration  ;  for  when  air  is  blown 
into  the  trachea  to  distend  the  lungs,  the  pressure  within 
the  chest  is  increased  instead  of  diminished.  Evidently  the 
explanation  given  above  is  not  valid  for  the  respiratory  un- 
dulations of  blood-pressure  which  occur  during  artificial 
respiration. 

But  another  explanation,  still  of  a  mechanical  nature, 
suggests  itself.  When  the  lung  is  expanded,  whether  by 
artificial  or  natnral  respiration,  i.  e.,  whether  by  means  of  a 
tracheal  positive  })ressure  or  a  pleural  negative  pressure, 
the  increase  in  the  area  of  the  wall  of  each  pulmonary  alve- 
olus tends  to  stretch  and  elongate  the  capillaries  lying  in 
the  alveolar  walls,  and  in  elongating  them  necessarily  nar- 
rows them,  just  as  an  india-rubber  tube  is  narrowed  when  it 
is  stretched  lengthways.  This  narrowing  ()f  the  capillaries 
is  an  obstacle  to  the  passage  of  blood  through  them  ;  and 
hence  the  expansion  of  the  alveoli  in  inspiration,  other  things 
being  equal,  will  be  unfavorable  to  the  How  of  blood  through 
the  lungs.  In  artificial  respiration  moreover  the  [)ositive 
pressure  on  the  alveolar  walls  will  tend  as  well  to  compress 
the  capillaries  and  still  further  to  hinder  the  flow  of  blood 
through  them  ;  and  diiect  experiments  show  that  when  blood 
is  driven  artificially  at  a  constant  rate  through  the  pulmon- 
ary artery,  the  outflow  through  the  pulmonar}'  veins  is 
diminished  when  the  lungs  are  inflated  (by  tracheal  positive 
pressure)  and  increases  again  when  the  lungs  are  allowed  to 
return  to  their  former  volume.^  The  diminislied  or  increased 
flow  of  blood  through  the  lungs  will  naturally,  by  diminish- 
ing or  increasing  the  quantity  in  the  lefi  heart,  diminish  or 
increase  the  l^lood-piessiire.  And  it  is  exceedingly  |)robable 
that  the  respiratory  undulations  seen  when  artificial  respi- 
ration is  carried  on  are  thus  brought  about  by  changes  in 
the  calibre  of  the  pulmonary  capillaries  and  small  vessels. 
The  case  of  natural  respiration  is  somewhat   difl'erent :  the 

1  Poiseuille,  Compt.  Rend.,  T.  xliv,  1855,  p.  1072.     Quincke  u.  Pfeif- 
fer,  Arch.  f.  Anat.  u.  Phys.,  1871,  p.  90. 


EFFECTS    ON    CIRCULATION.  4S5 

narrovN'ing  of  the  capillaries  due  to  the  increase  of  the  di- 
mensions of  the  pulmonary  alveoli  comes  into  play  as  before, 
but  instead  of  the  tracheal  positive  pressure  a  pleural  nega- 
tive pressure  is  brought  to  bear  on  the  capillaries,  and  this 
probabl}'  tends  to  widen  them  ;  but  the  problem  then  be- 
comes very  complicated,  and  though  it  is  stated^  that  when 
inspiration  is  carried  out  by  means  of  a  negative  pleural 
pressure,  the  artificial  flow^  through  the  lungs,  contrary  to 
the  case  when  positive  tracheal  pressure  is  employed,  is  in- 
creased, the  matter  is  too  unsettled  to  enal)le  us  to  state  how- 
far  the  undulations  of  blood-pressure  during  normal  respi- 
ration are  brought  about  by  changes  in  the  pulmonary  cir- 
culation. 

We  have  moreover  evidence  of  other  influences,  not  me- 
chanical but  nervous  in  nature,  having  at  least  some  share 
in  producing  the  phenomena  we  are  discussing.  One  strik- 
ing feature  of  the  respirator}'  undulation  in  the  blood-pres- 
sure curve  of  the  dog  is  the  fact  that  the  pulse- rate  is 
quickened  during  the  rise  of  the  undulation  and  becomes 
slower  during  the  fall.  The  quickening  of  the  beat  might 
be  considered  as  itself  partly  accounting  for  the  rise,  were 
it  not  for  two  facts.  In  the  rabbit,  the  respiratory  undula- 
tions, though  well  marked,  present  a  very  small  difference 
of  pulse-rate  in  the  rise  and  fall.  In  the  dog,  the  difference 
is  at  once  done  with,  without  an}'  other  essential  change  in 
the  undulations,  by  section  of  both  vagi.  Evidently  the 
slower  pulse  during  the  fall  is  caused  by  a  coincident  stim- 
ulation of  the  cardio-inhibitory  centre  in  the  medulla  oblon- 
gata, the  quicker  pulse  during  the  rise  being  due  to  the  fact 
that,  during  that  interval,  the  centre  is  comparativel}'  at 
rest.  We  have  here  most  important  indications  that,  while 
the  respirator}'  centre  in  the  medulla  oblongata  is  at  work, 
sending  out  rhythmic  impulses  of  inspiration  and  expiration, 
the  neighboring  cardio-inhibitory  centre  is,  as  it  were  by 
sympathy,  thrown  into  an  activity  of  such  a  kind  that  its 
influence  over  the  heart  waxes  and  wanes  with  each  respira- 
tory movement. 

But  if  the  cardio-inhibitory  centre  is  thus  synchronous!}'- 
affected,  ought  we  not  to  expect  that  the  vaso- motor  centre 
should  also  be  involved  in  the  action  ?  We  have  evidence 
that  it  is. 

When  artificial  respiration  is  stopped,  a  very  large  but 

1  Quincke  u.  PfeifTer,  op.  cit. 
41 


486      TISSUES    AND    MECHANISxMS    OF    RESPIRATION. 

steady  ris3  of  pressure  is  observed.  This  may  be  in  part 
due  to  the  increased  force  of  the  cardiac  beat,  caused  b\'  the 
increasingly  venous  character  of  the  blood  ;  but  only  in  part, 
and  that  a  small  part.     The  rise  so  witnessed  is  very  similar 


Fig.  128. 


A  r\  A  W 


.  A  A/\  Ar- aA  A/  I  a 

mmmm 


Traube's  Curves.    (To  be  read  from  left  to  right.) 

The  curves  1,  2,  .3,  4,  5,  were  taken  at  intervals,  and  all  form  part  of  one  experi- 
ment. Each  curve  is  placed  in  its  proper  position  relative  to  the  base  line,  which, 
to  save  space,  is  omitted.  During  1,  artificial  respiration  was  kept  up,  the  undula- 
tions visible  are  therefore  not  due  to  the  mechanical  action  of  the  chest.  AVhen  the 
artificial  respiration  was  suspended  these  undulations  for  awhile  disappeared,  and 
the  blood-pressure  rose  steadily  while  the  heart-beats  became  slower.  Soon,  as 
shown  in  curve  2,  the  undulations  reappeared.  A  little  later,  the  blood-pressure 
was  still  rising,  the  heart-beats  still  slower,  but  the  undulations  still  obvious  (curve 
3).  Still  later  (curve  4),  the  pressure  was  still  higher,  but  the  heart-beats  were 
quicker,  and  the  undulations  flatter.  The  pressure  then  began  to  fall  rapidly 
(curve  5),  and  continued  to  fall  until  some  time  after  ai'tificial  respiration  was 
resumed. 


t(^  that  brouglit  about  by  powerfull}^  stimulating  a  number  of 
vaso  constrictor  nerves  ;  and  there  can  be  no  doubt  that  it 
is  due  to  the  venous  blood  stimulating  the  vaso-motor  centre 
in  the  medulla,  and  thus  causins:  constriction  of  the  small 


EFFECTS    ON    CIRCULATION.  487 

arteries  of  the  body,  parti(;ularly  those  of  the  sj)lanchnic 
area.  We  sa}'  •'stimulating  the  medullary  vasomotor  cen- 
tre," because,  though  the  venous  blood  may  stimulate  other 
vaso-motor  centres  in  the  spinal  cord'  and  possibly  even  act 
directly  on  local  peripheral  mechanisms,  or  on  the  muscular 
coats  of  the  small  arteries  thetuselves,  since  a  rise  of  pres- 
sure follows  ui)on  dyspnoea  when  the  spinal  cord  has  been 
previously  divided  below  the  medulla,  yet  the  fact  that  it  is 
much  less  under  these  circumstances  shows  that  the  medul- 
lary centre  plays  the  chief  part.  Upon  the  cessation  of  the 
artificial  respiration,  the  respiratory  undulations  cease  also, 
so  that  the  blood-pressure  curve  rises  at  first  steadily  in  al- 
most a  straight  line;  yet  after  awhile  new  undulations,  the 
so-called  Traube's  curves,  make  their  appearance  (Fig.  12S, 
2,  3),  very  similar  to  the  previous  ones,  except  that  their 
curves  are  larger  and  of  a  more  sweeping  character.  These 
new  undulations,  since  they  appear  in  the  absence  of  all 
thoracic  or  pulmonary  movements,  passive  or  active,  and 
are  w^itnessed  even  when  both  vagi  are  cut,  must  be  of  vaso- 
motorial  origin  ;  the  rhythmic  rise  must  be  due  to  a  rhyth- 
mic constriction  of  the  small  arteries  due  to  a  rhythmic 
discharge  from  vaso-motor  centres  and  especially  from  the 
medullary  vaso-motor  centre,  since  the  undulations  are  far 
less  marked  when  the  spinal  cord  is  divided.  They  are 
maintained  as  long  as  the  blood  pressure  continues  to  rise. 
With  the  increasing  venosity  of  the  blood,  however,  both 
the  vaso-motor  centre  and  the  heart  become  exhausted; 
the  undulations  disappear,  and  the  blood-pressure  rapidly 
sinks. 

We  have,  then,  experimental  evidence  that,  in  the  entire 
absence  of  all  mechanical  causes,  undulations  of  blood- 
pressure,  of  direct  nervous  origin,  closely  simulating  those 
acc(nnpanying  natural  respiration,  may  be  brought  al»out 
whenever  the  blood  becomes  sufficiently  venous.  It  is  ditli- 
cult  to  imagine  why  the  vaso-motor  centre  should  exhibit 
the  rhythmic  activity  shown  in  Traube's  curves,  and  why 
that  rhythm  should  simulate  the  respiratory  rhythm,  unless 
the  vaso-motor  centre  had  been  i)reviously  accustomed  to  a 
rhythmic  activity  s3mchronous  with  the  rhythmic  activity 
of  the  respirator}'  centre.  It  is  impossil)le  to  give  direct 
experimental  proof  that  in  natural  respiration  the  vaso< 
motor  centre  is  stimulated  bj-  the  natural  venous  blood  to  a 

'  Liiclisinger,  Pfliiger's  Archiv,  xvi,  1878,  p.  510. 


488       TISSUES    AND    MECHANISMS    OF    RESPIRATION. 

rhythmic  activity  lil'^e  that  shown  in  Traube's  curves,  be- 
cause it  is  impossible  to  eliminate  the  mechanical  factors 
discussed  above.  And  the  argument  that  because  the  un- 
duhitions  seen  in  artificial  respiration  continue,  as  is  as- 
sorted, after  division  of  the  medulla,  tiie  vaso-motor  events 
can  have  no  sliare  in  producing  the  undulations  of  natural 
respiration,  is  invjdid,  since,  as  we  iiave  seen,  the  undula- 
tions of  artificial  respiration  have  a  distinctly  ditl'erent  me- 
dian ical  origin  from  those  of  natural  respiration.  On  the 
othei'  hand,  if,  as  is  stated  by  others,  the  undulations  even 
of  artificial  respiration,  though  not  obliterated,  are  dimin- 
ished by  section  of  the  medulla,  these  too  must  be  in  part  of 
vaso-motorial  origin  ;  for  the  mere  diminution  of  general 
blood-pressure  which  results  from  section  of  the  medulla 
ought  not  to  influence  largely  the  respiratory  undulations 
if  these  are  entirely  of  mechanical  origin. 

Mayer'  has  observed  in  perfect  quiet  normally  breathing  rab- 
bits, without  urari,  curves  very  similar  to  Traube's  curves,  on 
which  the  respirator}'  curves  may  be  seen  superimposed.  He 
regards  these  longer  curves  as  of  vaso-motorial  origin. 

We  may  conclude,  then,  that  the  respiratory  undulations 
of  blood-pressure  are  of  complex  origin,  being  partly  the 
mechanical  results  of  the  thoracic  movements,  possibly  also 
produced  l)y  the  alternate  exjjansion  and  collapse  of  the 
pulmonary  alveoli,  but  probably  in  addition  brought  about 
by  a  rhythmic  variation  of  the  vascular  peripheral  resistance, 
the  result  of  a  rhythmic  activit}-  of  the  vaso-motor  centre. 

In  estimating  the  mechanical  effects  on  the  flow  of  blood  to  and 
from  the  heart  produced  by  the  respiratory  movements,  atten- 
tion must  be  paid,  not  only  to  the  action  of  the  thorax,  but  also 
to  that  of  the  abdomen.  Thus  on  the  descent  of  the  diaphragm, 
though  the  flow  of  blood  to  the  right  heart  from  the  upper  part 
of  the  body  is  thereby  undoubtedly  assisted,  that  from  the  lower 
part  of  the  body  and  abdomen  is  diminished.  Conversely  in 
expiration  the  compression  of  the  abdomen  tends  at  first  to  drive 
the  blood  onward  to  the  heart,  though  subsequently,  especially 
if  loner  continued  and  labored,  it  may  prove  an  obstacle  both  to 
the  flow  to  the  heart  along  the  vena  cava  and  to  that  from  the 
heart  along  the  aorta. 

Funke  and  Latschenberger,-  who  insist  on  the  expansion  and 

1  Wien.  Sitzungsberichte,  bd.  74  (1876). 

2  Pfliigers  Arcliiv,  xv  (1877),  p.  405;  ibid.  (1878),  p.  547. 


ASPHYXIA.  489 


collapse  of  the  lungs  as  the  chief  factor  of  the  respiratory  undu- 
lations, point  out  that  while  the  main  effect  of  expansion  is,  by 
lengthening  and  narrowing  the  capillaries,  to  hinder  the  flow 
through  the  lungs,  3'et  the  initial  result  is  to  drive  an  extra  quan- 
tity of  blood  from  the  capillaries  onwards,  and  that  similarly  the 
inftial  result  of  the  collapse  is,  by  the  shortening  and  widening 
of  the  same  capillaries,  to  retain  a  certain  quantity  of  blood  for 
awhile  in  the  lungs.  The}'  offer  by  help  of  these  considerations 
very  ingenious  explanations  of  the  variations  in  the  character  of 
the  respiratory  undulations  accompanying  variations  in  the 
rhythm  and  character  of  the  respirator}-  movements.  And  they 
contend  that  their  explanations  are  valid,  not  only  in  artificial 
respiration,  but  also  in  natural  respiration,  even  when  the  nega- 
tive pleural  pressure  bears  on  the  large  vessels  of  the  chest  as 
well.  Kowalewsky,'  on  the  other  hand,  explains  the  undulations 
seen  in  artificial  respiration,  by  reference  not  so  much  to  the  nar- 
rowing and  Avidening  of  the  capillaries  due  to  their  longitudinal 
stretching  and  return,  as  to  the  variations  of  pressure  in  the  air 
of  the  puhnonary  alveoli  ;  but  argues,  in  opposition  to  Funke  and 
Latschenberger,  that  in  natural  respiration,  these  variations, 
produced  by  pleural  negative  pressure  and  not  by  tracheal  posi- 
tive pressure,  are  more  than  compensated  by  the  simultaneous 
etiects  of  the  same  pleural  pressure  on  the  great  vessels.^ 

It  has  been  suggested  that  the  increased  frequency  of  beat 
during  the  inspiratory  phase  may  be  due  to  the  mechanical  dis- 
tension of  the  lungs,  wherel)y  afferent  impulses  are  transmitted 
along  the  vagus,  which  by  inhibiting  the  cardio-inhibitory  centre 
cause  an  increased  frequency  of  beat.  But  the  experiments  on 
Avhich  this  view  is  based  are  not  conclusive. 


Sec.  8.  Effects  of  Changes  in  the  Air  Breathed. 

The  Effect  a  of  Leficient  Air — Asphyxia. 

When,  on  account  of  occlusion  of  the  trachea,  or  by 
breathing  in  a  confined  space,  a  due  supply  of  air  is  not  ob- 
tained, normal  respiration  gives  place  through  an  interme- 
diate phase  of  dyspnoea  to  tlie  condition  known  as  asphyxia  ; 
this,  unless  remedial  measures  be  taken,  rapidlv  proves 
fatal.  .    . 

Phenomena  of  Asphyxia. — As  soon  as  tlie  oxygen  in  the 
arterial  blood  sinks  below  the  normal,  the  respiratory  move- 
ments become  deeper  and  at  the  same  time  more  frequent ; 

^  Archiv.  f.  Anat.  u.  Phvs.,  1877,  Phvs.  Abth.,  p.  416. 
2  Cf.  Zuntz,  PHiiger's  Arcliiv,  xvii  (1878),  p.  374. 


490      TISSUES    AND    MECHANISMS    OF    RESPIRATION. 


both  the  inspiratory  and  expiratory  phases  are  exaggerated, 
the  supplementary  muscles  spoken  of  at  p.  482  are  brought 
into  play,  and  the  rate  of  the  rh3'thm  is  hurried.  In  this  re- 
spect, dyspncea,  or  hyperpnoea  as  this  first  stage  has  been 
called,  contrasts  very  strongly  with  the  peculiar  respiratory 
condition  caused  by  section  of  the  vagi,  in  which  the  respi- 
ratory movements,  while  much  more  profound  than  the 
normal,  are  diminished  in  frequency'. 

As  the  blood  continues  to  become  more  and  more  venous 
the  respirator}'  movements  continue  to  increase  both  in  force 
and  frequenc}',  a  larger  number  of  muscles  being  called  into 
action  and  that  to  an  increasing  extent.  Yery  soon,  how- 
ever, it  may  be  observed  that  the  expiratory  movements  are 
becoming  more  marked  than  the  inspiratory.  Every  muscle 
which  can  in  any  way  assist  in  expiration  is  in  turn  brought 
into  play;  and  at  last  almost  all  the  muscles  of  the  body 
are  involved  in  the  struggle.  The  orderly  expiratory  move- 
ments culminate  in  expiratory  convulsions,  the  order  and 
sequence  of  which  is  obscured  by  their  violence  and  extent. 
That  these  convulsions,  through  which  dyspnoea  merges 
into  asphyxia,  are  due  to  a  stimulation  of  the  medulla  ob- 
longata by  the  venous  blood,  is  proved  by  the  fact  that  they 
fail  to  make  their  appearance  when  the  spinal  cord  has  been 
previously  divided  below  the  medulla,  though  they  still  occur 
after  those  portions  of  the  brain  which  lie  above  the  medulla 
have  been  removed.  It  is  usual  to  speak  of  a  "convulsive 
centre"  in  the  medulla,  tiie  stimulation  of  which  gives  rise 
to  these  convulsions;  but  if  we  accept  the  existence  of  such 
a  centre  we  must  at  the  same  time  admit  that  it  is  connected 
b}'  the  closest  ties  with  the  normal  expiratory  division  of 
the  respiratory  centre,  since  every  intervening  step  may  be 
observed  between  a  simple  slight  expiratory  movement  of 
normal  respiration  and  the  most  violent  convulsion  of  as- 
phyxia. An  additional  proof  that  these  convulsions  are 
carried  out  by  the  agenc}'  of  the  medulla  is  afforded  by  the 
fact  that  convulsions  of  a  wholly  similar  character  are  wit- 
nessed when  the  supply  of  blood  to  the  medulla  is  suddenly 
cut  off  by  ligaturing  the  bloodvessels  of  tiie  head.  In  this 
case  the  nervous  centres,  being  no  longer  furnished  with 
fresh  blood,  become  rapidly  asphyxiated  through  lack  of 
oxygen,  and  expi-atory  convulsions  quite  similar  to  tiiose  of 
ordinary  asphyxia,  and  preceded  like  them  by  a  passing 
phase  of  dyspnoea,  make  their  appearance.  Similar  "  anae- 
mic "  convulsions  are  seen  after  a  sudden  and  large  loss  of 


ASPHYXIA.  491 

blood  from  the  body  at  large,  the  medulla  being  similarly 
stimulated  b}'  lack  of  arterial  blood. 

Such  violent  efforts  speedily  exhaust  the  nervous  system, 
and  the  convulsions  after  being  maintained  for  a  brief  pe- 
riod suddenly  cease  and  are  followed  by  a  period  of  calm. 
The  calm  is  one  of  exhaustion  ;  the  pupils,  dilated  to  the 
utmost,  are  unatfected  l\v  light :  touching  the  cornea  calls 
forth  no  movement  of  the  evelids,  and  indeed  no  reflex  ac- 
tions can  anywhere  be  produced  by  the  stimulation  of  sen- 
tient surfaces.  All  expiratory-  active  movements  have  ceased  ; 
the  muscles  of  the  bod}-  are  flaccid  and  quiet;  and  though 
from  time  to  time  the  respiratory  centre  gathers  sufficient  en- 
ergy to  develop  respiratory  movements,  these  resemble  those 
of  quiet  normal  breathing,  in  being,  as  far  as  muscular  ac- 
tions are  concerned,  almost  entirely  inspiratory.  They  occur 
at  long  intervals,  like  those  after  the  section  of  the  vagi; 
and  like  them  are  deep  and  slow.  The  exhausted  respira- 
tory centre  takes  some  time  to  develop  an  inspiratory  ex- 
plosion ;  but  the  impulse  when  it  is  generated  is  proportion- 
ately strong.  It  seems  as  if  the  resistance  which  had  in 
each  case  to  be  overcome  was  considerable,  and  the  etfort 
in  consequence,  when  successful,  productive  of  a  large  effect. 

As  time  goes  on,  these  inspirator}-  eflbrts  become  less  fre- 
quent ;  their  rhythm  becomes  irregular  ;  long  pauses,  each 
one  of  which  seems  a  final  one,  are  succeeded  b}'  several 
somewhat  rapidly  repeated  inspirations.  The  pauses  become 
longer,  and  the  inspiratory  movements  shallower.  Each 
inspiration  is  accompanied  b}-  the  contraction  of  accessory 
muscles,  especially  of  the  face,  so  that  each  breath  becomes 
more  and  more  a  prolonged  gasp.  The  inspiratory  gasps 
spread  into  a  convulsive  stretching  of  the  whole  body ;  and 
with  extended  limbs,  and  a  straightened  trunk,  with  the  head 
throv,n  back,  the  mouth  widel\-  open,  the  face  drawn,  and 
the  nostrils  dilated,  the  last  breath  is  taken  in. 

Thus  we  are  able  to  distinguish  three  stages  in  the  phe- 
nomena which  result  from   a  continued  deficiency  of  air: 

(1)  A  stage  of  dyspnoea,  characterized  by  an  increase  of  the 
respiratory  movements  both  of  inspiration  and  expiration. 

(2)  A  convulsive  stage,  characterized  by  the  dominance  of 
the  expiratory  efforts,  and  culminating  in  general  convul- 
sions. (3)  A  stage  of  exhaustion,  in  which  lingering  and 
long  drawn  inspirations  gradually  die  out.  When  brouglit 
about  by  sudden  occlusion  of  the  trachea  these  events  run 
through  their  course  in  about  4  or  5  minutes  in  the  dog,  and 


492      TISSUES    AND    MECHANISMS    OF    RESPIRATION. 


in  about  3  or  4  minutes  in  the  rabbit.  The  first  stage  passes 
gradually  into  the  second,  convulsions  appearing  at  the  end 
of  the  first  minute.  The  transition  from  the  second  stage 
into  the  third  is  somewhat  abrupt,  the  convulsions  suddenly 
ceasing  early  in  the  second  minute.  The  remaining  time  is 
occupied  in  the  third  stage. 

The  duration  of  asphyxia  varies  not  onlj^  in  different  animals 
but  in  the  same  animal  under  different  circumstances.  Newly 
born  and  young  animals  need  much  longer  immersion  in  water 
before  death  by  asphyxia  occurs  than  do  adults.  Thus  while  in 
a  full-grown  dog  recovery  from  drow^ning  is  unusual  after  1^  min- 
utes, a  new-born  puppy  has  been  know^n  to  bear  an  immersion  of 
as  much  as  50  minutes.  The  cause  of  the  difference  lies  in  the 
fact  that  in  the  young  animal  the  respiratory  changes  of  the  tis- 
sues are  much  less  active.  These  consume  less  oxygen,  and  the 
general  store  of  oxygen  in  the  blood  has  a  less  rapid  demand 
made  upon  it.  The  respiratory  activity  of  the  tissues  may  also 
be  lessened  by  a  deficiency  in  the  circulation  ;  hence  bodies  in  a 
state  of  syncope  at  the  time  when  the  deprivation  of  oxj'gen  be- 
gins can  endure  the  loss  for  a  much  longer  period  than  can  bodies 
in  which  the  circulation  is  in  full  swin^.  There  being  the  same 
store  of  oxygen  in  the  blood  in  each  case,  the  quicker  circulation 
must  of  necessity  bring  about  the  speedier  exhaustion  of  the  store. 
In  many  cases  of  drowning,  death  is  hastened  by  the  entrance  of 
water  into  the  lungs. 

By  training,  the  respiratory  centre  may  be  accustomed  to  bear 
a  scanty  supply  of  oxygen  for  a  much  longer  time  than  usual  be- 
fore dyspnoea  sets  in,  as  is  seen  in  the  case  of  divers. 

The  phenomena  of  slow  asphyxia,  wdiere  the  supply  of  air 
is  gradually  diminished,  are  fundamentall}^  the  same  as 
those  resulting  from  a  sudden  and  total  deprivation.  The 
same  stages  are  seen,  but  their  development  takes  place 
more  slowly. 

The  Circulation  ill  Asphyxia. — If  the  carotid  or  other  ar- 
ter}'  of  an  animal  be  connected  with  a  manometer  during 
the  development  of  the  asphyxia  just  described,  the  follow- 
ing facts  may  be  observed.  During  the  first  and  second 
stages  the  blood-pressure  rises  rapidly,  attaining  a  h-eight 
far  above  the  normal.  During  the  third  stage  it  falls  even 
more  rapidly,  repas'^ing  the  normal  and  becoming  nil  as 
death  ensues.  The  respiratory  undulations  of  the  pressure- 
curve  are  abrupt  and  somewdiat  irregular,  the  inspiratory 
movements  being  accompanied  by  a  fall  of  pressure.  When 
the  animal  has  been  previously  placed   under  urari,  so  that 


ASPHYXIA.  493 

the  respiratory  impulses  cannot  manifest  themselves  by  any 
muscular  mo^'ements,  the  rise  of  the  pressure  curve,  as  we 
have  already  said,  is  at  first  stead v  and  unbroken,  but  after 
a  variable  period  Traube's  curves  make  their  ai)pearance. 
As  during  the  third  stai;e  the  pressure  sinks,  these  undula- 
tions pass  away. 

The  heart-beats  are  at  first  somewhat  quickened,  but 
speedily  become  slow,  while  at  the  same  time  they  acquire 
great  force  :  so  that  the  pulse  curves  on  the  tracing  are  ex- 
ceedingly bold  and  striking,  Fig.  128.  Even  while  the  blood- 
pressure  is  sinking,  the  pulse-curves  still  maintain  somewhat 
these  characters  \  and  the  heart  continues  to  beat  for  some 
seconds  after  the  respiratory  movements  have  ceased,  the 
strokes  at  last  rapidly  failing  in  frequency  and  strengtli. 

If  the  chest  of  an  animal  be  o[)ened  under  artificial  res- 
piration, and  asphyxia  brouglit  on  by  cessation  of  the 
respiration,  it  will  be  «een  that  tlie  heart  during  the  second 
and  third  stages  hecomes  completely  gorged  with  venous 
blood.  all*the  cavities  as  well  as  the  large  veins  being  dis- 
tended to  the  utmost.  If  the  heart  be  watched  to  the  ch)se 
of  the  events,  it  will  be  seen  that  the  feebler  strokes  which 
come  on  towards  the  end  of  the  third  stage  are  quite  unable 
to  empty  its  cavities  ;  and  when  tlie  last  beat  has  passed 
away  its  parts  are  still  choked  with  blood.  The  veins  spirt 
out  when  pricked  ;  and  it  ma}^  frequently  be  observed  tliat 
the  beats  recommence  when  the  overdistension  of  tlie 
heart's  cavities  is  relieved  by  puncture  of  the  great  vessels. 
When  rigor  mortis  sets  in  alter  death  by  asphyxia,  tlie  left 
side  of  the  heart  is  more  or  less  emptied  of  its  Contents; 
but  not  so  the  riglit  side.  Hence  in  an  ordinary  post-mor- 
tem examination  in  cases  of  death  by  asphyxia,  while  the 
left  side  is  found  comparativel}'  empty,  the  right  ap[)ears 
goi-ged. 

These  various  phenomena  are  probabl}-  brought  about  in 
the  following  way  : 

The  increasingly  venous  character  of  the  blood  augments 
the  action  of  the  general  vaso-motor  centre,  and  thus  leads 
to  a  general  constriction  of  the  small  arteries.  This  is  the 
cause  of  the  markedly  increased  blood  pressure;  though,  as 
we  have  alread}'  said,  the  venous  blood  may  also  act  directly 
on  the  otlier  spinal  vaso-motor  centres,  and  possibly  on 
peripheral  vasomotor  mechanisms,  or  on  tlie  muscular 
arterial  coats,  or  may  even  affect  the  peripheral  resistance 
by  modifying  the  changes  in  the  capillar}-  regions,  see  p.  290. 

42 


494      TISSUES    AND    MECHANISMS    OF    RESPIRATION. 

This  increased  peripheral  resistance,  while  indirectly  (p. 
255)  lielping  to  augment  the  force  of  the  heart's  heat,  is  a 
direct  ohstacle  to  tlie  heart  emptying  itself  of  its  contents. 
On  the  other  hand,  the  increased  respiratory  jnoveinents 
favor  the  flow  of  venous  blood  towards  the  heart,  which  in 
consequence  becomes  more  and  more  full.  This  repletion 
is,  moreover,  assisted  by  the  marked  infrequency  of  the 
beats.  This  in  turn  depends  in  part  on  tlie  cardio-inhil)it()ry 
centre  in  the  medulla  l>eing  stimidated  l)y  the  venous  blood; 
since  when  the  vagi  are  divided  the  infrequency  is  much 
less  [)ronounced.  It  does  not,  however,  disappear  altogether, 
and  we  are,  therefore,  driven  to  suppose  it  is  in  part  due  to 
the  venous  blood  acting  in  an  iniiibitory  manner  directly  on 
the  heart  itself.  The  increased  resistance  in  front,  the 
augmented  supply  from  behind,  and  the  long  pauses  between 
the  strokes,  all  concur  in  distending  the  iieart  more  and 
more. 

When  the  large  veins  have  become  full  of  blood  the  in- 
spiratory movements  can  no  longer  have  their  usual  effect 
in  increasing  the  blood-pressure.  The  whole  force  of  the 
chest  movement,  as  far  as  the  circulation  is  concerned,  is 
spent  in  diminishing  the  pressure  around  the  large  arteries  ; 
and  hence  the  sinking  of  the  l)lood-i)ressure  during  each  in- 
spiratory movement. 

The  distension  of  the  cnrdiac  cavities,  at  first  favoi'able 
to  the  heart-beat,  as  it  increases  becomes  injurious.  At  the 
same  time  the  cardiac  tissues,  wMiich  at  first  i^robably  are 
stimulated,  after  awhile  become  exhausted  by  the  action  of 
the  venous  blood  ;  and  the  strokes  of  the  he:irt  become 
feebler  as  well  as  slower. 

On  account  of  this  increasing  slowness  and  feebleness  of 
the  heart's  beat,  the  blood-pressure,  in  spite  of  the  continued 
arterial  constriction,  begins  to  fall,  since  less  and  less  blood 
is  pumped  into  the  arterial  system  ;  the  boldness  of  the 
pulse-curves  at  this  stage  being  chiefly  due  to  the  infre- 
quency of  the  strokes.  As  the  quantity  which  passes  from 
the  heart  into  the  arteries  becomes  less  second  by  second, 
the  pressure  gets  lower  and  lower,  the  descent  being  assisted 
by  the  exhaustion  of  the  vaso-motor  centre,  until  almost  be- 
fore the  last  beats  it  has  sunk  to  zero.  Thus  at  the  close  of 
asphyxia,  while  the  heart  and  venous  system  are  distended 
with  blood,  the  arterial  system  is  less  than  normally  full. 


APNCEA.  495 


The  Effects  of  an  Increased  Supply  of  Air — Apncea. 

It  is  a  matter  of  common  experience  that  after  several 
inspiratory  efforts  of  greater  force  than  ordinary,  the  breath 
can  be  held  for  a  mnch  longer  time  tlian  usual.  In  other 
words,  by  an  increased  respir.atory  action,  the  blood  can  be 
bronght  into  such  a  condition  that  the  generation  of  the 
respiratory  impulses  in  the  medulla  is  dela3ed  beyond  the 
nsual  time  ;  the  desire  to  breathe  can  then  be  resisted  for  a 
longer  time  than  usual.  This  state  of  things,  which  we  can 
easily  produce  in  ourselves,  is  the  beginning  of  that  peculiar 
condition  brought  about  by  a  too  vigorous  respiration,  or 
by  the  inhalation  of  ox3'gen,  to  which  we  have  already  (p. 
477)  referred  under  the  name  of  "  apnoea."^  Tlie  essential 
feature  of  apnoea  consists  in  the  blood  containing  for  the 
time  being  more  oxygen  than  usual.  In  consequence  of  this 
a  longer  time  is  needed  before  the  deficiency  of  oxygen  in 
the  blood  of  the  capillaries  of  the  medulla  oblongata,  or 
rather  in  the  nerve-ceils  constituting  the  respiratory  centre, 
reaches  the  limit  which  determines  the  discharge  of  a  resjji- 
ratory  impulse.  The  molecular  processes  of  these  cells  are 
so  arranged,  that  whencAer  tiie  oxygen  whicii  is  available 
for  their  use  sinks  below  a  certain  level,  respiratory  explo- 
sions occur  whereby  a  fresh  snpply  of  oxygen  is  gained. 
By  increasing  their  available  oxygen,  the  explosive  action 
of  the  cells  is  deferred  and  diminished  ;  that  is,  apno?a  is 
estai'lished.  Similarly  when  the  sujipl^'  of  oxygen  is  di- 
minished, the  explosions  are  hastened  and  increased,  that 
is,  d3'spna\a  is  brougiit  about.  The  different  conditions  of 
the  respiratory  centre  during  apnoea,  normal  breathing  or 
eupncea,  and  d\  spncea,  are  well  shown  by  the  different  effects 
produced  by  stimulating  the  afferent  fibres  of  the  trunk  of 
the  vagus  with  the  same  stimulus  during  the  three  stages. 
If  the  current  chosen  be  of  such  a  strength  as  will  gently 
increase  tlie  rhythm  of  normal  breathing,  it  will  be  found  to 
have  no  effect  at  all  in  apna?a,  while  in  dyspna^a  it  may  pro- 
duce almost  convulsive  movements.  Indeed,  in  well-marked 
apnoea  even  strong  stimulation  of  the  vagus  may  produce 
no  effect  whatever. 


^  It  is  to  be  regretted  that  this  name  is  used  by  some  medical  authori- 
ties in  a  sense  almost  identical  with  asphyxia.  In  its  pliysiological 
sense,  as  here  used,  it  is  the  very  opposite  of  asphyxia. 


496       TISSUES    AND     MECHANISMS    OF    RESPIRATION. 


According  to  Ewald'  the  hsemoglobin  of  the  blood  during  apncea 
becomes  perfectly  or  almost  perfectly  saturated  with  oxygen.  The 
absolute  increase  does  not  seem  great,  from  .1  to  .9  per  cent.  vol. 
The  tension  at  which  this  increment  exists  is,  however,  very 
great.  The  venous  blood,  if  the  artificial  respiration,  used  to 
produce  the  apnoea,  be  carefully  carried  out,  contains  more  oxy- 
gen than  the  normal,  and  appears  of  a  bright-red  color.  In  cases 
where  the  artificial  respiration  interferes  with  the  pulmonary 
circulation  and  so  reduces  the  rapidity  of  the  general  flow  of 
blood,  the  venous  blood  may  be  even  darker  than  usual. ^ 


The  Effects  of  Changes  in  the  Composition  of  Air  breathed.^ 

We  have  already  discussed  the  effects  of  such  changes  as 
are  produced  by  the  act  of  resi)iralion  itself,  viz..  a  defi- 
ciency of  oxygen  and  an  excess  of  carbonic  acid.  We  have 
only  to  add,  that  the  result  of  an  excess  of  oxygen,  except 
in  the  cases  of  extreme  pressure  to  be  mentioned  imme- 
diately, is  simply  apnoea,  and  that  variations  in  amount  of 
nitrogen  have  of  themselves  no  effect,  this  gas  being  emi- 
nentl}'  an  indifferent  gas  as  far  as  physiological  processes 
are  concerned. 

Poisonous  Gases. — Carbonic  oxide  produces  the  same 
effects  as  deficiency  of  oxygen,  inasmuch  as  it  preoccupies 
the  h{Bmoglobin  and  so  prevents  the  blood  from  becoming 
properly  oxygenated,  see  p.  453.  Sulphuretted  hydrogen 
produces  similar  effects,  but  in  a  different  manner;  it  acts 
as  a  reducing  agent,  see  p.  450.  Some  gases  are  irre8piral)ie, 
on  account  of  their  causing  spasm  of  the  glottis,  and  this  is 
said  to  be,  to  a  certain  extent,  the  case  with  carbonic  acid. 
[The  anaesthesia  produced  l)y  nitrous  oxide  gas  is  probably 
nothing  but  a  result  of  asphyxia,  which  is  due  to  a  deficient 
supply  of  oxygen,  caused  by  the  presence  of  the  nitrous 
oxide  gas  in  the  lungs.] 

The  Effects  of  Changes  in  the  Pressure  of  Air  breathed.^ 

Gradual  Diminution  of  Pressure. — The  symptoms  are  those 
of  deficiency  of  oxygen  ;  the  animals  die  of  asphyxia.     The 


^  Pfluger's  Archiv,  vii  (1873),  575. 

2  Finkler  and  Oertmann,  Pfluger's  Archiv,  xiv    (1877),  38. 

^  Paul  Bert,  Rech.  Exp.  sur  la  Pression  Baroiuet.,  1874. 


MODIFIED    RESPIRATORY    MOVEMENTS.  497 

blood  contains  less  and  less  oxysen  as  the  pressure  is  re- 
duced, the  quantit}'  present  in  tlie  arterial  Mood  soon  be- 
coming less  than  that  in  normal  venous  blood.  The  quan- 
tity of  carbonic  acid  in  the  blood  is  also  diminished.  The 
increasinof  dyspnoea  is  acconq);mied  by  great  general  feel)le- 
ness  ;  and  convulsions  though  frequent  are  not  invariable. 
The  occurrence  of  these  seems  to  depend  on  the  sudden- 
ness with  which  the  ox3gen  of  the  blood  is  diminished. 

Sudden  Diminution. — Death  in  these  cases  ensues  from 
the  libei'ation  of  gases  within  the  bloodvessels  and  the  con- 
sequent mechanical  interference  with  the  circulation.  The 
gas  which  is  found  in  the  bloodvessels  on  examination  after 
death  consists  chiefly  of  nitrogen. 


Increase  X)f  Pressure. — Up  to  a  pressure  of  several  atmos- 
pheres of  air,  merely  symptoms  of  narcotic  poisoning,  alto- 
gether like  those  of  breathing  an  excess  of  carbonic  acid, 
are  developed,  and  there  can  be  little  doubt  that  they  origi- 
nate from  the  same  cause,  viz.,  the  excess  of  carl)onic  acid 
in  the  blood.  At  a  pressure,  howeyer,  of  four  atmospheres 
of  oxygen,  corresi)onding  to  twenty  atmospheres  of  air,  and 
upwards,  very  remarkalde  phenomenon  presents  itself.  The 
animals  die  of  asi)hyxia  and  convulsions,  exactly  in  the 
same  way  as  when  oxygen  is  deficient.  Corresponding 
with  this  it  is  found  that  the  production  of  carbonic  acid  is 
diminished.  That  is  to  say,  when  the  pressure  of  the  oxygen 
is  incieased  beyond  a  certain  limit,  tiie  oxidations  of  the 
body  are  diminished,  and  with  a  still  further  increase  of  the 
oxygen  are  arrested  altogether.  The  oxidation  of  phos- 
phorus is  quite  analogous  ;  at  a  high  i)ressure  of  oxygen 
phosi)horus  will  not  burn.  Bert  has  further  shown  that 
plants,  b.acteria,  and  organized  ferments,  are  similarly  killed 
l>y  a  too  great  pressure  of  oxygen. 


Sec.  9.  Modified  Respiratory  Movements. 

The  respiratory  mechanism  with  its  adjuncts,  in  addition 
to  its  respiratory  function,  becomes  of  service,  especially  in 
the  case  of  man,  as  a  means  of  expressing  emotions.  The 
respirator}^  column  of  air,  moreover,  in  its  exit  from   the 


498      TISSUES    AND    MECHANISMS    OF    RESPIRATION. 

chest  is  freqnentl3^  made  use  of  in  a  mechanical  way  to 
expel  hodies  from  the  upper  air-passages.  Hence  arise  a 
number  of  peculiarly  modified  and  more  or  less  complicated 
respiratory  movements,  sighing,  coughing,  laugliter,  etc., 
adapted  to  secure  special  ends  which  are  not  distinctly  re- 
spiratory. They  are  all  essentially  reflex  in  character,  the 
stimulus  determining  each  movement,  sometimes  affecting 
a  peri[)heral  afferent  nerve  as  in  the  case  of  coughing,  some- 
times working  through  the  higher  parts  of  the  brain  as  in 
laughter  and  crying,  sometimes,  possibly,  as  in  yawning  and 
sighing,  acting  on  the  respiratory  centre  itself.  Like  the 
simple  respiratory  act,  they  may  with  more  or  less  success 
be  carried  out  by  a  direct  effort  of  the  will. 

Sighing  is  a  deep  and  long-drawn  inspiration  chiefly 
through  the  nose,  followed  by  a  somewhat  shorter,  but  cor- 
respondingly large  expiration. 

Yawning  is  similarly  a  deep  inspiration,  deei)er  and  longer 
continued  than  a  sigh,  drawn  through  the  widely  open  mouth, 
and  accompanied  by  a  peculiar  depression  of  the  lower  jaw 
and  frequently  by  an  elevation  of  the  shoulders. 

Hiccough  consists  in  a  sudden  inspiratory  contraction  of 
the  diai)hragm,  in  the  course  of  which  the  glottis  suddenly 
closes,  so  that  the  further  entrance  of  air  into  the  chest  is 
prevented,  while  the  impulse  of  the  column  of  air  just  en- 
tering, as  it  strikes  ui)on  tiie  closed  glottis,  gives  rise  to  a 
well-known  accompanying  sound.  The  afferent  impulses  of 
the  reflex  act  are  conveyed  by  the  gastric  branches  of  the 
vagus.  Tiie  closure  of  the  glottis  is  carried  out  b}'  means 
of  the  inferior  laryngeal  nerve.     See   Voice. 

In  sobbing  a  series  of  similar  convulsive  inspirations  fol- 
low each  other  slowly,  the  glottis  being  closed  earlier  than 
in  the  case  of  hiccough,  so  that  little  or  no  air  enters  into 
the  chest. 

Coughing  consists  in  the  first  place  of  a  deep  and  long- 
drawn  inspiration  by  which  the  lungs  are  well  filled  with 
air.  This  is  followed  i)y  a  complete  closure  of  the  glottis, 
and  then  comes  a  sudden   and   forcible   expiration,  in   the 


MODIFIED    RESPIRATORY    MOVEMENTS.  499 

midst  of  whie'h  the  glottis  siuldenly  opens,  and  thus  a  blast 
of  air  is  driven  through  the  ui)per  respirator}'  passages. 
The  afferent  impulses  of  this  retlex  act  are  in  most  eases,  as 
when  a  foreign  body  is  lodged  in  the  larynx  or  by  the  side 
of  t5»e  epigloTtis,  conveyed  by  the  superior  laryngeal  nerve  ; 
but  the  movement  may  arise  from  stimuli  applied  to  other 
afferent  branches  of  the  vagus,  such  as  those  supplying  the 
bronchial  passages  and  stomach  (?)  and  the  auricular  branch 
distributed  to  the  meatus  ej-ternus.  Stimulation  of  other 
nerves  also,  such  as  those  of  the  skin  by  a  draught  of  cold 
air,  may  develop  a  cough. 

In  sneezing  the  general  movement  is  essentially  the  same, 
except  that  tlie  opening  from  the  pharynx  into  the  mouth 
is  closed  by  the  contraction  of  the  anterior  pillars  of  the 
fauces  and  the  descent  of  the  soft  palate,  so  that  the  force 
of  the  blast  is  driven  entirely  through  the  nose.  The  affer- 
ent impulses  here  usually  come  from  tiie  nasal  branches  of 
the  fifth.  When  sneezing,  however,  is  produced  by  a  bright 
light,  the  optic  nerve  would  seem  to  be  the  afferent  nerve. 

Laughing  consists  essentially  in  an  inspiration  succeeded, 
not  by  one,  but  by  a  whole  series,  often  long  continued,  of 
short  spasmodic  exp.irations,  the  glottis  being  freely  open 
during  the  whole  time,  and  the  vocal  cords  being  thro\^n 
into  characteristic  vibrations. 

In  crying  the  respiratory  movements  are  modified  in  the 
same  way  as  in  laughing;  the  rhythm  and  the  accompany- 
ing facial  expressions  are,  however,  different,  though  laugh- 
ing and  crying  frequently  l>ecome  indistinguishable. 

Our  real  knowledge  of  the  physiology  of  res])iration  dates  back 
from  1777.  when  Lavoisier  showed  the  true  nature  of  combustion, 
following  close  as  this  did  upon  Priestley's  demonstration  of  the 
identity  of  respiration  and  combustion  (1771),  and  discovery  of 
oxygen  (1774).  Before  that  time  the  chief  steps  of  progress  were, 
the  discovery  by  Van  Helmout  (1648)  that  gas  sylvestre  (car- 
bonic acid  gas  was  unfit  for  respiration  ;  the  demonstration  by 
Hook  (IGHljof  the  effects  of  artificial  respiration  ;  b}'  Lower  .  1(309) 
of  the  connection  with  respiration  of  the  difference  in  color  be- 
tween venous  and  arterial  blood  ;  by  Boyle  (1670)  of  the  necessity 
for  respiratory  purposes  of  the  air  dissolved  in  water  ;  the  ob- 
servations and  reflections  of  Mayow  (1674j  on  the  spiritus  nitro- 


500  THE    SKIN    AND    ITS    APPENDAGES. 


aereus  (oxygen),  in  which  he  narrowly  missed  anticipating  Lavoi- 
sier by  a  century,  and  the  discovery  by  Black  (1757)  of  carbonic 
acid  in  air.  Lavoisier,  however,  held  that  the  respiratory  com- 
bustion took  place  in  the  bronchial  tubes,  a  hydro-carbonous 
substance  being  secreted  for  that  purpose  from  the  blood  ;  and, 
though  Lagrange  suggested  that  the  oxygen  might  be  absorbed 
into  and  the  carbonic  acid  exhaled  froni  the  blood,  the  combus- 
tion occurring  in  the  blood  or  tissues  ;  and  Spallanzani  (1803) 
and  W.  F.  Edwards  (1823)  showed  that  snails,  frogs,  and  young 
mammals  continued  to  produce  carbonic  acid  in  an  atmosphere 
of  hydrogen,  whereby  direct  combustion  in  the  lungs  was  ren- 
dered impossible,  Lavoisier's  view  held  its  ground,  owing  to  the 
ditticulty  of  extracting  gases  from  the  blood,  until  in  1837  Magnus 
used  the  mercurial  air-pump  and  proved  that  both  venous  and 
arterial  blood  contained  both  oxygen  and  carbonic  acid.  His 
researches,  and  those  of  Lothar  Meyer  and  Fernet,  which  fol- 
lowed soon  after,  form  the  basis  of  our  present  knowledge.  The 
labors  of  Ludwig  and  his  school,  of  Pliuger  and  his  pupils,  and 
of  others,  have  advanced  this  subject  to  its  present  condition. 
The  spectroscopic  discoveries  of  Hoppe-Seyler  and  Stokes  have 
proved  of  great  and  increasing  importance  ;  and  we  are  indebted 
to  Rosenthal  for  a  clear  exposition  of  the  nervous  mechanism  of 
respiration. 


CHAPTER    III. 


[  The  Phijmological  Anatomy  of  the  Skin  and  itii  Appendages. 

The  skin  is  divided  into  two  principal  portions:  the 
epidermi^.^  cuticle  or  scarf-skin,  and  tlie  derma  or  true  skin. 
These  layers  can  readily  be  demonstrated  l)y  maceration. 

Tlie  ep)idermif^^  or  most  superficial  layer,  is  a  cellular 
structure,  composed  entirely  of  superimposed  stratifications 


TUE    SKIN    AND    ITS    APPENDAGES. 


501 


of  epithelium  cells,  which  differ  in  diameter  in  the  superfi- 
cial and  deep  layers.  The  superficial  layers  are  com|)osecl 
of  flat,  nucleated, horny  epithelium  cells,  which  are  detached 
from  the  cutaneous  surface  in  ^^^  ^^^ 

tiie  form  of  scales.  In  the 
deeper  layers,  the  cells  are 
rounded  or  prismoidal  in 
form,  soft  and  pi^^mented. 
The  pigment  is  most  al)un- 
dant  in  the  layers  of  cells 
which  immediately  surround 
the  papillary  layer  of  the 
derma,  and  gradually  he- 
comes  less  aV)undant  as  the 
superficial  layers  of  the  epi- 
dermis are  ai)proached.  The 
difference  in  the  color  of  the 
skin  of  different  races  is  due 
to  the  piumentary  deposit  in 
those  cells.  The  superficial 
layers  of  the  epidermis  are 
termed  the  horny  layers  ;  the 
deeper  layers  are  termed  the 
rete  mucosum,  Mali)ighian 
or  mucous  layers.  (Fig  129.) 
The  cells,  which  are  being 
constantly  desquamated  from 
the  horny  layers,  are  replaced 

by  cells  "from  the  deeper  layers,  which  undergo  the  modifi- 
cations in  foim  from  a  })rismoidal  to  a  rounded  and  ulti- 
mately to  a  flattened  condition  as  they  are  pushed  up  by 
the  new  cells,  which  are  continually  being  reproduced  in  the 
rete  muco>?uin.  The  epidermis  forms  a  protective  C(n'ering 
for  the  body,  by  preserving  the  soft  and  more  delicate 
superficial  structures  from  the  effects  of  friction,  by  dimin- 
ishing the  evolution  of  heat,  and  by  limiting  the  amount  of 
watery  evaporation-. 

The  derma  or  true  skin  is  composed  of  two  layers,  the 
papilla j^y  layer  and  the  corium. 

The  corium^  or  deep  layer  is  dense,  tough  and  elastic, 
and  composed  of  fasciculi  of  white  fibrous  tissue,  which 
are  interlaced  in  various  directions,  and  forming  spaces 
between  their  interlacements  which  are  termed  areolae. 
Intermixed    with    the    white    fibrous    tissue    is    a    variable 


Skin  of  the  Negro,  in  a  Vertical  Sec- 
tion, niajinifit  d  250  diameters,  a,  a,  cu- 
taneous papillae  ;  h,  undermost  and  dark- 
colored  layer  of  prismoidal  epidermis 
cells  of  the  mucous  or  Malpighian  lay- 
ers ;  (/,  horny  layer.— After  Shakpey. 


502 


THE    SKIN    AND    ITS    APPENDAGES. 


amount  of  yellow  elastic  fibres.  In  the  deeper  portions  of 
tliecoriiiin  the  fasciculi  are  not  so  closely  interwoven,  and 
they  become  blended  with  the  subcutaneous  tissue;  the 
areoke  are  larger  and  contain  fat,  hair-follicles  and  cutaneous 
glands.  Approaching  the  superficial  surface  the  fasciculi 
become  more  closely  interwoven,  and  in  some  parts  so 
closely  as  to  entirely  obliterate  the  areolae.  The  most 
superficial  portion  of  the  corium  is  of  a  homogeneous  nucbs 
ated,  transparent  structure.  The  papillary  layer  consists  of 
numerous  extremely  sensitive,  vascular,  conical  projections, 
which  are  homogeneous  in  structure,  and  appear  to  be  but 
prolongations  of  the  corium,  from  which  it  has  no  distinct 
line  of  separation.  The  papilhe  are  of  two  kinds  :  tiie  simple 
and  compound.    The  simple  papillae  (Fig.  180)  are  single  con- 


FiG.  130. 


Fir,.   131 


/  .-^ 


__       /^.'T^'^ 


Fig.  130.— Papillffi,  as  seen  with  a  Microscope,  on  a  portion  of  the  true  Skin,  from 
which  the  Cuticle  has  been  removed. — After  Breschet. 

Fig.  131. — Compound  Papillae  from  the  Palm  of  Ihe  Hand,  magnified  60  diameters; 
a,  bases  of  a  papilhi ;  6,  b,  divisions  or  branches  of  the  same ;  c,  c,  branches  belonging 
to  papillae,  of  which  the  bases  are  hidden  from  view. — After  Kolliker. 


leal  eminences,  which  are  scattered  irregularly  over  the  gen- 
eral cutaneous  surface.  The  compound  papillte  i  Fig.  131 )  are 
conical  elevations,  which  have  a  variable  number  of  simple 
papillae  projecting  from  their  free  extremities.  The  compound 
papillae  are  most  abundant  upon  the  palmar  surface  of  the 
hands  and  fingers  As  seen  in  this  situation  they  are  ar- 
ranged in  the  form  of  parallel  curved  ridges,  each  of  which  is 
formed  of  a  double  row  of  papillae,  wiiich  are  placed  in  pairs. 
Transverse  grooves  are  seen  upon  the  surfaces  of  the  ridges, 


THE    SKIN    AND    ITS    APPENDAGES. 


503 


which  correspond  to  the  interspaces  between  the  pairs  of 
papilhe  forming  the  rows. 
In  the  centre  of  each  trans- 
verse groove  is  a  small 
opening,  which  is  an  orifice 
of  a  sudoriparous  duct. 
(Fig.  132.) 

Tlie  mode  by  which  the 
nervous  filaments  termi- 
nate in  the  skin  is  of 
great  physiological  inter- 
est, but  unfortunately  our 
knowledge  on  the  subject 
is  still  unsatisfactory.  Thus 

far  we   know    that  the  nerves  after  passing    through  the 
subcutaneous  cellular  tissue  form   plexuses  of  minute  fila- 


Portion  of  Skin  from  the  Palmar  Surface 
of  the  end  of  the  Thumb,  slightly  magni- 
fied, showing  the  curved  ridges  and  inter- 
mediate farrows.  Upon  the  ridges  are  seen 
the  orifices  of  the  ducts  of  the  sweat-glands. 
—After  Marshall. 


Fig.  133. 


/^ 


End-bulbs  in  Papiils  (magnified)  treated  with  Acetic  Acid,  a,  from  the  lips;  the 
white  loops  in  one  of  them  are  capillaries.  B,  from  the  tongue.  Two  end-liulbs  seen 
in  the  midst  of  the  simple  papillie  ;  «,  a,  nerves. — After  Kolliker. 


ments  in  the  more  superficial  layers  of  the  coriunj.  Some  of 
these  are  soon  lost  in  the  tissues :  others  are  traced  to  small  cor- 
puscular elements  situated  in  the  papillae,  which  are  thought 
to  be  the  essential  terminal  organs   connected  with  tactile 


504 


THE    SKIN    AND    ITS    APPENDAGES. 


sensibilit3\  These  corpuscles  are  of  two  kinds :  the  cor- 
puscles or  terminal  bulbs;  of  Krause,  and  the  tactile  or  axile 
corpuscles.  The  bulbs  of  Krause  (Fig.  133)  are  found  prin- 
cipally in  the  conjunctiva,  the  lips  and  tongue,  and  tiie  glans 
penis  and  clitoris.  The}'  are  in  the  form  of  oval,  oi)long, 
or  rounded  bodies,  composed  of  a  homogeneous  structure, 
having  a  delicate  connective  tissue  investment.  The  nerve- 
fdament,  vvliicii  consists  alone  of  the  axis  cylinder,  after 
entering  the  corpuscle  becomes  very  much  convoluted,  or 
else  appears  in  the  centre  as  a  straight  axial  filament. 

The  tactile  or  axile  corpuscles  (Fig.  134)  are  found  most 

Fig.  134. 


A     *^ 


Papillte  from  the  Skin  of  the  Hand,  freed  from  the  cuticle  and  exhil»iting  the  tac- 
tile corpuscles.  Magnified  ;J50  diameters,  a.  Simple  papilla  with  four  nerve-fibres: 
a,  tactile  corpuscle;  b,  nerves,  b.  Papilla  treated  with  acetic  acid  :  a,  coitical  layer 
■with  cells  and  fine  elastic  filaments;  ft,  tactile  corpuscle  with  transverse  nuclei;  c, 
entering  nerve  with  neurilemma;  d,  nerve-fibres  winding  round  the  corpuscle,  c. 
Papilla  viuwed  from  altove  so  as  to  appear  as  a  cro-s-section  :  fr,  cortical  layer;  b, 
nerve-fibre;  c,  sheath  of  the   tactile   corpuscle  containing  nuclei;  d,  core. — After 

KOLLIKER. 


thickly  distributed  where  the  sense  of  touch  is  most  acute. 
They  appear  as  oblong  or  oval  l)odies,  composed  of  a  gran- 
ular connective  tissue  which  is  almost  homogeneous.  Ac- 
cording to  Kolliker,  the  corpuscles  consist  of  a  core  of 
homogeneous  or  granular  connective  tissue,  which  is  sur- 
rounded by  an  outer  layer  or  sheath  of  fibro-elastic  tissue, 
having  elongated  nuclei,  situated  transversely.  Covering 
this  is  a  cortex  of  plasmatic  cells  and  elastic  tilaments.  The 


THE    SKIN    AND    ITS    APPENDAGES. 


505 


Fig. 135. 


nerve  filaments,  which  may  he  three  or  four  in  numher.  after 

reaciiinir  the  hase  of  the  corpuscle,  form  several  irregular 

spiral   coils    around    it    as 

they  approach  the  apex,  at 

wh.ich  [)oint  they  prohably 

terminate  in  a  filamentous 

extremity. 

Another  variety  of  cor- 
puscle has  been  described 
by  Pacini.  These  are 
known  as  the  Pacinian 
corpuscle.s.  (Fig.  135.) 
They  are  found  principally 
in  the  subcutaneous  cellu- 
lar tissue  of  the  palmar  sur- 
face of  the  hands  and  feet, 
and  most  numerous  in  the 
fingers  and  toes.  They  are 
found  connected  with  the 
nerves  of  the  joints,  ines- 
eutery,  and  other  parts. 
They  consist  of  a  corpus- 
cular body,  wh  ch  is  joined 
by  a  pedicle  to  the  nerve 
with  which  it  is  connected. 
Tile  body  is  of  an  oval 
form,  and  consists  of 
superimposed  concentric 
layers  of  connective  tissue, 
wliich  foim  a  series  of 
capsules  around  a  common 
centre  or  bulb.  Between 
the  capsules,  especiall}- 
the  most  external,  spaces 
exist,  which  are  filled  with 
a  clear  fluid.    The  bulb  con- 


sists of  granular  nucleated 
matter,    which    surrounds 


Pacinian  Corpuscles  from  the  ^Nlesentei  y  of 
a  Cut;  intended  to  show  the  general  con- 
struction of  these  bodies.  The  stalk  and  bo<ly, 
the  outer  and  inner  sysJeni  I'f  capsules  with 
tile  central  cavity  areseen.  a.  Arterial  IwIl', 
ending  in  capillaries,  which  form  loops  in 
souie  of  the  iutercapsnlar  spaces,  and  one 
penetrates  to  the  central  capsule,  b.  The 
fibrous  tissue  of  the  stalk,  prolonged  from 
the  neurilemma,  n.  Nerve-tube  advancing 
to  the  central  capsule,  there  losing  its  white 
substance,  and  stretching  along  the  axis  to 
tlie  opposite  end.  where  it  is  fixed  by  a  tu- 
bercular enlargement. 


the  nerve-tube.    The  nerve 

loses    its     medullary    sul)- 

stance    and    sheath    as    it 

penetrates  the  axis  of  the 

bulb, and  is  continued  through  the  bulb  to  the  opposite  end, 

where  the  filament  ends  as  a  tubercular  enlaro-ment.     The 


506  THE    SKIN    AND    ITS    APPENDAGES. 


situation  of  these  hulbs  in  the  subcutaneous  tissue,  as  well  as 
in  positions  of  the  body  not  concerned  in  the  tactile  sense, 
indicates  that  they  are  not  connected  with  special  sensation, 
but  are  only  one  of  tiie  modes  of  termination  of  the  sen- 
sory nerves. 

Appendages  of  the  Skin. — The  nails  are  formed  of  modi- 
fied epithelium  cells  of  the  epidermis.  They  are  convex, 
flattened,  smooth,  horny  structures,  which  are  placed  upon 
the  dorsal  surface  of  the  last  phalanges  of  the  fingei's  and  toes. 

The  nails  consist  of  a  root^ 
Fif'i-'^G.  ftor/^/,  and  free  edge.     (Fig. 

^_!L_i^  13B.)     The  root  is  thin,  soft, 

^i^i<<^^^^"^"""^^^^''^^^'        ^ith  an  irregular  margin.    It 
'  &i^  ^*3«       iscoveredby  afoldof  theskin 

which    is    extended    around 
the  sides  of  the  body.     The 
body   is   that   portion   which 
,,     .       ^  ,u    X   •,      .  •      extends  fi'om  the  root  to  the 

Transverse  Section  of  the  Isail.aud  i'^  n  T      •       /•        i 

Matrix,    b.  Longitudinal  section    of   the  "'^^    edge.  ^    It    IS    lirmly     at- 

sarae.    Both  figures  are  diagrammatic.    1,  tached    by  itS  under    SUrfaCG 

the  outer  cuticuhir  layer;  2,  the  re/e77i?<co-  tO  the    COrium    Or    trUC    skiu. 

*;/m;  3,thecutis;  4,then«il.M.bsianoe;  .5,  The  COrium  at    this    poiut    is 
the  ridges  of  the  cutis,  of  which  the  mati'" 
or  end  of  the  nail  consists. 


very  vascular  and  marked  by 
longitudidal  rows  of  papilla?. 
The  portion  beneath  the  body  of  the  nail  is  termed  the 
matrix  or  bed.  At  the  root  of  the  nail  is  frequently  seen  a 
white  semilunar  spot,  called  the  hinula.  The  whitish  color 
is  due  to  the  lessened  vascularity  and  fewer  papiihe,  as 
compared  with  the  i"est  of  the  matrix.  'Y\iq  free  j^ortiou  of 
the  nails  is  that  i)art  which  is  detached  from  the  matrix 
and  projects  from  the  cutaneous  surface. 

The  nails  consist  of  a  superficial  hard  horny  layei',  and  a 
deeper  and  softer  Malpighian  or  mucous  layer,  which  rests 
upon  the  matrix  and  completely  fills  the  interpapillary 
spaces.  The  nails  grow  by  a  continual  addition  of  new  cells 
on  their  undersurface  and  root.  The  Malpighian  layer 
remains  stationary,  and  the  horny  layer  alone  is  gradually 
increased  in  thickness  by  a  deposition  of  cells  underneath 
and  on  the  root,  and  is  pushed  forward  b}'  the  growth  of  the 
root,  and  worn  away  at  its  fiee  edge  by  attrition,  or  else 
cut  off. 

The  hairs^  like  the  nails,  are  formed  of  modified  epidermis 
cells.  The  hairs  consist  of  a  root  or  bulb,  a  ^haft  or  stem, 
and   a   point.  (Figs.  137,  138.)     The  shaft  is  of  a  flattened 


THE    SKIN    AND    ITS    APPENDAGES. 


507 


cylindrical  shape,  and  is  composed  of  an  external  portion  or 
cortex  and  an   internal  fibrous  substance.     The  cortex  is 


Fig.  137. 


Fig. 138. 


Fig.  137.— Medium-sized  Hair  in  its  Follicle.  Magnified  50 diameters  a,  stem  cut 
pliort ;  h,  root ;  c,  knob  ;  d,  hair-cuticle  ;  e,  internal,  and  /,  external  root-sheath  ;  g, 
h,  dermic  coat  of  follicle;  /,  papilla;  k,  k,  ducts  of  sebaceous  glands;  /,  corium  ;  m, 
mucous  layer  of  epidermis;  o,  upper  limit  of  internal  root-sheath. — After  Kolliker. 

Fig.  138.— Magnified  View  of  the  Root  of  a  Hair,  a,  stem  or  shaft  of  hair  cut 
across  ;  6,  inner,  and  c,  outer  layer  of  the  epidermal  lining  of  the  hair-lbllicle,  called 
also  the  inner  and  outer  root-sheath  ;  d,  dermal  or  external  coat  of  the  hair-follicle, 
shown  in  part;  e,  imbricated  scales  about  to  form  a  cortical  layer  on  the  surface  of 
the  hair.  The  adjacent  cuticle  of  the  root-sheath  is  not  represented,  and  the  papilla 
is  hidden  in  the  lower  part  of  the  knob  where  that  is  represented  lighter. — After 

KOHLRAUSCH. 

formed  of  a  layer  of  fine  imbricated  cells,  having  tiieir  free 
extremities  looking  towards  th«  point  of  a  liair.     The  cortex 


608  THE    SKIN    AND    ITS    APPENDAGES. 

incloses  the  fihrou^  structure  wliich  constitutes  the  bulk  of 
the  hair  substance.  It  is  composed  of  elongated  longitudinal 
cells,  which  coutain  pigmeut,  and  occasioually  air-cavities. 
In  the  axis  of  the  fibrous  portion,  extending  from  the  root 
to  near  the  point  of  the  hair,  a  deposition  of  granular  matter 
is  found,  which  is  composed  of  irregularly  shaped  cells, 
pigment,  and  fat.  This  is  called  the  medulla  or  pith.  In 
the  medulla  air  cells  and  air-spaces  are  found.  KoUiker 
supposes  that  the  dark  pigment-granules  of  the  medulla  are 
nothing  more  tiiau  the  gloi)ules  of  air  in  tiie  air-cells. 

The  I'oot  or  bulb  of  the  iiair  is  inclosed  in  a  follicle  which 
is  formed  by  an  involution  of  the  epidermis.  In  the  smaller 
hairs  the  follicle  merely  extends  into  the  corium  ;  in  the  larger 
hairs  it  extends  through  into  the  deep  layers  of  the  sul)cu- 
taneous  tissue.  At  its  deepest  part  it  is  expanded  into  a 
bulbous  enlargement,  which  receives  the  expanded  portion 
of  the  root,  called  \.\\Qknoh.  The  foHicle  is  lined  by  a  contin- 
uation of  tiie  epidermis  cells,  wdiicii  forms  tlie  r^oot-Kheath  of 
the  hair.  This  sheath  consists  of  two  layers,  the  inner  of 
which  is  closely  attached  to  the  imluicnted  cells  of  the 
cortex,  and  extends  to  a  point  below  the  orifice  of  the  seba- 
ceous ducts.  (Fig.  137.)  The  outer  layer  is  closely  attached 
to  the  wall  of  the  follicle.  The  wall  of  the  follicle  is  formed 
by  a  fibro-cellular  tissue,  which  is  continuous  with  the 
corium.  A  highly  nervous  and  vascular  papilla  projects 
from  the  corium  into  the  bottom  of  the  follicle.  On  the 
surface  of  the  papilla  the  cells  are  produced  which  are  des- 
tined to  form  the  hair.  The  bulbous  portion  of  the  root  or 
knob  completely  envelops  the  free  portion  of  the  papilla,  and 
consists  of  nucleated  cells,  which  are  continuous  with  the 
cuticular  lining  of  the  follicle. 

The  sebaceoiiii  glands  are  found  distributed  in  most  por- 
tions of  the  skin,  but  most  abundantly  in  the  scalp  and  face, 
and  about  the  nose,  mouth,  and  external  ear.  They  are 
absent  in  the  palmar  surface  of  the  hands  and  feet. 

The}'  are  sacculated  glands,  which  are  situated  either  in 
the  corium  or  subcutaneous  tissue.  The  walls  of  the  gland 
consist  of  a  fibrous  tissue,  which  is  lined  with  a  basement 
membrane  covered  with  a  layer  of  granular  nucleated  epi- 
thelium cells.  These  cells  contain  an  opaque,  oily  matter, 
which  is  formed  by  a  metal)olism  of  the  cells  and  consti- 
tutes the  secretion  of  the  gland.  Each  gland  has  a  single 
duct,  which  is  lined  with  epithelium,  and  opens  by  a  pivot- 


THE    SKIN    AND    ITS    APPENDAGES. 


500 


like  orifice,  either  on    the  cutaneous   surface  or   into   the 
upper  portion  of  the  hair-follicle.  (Fig.  137.) 

The  sudoriparous  or  sweat 
glands  (Fig.  189)  are  found  pro- 
fusely distributed  over  nearly 
evei'y  portion  of  the  skin.  Their 
total  number  has  been  esti- 
mated to  be  about  2,400,000. 
The  orifices  of  the  ducts  are 
irregularis'  dispersed  over  the 
general  cutaneous  surface,  be- 
tween the  papillae.  On  the 
palmar  surface  of  the  hand  and 
fingers  the  orifices  are  arranged 
in  curved  lines  in  the  middle  of 
the  double  rows  of  papilla 
forming  the  ridges.  (Fig.  182.) 
These  glands  are  of  the  tubu- 
lar variety.  Each  consists  of 
a  tubule,  liaving  one  extremity 
terminating  in  an  orifice  on 
the  cutaneous  surface,  and  the 
other  extremity  forming  a  con- 
voluted coil,  wliich  is  located  in 
the  subcutaneous  tissue.  That 
part  of  the  tubule  between 
the  orifice  and  convoluted  por- 
tion is  called  the  duct.  The 
convoluted  portion  consists  of 
one  or  more  tubuli,  which  are 
formed  by  the  subdivision  of 
the  primary  tubule.  The  tubuli 
end  in  c?ecal  extremities.  These 
glands  are  composed  of  a  fibro- 
cellular  wall,  which  is  lined  with 
granular  nucleated  epithelium. 
The  duct  in  its  passage  from 
the  convoluted  portion  to  the 
orifice  assuuies  a  spiral  or  un- 
dulating course  through  the 
corium,  becomes  straightened 
in  the  papillary  layer,  and  again 
assumes  a  spiral  course,  but 
much  more  marked,  in  its  pas- 
sage  through    the    epidermis. 

43 


Sudoriparous  O  land  from  the  Palm  of 
the  Hand;  magnified 40diameter.s.  1,1, 
contorted  tubes,  composing  the  glaud, 
andnnitingin  two  excretory  ducts;  2, 
2,  which  unite  into  one  spiral  canal  that 
perforates  the  epidermis  at  c,  and  opens 
its  surface  at  4  ;  the  gland  is  imbedded 
in  fat-vesicles,  which  are  seen  at  5,  5. 


510  SECRETION    BY    THE    SKIN. 

They  are  abiindantly  supplier!  with  bloodvessels  and  nerves. 
The  bloodvessels  form  a  capillary  plexus  around  the  convo- 
luted portion.] 

SECRETIOX  BY  THE  SKI]^. 

We  have  traced  the  food  from  the  alimentary  canal  into 
the  blood,  and,  did  the  state  of  our  knowledge  permit,  the 
natural  course  of  our  study  would  be  to  trace  the  food  from 
the  blood  into  the  tissues,  and  then  to  follow  the  products 
of  the  activity  of  tlie  tissues  back  into  the  blood,  and  so 
out  of  the  body.  This,  however,  we  cannot  as  yet  satisfac- 
torily do ;  and  it  will  be  more  convenient  to  study  first  the 
final  prodiicts  of  the  metabolism  of  the  body,  and  the  man- 
ner in  which  they  are  eliminated,  and  afterwards  to  return 
to  the  discussion  of  the  intervening  steps. 

Our  food  consists  of  cartain  food  stuffs,  viz.,  proteids, 
fats,  and  carbo-hydrates,  of  various  salts,  and  of  water.  In 
their  passage  through  the  blood  and  tissues  of  the  body  the 
proteids,  fats,  and  carbo-hydrates  are  converted  into  urea 
(or  some  closely  allied  body),  carbonic  acid,  and  water,  the 
nitrogen  of  the  urea  being  furnished  by  the  proteids  alone. 
Many  of  the  proteids  contain  sulphur,  and  also  iiave  phos- 
phorus attached  to  them  in  some  combination  or  other,  and 
some  of  the  fats  taken  as  food  contain  phosphorus  ;  these 
elements  ultimately  sufler  oxidation  into  phosphates  and 
sulphates,  and  leave  the  body  in  that  form  in  company  with 
the  other  salts. 

Broadly  speaking,  then,  the  waste  products  of  the  animal 
economy  are  urea,  carbonic  acid,  salts,  and  water.  Of  tiiese 
a  large  portion  of  the  carbonic  acid  and  a  considerable 
quantity  of  water  leave  the  body  by  the  lungs  in  respiration ; 
while  all  (or  nearly  all)  the  urea,  the  greater  portion  of  the 
salts,  and  a  large  amount  of  water,  with  an  insignificant 
quantity  of  carbonic  acid,  pass  away  by  the  kidneys.  The 
work,  therefore,  of  the  remaining  excretory  tissue,  the  skin, 
is  confined  to  the  elimination  of  a  comparatively  small  quan- 
tity of  salts,  a  little  carbonic  acid,  and  a  variable,  but  on 
the  whole  large  quantity  of  water  in  the  form  of  perspira- 
tion. The  actual  excretion  by  tlie  bowel,  that  is  to  say, 
that  portion  of  the  faeces  which  is  not  simplj^  undigested 
matter,  we  have  seen  to  be  ver}'  small. 


SENSIBLE    AND    INSENSIBLE    PERSPIRATION.       511 

The  Nahire  and  Amount  of  Perspiration. 

The  quantity  of  matter  vvliicli  leaves  the  human  l)orly  by 
way  of  the  skin  is  very  considerable.  Thus  Sequin'  esti- 
mated that,  while  7  grains  passed  away  through  the  lungs 
per  minute,  as  much  as  1 1  grains  escaped  through  the  skin. 
Tlie  amount  varies  extremely  ;  Funke"'  calculated,  from  data 
<::ained  by  inclosing  the  arm  in  a  caoutchouc  bag,  that  the 
total  amount  of  persj)iration  from  tlie  wliole  body  in  twenty- 
four  hours  might  range  from  2  to  20  kilos  ;  but  such  a  mode 
of  calculation  is  obviously  open  to  man}-  sources  of  error. 

Of  the  whole  amount  tlius  dischai'ged,  part  passes  away 
at  once  as  watery  vapor  containing  volatile  matters,  while 
part  may  remain  for  a  time  as  a  flui(l  on  the  skin  ;  the  former 
is  frequently  spoken  of  as  insensible,  the  latter  as  sensible 
}jeis[)iration.  The  proportion  of  tlie  insensihle  to  the  sen- 
sible perspiration  will  depend  on  the  rapidity  of  the  secre- 
tion in  reference  to  the  dryness,  temperature,  and  amount 
of  movement  of  the  surrounding  atmosphere.  Thus,  sup- 
posing the  rate  of  secretion  to  remain  constant,  the  dryer 
and  hotter  the  air,  and  the  more  rapidly  the  strata  of  air  in 
contact  with  the  body  are  renewed,  the  greater  is  the  amount 
of  sensible  perspiration  which  is  by  evaporation  converted 
into  the  insensible  condition  ;  and  conveisely  when  the  air 
is  cool,  moist,  and  stagnant,  a  large  amount  of  the  total  per- 
sjjiration  may  remain  on  tlie  skin  as  sensible  sweat.  Since, 
as  the  name  implies,  we  are  ourselves  aware  of  the  sensible 
perspiration  only,  it  may  and  frequently  does  happen  that 
we  seem  to  ourselves  to  be  perspiring  largely,  when  in  re- 
ality it  is  not  so  much  the  total  perspiration  which  is  heing 
increased  as  the  relative  proportion  of  the  sensible  perspira- 
tion. The  rate  of  secretion  may,  however,  be  so  much  in- 
creased that  no  amount  of  diyness,  or  heat,  or  movement  of 
tile  atmosphere,  is  suflicicnt  to  carry  out  the  necessarN'  evap- 
oration, and  thus  the  sensible  perspiration  may  become 
abundant  in  a  hot,  dry  air.  And  practically  this  is  the 
usual  occurrence,  since  certainly  a  high  temperature  con- 
duces, as  we  shall  point  out  presently,  to  an  increase  of  the 
secretion,  and  it  is  possible  that  mere  drj'ness  of  the  air  has 
a  similar  effect. 

Tlie  total  amount  of  perspiration  is  affected  not  only  by 
the  condition  of  the  atmosphere,  but  also  by  the  nature  and 
quantity  of  food  eaten,  b}^  the  amount  of  fluid  drunk,  and 

'  Ann.  d.  Chim.,  xc,  pp.  52,  403. 
2  Molesehott's  Untersnch.,  iv,  p.  36. 


512  SECRETION    BY    THE    SKIN. 

by  the  amount  of  exercise  taken.  It  is  also  influenced  by 
mental  conditions,  by  medicines  and  poisons,  by  diseases, 
and  by  tlie  relative  activity  of  the  other  excreting  organs, 
more  particularly  of  the  kidney. 

The  fluid  perspiration,  or  sweat,  when  collected,  is  found 
to  be  a  clear,  colorless  fluid,  with  a  strong  and  distinctive 
odor,  varying  according  to  the  part  of  the  body  from  which 
it  is  taken.  Besides  accidental  epidermic  scales,  it  contains 
DO  structural  elements.  The  reaction  of  the  secretion  of 
the  sweat-glands,  apart  from  that  of  the  sel^aceous  glands, 
appears  to  be  alkaline.  This  is  well  seen  when  the  sweat 
becomes  abundant.  An  admixture  of  sebaceous  secretion 
may,  when  the  sweat  itself  is  scanty,  give  rise  to  an  acid 
reaction,^  probably  from  the  sebaceous  fats  becoming  con- 
verted into  fatty  acids.  The  average  amount  of  solids  is 
about  1.81  per  cent  ,^  of  which  about  two-thirds  consist  of 
organic  substances.  The  chief  noimal  constituents  are  : 
(1.)  Sodium  chloride,  with  small  quantities  of  other  inor- 
ganic salts.  (2.)  Various  acids  of  the  fatty  series,  such  as 
formic,  acetic,  butyric,  with  probably  propionic,  caproic, 
and  caprylic.  The  presence  of  these  latter  is  inferred  from 
the  odor ;  it  is  probable  that  many  various  volatile  acids  are 
present  in  small  quantities.  Lactic  acid,  which  Berzelius 
reckoned  as  a  normal  constituent,  is  stated  not  to  be  present 
in  health.  (3.)  Neutral  fats  and  cholesterin  ;  these  have 
been  detected  even  in  places,  such  as  the  palms  of  the  hand, 
wdiere  sebaceous  glands  are  absent.  (4. J  Ammonia  (urea;, 
and  possibly  other  nitrogenous  bodies. 

Funke^  detected  a  very  considerable  amount  of  urea  in  the 
sweat  gained  by  his  method,  so  much  so  that  he  calculated  the 
total  amount  given  oft'  by  the  skin  in  24  hours  at  about  10  grams. 
Eanke*  on  the  other  hand,  who  collected  some  of  the  sweat  given 
oft"  when  the  body  w^as  exposed  in  a  large  space  to  an  abundant 
atmosphere,  found  no  evidence  whatever  of  urea-.  This  striking 
contradiction  has  not  yet  been  explained,  though,  as  will  be  seen 
in  dealing  with  nutrition,  the  satisfactory  results  which  are 
gained  by  supposing  that  under  normal  conditions  all  the  urea 
passes  out  by  the  kidneys,  render  it  probable  that  Funke's  result 
is  essentially  an  abnormal  one.  In  various  forms  of  disease  the 
sweat  has  been  found  to  contain,  sometimes  in  considerable  quan- 
tities, blood  (in  bloody  s\veat),  albumin,  urea  (particularly  in 
cholera),  uric  acid,  calcium  oxalate,  sugar,  lactic  acid,  indigo, 

'   Cf.  Triimpy  and  Luchsinger,  Pfliiger's  Archiv,  xviii  (1878),  p.  494. 

-  Funke,  op.  cit. 

^  Op.  cit.  *  Tetanus,  p.  247. 


CUTANEOUS    RESPIRATION.  513 


bile  and  other  pigments.  Iodine  and  potassium  iodide,  succinic, 
tartaric,  and  benzoic  (partly  as  hippuric)  acids  have  been  found 
in  the  sweat  when  taken  internally  as  medicines. 

Cutaneous  Respiration. 

A  frog,  the  lungs  of  which  have  been  removed,  will  con- 
tinue to  live  for  some  time;  and  during  tluit  period  will 
continue  not  only  to  produce  carl)onic  acid,  but  also  to  con- 
sume oxygen.  In  other  words,  the  frog  is  aide  to  breathe 
without  lungs,  respiration  being  carried  on  efficiently  by 
means  of  the  skiji.  In  mammals  and  in  man  this  cutaneous 
respiration  is,  by  reason  of  the  thickness  of  the  epidermis, 
restricted  to  within  very  narrow  limits  ;  nevertheless,  when 
the  body  remains  far  some  time  in  a  closed  chamber  to  which 
the  air  passing  in  and  out  of  the  lungs  has  no  access  (as 
when  the  body  is  inclosed  in  a  large  air-tight  bag  fitting 
tightly  round  the  neck,  or  where  a  tube  in  the  trachea  car- 
ries air  to  and  from  the  lungs  of  an  animal  placed  in  an 
air-tight  box),  it  is  found  that  the  air  in  the  chamber  loses 
oxygen  and  gains  carbonic  acid.  The  amount  of  carbonic 
acid  which  is  thus  thrown  off  by  the  skin  of  an  average  man 
in  24  hours  amounts  according  to  Scluirling  to  no  more  than 
about  10  grams,  according  to  Aubert^  to  about  4  grams, 
increasing  with  a  rise  of  temperature,  and  being  very  mark- 
edly augmented  b}'  bodily  exercise.  Hegnault  and  Keiset 
state  that  the  amount  of  oxygen  consumed  is  about  ecpial 
in  volume  to  that  of  the  carbonic  acid  given  off,  but  Gei"- 
lach''  makes  it  rather  less.  It  is  evident  therefore  that  the 
loss  wiiicii  the  bod}'  suffers  through  the  skin  consists  chiefly 
of  water. 

The  thickness  of  the  mammalian  or  human  epidermis  must 
afford  a  great  obstruction  to  any  diffusion  between  the  blood  in 
the  cutaneous  capillaries  and  the  external  air.  It  has  been  sug- 
gested that  the  carbonic  acid  makes  its  exit  in  the  form  of  car- 
bonates present  in  the  sweat,  and  that  these  being  decomposed 
by  the  acids  also  present  in  sweat,  their  carbonic  acid  is  set  free. 

AVhen  an  animal,  such  as  a  rabbit,  is  covered  over  with 
an  impermea.ble  varnish,  such  as  gelatin,  so  that  all  exit  or 
entrance  of  gases  or  liquids  by  the  skin  is  prevented,  death 
shortly'  ensues.  This  result  cannot  f)e  due,  as  was  once 
thought,  to  arrest  of  cutaneous  respiration,  seeing  how  in- 

'  Pfliiger's  Archiv,  vi  (1872),  p.  539. 
2  Miiller's  Archiv,  1851,  p.  431. 


514  SECRETION    BY    THE    SKIN, 

significant  is  the  gaseons  interchange  by  the  skin  as  com- 
pared with  that  b}^  the  lungs.  Xor  are  the  symptoms  those 
of  asphyxia,  but  rather  of  some  kind  of  poisoning,  marked 
by  a  very  great  fall  of  temperature,  which  however  does  not 
seem  to  be  the  result  of  diminished  production  of  heat,  since 
according  to  Burdon-Sanderson  it  is  coincident  with  an  ac- 
tual increase  of  the  discharge  of  heat  from  the  surface. 
The  animul  may  be  restored,  or  at  all  events  its  life  may  be 
prolonged  with  abatement  of  the  symptoms,  if  the  great 
loss  of  heat  which  is  evidently  taking  place  be  prevented  by 
covering  tlie  body  thickly  with  cotton-wool,  or  keeping  it 
in  a  warm  atmosphere.  The  symptoms  liave  not  as  yet  been 
clearly  analyzed,  but  they  seem  to  be  due  in  part  to  a  py- 
rexia or  fever  possibly  caused  by  the  retention  within  or 
reabsorption  into  the  blood  of  some  of  the  constituents  of 
the  sweat,  or  by  the  products  of  some  abnormal  metabolism, 
and  in  part  to  a  dilation  of  the  cutaneous  vessels,  which 
causes  an  abnormally  large  loss  of  heat,  even  through  the 
varnish. 

According  to  RJihrig'  the  injection  of  fresh  filtered  human 
sw^eat  into  the  veins  of  a  rabbit  causes  pyrexia  and  albuminuria, 
and  thus  produces  some  of  the  effects  of  "  varnishing." 

The  Secretion  of  Pen^piration. 

The  skin  contains,  besides  the  ordinary  sudoriparous 
glands,  the  sebaceous  glands,  and  tiie  special  odoriferous 
glands  of  the  axilla,  anus,  and  other  regions.  With  regard 
to  the  various  volatile  and  odorifer(nis  substances  peculiar 
to  sweat,  and  especially  with  regard  to  those  peculiar  to  the 
sweat  of  particular  regions  of  the  skin,  there  can  be  no 
doubt  that  these  are  secreted  by  the  epithelium  of  the  ap- 
propriate glands.  There  can  be  equally  no  doubt  that  the 
fats  which  come  to  the  surface  of  the  skin  from  the  sebaceous 
glands  arise  from  a  metabolism  of  the  cells  of  those  glands. 
And  we  shall  probal)ly  not  go  far  wrong  in  regarding  the 
sweat  as  a  wiiole  as  supplied  by  the  sweat-glands  alone. 
For  though  it  seems  evident  that  some  amount  of  fluid  must 
pass  l\y  simple  transudation  through  the  ordinary  epidermis 
of  the  portions  of  skin  intervening  between  the  mouths  of 
the  glands,  yet  on  the  whole  it  is  probable  that  the  portion 
which  so  passes  is  a  small  fraction  onlyof  tiie  total  quantity 
secreted   b^^  the  skin  ;  and   Erismann''^  finds   that  even  the 

1  Jahrb.  f.  Bain.,  i,  1.  ^  Zeitschrift  f.  Biol.,  xi,  1. 


NERVOUS    MECHANISM    OF    PERSPIRATION.        515 

simple  evaporation  of  water  is  much  greater  from  those  parts 
of  tlie  skin  in  which  the  glands  are  abundant  than  from  those 
in  wliich  the}'  are  scant}'. 

The  Nervous  Mechanism  of  Perspiration.^— The  secreting 
activity  of  the  skin,  like  that  of  other  glands,  is  usually  ac- 
companied and  aided  by  vascular  dilation.  In  one  of  Ber- 
nard's early  experiments  on  division  of  the  cervical  sympa- 
thetic, it  was  observed  that  in  the  case  of  the  horse,  the 
vascular  dilation  of  the  face  on  the  side  operated  on  was 
accompanied  by  increased  perspiration.  ludeed  the  con- 
nection between  the  state  of  tlie  cutaneous  bloodvessels  and 
the  amount  of  perspiration  is  a  matter  of  daily  observation. 
AYhen  the  vessels  of  the  skin  are  contracted,  the  secretion 
of  the  skin  is  diminished  ;  when  they  are  dilated  it  becomes 
abundaut.  And  in  this  way,  as  we  shall  later  on  point  out, 
the  temperature  of  tlie  body  is  largely  regulated.  When  the 
surrounding  atmosphere  is  warm,  the  cutaneous  vessels  are 
dilated,  the  amount  of  sweat  secreted  is  increased,  and  the 
consequently  augmented  evaporation  tends  to  cool  down  the 
body.  On  the  other  hand,  when  tlie  atmospliere  is  cold,  the 
cutaneous  vessels  are  constricted,  perspiration  isscant}-,  and 
less  heat  is  lost  to  the  body  l)y  evaporation. 

The  analogy  with  the  other  secreting  organs  which  we 
have  already  studied  leads  us  however  to  infer  that  there  are 
special  nerves  directly  gt)verning  the  activity  of  the  sudori- 
parous glands,  independent  of  variations  in  the  vascular 
supply.  And  not  only  is  this  view  supported  by  many  path- 
ological facts,  such  as  the  profuse  perspiration  of  the  death 
agony,  of  various  crises  of  disease,  and  of  certain  mental 
emotions,  and  the  cold  sweats  occurring  in  phthisis  and 
other  maladies,  in  allot  which  the  skin  is  ana?mic  rather  than 
hypersemic  ;  but  we  have  direct  experimental  evidence  of  a 
nervous  mechanism  of  perspiration  as  complete  as  the  vaso- 
motor mechanism. 

If  in  the  dog  or  cat  (the  latter  animal  being  especially 
suitable  for  these  p4irposes)   the   peripheral   stump  of  the 

^  Luchsinger  and  Kendall,  Pfliiger's  Archiv,  xiii  (1876),  p.  212. 
Luchsinger,  ibid.,  xiv  (1877),  p.  369  ;  xv  (1877),  p.  482  ;  xvi  (1878),  p. 
545;  xviii  (1878),  p.  478,  p.  483.  OstroumofF,  Moskauer  iirztlicher  An- 
zeiger,  1876.  Nawrocki,  Cbt.  f.  med.  Wiss.,  1878,  pp.  2,  17,  721.  Adam- 
kiewicz,  Die  Secretion  des  Schweisses,  1878.  Vulpian,  Compt.  Rend., 
T.  86  (1878),  pp,  1233,  1308,  1438;  T.  87  (1878),  pp.  311,  350,471. 
Coyne,  ibid.,  T.  86  (1878),  p.  1276. 


516  SECRETION    BY    THE    SKIN. 

divided  sciatic  nerve  be  stimulated  with  the  interrupted  cur- 
rent, a  profuse  sweat  breaks  out  in  the  foot,  and  ma}-  readily 
be  observed  in  the  balls  of  the  toes.  Not  only  may  the 
secretion  be  observed  wdien  the  cutaneous  vessels  are  thrown 
into  a  state  of  constriction  by  the  stimulus,  but  it  also  ap- 
l)ears  when  the  aorta  or  crural  artery  is  clamped  previous 
to  the  stimulation,  or  indeed  when  the  leg  is  amputated. 
Moreover  when  atropia  has  been  injected,  the  stimulation 
))roduces  no  sweat,  though  vaso-motor  effects  follow  as  usual. 
The  analogy  between  the  sweat-glands  of  the  foot  and  such 
a  gland  as  the  submaxillary  is  in  fact  very  close,  and  we  are 
justified  in  speaking  of  the  sciatic  nerve  as  containing  secre- 
tory fibres  distributed  to  the  sudoriparous  glands  of  the  hind 
limb.  Similar  results  may  be  obtained  with  the  nerves  of 
the  foie  limb  and  of  other  parts  of  the  body.  And  in  our- 
selves a  copious  secretion  of  sweat  may  be  induced  by 
tetanizing  through  the  skin  tiie  nerves  of  the  limbs  or  the 
face. 

If  a  cat  in  which  the  sciatic  nerve  lias  been  divided  on 
one  side  be  exposed  to  a  high  temperature  in  a  heated  cham- 
ber, the  limb  the  nerve  of  which  has  been  divided  remains 
dry,  while  the  whole  of  the  rest  of  the  skin  sweats  freely. 
This  result  shows  that  the  sweating  which  is  caused  by  ex- 
posure of  the  itody  to  high  temperatures  is  brought  about 
not  by  a  local  action  on  the  sweat-glands  but  by  the  agency 
of  the  central  nervous  system.  A  high  temperature  up  to 
a  certain  limit  increases  the  irritability  of  the  epithelium  of 
the  sweat-glands  as  it  does  that  of  other  forms  of  proto- 
plasm ;  thus  stimulation  of  the  sciatic  in  the  cat  produces 
a  much  more  abundant  secretion  in  a  limb  exposed  to  a  tem- 
perature of  35°  or  somewhat  above,  than  in  one  which  has 
been  exposed  to  a  distinctly  lower  temperature,  and  in  a  limb 
which  has  been  placed  in  ice-cold  water  hardly  any  secretion 
at  all  can  be  gained  ;  but  apparently  mere  rise  of  tempera- 
ture without  nerve-stimulation  will  not  give  rise  to  a  secre- 
tory activity-  of  the  glands.  The  sweating  caused  by  a 
dyspnoeic  condition  of  blood,  and  such  appears  to  be  the 
sweat  of  the  death  agony,  is  similarly  brought  about  by  the 
agency  of  the  central  nervous  system.  When  an  animal 
with  the  sciatic  nerve  divided  on  one  side  is  made  dyspnoeic, 
no  sweat  appears  in  the  hind  limb  of  that  side,  though 
abundance  is  seen  in  other  parts  of  the  body. 

Sweating  may  be  brought  aliout  as  a  reflex  act.  Thus 
when  the  central  stump  of  the  divided  sciatic  is  stimulated 


NERVOUS    MECHANISM    OF    PERSPIRATION.        517 

sweating  is  induced  in  the  other  limbs,  and  the  introduction 
of  pungent  substances  into  the  mouth  will  frequently  give 
rise  to  a  copious  perspiration  over  the  side  of  the  face.  V\^e 
are  thus  led  to  speak  of  sweat  centres,  analogous  to  the 
vaso-motor  centres,  as  existing  in  the  central  nervous  sys- 
tem ;  and  as  in  the  case  of  vaso-motor  centres,  a  dispute 
has  arisen  as  to  whether  there  is  a  dominant  sweat  centre 
in  the  medulla  ol)longata  or  whether  such  centres  are  more 
generally  distril)uted  over  the  whole  of  the  spinal  cord. 

It  does  not  at  present  appear  certain  whether  the  sweat- 
ing caused  by  heat  is  carried  out  by  direct  action  on  the 
sweat  centres,  or  by  the  higher  temperature  affecting  the 
skin,  and  so  producing  its  effect  in  a  reflex  manner;  but  in 
the  case  of  dyspnoea  at  least  we  may  fairly  suppose  that 
the  action  of  the  venous  blood  is  chiefly  if  not  exclusively 
on  the  nerve  centres.  Drugs,  such  as  pilocarpin,  which 
cause  sv\ eating,  appear  to  act  locally  on  the  glands  (though 
pilocarpin  at  least  has  as  well  some  action  on  the  nerve 
centres),  and  the  antagonistic  action  of  atropia  is  similarly 
local.  Xicotin  appears  to  produce  its  sweating  action  chiefly 
b}'  acting  on  the  central  nervous  system. 

The  sweat-fibres  for  the  hind  foot  (in  the  cat),  according  to 
Nawrocki  and  Luchsinger,^  leave  the  spinal  cord  bj^  the  roots  of 
the  last  dorsal  and  first  two  lumbar  or  last  two  dorsal  and  first 
four  lumbar  nerves,  pass  along  the  rami  communicantes  to  the 
abdominal  sympathetic,  and  thus  reach  the  sciatic  nerve.  .Simi- 
larly the  sweat-nerves  for  the  fore-foot  leave  the  spinal  cord  by 
the  roots  of  the  fourth  (or  fourth,  fifth,  and  sixth)  dorsal  nerves, 
pass  into  the  thoracic  sympathetic,  thence  into  the  ganglion  stel- 
latum,  and  thus  join  the  brachial  plexus  ;  the  course  to  the  foot 
is  finally  along  the  median  and  ulnar  nerves  respectively.  Ac- 
cording to  them,  when  the  abdominal  S3anpathetic  below  the 
junction  with  the  second  or  fourth  lumbar  root  is  divided  sweat- 
ing cannot  be  induced  by  nervous  agency  in  the  hind-foot ;  and 
section  of  the  thoracic  sympathetic  above  the  junction  with  the 
fourth  dorsal  root  or  removal  of  the  ganglion  stellatum  similarly 
prevents  the  sweating  of  the  fore-foot.  Yulpian,^  on  the  other 
hand,  finds  that  the  s.Aveat-fibres  pass  in  a  direct  course  along  the 
roots  of  the  sciatic  or  brachial  plexus,  and  sees  reason  to  believe 
that  the  sympathetic  tracts  contain  inhibitor}' fibres,  since  he  has 
been  able  to  check  perspiration  by  stimulating  these  nerves. 

NaAvrocki^  found  tliat  the  reflex  excitation  of  sweat  by  stimu- 
lation of  the  central  sciatic  failed  when  the  spinal  cord  was  di- 
vided below  the  medulla.    Hence  he  believed  that  a  general  sweat 

^  Op.  cit. 
44 


518  SECRETION    BY    THE    SKIN. 


centre  was  situate  in  the  medulla  oblon2:ata.  Sweating  in  the 
hind  limbs  may,  however,  be  produced  after  section  of  the  cord 
in  the  dorsal  region  eiiher  by  dyspnoea  or  by  heating,  and  these 
act,  as  we  have  seen,  through  a  nerve  centre.  Luchsinger,^ 
indeed,  found  that  so  long  as  a  portion  of  the  cord  in  the  lower 
dorsal  and  upper  lumbar  region  was  left  intact,  sweating  could 
thus  be  induced  in  the  hind  limbs  even  when  all  the  nerve-roots 
had  been  divided,  except  those  springing  from  the  intact  portion 
of  the  cord  ;  but  that  the  effect  entirely  ceased  when  this  portion 
of  the  cord  was  destro3'ed.  He  accordingl}^  inferred  that  a  sweat 
centre  for  the  hind  limbs  existed  in  this  part  of  the  cord. 

Absorption  by  the  Skin. 

Although  under  normal  circumstances  the  skin  serves 
only  as  a  cliannel  of  loss  to  the  body,  there  are  facts  whicli 
seem  to  show  that  it  may.  under  particular  circumstances, 
be  a  means  of  gain.  Cases  are  on  record  where  bodies  have 
been  ascertained  to  iiave  gained  in  weight  hy  immersion  in 
a  batli,  or  by  exposure  to  a  moist  atmosphere  during  a  given 
period,  in  which  no  food  or  drink  was  taken,  or  to  have 
gained  more  tiian  the  weight  of  the  food  or  drink  taken. 
The  gain  in  such  cases  must  have  been  clue  to  the  absorp- 
tion of  vvater.  It  is  doubtful  whether  substances  in  aqueous 
solution  can  be  absorbed  by  the  skin  when  the  epidermis  is 
intact,  the  evidence  on  tiiis  point  being  contradictory;  but 
absorption  takes  place  very  readily  from  abraded  surfaces, 
and  even  solid  particles  rubbed  into  tlie  sound  skin  may, 
especially  wiien  applied  in  a  fatty  vehicle,  as  ex.gr.^  in  the 
well-known  mercury  ointment,  find  tlieir  way  into  the  under- 
lying l\mphatics. 

In  the  case  of  the  sound  human  skin  the  balance  of  conflicting 
evidence  is  in  favor  of  the  view  that  sokil)le  non-volatile  sub- 
stances are  not  absorbed,  and  that  volatile  substances  sucli  as 
iodine  which  may  be  detected  in  the  system  after  a  bath  contain- 
ing them  are  absorbed,  not  by  the  skin  but  by  the  mucous  mem- 
brane of  the  respiratory  organs,  the  substance  making  its  way  to 
the  latter  by  volatilization  from  the  surface  of  the  bath. 

In  the  case  of  the  skin  of  the  frog  an  absorption  of  water  and 
of  various  soluble  substances  would  certainly  appear  to  take 
place. '^ 

^  Op.  cit. 

2  Guttman,  Virchow's  Arcliiv,  Bd.  35  (1865),  p.  451  ;  Bd.  41  (1867), 
p.  105.  Stirling,  Journ.  Anat.  and  Phys.,  xi  (1877),  p.  529  ;  V.  Wittich, 
Mitth.  a.  d.  Konigsberger  Physiolog.  Laborat.,  1878,  p.  24. 


ANATOMY    OF    THE    KIDNEYS. 


519 


CHAPTER    IV. 


^" 


T 


\_Phl/sioIogical  Anatomy  of  the  Kidnei/ii. 

The  kidneys  are  tnlmlar  glands.  Tliey  are  invested  by  a 
fihroiis  capsule,  whicii  is  loosely  connected  to  the  surface  of 
the  organ  hy  delicate  processes  and  Moodvessels.  At  the 
hilum  or  notch,  tiie  capsule  is  prolonged  inwards  and  forms 
the  lining  of  the  sinus,  and  a  sheath  around  the  bloodves- 
sels. 'V\\*i  pelvis  of  the  kidney  is  formed  hy  a  trumpet  like 
expansion  of  the  ureter.  At  its  widest  [)ai-t  it  divides  into 
three  infundil)ula,  and  these  in 
turn  are  snixlivided  into  ten  or  Fig.  140. 

twelve  smaller  divisions  or  call-  J^'^a^'    ^^ 

cps,  each  of  vvhicii  embrace  one  y'    '' j^*" .' 

or  more  small  papillary  i)rojec- 
tions. 

If  a  vertical  section  be  made 
of  the  kidne^'.  as  is  shown  in 
Fig.  140,  the  substance  of  tiie 
gland  will  appear  to  consist  of 
two  distinct  portions,  wliicli 
from  their  positions  are  termed 
the  medullary  and  cortical  por- 
tions. The  medullary  sul)stance 
consists  of  a  number  of  conical- 
shaped  bodies,  which  are  termed 
tiie  'pyra mids of  Malpigh i.  The 
bases  and  sides  of  these  bodies 
are  enveloped  by  the  cortical 
substance;  the  apices  project 
into  the  calices  as  papillae.  The 
pyramids  have  a  striated  ap 
pearance,  and  when  more  mi- 
nutely examined  are  seen  to 
consist  of  a  number  of  diverg- 
ing tubules,  which  are  bound 
together   by   a    fibrous    stroma 

containing  bloodvessels.  The  cortical  suiistance  constitutes 
about  three-fourths  of  the  gland  substance,  and  is  composed 
of  a  mass  of  convoluted  tubules  v.-liich  are  continuous  with 
those  of  tlie  pyramids,  and  of  small  reddish  bodies  called  the 
Malpighian  corpiiaclea  or  glomeruli ;  all  of  which  are  im- 


§      '"-i'r 


Section  throujih  the  Ki'lnoy,  sliow- 
inji  tlie  Medullary  ami  Conical  Por- 
tions, and  the  beginning  of  the  Ureter. 
— H  EXLE. 

a,  ureter;  b,  pelvis  of  the  ureter;  c, 
papilise  surrounded  hy  calices  of  tiie 
excretory  tube;  (/.pyramidal  i)oriions; 
e,  cortical  portion  of  ilie  kidney. 


520 


ANATOMY    OF    THE    KIDNEYS. 


bedded   in   a   fibrous  matrix   which  contains   bloodvessels, 
nerves,  and  lymphatics. 

The  tubules  are  called  the  tuhuli  urwiferi^  and  are  com- 
posed of  a  homogeneous  transparent  membrane,  lined  with 
granular,  nucleated  epithelium.     In  their  passage  from  the 


Fig.  141. 


Diagram  of  the  course  of  tlie  Uriniferous  Tubules,  a,  orifice  of  tubule  at  apex  of 
Malpighian  pyramid;  />,  intermediary  portion,  continuous  with  recurrent  branches, 
which  form  htops,  c.  in  the  medullary  portion  of  the  kidney,  and,  reascending,  ter- 
minate in  Malpigtiian  capsules  in  the  cortical  portion. 

pa[)illary  orifices  to  the  cortex  they  divide  dichotomously  at 
acute  angles  and  form  bundles  of  straight  or  slightly  wavy 
tubides,  which  constitute  the  pyramids  of  Ferrein.  From 
these  straight  tubules  (tubules  of  Bellini)  the  intermediary 
branches  arise.  (Fig.  141,6  )  These  branches  are  somewhat 
enlarged  and  more  or  less  twisted  and  tortuous  ;  they  then 
become  much  diminished  in  size,  and  return  towards  the 
papillae  in  a  direction  nearly  parallel  with  the  tubules  of  Bel- 


ANATOMY    OF    THE    KIDNEYS. 


521 


lini,  and  after  pursuing  a  variable  distance  retrace  their  way, 
being  still  more  reduced  in  size,  and  then  running  into  the 
substance  of  the  cortex  where  they  become  enlarged  and 
convoluted,  finally  terminate  in  saccular  dilatations,  termed 
Malpighian  capHule>i.  The  recurrent  branches  or  loops  above 
described  are  known  as  the  nari^ow  tubes  or  loops  of  Henle. 

Fig.  142. 


5^       /      A''  '^- 


■  ^    X  VJjf^ 


^    6 

5'" 


Transverse  Section  of  a  Renal  Papilla  (from  Kolliker),  3.oo  a,  larger  tubes  or 
papillary  ducts;  6,  smaller  tubes  of  Henle;  j,  bloodvessels  distinguished  by  their 
flatter  epithelium;  d,  nuclei  of  the  stroaia. 

The  i)ortion  of  the  tubules  between  the  straight  tubules 
of  Bellini  and  the  ]\[alpighian  capsules  presents  three  dis- 
tinct anatomical  varieties.  The  convoluted  portion  (''secret- 
ing tubules")  near  the  capsule,  is  enlarged  and  lined 
throughout  with  glandular  epithelium ;  the  capsular,  or 
smaller  portion  of  the  loop  of  Henle,  is  about  one-fourth 
the  size  of  the  convoluted  portion,  and  is  lined  with  small 
clear  nucleated  cells;  the  larger  portion  of  the  loop  is 
about  double  the  size  of  the  capsular  ))ortion,  and  is  lined 
with  epithelium  of  a  columnar  variety,  having  somewhat  of 
an  imbricated  arrangement;  the  intermediate  or  "interca- 
lated "  portion,  which  connects  the  loop  of  Henle  with  the 
tubules  of  Bellini,  is  lined  with  an  epithelium  similar  to 
that  which  lines  the  convoluted  portion  near  the  capsule. 
The  tubules  of  Bellini  as  well  as  the  main  tubules  are  lined 
b}'  epithelium  of  a  columnar  variety,  with  broad  bases. 


522 


ANATOMY    OF    THE    KIDNEYS. 


Eachof  tlie  MnJpighian  corpvi^cle^  is  coini)oserl  of  a  Malpior- 
hian  capsule,  and  an  inclosed  vascular  tuft.  (Figs.  14^^  and 
144.)  The  tuft  is  composed  of  an  afferent  and  eflerent  vessel 
and  their  intei'niediate  plexus  of  capillaries.  The  aflerent 
vessel  is  formed  b}*  one  of  the  ramifications  of  the  renal  artery, 

Fig.  143.  Fig.  144. 


Fig.  143. — Plan  of  tlie  Renal  Circulation  in  Man  and  the  Mammalia,  a,  termirial 
braiicli  of  the  artery,  giving  the  terminal  twi;^  1,  to  the  Malpigliian  tuft  m,  from 
wliich  emerges  the  efferent  or  portal  ve.'^s  1,  2.  Other  (  ffereiit  vessels,  2,  are  seen 
entering  the  plexus  of  capillaries,  surrounding  the  uiiiiiferous  tube,  <.  From  the 
plexus,  the  emulgent  vein,  ri,  springs. 

Fig  144.— Semi-diagrammatic  Represen  ation  of  a  Malpighian  Body  in  its  relations 
to  the  Uriniferous  Tube  (from  Koliiker; -f-.  a,  capsule  of  the  Malpighian  body  ; 
d,  epithelium  of  the  uriniferous  tube  ;  e,  ueiached  epithelium  ;  /,  afferent  vessel ;  g, 
efferent  vessel  ;  //,  convoluted  vessels  of  the  glomerulus. 

which  after  piercing  the  capsule  rapidly  subdivides  into 
minute  capillaries  forming  an  intricate  convoluted  plexus 
which  finally  anastomoses  to  form  one  or  more  efl!erent  vessels 
or  veins.  The  etferent  vessels  make  their  exit  adjacent  to  the 
point  of  entrance  of  the  afferent  vessel,  and  then  form  anasto- 
moses with  the  efferent  vessels  of  other  glomeruli  to  form 
dense  plexuses  of  capillaries  around  the  tiibuli  uriniferi. 
These  capillaries  finnll^^  form  larger  branches,  which  ulti- 
mately unite  to  form  the  renal  vein.  The  system  of  venous 
capillaries  around  the  tul)ules  is  termed  the  nnial  vena 
jjortal  aystem.  The  interior  of  the  capsules  is  lined  by  ovoid, 
granular  nucleated  cells.  According  to  some  observers 
the  tuft  is  covered  by  a  layer  of  cells  similar  to  those  lining 
the  convoluted  portion  of  the  tubules.] 


COMPOSITION    OF    URINE.  523 


SECRETIOX  BY  THE  KIDXEYS. 

TIie  epithelium  of  the  kidney,  like  that  of  the  alimentary 
canal,  is  a  secretino;  tissue.  The  protoplasmic  cells  which 
line  at  least  a  large  portion  of  the  tiibuU  uriniferi  elaborate 
from  the  blood,  in  a  manner  which  we  shall  presently  dis- 
cuss, certain  snbstances,  and  discharge  them  into  the  chan- 
nels of  the  tubules.  Besides  these  distinctly  active  secret- 
ing structures,  however,  the  kidne}'  exhibits  in  its  Mal- 
pighian  bodies  an  arrangement  very  analogous  to  that  which 
obtains  in  the  lungs.  Just  as  in  the  latter  the  functions  of 
the  alveolar  epithelium  are  reduced  to  a  minimum,  and  the 
entrance  and  egress  of  the  gases  of  respiration  are  mainly 
carried  on  by  diffusion,  so  in  the  former  tiie  epithelium  cov- 
ering the  glomeruli  can  have  but  little  secreting  activity, 
and  the  passage  of  material  from  the  interior  of  the  convo- 
luted l)lood vessels  into  the  cavities  of  the  tubules  must  be 
chieflv  a  matter  of  simple  filtration.  What  substances  pass 
in  this  way,  and  what  sulistances  are  secreted  by  the  direct 
action  of  the  epithelium  of  the  secreting  tul)ules,  we  shall 
shortly  consider.  Tlie  vaiious  substances  passing  in  either 
the  one  or  tlie  other  way,  in  company  with  a  large  amount  of 
water,  into  the  ducts  of  the  gland,  constitute  the  secretion 
called  urine.  And  since  none  of  the  substances  so  thrown 
out  are  of  any  further  use  in  the  economy,  but  are  at  once 
carried  away,  urine  is  generally  spoken  of  as  an  excretion. 

Sec.  I.  Composition  of  Urine. 

The  heallhy  urine  of  man  is  a  clear  yellowish  fluorescent 
fluid,  of  a  peculiar  odor,  saline  taste,  and  acid  reaction,  hav- 
ing a  mean  specific  gravity  of  1.020,  and  generally  holding 
in  suspension  a  little  mucus.  The  normal  constituents  may 
be  arranged  in  several  classes. 

1.  Water. 

2.  Inorganic  Salts. — These  for  the  most  part  exist  in  urine 
in  natural  solution,  the  composition  of  the  ash  almost  exactly 
corresponding  with  the  results  of  the  direct  analysis  of  the 
fluid  ;  in  this  respect  urine  contrasts  forcibly  with  blood, 
the  ash  of  which  is  largely  composed  of  inorganic  substances, 
which  previous  to  the  combustion  existed  in  peculiar  com- 


524 


SECRETION    BY    THE    KIDNEYS. 


bination  with  proteid  and  other  complex  bodies.  In  the  ash 
of  urine  there  is  rather  more  sulphur  than  corresponds  to  the 
sulphuric  acid  directly  determined  ;  this  indicates  the  ex- 
istence in  urine  of  some  sulphur-hohling  complex  body. 
And  there  are  traces  of  iron,  pointino^  to  some  similar  iron- 
holding  substance.  But  otherwise,  all  the  substances  found 
in  the  ash  exist  as  salts  in  the  natuial  fluid.  The  most 
abundant  and  important  is  sodium  chloride.  There  are 
found  in  smaller  quantities,  calcium  chloride,  potassium,  and 
and  sodium  stdphates, sodium,  calcium, and  magnesium  phos- 
phates, with  traces  of  silicates.  Alkaline  carbonates  are  fre- 
quently found,  and  nitrates  in  small  quantity  are  also  said 
to  be  sometimes  present. 

The  phospliatcs  are  derived  partly  from  the  phosi)hates 
taken  as  such  in  food,  parti}'  from  the  phosphorus  or  jjhos- 

phates  peculiarly   associated 
r^^"-  i"^"*  with  the  proteids,  and  partly 

from  the  phospliorus  of  cer- 
tain complex  fats,  such  as 
lecithin.  When  urine  be- 
comes alkaline,  the  calcic 
and  magnesic  phosphates  are 
precipitated  (Fig.  145),  the 
sodium  phosphates  remain- 
ing in  solution.  The  sul- 
phates are  derived  partly 
from  the  sulphates  taken  as 
such  in  food  and  partly  from 
the  sulphur  of  the  proteids. 
The  carbonates,  when  occur- 
ring in  large  quantity,  gener- 
ally have  their  origin  in  the 
oxidation  of  such  salts  as 
citrates,  tartrates,  etc.  The 
bases  present  depend  largely  on  the  nature  of  the  food  taken. 
Thus,  with  a  vegetable  diet,  the  excess  of  the  alkalies  in  the 
food  reappears  in  the  urine  ;  with  an  animal  diet,  the  earthy 
bases  in  a  similar  wa^-  come  to  the  front. 

.3.  Nitrogenous  Crystalline  Bodies,  derivatives  of  the  meta- 
bolism of  the  proteids  of  the  l)ody  and  food.  First  and  fore- 
most come  urea  and  its  immediate  ally,  uric  acid.  -These 
will  be  considered  in  detail  hereafter;  they  are  the  typical 
products  of  the  metabolism  of  proteids.     Existing  in  much 


Urinary  sediment,  of  trij)le  phosphates 
(hirge  prismatic  crx'stals)  and  urate  of 
ammonia,  from  urine  which  had  under- 
gone alkaline  fermentation.] 


COMPOSITION    OF    URINE.  525 

smaller  quantities  are  a  number  of  bodies  more  or  less 
closely  related  to  urea,  wliich  may  for  the  most  part  be  re- 
garded as  less  completely  oxidized  products  of  metaltolism. 
Such  are:  kreatinin,  xanthin,  hypoxanthin,  and  occasionally 
allantoin.  To  these  may  be  added  hippuric  acid,  ammonium 
oxalurate,  and,  at  times,  taurin,  cystin.  leucin,  and  tyrosin. 
These  two  we  shall  have  to  consider  in  dealing  with  the 
metabolism  of  the  body. 

4.  Non-nitrogenons  Bodies. — These  exist  in  very  small 
quantities,  and  many  of  them  are  probably  of  uncertain  oc- 
currence. They  are  organic  acids,  such  as  lactic,  succinic, 
formic,  oxalic,  p^henyiic,  etc.  It  has  been  maintained  that 
minute  quantities  of  sugar  are  invariably  present  in  even 
healthy  urine;  this,  however,  has  not  as  yet  been  placed  be- 
yond all  doubt. 

5.  Pigments. — These  are  at  present  very  imperfectly  un- 
derstood. Whether  the  natural  yellow  color  of  urine  be 
due  to  a  single  pigment,  the  urodirome  of  Thudichum,  or 
to  more  than  one,  and  what  is  the  exact  nature  of  these 
pigments,  must  be  left  undecided.  As  was  stated  above 
(p.  59),  the  urine  frequently  contains  vrnhilin  ;  and  the  pe- 
culiar red  color  of  some  rheumatic  urines  is  due  to  the  pres- 
ence of  a  body  called  by  Prout  purpurin  and  by  Heller 
uroerythrin.  The  urine  of  man  and  of  many  animals,  espe- 
cially of  the  dog,  contains  indican,  which  under  certain  cir- 
cumstances may  give  rise  to  the  production  of  indigo-blue. 

6.  Other  Bodies. — Urine  treated  with  many  times  its  vol- 
ume of  alcohol  gives  a  precipitate.  In  this  precipitate  is 
found  a  body,  giving  proieivd  reactions  ;  and  an  aqueous 
solution  of  the  precipitate  is  both  amylolytic  and  proteo- 
lytic, i.  e.,  appears  to  contnin  some  of  both  tiic  salivar3"  (pan- 
creatic) ferment  and  pepsin. 

1.  Gases. — Those-gases  which  can  be  extracted  from  urine 
by  the  mercurial  pump  are  chiefly  nitrogen  and  carbonic 
acid,  oxygen  occurring  in  very  small  quantities  or  being 
wholly  absent. 

The  quantities  in  which  these  multifarious  constituents 
are  present  vary  within  very  wide  limits,  being  dependent 
on  the  nature  of  the  food   taken,  and  on  the  circumstances 


526 


SECRETION  BY  THE  KIDNEYS. 


of  tlie  bc)(ly.  These  points  will  he  considered  in  tlie  snc- 
ceediiit!;  chapter.  What  may  be  called  the  average  compo- 
sition of  human  urine  is  shown  in  the  foUowinir  table. 


Amounts  of  the  Several  Urinari/  Constituents  passed  in  twenty-four 
hours. — (After  Pakkes.) 


By  an  average 

P-r  1  kilo 

mini  of  66  kilos. 

of  l.<.(ly  w.ight. 

Water 

1500.000  grams 

23.0000  grams 

Total  solids,     .     . 

72.000 

1.1000 

Urea,       .... 

33.180 

.5000 

Uric  acid,    .     .     . 

.555 

.0084 

Hippuric  acid, 

.400 

.00(30 

Kreatinin,    .     .     . 

.910 

.0140 

Pigment,  and 

other  substances, 

10.000 

.1510 

Sulphuric  acid, 

2.012 

•0305 

Phosphoric  acid,  . 

3.104 

.0480 

Chlorine,      .     .     . 

7.000  (8.21) 

.1200 

Ammonia, 

.770 

Potassium,  .     .     . 

2.500 

Sodium,  .... 

11.090 

Calcium,      .     .     . 

.200 

Magnesium,     .     . 

.207 

Acidity  of  Urine. — The  healthy  urine  of  man  is  acid,  the 
amount  of  acidity  being  about  equivalent  to  2  grams  of  ox- 
alic acid  in  twent^'-four  hours.  It  is  due  to  the  presence  of 
acid  sodium  phosphate,  the  absence  of  free  acid  being  shown 
by  the  fact  that  sodium  hyposulphite  gives  no  precipitate. 
The  amount  of  acidity  varies  much  during  the  twenty-four 
hours,  being  in  an  inverse  ratio  to  the  amount  of  acid  se- 
creted by  the  stomach  ;  thus  it  decreases  after  food  is  taken, 
and  increases  as  gastric  digestion  becomes  complete.  It 
varies  with  the  nature  of  the  food  ;  with  a  vegetable  diet 
the  excess  of  alkalies  secreted  leads  to  alkalinity,  or  at  least 
to  diminished  acidity,  whereas  this  etfect  is  wanting  with 
an  animal  diet,  in  which  the  earthy  bases  preponderate. 
Hence  the  urine  of  carnivora  is  generally  very  acid,  while 
that  of  herbivora  is  alkaline.  The  latter,  when  fasting,  ai-e 
for  the  time  lieing  carnivorous,  living  entirely  on  their  own 
bodies,  and  hence  their  urine  becomes  under  these  circum- 
stances acid. 

The  natural  acidity  increases  for  some  time  after  the  urine 


SECRETION    OF    URINE.  527 

has  been  discharged,  owing  to  the  formation  of  fresh  acid, 
apparently-  by  some  kind  of  fermentation.  Tliis  increase  of 
acid  frequently  causes  a  precipitation  of  nrates,  which  the 
previous  acidity  has  been  insuMicient  to  throw  down.  After 
awhile  however  the  acid  reaction  gives  way  to  alkalinity. 
This  is  caused  b}'  a  conversion  of  the  urea  into  ammonium 
carbonate  through  the  agency  of  a  specific  ferment.  Tiiis 
ferment  as  a  general  rule  does  not  make  its  appearance  ex- 
cept in  urine  exposed  to  the  air  ;  it  is  only  in  unhealthy 
conditions  that  the  fermentation  takes  place  within  the 
bladder. 

Abnormal  Constituents  of  Urine. — Tiie  structural  elements 
found  in  the  urine  under  various  circumstances  are  blood, 
pus  and  mucus  corpuscles,  epithelium  from  the  bladder  and 
kidney,  and  spermatozoa.  Serum-albumin,  fibrin  (frequently 
as  "  casts  "),  alkali-albumin,  globulin,  a  peculiar  form  of  al- 
bumin (discovered  by  Bence-Jones  in  mollitiesoHsinm,  char- 
acterized by  being  soluble  at  high  temperatures,  and  redis- 
covered by  Kiihne  as  a  product  of  digestion),  fats,  choles- 
terin,  sugar,  leucin,  tyrosin,  oxalic  acid,  bile  acids,  and  bile 
pigment  may  be  enumerated  as  the  most  important  meta- 
bolic products  abnormally  present  in  urine.  Besides  these 
the  urine  serves  as  the  chief  channel  of  elimination  for  va- 
rious bodies,  not  proper  c(^nstituents  of  food,  which  may 
happen  to  liave  been  taken  into  the  system.  Thus  various 
minerals,  alkaloids,  salts,  pigmentary  and  odoriferous  mat- 
ters may  be  passeci  unchanged.  Many  substances  thus  oc- 
casionally taken  suifer  ciianges  in  passing  through  the  body  ; 
the  most  important  of  these  will  be  considered  in  a  succeed- 
ing chapter. 

Sec.  2.  The  Secretion  of  Urine. 

We  have  already  called  attention  to  the  fact  that  the  kid- 
ney, unlike  the  otliei'  secreting  oigms  which  we  have  hith- 
erto studied,  consists  of  two  distinct  parts  :  of  an  actively 
secreting  part,  the  epithelium  of  the  secreting  tubules,  and 
of  what  may  be  called  a  filtering  part,  the  Malpighian  bodies. 
Corresponding  to  this  double  structure  vve  find  that,  of  the 
various  urinary  constituents  enumerated  in  the  preceding 
section,  some,  such  as  sodium  chloride,  are  known  to  be 
present  in  the   blood   independently  of  any  activity  of  the 


528  SECRETION    BY    THE    KIDNEYS. 

kidney;  others,  such  as  the  urinary  pigments,  appear  to  be 
absent  from  the  blood  ;  while  of  others,  such  as  urea,  it  is 
probable  that  their  occurrence  in  the  blood  is  in  part  the 
result  of  some  previous  renal  action,  or  at  least  it  is  not  cer- 
tain that  this  is  not  the  case.  The  first  of  tiiese  we  may 
fairly  su|)pose,  as  Bowman^  l^'ig  ago  suggested,  to  be  in  large 
part  at  least  simply  filtered  through  the  renal  glomeruli  ; 
the  others  we  may  regard  provisionally  as  the  products  of 
tlie  activity  of  the  renal  epithelium.  Since  the  passage  of 
fluids  and  dii^solved  substances  through  membranes  is  in 
large  pait  directly  dependent  on  pressure,  the  extent  and 
rapidity  of  that  part  of  the  whole  process  of  the  secretion 
of  urine  which  is  a  mere  filtration,  will  be  directly  affected 
by  the  amount  of  arterial  pressure  in  the  renal  arteries, 
while  the  eflTect  of  variations  of  arterial  pressure  on  that 
part  of  the  i)rocess  which  is  a  real  active  secretion,  will  be 
an  indirect  one  only.  Since,  then,  the  discharge  of  urine 
by  the  kidneys  must  be  to  a  much  greater  extent  than  is  the 
case  with  the  secretion  of  saliva  or  of  gastric  juice  a  mere 
matter  of  pressure,  it  will  be  more  convenient  to  study  the 
relations  of  urinary  secretion  to  blood-pressure  before  we 
enter  upon  the  discussion  of  t'ne  active  secretion  itself. 

The  Relation  of  the  Secretion  of  Ursine  to  Artei^ial  Pressure. 

The  circumstance  to  which  we  have  to  direct  our  atten- 
tion is  the  extent  of  pressure  present  in  the  small  vessels  of 
the  renal  glomeruli.  The  more  the  pressure  of  the  blood 
in  these  exceeds  the  pressure  of  the  fluid  in  the  channels  of 
the  uriniferous  tubules,  the  more  rapid  and  extensive  will 
be  the  filtration  from  the  one  into  the  other. 

This  local  blood-pressure  in  the  small  vessels  of  the 
glomeruli  may  be  increased — 

1.  By  an  increase  of  the  general  blood-pressure,  brought 
about  (fl)  by  an  increased  force,  frequency,  etc.,  of  the  heart's 
beat;  {h)  by  the  constriction  of  the  small  arteries  supply- 
ing areas  other  than  the  kidney  itself. 

2.  By  a  relaxation  of  the  renal  artery,  which,  as  we  have 
previously  pointed  out  (p.  285),  while  diminishing  the  pres- 

'  Phil.  Trans.,  1842. 


RELATIONS    TO    BLOOD-PRESSURE.  529 

sure  in  the  artery  itself,  increases  the  pressure  in  the  capil- 
laries and  small  veins  which  the  artery  supplies.  It  need 
hardly  be  added  that  this  local  relaxation  must  either  he 
accompanied  by  constriction  in  other  vascular  areas,  or  at 
all  events  must  not  be  accompanied  by  a  sntliciently  com- 
pensating dilation  elsewhere. 

The  same  local  pressure  may  similarly  be  diminished — 

1.  By  a  constriction  of  the  renal  artery,  which,  while  in- 
creasing the  pressure  on  the  cardiac  side  of  the  artery, 
diminishes  the  pressure  in  the  capillaries  and  veins  which 
are  supplied  by  the  artery.  This  again  must  either  be  ac- 
companied by  dilation  in  other  vascular  areas,  or  at  least 
not  accompanied  by  a  compensating  constriction. 

2.  Bn'  a  lowering  of  tlie  general  blood-pressure,  brought 
about  (a)  by  diminished  force,  etc.,  of  tlie  heart's  beat;  (6  , 
by  a  general  dilation  of  the  small  arteries  of  the  bo(iy  at 
large,  or  by  a  dilation  of  vascular  areas  other  than  the 
kidneys. 

Bearing  these  facts  in  mind,  it  !)ecf'mes  easy  to  explain 
many  of  the  instances  in  which  an  increase  or  diminution 
of  urine  is  produced  by  natural  or  artificial  means.  Thus 
section  of  the  spinal  cord  below  the  medulla  causes  a  gieat 
diminution,  and,  indeed,  in  most  cases,  a  comi)lete  or  almcjst 
complete  arrest  of  the  seci-etion  of  urine.  This  operation, 
by  cutting  off  so  many  vascular  areas  from  the  medullary 
vaso-motor  centre  (and  possil>ly  also  by  giving  rise  to  a  con- 
dition of  shock  in  the  s{)inal  cord)  leads  to  a  very  general 
vascular  dilation,  in  consequence  of  which  there  ensues  a 
great  fall  of  the  general  blood-i^ressure.  Although  the 
renal  arteries  suffer  with  the  rest  in  this  dilation,  still  this 
is  insufficient  to  compensate  the  greatly  diminished  pressure  ; 
and  when  the  general  blood-pressure  falls  sufficiently  low 
(below  30  mm.  mercury  in  the  dog)  the  secretion  of  urine  is 
totally  arrested. 

Stimulation  of  the  spinal  cord  below  the  medulla,  though 
acting  in  the  converse  direction,  brings  about  the  same  re- 
sult, arrest  of  the  secretion.  By  the  stimulation  the  action 
of  the  vaso-motor  nerves  is  augmented,  and  constriction  of 
the  renal  arteries  as  well  as  of  other  arteries  in  the  body  is 
brought  about.  The  increase  of  general  blood-pressure  thus 
produced  is  insufficient  to  compensate  for  the  increased  re- 


530  SECRETION    BY    THE    KIDNEYS. 

sistance  in  the  renal  arteries;  and  as  a  consequence  the  flow 
of  blood  into  tlie  glomeruli  is  larij;ely  reduced  Indeed,  on 
inspection  tlie  kidneys  are  seen  during  the  stimulation  to 
become  pale  and  bloodless. 

Section  of  the  r^nal  nerves  is  followed  by  a  most  copious 
secretion,  by  what  has  been  called  hydruria  or  pol3'uria,  the 
urine  at  the  same  time  frequently  becoming  albuminous. 
The  section  of  the  nerves,  by  interrupting  the  vaso-motor 
tracts,  leads  to  dilation  of  the  renal  arteries,  and  this  to  in- 
creased pressure  in  the  small  vessels  of  the  glomeruli.  If, 
after  section  of  the  renal  nerves,  the  cord  be  divided  below 
the  medulla,  the  polyuria  disappears;  for  the  diminution  of 
general  blood -pressure  thns  produced  more  than  compen- 
sates for  the  special  dilation  of  the  renal  artei-ies.  Con- 
versely, if  after  section  of  the  renal  nerves  the  cord  be 
stimulated,  the  flow  of  urine  is  still  further  increased,  since 
the  rise  of  general  blood-pressure  due  to  the  general  arterial 
constriction  caused  by  the  stimulation  tends  to  throw  still 
more  blood  into  the  renal  arteries,  on  vvh.ich,  owing  to  tiie 
division  of  their  nerves,  the  spinal  stimulation  is  i)owerless. 

Section  of  the  splanchnic  nerves,  along  which  apparently 
the  vaso-motor  tracts  from  the  spinal  cord  to  the  kidneys 
run,  produces  also  an  increased  flow  of  urine.  But  the  aug- 
mentation in  this  case  is  smaller  and  less  certain  than  in 
the  case  of  section  of  the  renal  nerves  themselves,  since  the 
splanchnic  nerves  govern  the  whole  splanchnic  area,  and 
hence  a  large  portion  of  the  increased  supply  of  blood  is 
diverted  from  tlie  kidney  to  other  abdominal  organs.  Con- 
versely stimulation  of  the  splanchnic  nerves  arrests  the  flow 
of  urine  by  producing  constriction  of  the  renal  arteries. 

We  shall  have  occasion,  in  the  succeeding  chapter,  to  call 
attention  to  the  fact  that  puncture  of  the  fourth  ventricle, 
or  mechanical  irritation  of  the  first  thoracic  ganglion,  gives 
rise  to  the  appearance  of  a  large  quantity  <jf  sugar  in  the 
urine,  and  at  the  same  time  causes  a  more  copious  flow  of 
that  fluid  ;  the  condition  of  body  thus  brought  about  is 
known  as  artificial  diabetes.  The  increased  flow  of  urine  in 
this  case  cannot  be  ac(*ounted  for  by  suppr)sing  that  the 
increased  quantity  of  sugar  in  the  blood  in  passing  out  by 
the  kidney  leads  in  some  way  or  other  to  an  increased 
excretion  of  water;  for  the  same  operation,  or  a  similar 
injury  to  certain  parts  of  the  cerebellum,'  may  give  rise  to 

»  Eckhard,  Beitrage,  v  (1870),  153;  vi,  1,  51,  117,  175. 


RELATIONS    TO    BLOOD-PRESSURE.  531 

an  excessive  secretion  of  urine  without  any  sugar  l)eing 
present.  It  is  probable,  but  not  as  yet  clearly  proved,  that 
the  increase  of  urine  is  due  to  dilation  of  the  renal  arteries; 
and  this  view  is  supported  by  the  fact  that  the  increase  is 
temporarily  prevented  (as  is  also  a  similar  diabetic  increase 
of  flow  in  carbonic-oxide  poisoning)  b\'  stimulation  of  the 
splanchnic  nerves. 

Irritation  of  the  central  end  of  the  vagus  causes  an  increased 
flow  of  urine.  This  nia}'  be  explained  by  supposing  that  the 
afferent  impulses  ascending  the  vagus  inhibit  the  vaso-motor 
centre  which  governs  the  renal  arteries,  and  so  produce  dilation 
of  those  arteries.  Possibly  at  the  same  time,  as  in  the  case  of 
the  rabbit's  ear  ip.  209),  some  amount  of  general  constriction  is 
brought  about. 

The  experimental  phenomena  recorded  above  are  thus 
seen  to  receive  a  fairly  satisfactory  explanation  when  they 
are  referreci  exclusively  to  variations  in  blood-pressure. 
And  many  of  the  natural  variations  in  the  flow  of  ui-ine  may 
be  interpreted  in  this  way.  No  fact  in  the  animal  economy 
is  oftener  or  more  strikingly  brought  home  to  us  than  tlie 
correlation  of  the  skin  and  the  kidneys  as  far  as  their  se- 
cretions are  concerned  ;  and  this  seems  to  be  maintained 
by  means  of  the  vaso-motor  nervous  mec'ianism.  Thus, 
when  the  skin  is  cold,  its  bloodvessels  are,  as  we  know,  con- 
s'ricted.  This,  by  causing  an  increase  of  general  blood- 
pressure,  accompanied  possibl\'  by  a  dilation  of  the  renal 
arteries,  will  augment  the  flow  through  the  kidneys.  C'on- 
versely  the  dilated  condition  of  the  arteries  of  a  warm  skin, 
with  the  consequent  diminution  of  general  blood-pressure, 
accompanied  possibly  with  a  corresponding  constiiction  of 
the  renal  arteries,  will  give  rise  to  a  diminished  renal  dis- 
charge. The  effects  of  emotions  may  i)0ssibly  be  explained 
in  a  similar  way  as  essentially  vaso  motor  phenomena. 

The  increase  of  urine  observable  after  taking  fluids  cannot  be 
explained  by  reference  to  any  direct  increase  of  blood-pressure 
due  to  an  augmentation  of  the  cpiantity  of  blood  ;  for,  as  we  have 
seen  (p.  291),  an  increase  of  the  quantity  of  blood  does  not  raise 
the  general  blood-pressure.  The  increased  flltration  may  be  due 
simply  to  the  more  diluted  condition  of  the  blood,  though  pos- 
sibly the  introduction  of  the  fluid  into  the  alimentary  canal  may 
cause  a  dilation  of  the  splanchnic  or  renal  areas,  either  directh' 
or  indirect!}',  in  a  reflex  manner  by  the  help  of  the  vagi.  This 
observation  refers  of  course  to  inert  fluids,  such  as  water ;  the 


532         SECRETION  BY  THE  KIDNEYS. 


introduction  of  various  substances  in  an  ordinary  meal  may  affect 
the  flow  of  urine  in  otlier  ways  to  be  presently  stated. 

Secretion  of  the  Renal  Epithelium. 

While  thus  recognizing  the  importance  of  the  relations  of 
the  flow  of  urine  to  blood-pressure,  we  must  not  be  led  into 
the  error  of  supposing  that  the  work  of  tlie  kidney  is  wholly 
a  matter  of  filtration.  The  glomerular  mechanism,  so  spe- 
cially fitted  for  filtration,  is  after  all  a  small  portion  only  of 
the  whole  kidney,  and  the  epithelium  over  a  birge  part  of 
the  course  of  the  tuhuli  uriniferi  bears  most  distinctly  the 
characters  of  an  active  secreting  epithelium.  These  facts 
would  lead  us  a  priori  to  suj)pose  that  the  flow  of  urine  is 
in  part  the  result  of  an  active  secretion  comparable  to  that 
of  the  salivary  or  other  glands  which  we  have  already 
studied.  And  we  have  experimental  evidences  that  such  is 
the  case. 

For  a  flow  of  urine  may  be  artificially  excited  even  when 
the  natural  flow  has  been  arrested  by  diminution  of  blood- 
pressure.  Thus  if,  when  the  urine  has  ceased  to  flow  in  con- 
sequence of  a  section  of  the  medulla  oblongata,  certain  sub- 
stances, such  as  urea,  urates,  etc.,  be  injected  into  tiie  blood, 
a  copious  secretion  is  at  once  set  up.  This  secretion  is 
unaccompanied  bj^  any  rise  of  blood-pressure  sufficient  to 
account  for  the  flow  on  any  filtration  hypothesis.'  The  most 
natural  way  of  explaining  the  phenomena  is  to  suppose  that 
the  presence  of  these  substances  in  the  blood  excites  the 
renal  epithelium  to  an  unwonted  activity,  causing  them  to 
pour  into  the  interior  of  the  tubules  a  copious  secretion,  just 
as  the  presence  of  pilocarpin  in  the  blood  will  cause  the 
salivary  cells  to  pour  forth  tiieir  secretion  into  the  lumen 
of  their  ducts.  This  explanation  of  course  supposes  that, 
in  the  ordinary  state  of  the  blood,  the  epithelium  cells  are 
quiescent,  or  at  least  do  not  secrete  any  apjjreciable  qnan- 
tity  of  fluid,  otherwise  the  mere  interference  of  the  pressuie 
arrangements  due  to  the  section  of  the  medulla  oblongata 
would  not  arrest  the  flow.  And,  indeed,  this  abnormal  ac- 
tivity of  the  epithelium  is  in  itself  no  sufficient  proof  that 
any  large  part  of  the  normal  flow  of  urine  is  due  to  a  normal 
action  of  the  epithelium.  There  remains,  however,  the  fact 
that,  in  the  absence  of  the  usual  blood-pressure,  a  consider- 


I  Cf.  Ustimowitsch,  Liidwig's  Arbeiten,  1870,  p.  199. 


SECRETION    OF    THE    RENAL    EPITHELIUM.        533 

able  quantitv  of  fluid  may.  under  the  influence  of  suitable 
stimuli,  be  secreted  into  the  interior  of  the  tubuli  uriniferi, 
and  so  give  rise  to  even  a  copious  flow  of  urine.  And  this 
warns  us  to  be  cautious  in  accepting  in  all  cases,  even  in 
the  instances  quoted  previously,  a  vaso-motor  explanation 
of  increased  or  diminished  activity  of  the  kidney,  simple 
and  straightforward  as  that  explanation  may  seem.  It  may 
be  that  in  some  cases  what  appears  to  l)e  simply-  a  vaso- 
motor action  is  after  all  a  direct  action  of  nerves  on  secret- 
ing cells,  accompanied  by  adjuvant  but  not  indispensable 
vascular  changes. 

Tliat  it  is  tiie  epithelium,  and  not  an}^  other  portion  of  the 
renal  apparatus,  which  gives  rise  to  the  flow  of  urine  when 
urea  or  urates  are  injected  into  the  bloodvessels  of  animals 
in  which  the  normal  secretion  has  been  arrested  by  section 
of  the  medulla,  appears  probable  from  the  following  con- 
siderations. 

Heidenhain^  has  brought  forward  distinct  experimental 
evidence  that,  with  regard  to  one  substance  at  least,  the 
renal  epithelium  does  exercise  a  distinct  seci'eting  ai'tivity, 
independent  of  and  distinct  from  the  relations  of  blood- 
pressure.  Into  the  veins  of  animals  in  which  the  urinary'- 
flow  had  been  arrested  by  section  of  the  spinal  cord  below 
the  medulla,  Heidenhain  injected  the  sodium  sulphindigo- 
tate.  or  so-called  indigo-carmine.  By  killing  the  animals  at 
appropriate  times  and  examining  the  kidneys  microscopi- 
cally and  otliervvise,  lie  was  enabled  to  ascertain  that  the 
pigment  so  injected  passed  from  the  blood  into  the  renal 
epithelium,  and  from  thence  into  the  channels  of  the  tubules, 
where  it  was  precipitated  in  a  solid  form.  There  being  no 
stream  of  fluid  through  the  tubules,  owing  to  the  arrest  of 
urinary  flow  by  means  of  the  preliminary  operation,  the 
pigment  travelled  a  very  little  way  down  the  interior  of  the 
tubules,  and  remained  very  much  where  it  was  cast  out  by 
the  epithelium  cells.  There  were  no  traces  whatever  of  the 
pigment  having  passed  l)y  the  glomeruli:  and  the  cells  which 
could  be  seen  distinctly  to  take  up  and  eject  it  were  those 
lining  such  portions  of  the  tubules  (viz.,  the  so-called  secret- 
ing tubules,  intercalated  tubules,  and  portions  of  the  loops 
of  Henle)  as  from  their  microscopic  features  have  been  sup- 
posed to  be  the  actively  secreting  portions  of  the  entire 
tubules.     By  varying  the  quantity  injected,  and   the  time 

1  Pfliiger's  Archiv,  ix  (1874),  1. 
45 


534         SECRETION  BY  THE  KIDNEYS. 

which  was  allowed  to  elapse  between  the  injection  and  sub- 
sequent inspection,  Heidenhain  was  able  to  trace  the  material 
step  by  step  into  the  cells,  out  of  the  cells  into  the  interior 
of  the  tubules,  and  for  some  little  distance  along  the  tubules. 
The  advantage  of  the  absence  of  a  large  flow  of  urine  is 
obvious ;  had  this  been  present,  the  pigment  would  have 
been  rapidly  carried  off  immediately  that  it  issued  from  the 
cells  into  the  interior  of  the  tubules.  One  observation  he 
made  of  a  peculiarly  interesting  character.  After  injecting 
a  certain  quantity  of  pigment,  and  allowing  sucli  a  time  to 
elapse  as  he  knew  from  previous  experiments  would  suffice 
for  the  passage  of  the  material  through  the  epithelium  to  be 
pretty  well  completed,  he  injected  a  second  quantity.  He 
found  that  the  excretion  of  tiiis  second  quantity  was  most 
incomplete  and  imperfect.  It  seemed  as  if  the  cells  were 
exhaaated  bi/  their  pre mous  efforts^  just  as  a  muscle  which 
has  been  severely  tetanized  will  not  respond  lo  a  renewed 
stimulation. 

As  far  as  indigo-carmine  is  concerned  then,  we  are  justi- 
fied in  speaking  of  an  active,  though  not  a  formative  secre- 
tion, an  excretion  rather  than  a  secretion,  by  means  of  the 
renal  epitlielium,  the  cells  taking  up  the  pigment  out  of  the 
blood  and  passing  it  on  into  the  channel  of  the  tubules. 

This  activity  of  the  epithelium  cells  cannot  be  shown  in 
the  same  way  with  natural  constituents  of  urine,  with  urea 
or  urates,  for  instance,  as  with  indigo-carmine,  for  the  very 
reason  that  these  sul^stances  give  rise,  as  we  have  seen,  to 
such  a  copious  flow  of  urine  that  the  contents  of  the  tubules 
are  swept  away,  and  the  evidences  of  local  activity  are  thus 
lost.  But  we  have  evidence  of  another  kind  that  the  urea 
which  appears  in  urine,  passes  from  the  blood  into  the  renal 
ducts  through  the  epithelium  of  the  tubuli  uriniferi  and  not 
through  the  glomeruli;  and  if  so  it  can  hardly  be  doubted 
tliat  the  flow  of  urine  which  follows  the  injection  of  urea 
into  the  bloodvessels  after  section  of  the  medulla,  is  caused 
by  the  efforts  of  the  epithelium  to  carry  oif  from  the  blood 
the  excess  of  urea,  though  wh}'  the  passage  of  urea  should 
thus  necessitate  the  concomitant  secretion  of  fluid  while  the 
indigo  carmine  is  carried  through  without  any  such  ac- 
comi)anying  fluid  is  at  present  a  matter  of  obscurity.  The 
evidence  that  urea  passes  by  the  epithelium  of  the  tubules 
and  not  by  the  glomeruli  is  of  the  following  kind: 

In  the  ami>hibia,  the  kidney  has  a  double  vascular  supply  ; 
it  receives  arterial  blood  from  the  renal  artery,  but  tiiere  is 


ACTIVITY    OF    THE    EPITHELIUM.  535 

also  ponred  into  it  venous  blood  from  another  source.  The 
femoral  vein  divides  at  the  top  of  the  thigh  into  two  branches, 
one  of  which  runs  along-  the  front  of  the  aV)domen  to  meet 
its  fellow  in  the  middle  line  and  form  the  anterior  abdominal 
vein,  while  the  other  passes  to  the  outer  border  of  the  kid- 
ney and  branches  in  the  substance  of  that  organ,  forming 
the  so-called  renal  portal  system.  Xow  the  glomeruli  are 
supplied  e  clusively  by  the  i)ranches  of  the  renal  artery,  the 
renal  vena  porta?  only  serving  to  form  the  capillaiy  plexus 
around  the  tubuli  uriniferi,  where  its  branches  are  joined  b}^ 
the  efferent  vessels  of  the  glomeruli.  From  this  it  is  obvi- 
ous that  if  the  renal  artery  be  tied,  the  blood  is  shut  off 
entireh'  from  the  glomeruli,  and  the  kidney  by  this  simple 
operation  is  transformed  into  an  ordinar}'  secreting  gland 
devoid  of  any  special  filtering  mechanism  ;  an<l  actual  ob- 
servation of  the  kidney  of  the  newt  has  shown  that  under 
these  circumstances  there  is  no  reflux  from  the  capillary  net- 
work surrounding  the  tubuli  back  to  the  glomeruli.  Xuss- 
baum^  has  ingeniously  made  use  of  such  a  kidney  to  ascer- 
tain what  substances  are  excreted  by  the  glomeruli,  and 
what  by  the  tubuli  in  some  other  part  of  their  course.  He 
finds  that  sugar,  peptones,  and  albumin,  which  injected  into 
the  blood  readily  pass  through  the  untouched  kidney  and 
appear  in  the  urine,  do  not  pass  through  a  kidney  the  renal 
arteries  of  which  have  been  tied.  These  substances,  there- 
fore, are  excreted  by  the  glomeruli.-  Urea,  on  the  other 
hand,  injected  into  the  blood,  gives  rise  to  a  secretion  of 
urine,  when  the  renal  arteries  are  tied  ;  this  sul)stance,  there- 
fore, is  secreted  by  the  ei)it helium  of  the  tubules,  and  in 
being  so  secreted  gives  rise  at  the  same  time  to  a  flow  of 
water  through  the  cells  into  the  interior  of  the  tubuli. 
When  indigo-carmine  is  injected  after  ligature  of  the  renal 
arteries,  no  urine  is  found  in  the  bladder,  but  the  pigment 
can  be  traced,  as  in  Heidenhain's  experiment,  through  the 
epithelium  of  the  secreting  portions  of  the  tubuli. 

Xussbaum^  also  made  an  interesting  experiment  on  the  artifi- 
cial production  of  albuminuria  in  the  frog.  The  renal  arteries 
being  tied,  an  injection  of  urea  (1  cm.  of  a  10  per  ceut.  solution) 
into  the  blood  gave  rise  to  a  flow  of  urine  which  was  free  from 
albumin.  Upon  loosing  the  ligatures  so  as  to  re-establish  the 
flow  of  blood  through  the  glomeruli,  the  urine  at  once  became 

1  Pfluger's  Archiv,  xvi  (1877),  p.  139;  xvii  (1878),  p.  580. 
■^  Op.  cit. 


636  SECRETION    BY    THE    KIDNEYS. 


albuminous.  The  arrest  of  the  circulation  through  the  glome- 
ruli had  damajjed  the  capillary-walls,  and  so  allowed  the  passage 
through  them  into  the  interior  of  the  Malpighian  cai)sules  of  the 
natural  proteids  of  the  blood,  which  in  a  normal  condition  of  the 
capillaries  cannot  effect  such  a  passage.  The  injury,  however, 
was  temporar}^  only  ;  in  a  short  time  the  capillary  walls  were 
restored  to  health,  and  the  urine  ceased  to  be  all)uminous. 

Experimental  evidence  tlien  justifies  the  conception  which 
the  structure  of  the  kidney  led  us  to  adopt.  The  secretion 
of  urine  by  the  kidney  is  a  double  process.  It  is  partly  a 
process  of  filtration,  whose  object  is  to  remove  as  rapidl}' 
as  possible  a  quantity  of  water  from  the  body,  and  this  part 
of  the  work  of  tlie  kidney  is  directly  dependent  on  blood- 
pressure.  It  is  also,  however,  a  process  of  active  secretion 
l3y  the  epithelium  of  the  tubuli,  and  this  part  of  the  work 
of  the  kidney  is,  in  an  indirect  manner  only,  dependent  on 
blood-pressure.  Both  processes  may  give  rise  to  a  discharge 
of  water  from  the  blood,  and  both  may  give  rise  to  the  pres- 
ence of  the  solid  constituents  of  the  urine,  in  solution  in 
that  water.  In  the  first  process  the  discharge  of  water  is 
the  primary  olject,  and  the  solid  matters  which  escape  at 
the  same  time  are  of  secondary  importance;  in  the  second 
process  tiie  excretion  of  the  solid  substance  is  the  primary 
object,  and  the  accompanying  water  of  secondary  impor- 
tance, and  indeed  sometimes  absent.  The  first  process  is 
governed  (mainly  at  least)  b}*  the  vaso-motor  nervous  sys- 
tem ;  the  second  process  is  excited,  as  far  as  we  know  at 
present,  Uy  substances  in  the  blood  acting  directly  as  chemi- 
cal stimuli  to  the  epithelium;  but  future  researches  may 
disclose  the  existence  of  a  secretory  nervous  mechanism 
analogous  to  that  of  other  secretory  glands. 

Future  investigations  must  determine  what  constituents  of  the 
urine  besides  urea,  urates,  etc.,  are  thrown  into  the  urine  by  the 
active  secretory  process,  and  wdiat  simply  pass  by  filtration 
through  the  glomeruli.  The  whole  subject  of  diuretics  requires 
to  be  studied  afresh  by  the  help  of  Nussbaum's  method. 

One  consideration,  of  quite  secondary  importance  in  the 
glands  which  have  been  previously  studied,  acquires  great 
prominence  when  the  kidney  is  being  studied.  In  studying 
the  pancreas  and  gastric  glands,  we  concluded  without  much 
discussion  that  the  zymogen  and  pepsinogen  were  formed 
in  the  epithelium  cells;  for  no  great  manufacture  of  these 


xMICTURITION.  537 

snlistances  is  going  on  in  other  parts  of  the  body.  The 
kidney,  however,  is  empliatically  an  excreting  organ  ;  its 
great  fnnction  is  to  get  rid  of  substances  produced  by  the 
activity  of  other  tissues  ;  its  work  is  not  to  form  but  to  eject. 
There  can  be  no  doubt,  to  put  forward  a  strong  instance, 
that  with  regard  to  urea  it  would  be  absurd  to  suppose  that 
tlie  whole  series  of  changes  from  the  proteid  condition  to 
the  urea  stage  is  carried  on  by  the  kidney.  But  there  still 
remains  the  question,  Are  any  of  the  stages  carried  on  in 
the  kidney,  and  if  so,  what?  Is  the  secreting  activity  of 
the  renal  epithelium  confined,  as  was  suggested  in  our  early 
remarks  on  secretion,  p.  346,  to  picking  out  the  already 
formed  urea  from  the  blood  ?  Or  dr>es  the  secreting  cell  of 
the  tubule  receive  from  the  blood  some  antecedent  of  urea, 
and  in  the  laboratory  of  its  protoplasm  convert  that  antece- 
dent of  urea  into  urea  itself?  and  if  so,  what  is  that  antece- 
dent which  comes  to  the  kidney  in  the  blood  of  the  renal 
artery?     And  so  witli  many  of  the  urinary  constituents. 

In  order  to  complete  our  study  of  renal  activity,  this 
question  ought  to  be  considered  now  ;  but  for  many  reasons 
it  will  be  more  convenient  to  defer  the  matter  to  the  suc- 
ceeding chapter,  in  which  we  deal  with  the  metabolic  events 
of  the  body  in  general. 

Sec.  3.  Micturition. 

The  urine,  like  the  bile,  is  secreted  continuously;  the 
flow  may  rise  and  fall,  but,  in  health,  never  absolutely  ceases 
for  any  length  of  time.  The  cessation  of  renal  activity,  the 
so-called  suppression  of  urine,  entails  speedy  death.  The 
minute  streams  passing  continuously,  now  more  rapidly 
now  more  slowly,  along  the  collecting  and  discharging  tu- 
bules, are  gathered  into  the  renal  pelvis,  whence  the  fluid  is 
carried  along  the  ureters  by  the  peristaltic  contractions  of 
the  muscular  walls  of  those  channels  (see  p.  151)  into  the 
urinary  bladder.  When  a  ureter  is  divided  in  an  animal, 
and  a  canula  inserted,  the  urine  may  be  observed  to  flow 
from  the  canula  drop  by  drop,  slowly  or  rapidl}'  according 
to  the  rate  of  secretion.  In  the  urinary  bladder,  the  urine 
is  collected,  its  return  into  the  ureters  being  prevented  by 
the  oblique  valvular  nature  of  the  orifices  of  those  tubes, 
and  its  discharge  from  thence  in  considerable  quantities  is 
effected  from  time  to  time  by  a  somewluit  comi)lex  muscular 
mechanism,  of  the  nature  and  vvorking  of  which  the  follow- 


538         SECRETION  BY  THE  KIDNEYS. 

ing  is  a  brief  account.  The  involuntary  muscular  fibres 
forming  the  greater  part  of  the  vesical  walls  are  arranged 
partly  in  a  more  or  less  longitudinal  direction  forming  the 
so-called  det?^usor  uririce^  and  partly  in  a  circular  manner, 
the  circular  fibres  being  most  developed  round  the  neck  of 
the  bladder,  and  for;ning  there  tlie  so-called  i^pliincter  vesicae. 
After  it  has  been  emptied  the  bladder  is  contracted  and 
thrown  into  folds;  as  the  urine  gradually  collects. the  bladder 
l)ecomes  more  and  more  extended.  The  escape  of  the  fluid 
is  however  prevented  by  the  resistance  offered  by  the  elastic 
fibres  of  the  urethra  which  keep  the  urethral  channel  closed. 
Some  maintain  that  a  tonic  contraction  of  the  sphincter 
vesicae  aids  in  or  indeed  is  the  chief  cause  of  this  retention. 
When  the  bladder  has  become  full,  we  feel  the  need  of 
making  water,  the  sensation  being  hightened  if  not  caused 
by  the  trickling  of  a  few  drops  of  urine  from  the  full  bladder 
into  the  urethra.  We  are  then  conscious  of  an  effort ;  during 
this  effort  the  bladder  is  thrown  into  a  long-continued  con- 
traction of  an  obscurely  peristaltic  nature,  the  force  of 
which  is  more  than  sufficient  to  overcome  the  elastic  resist- 
ance of  the  urethra,  and  the  urine  issues  in  a  stream,  the 
sphincter  vesicae,  if  it  act  as  a  sphincter,  i)eing  at  the  same 
time  relaxed  after  the  fashion  of  the  sphincter  aui.  In  its 
passage  along  the  urethra,  the  exit  of  the  urine  is  forwarded 
by  irregularly  rhj'thmic  contiactions  of  the  bulbo-caverno- 
sus  or  ejaculator  urinae  muscle,  and  the  whole  act  is  further 
assisted  by  pressure  on  the  hladder  exerted  by  means  of  the 
abdominal  muscles,  very  much  the  same  as  in  defecation. 

The  continuit}'^  of  the  sphincter  vesicae  with  the  rest  of  the  cir- 
cular fibres  of  the  bladder  suggests  that  it  probably  is  not  a 
sphincter,  but  that  its  use  lies  in  its  contracting  after  the  rest  of 
the  vesical  fibres,  and  thus  finishing  the  evacuation  of  the  bladder. 
On  the  other  hand,  the  fact  that  the  neck  of  the  bladder  can  with- 
stand a  pressure  of  twenty  inches  of  water  so  long  as  the  bladder 
is  governed  by  an  intact  spinal  cord,  but  a  pressure  of  six  inches 
only  when  the  lumbar  spinal  cord  is  destroyed  or  the  vesical 
nerves  are  severed,  aftbrds  very  strong  evidence  in  favor  of  the 
view  that  the  obstruction  at  the  neck  of  the  bladder  to  the  exit 
of  urine  depends  on  some  tonic  muscular  contraction  maintained 
b}^  a  reflex  or  automatic  action  of  the  lumbar  spinal  cord.' 

Micturition,  therefore,  seems  at  first  sight,  and  especially 
when  we  appeal  to  our  own  consciousness,  a  purely  volun- 

'  Cf.  Ott,  Journ.  Phys.,  ii  (1879),  p.  59. 


MICTURITION.  539 

tarv  act.  A  voluntary  effort  tlirows  the  Madder  into  con- 
tractions, an  accompanying  voluntary  eftbrt  throws  the 
ejaculator  and  abdominal  muscles  also  into  contractions, 
and  the  resistance  of  the  urethra  i)eing  thereby  overcome 
the  exit  of  the  urine  naturally  follows.  If  we  adopt  the 
view  of  a  sphincter  vesicae,  we  iiave  to  add  to  the  above 
simple  statement  the  supposition  that  the  will,  wliile  causing 
the  detrusor  urinae  to  contract,  at  the  same  time  lessens  the 
tone  of  the  sphincter,  probably  by  inhibiting  its  centre  in 
the  lumbar  cord 

There  are  two  facts,  however,  which  prevent  the  accept- 
ance of  so  simple  a  view.  In  the  first  place  Goltz^  has 
shown  that  quite  normal  micturition  may  take  place  in  a 
dog  in  which  the  lumbar  region  of  the  spinal  cord  has  been 
completely  separated  by  section  from  the  dorsal  region.  In 
such  a  case  there  can  be  no  exercise  of  volition,  and  the 
whole  process  aj^penrs  as  a  reflex  action.  When  the  bladder 
is  full  (and  otherwise  apparently  under  the  circumstances 
the  act  fails),  any  sliglit  stiuiulus.  sucli  as  sponging  the 
anus  or  slight  pressure  on  the  altdominal  walls,  causes  a 
complete  act  of  micturiticMi  ;  the  bladder  is  entirely  emptied, 
and  the  stream  of  urine  towards  the  end  of  the  act  under- 
goes rhythmical  augmer.tatit)us  due  to  contractit^is  of  the 
ejaculator  urinne.  These  facts  can  only  be  interpreted  on 
the  view  that  there  exists  in  the  lumbar  cord  (of  the  dog)  a 
micturition  centre  capable  of  being  thrown  into  action  by 
appropriate  afferent  impulses,  the  action  of  the  centre  being 
such  as  to  cause  a  contraction  of  the  walls  of  the  bladder 
and  of  the  ejaculator  urinse,  and  possibly  at  the  same  time 
to  suspend  the  tone  of  the  sphincter  vesicai.  Similar  in- 
stances of  reflex  micturition  have  been  observed  in  cases  of 
paralysis  from  disease  or  injury  of  the  spinal  cord  ;  and  in- 
voluntary micturition  is  common  in  children,  as  the  result 
of  irritation  of  the  pelvis  and  genital  organs,  or  of  emotions. 
In  the  adult,  too,  emotions,  or  at  least  sensory  impressions, 
may  in  a  reflex  manner  be  the  cause  of  micturition.  In 
such  cases  we  may  fairly  suppose  that  the  centre  in  the 
lumbar  cord  is  affected  by  afferent  impulses  descending  from 
the  brain.  And  this  leads  us  to  the  conception  that  when  we 
make  water  by  a  conscious  effort  of  the  will,  what  occurs  is 
not  a  direct  action  of  the  will  on  the  muscular  walls  of  the 
bladder,  but  that  impulses  started  by  the  wdll  descend  from 

'  Pfliiger's  Archiv,  viii  (1874),  p.  474. 


540         SECRETION  CY  THE  KIDNEYS. 

the  brain  after  the  fashion  of  afferent  impulses,  and  thus  in 
a  reflex  manner  throw  into  action  the  micturition  centre  in 
the  lumbar  spinal  cord.  Nor  is  this  view  negatived  by  the 
fact  that  paral}  sis  of  the  bladder,  or  rather  inability  to  make 
water  either  voluntarily  or  in  a  reflex  manner,  is  a  common 
symptom  of  spinal  disease  or  injury.  Putting  aside  the 
cases  in  which  the  reflex  act  is  not  called  forth  because  the 
api)ropriate  stimulus  has  not  been  applied,  the  failure  in 
micturition  under  these  circumstances  may  be  explained  by 
supposing  that  the  shock  of  the  spinal  injury  or  some  ex- 
tension of  the  disease  has  rendered  the  lumbar  centre  unable 
to  act. 

In  the  second  place,  in  cases  of  urethral  obstruction,  where 
the  i)ladder  cannot  be  emptied  when  it  reaches  its  accus- 
tomed fulness,  tiie  increasing  distension  sets  up  fruitless 
but  powerful  contractions  of  the  vesical  walls,  contractions 
which  are  clearly  involuntary  in  nature,  which  wane  or  dis- 
appear, and  return  again  and  again  in  a  completely  rhythmic 
manner,  and  which  ma}'  be  so  strong  and  powerful  as  to 
cause  great  sulfei'ing.  It  seems  that  fibres  of  tiie  bladder, 
like  all  other  muscular  fibres,  have  their  contractions  aug- 
mented in  propoi-tion  as  they  are  sul>jected  to  tension  (see 
p.  119).  Just  as  a  previously  quiescent  ventricle  of  a  frog's 
heart  may  be  excited  to  a  rhythmic  beat  by  distending  its 
cavity  with  blood,  so  the  quiescent  bladder  is  excited,  i»y 
the  distension  of  its  cavity,  to  a  peristaltic  action  which  in 
normal  cases  is  never  carried  be3'ond  a  first  effort,  since 
with  tiiat  the  bladder  is  emptied  and  tiie  stimulus  is  re- 
moved, but  in  cases  of  obstruction  is  enabled  clearly  to 
manilest  its  rhythmic  nature. 

The  so-called  incontinence  of  urine  in  children  is  in  reality 
an  easily  excited  and  frequently  repeated  reflex  micturi- 
tion. In  cases  of  spinal  disease  another  form  of  inconti- 
nence is  common.  The  bladder  becoming  full,  but,  owing 
to  a  failure  in  the  mechanism  of  voluntary  or  reflex 
micturition,  being  unable  to  empty  itself  by  a  complete 
contraction,  a  continual  dribbling  of  urine  takes  place 
thiough  the  urethra,  the  fulness  of  the  bladder  being  sufiS- 
cient  to  overcome  the  elastic  resistance,  or  the  tone  of  the 
sphincter  suffering  from  the  spinal  affection  and  becoming 
permanently  inhibited. 

The  latter  view  seems  improbable,  and  there  is  no  satisfactory 
evidence  that  intrinsic  contractions  of  the  bladder  do  not  occur 
in  these  cases. 


THE    xMETABOLIC    PHENOMENA    OF    THE    BODY.       541 


According  to  Sokowin/  contractions  of  the  bladder  may  be 
brought  about  in  cats  in  a  rellex  manner  by  two  mechanisms : 
by  one  in  which  the  centre  lies  in  the  spinal  cord  at  about  the 
region  of  the  fourth  lumbar  vertebra,  and  the  sacral  nerves  sup- 
ply both  the  atferent  and  efferent  tracts,  and  another  in  which 
the  inferior  mesenteric  ganglion  serves  as  a  centre,  the  atferent 
and  efferent  fibres  passing  along  the  branches  connecting  that 
ganglion  with  the  hypogastric  plexus.  He  finds,  in  fact,  that  the 
inferior  mesenteric  ganglion  will  act  as  a  centre  for  reflex  action. 
When  the  history  of  the  submaxillar}-  ganglion  (p.  848)  is  borne 
in  mind,  such  a  conclusion  will  naturally  be  received  with  great 
caution. 


CHAPTEK    V. 

THE  METABOLIC   PHEXOMEXA   OF   THE   BODY. 

We  have  followed  the  food  through  its  changes  in  the 
alimentary  canal,  and  seen  it  enter  into  the  blood,  either 
directly  or  by  tlie  intermediate  channel  of  the  chyle,  in  the 
form  of  peptone  (or  otherwise  modified  albumin),  sngar 
(lactic  acid),  and  fats,  accompanied  by  various  salts.  \Ve 
have  further  seen  thai  the  waste  products  which  leave  the 
body  are  urea,  carbonic  acid,  and  salts  We  have  now  to 
attempt  to  connect  together  the  food  and  the  waste  prod- 
ucts ;  to  trace  out  as  far  as  we  are  able  the  various  steps 
by  which  the  one  is  transformed  into  the  other,  and  to 
inquire  into  the  manner  in  which  the  energy  set  free  in  this 
transformation  is  distributed  and  made  use  of. 

Tlie  master  tissues  of  the  body  are  the  muscular  and 
nervous  tissues  ;  all  the  other  tissues  ma}'  be  regaided  as  tiie 
servants  of  these.  And  we  may  fairly  presume  that  besides 
the  digestive  and  excretory  tissues  which  we  have  already 

^  Hofmann  u.  Schwalbe,  Jahresberichte,  iv  (1877),  Abth.,  iii,  p.  87. 

46 


542       THE    METABOLIC    PHENOMENA    OF    THE    BODY. 

stiidied,  many  parts  of  the  body  are  engaged  either  in 
further  elaborating  tiie  comparatively  raw  food  which  enters 
the  blood,  in  order  that  it  may  be  assimilated  with  the  least 
possible  labor  b}'  the  master  tissues,  or  in  so  modifying  the 
waste  products  which  arise  from  tiie  activity  of  the  master 
tissues  that  they  may  be  removed  from  the  body  as  speedily 
as  possil)le.  Tliere  can  be  no  doubt  tiiat  manifold  interme- 
diate changes  of  this  kind  do  take  place  in  tiie  body  ;  but 
our  knowledge  of  the  matter  is  at  present  very  imperfect. 
In  one  or  two  instances  only  can  we  localize  these  metabolic 
actions  and  speak  of  distinct  metal)olic  tissues.  In  tiie 
majority  of  cases  we  can  only  trace  out  or  infer  chemical 
changes  without  being  able  to  say  more  tiian  that  they  do 
take  place  somewhere  ;  and  in  consequence,  perliaps  some- 
what loosely,  speak  of  them  as  taking  place  in  the  blood. 


Sec.  1.    Metabolic  Tissues. 

The  Hidory  of  Glycogen. 

Tlie  best-known  and  most  carefully  studied  example  of 
metabolic  activity  is  the  formation  of  glycogen  in  tlie  he- 
patic cells. 

Claude  Bernard,^  in  studying  the  history  of  sugar  in  the 
economy,  was  led  to  compare  the  relative  quantities  of  sugar 
in  the  portal  and  hepatic  veins,  expecting  to  find  that  tlie 
sugar  possibly  diminished  in  the  passage  of  the  blood  through 
the  liver  ;  he  was  astonished  to  discover  that,  on  tlie  con- 
trary, the  quantity  was  vastly  increased.  He  found,  and 
any  one  can  make  the  observation,  tliat  when  an  animal  liv- 
ing under  ordinary  conditions  is  killed,  the  hepatic  blood 
after  death  contains  a  considerable  amount  of  sugar  (grape- 
sugar),  even  wlien  tliere  is  little  or  none  in  tlie  portal  blood  ; 
moreover  a  simple  aqueous  infusion  of  the  liver  is  rich  in 
sugar.  Not  only  so,  but  the  sugar  continues  to  be  present 
in  the  liver  when  all  blood  lias  been  washed  out  of  the  organ 
by  a  stream  of  water  driven  through  the  portal  vein,  and 
goes  on  increasing  in  amount  for  some  hours  after  death. 
Only  one  interpretation  of  these  facts  is  possible  ;  so  far 
from  the  liver  destroying  or  convertingthe  sugar  brought  to 
it  by  the   portal  vein,  it  is  clearly  a  source  of  sugar;  the 


Nouv.  Fonct.  du  Foie,  1853. 


GLYCOGEN.  54o 

hepatic  tissue  evidently'  contains  some  substance  capable  of 
giving  rise  to  tiie  presence  of  sugar.  Bernard  further  found 
that  when  the  liver  was  removed  from  tiie  !)ody  inime(]iately 
after  death,  and,  after  being  divided  into  small  pieces,  was 
thrown  into  boiling  water,  the  infusion  or  decoction  con- 
tained very  little  sugar,  and  that  the  small  quantity  wdiich 
was  present  did  not  increase  even  wiien  the  decoction  was 
allowed  to  stand  for  some  time.  The  decoction,  however, 
was  peculiarly  opalescent,  indeed  milky  in  appearance; 
whereas  the  decoction  of  a  liver  which  had  been  allowed  to 
remain  exposed  to  warmth  for  some  time  after  deatli,  before 
being  boiled,  and  which  accordingly  contained  a  large  amount 
of  sugar,  was  quite  clear.  On  adding  saliva,  or  other  amy- 
lolytic  ferment,  to  the  o[>alescent,  sugarless,  or  nearly  sugar- 
less, decoction  and  exposing  it  to  a  gentle  warmtb  (35^- 
40°),  the  opalescence  disappeared;  the  tluid  became  clear, 
and  was  tiien  found  to  contain  a  considerable  quantity  of 
sugar.  Here  again  the  explanation  was  obvious.  The  opa- 
lescence of  the  decoction  of  boiled  liver  is  due  to  the  pres- 
ence of  a  body  which  is  capable  of  being  converted  by  the 
action  of  a  ferment  into  grape-sugar,  and  is  therefore  of  tiie 
nature  of  starch.  At  the  moment  of  deatli  the  liver  must 
contain  a  considerable  quantity  of  this  sui)Stance,  which 
after  death  becomes  gradualh'  converted  into  sugar,  either 
through  the  action  of  some  amylolytic  ferment  present  in 
the  hepatic  cells  or  in  the  blood  of  tiie  hepatic  vessels,  or 
possil)ly  by  some  special  agency.  Hence  the  post-mortem 
appearaiu-e  of  a  continually  increasing  quantity  of  sugai". 
By  precipitating  tiie  opalebcent  decoction  with  alcohol,  by 
boiling  the  precipitate  with  alcohol  containing  potash, 
whereby  the  proteid  impurities  clinging  to  it  were  destroyed, 
and  by  removing  adherent  fats  by  etlier,  Bernard  was  able 
to  obtain  this  sugar-producing  or  glycogenic  substance  in  a 
pure  srate  as  awhile  amorphous  i)Owder,  with  a  composition 
of  CyH,„0^,  and  therefore  evidently  a  kind  of  starch.  Its 
most  striking  ditlVrences  from  ordinary  starch  were  that  it 
gave  a  deep-red  ftnd  not  a  blue  color  with  iodine,  and  tlmt 
when  dissolved  in  water  it  formed  a  milky  fluid.  He  gave 
to  it  the  name  of  glycogen. 

Since  Bernard's  discovery  glycogen  has  been  recognized 
as  a  normal  constituent,  variable  in  quantity,  of  iiepatic 
tissue  both  in  vertebrate  and  invertebrate  animals.  That  it 
is  piresent  in  the  iiepatic  cells,  and  not  simply  contained  in 
the  hep9,tic   blood,  is   shown    by  the  fact  that  it  remains  in 


544      THE    METABOLIC    PHENOMENA    OF    THE    BODY. 

the  liver  after  all  blood  has  been  washed  out  of  that  organ. 
It  has  also  been  found  in  the  placenta,  in  muscle,  white 
corpuscles,  testes,  brain,  and  in  other  situations  ;  the  tis- 
sues of  the  embryo  at  an  early  stage,  especially  before  the 
liver  has  become  functionally  active,  are  particularlv  rich 
in  it. 

Formation  and  Uses  of  Glycogen. — The  amount  of  glyco- 
gen present  in  tlie  liver  of  an  animal  at  any  one  time  is 
largely  dependent  on  the  amount  and  nature  of  the  food 
previously  taken.^  Wiien  all  food  is  withheld  from  an  ani- 
mal, the  glycogen  in  the  liver  diminishes,  rapidly  at  tirst, 
but  more  slowly  afterwards.  Even  after  some  days'  star- 
vation a  small  quantity  is  frequentl}'  still  found  ;  but,  in 
rabbits,  at  all  events,  the  whole  may  eventually  disappear. 

If  an  animal,  after  having  been  starved  until  its  liver  may 
be  assumed  to  be  free  or  almost  free  from  glycogen,  be  fed 
on  a  diet  rich  in  carbohydrates  or  on  one  consisting  exclu- 
sively of  carbohydrates,  the  liver  will  in  a  short  time  (one 
or  two  days)  be  found  to  contain  a  very  large  quantity  of 
glycogen.  Obviousl}^  the  presence  of  carbohydrates  in  food 
lea  Is  to  an  accumulation  of  glycogen  in  the  liver  ;  and  this 
is  true  both  of  starch  and  of  dextrin  and  of  the  various 
forms  of  sugar,  cane,  grape  and  milk  sugar.  The  effect  may 
be  quite  a  rapid  one,  for  glycogen  has  been  found  in  the 
liver  in  considerable  quantity  within  a  few  hours  after  the 
introduction  of  sugar  into  the  alimentary  canal  of  a  starving 
animal."^ 

If  an  animal,  similarly  starved,  be  fed  on  an  exclusively 
meat  diet  a  certain  amount  of  glycogen  is  found  in  the  liver. 
This  appears  to  be  especially  the  case  with  dogs  (probal)ly 
with  other  carnivorous  animals  also) ;  and  in  Ids  earlier  re- 
searches Bernard  was  led  to  regard  the  constant  presence 
of  glycogen  in  the  livers  of  dogs  fed  on  meat  as  an  impor- 
tant indication  of  the  conversion  within  the  body  of  nitro- 
genous into  non-niti-ogenoiis  material.  But  in  the  first  place, 
the  quantity  of  glycogen  thus  stored  up  in  the  liver  as  the 
result  of  a  meat  diet   is  much  less  than  that  which  follows 


1  MacDonnel,  Nat.  Hist.  Rev.,  1863,  p.  541.  TscherinofF,  Molescliott's 
Unlersuch.,  x  (1870),  p.  226.  Dock,  Pfluger's  Archiv,  v  (1872),  571. 
Mering,  Pfiiiger's  Archiv,  xiv  (1877),  274.  Cf.  also  Pavy  on  Dia- 
betes. 

^  Dock,  op.  cit. 


GLYCOGEN.  545 

upon  a  carbohydrate  diet ;  and  in  the  second  place,  ordinary 
meat,  especially  horse-flesh  on  which  dogs  are  ordinarily  fed, 
contains  in  itself  a  certain  amount  either  of  glycogen  or 
some  form  of  sugar.  Moreover  when  animals  are  fed  not 
on  meat  but  on  purified  proteid,  such  as  filjrin,  casein,  or 
albumin,  the  quantity-  of  glycogen  in  the  liver  becomes  still 
smaller,  though  according  to  most  observers  remaining 
greater  than  during  starvation.  We  may  infer  therefore  that 
part  of  the  glycogen  which  appears  in  the  liver  after  a  meat 
diet  is  really  due  to  carbohydrate  materials  present  in  the 
meat.  Part  however  would  appear  to  be  the  result  of  the 
simple  proteid  food  ;  but  in  tliis  respect  proteid  falls  very 
far  short  indeed  of  carbohydrate  materials. 

With  regard  to  fats,  all  observers  are  agreed  that  these 
lead  to  no  accumulation  of  glycogen  in  the  liver;  an  animal 
fed  on  an  exclusively  fatty  diet  has  no  more  glycogen  in  its 
liver  than  a  starving  animal. 

Hence  of  the  thi-ee  great  classes  of  food-stuff's,  the  carbo- 
hydrates stand  out  prominently  as  the  substances  which 
taken  as  food  lead  to  an  accumulation  of  glycogen  in  the 
liver.  Confining  our  attention  for  the  present  to  this  chief 
source  of  glycogen,  the  question  naturally  presents  itself: 
What  is  the  exact  mode  in  which  the  carbohydrates  of  food 
thus  give  rise  to  an  excess  of  glycogen  in  the  hepatic  cells  ? 
Is  it  that  they  reaching  the  liver  as  sugar  in  the  portal  blood 
(we  may  accept  for  the  present  purpose  at  all  events  the  view 
that  the  carbohydrates  are  converted  into  sugar  and  ab- 
sorbed by  the  portal  vein)  are  in  some  direct  manner  recon- 
verted into  the  starchlike  glycogen  and  deposited  in  the 
hepatic  cells  ? 

Or  has  the  hepatic  glycogen  quite  a  different  oi-igin,  being- 
formed  in  the  hepatic  cells  out  of  the  breaking  up  of  their 
protoplasm,  and  being  carried  thence  and  consumed  in  some 
way  or  other,  as  the  needs  of  the  economy  for  carbohydrate 
material  demand,  so  that  the  excess  which  appears  in  the 
liver  after  an  amylaceous  diet  is  due  to  the  fact  that  the  car- 
bohydrates taken. as  food  cover  the  necessary  expenditure, 
and  prevent  any  demand  being  made  on  the  hepatic  store? 
.  Before  we  attempt,  however,  to  answer  these  questions, 
we  must  turn  aside  to  consider  another  question  :  What  be- 
comes of  the  hepatic  gl^'cogen  during  life  ?  Is  it  reconverted 
little  by  little  into  sugar,  which,  passing  into  the  blood  of 
the  hepatic  veins,  is  oxidized  or  otherwise  made  use   of,  or 


546      THE    METABOLIC    PHENOMENA    OF    THE    BODY. 

is  it  in  the  liepalic  cells  converted  into  some  more  complex 
sii Instance,  it  may  he  fat  or  some  otiier  body  ? 

The  view  tliat  glycogen  is  converted  into  fat  is  hased 
chiefly  on  the  fact  that,  as  we  sliall  see  later  on,  the  carl>o- 
hydrates  of  the  food  are  undoubtedly,  in  some  way  or  otiier, 
a  source  of  the  fat  of  the  body,  that  a  large  quantity,  fre- 
quently a  very  large  quantity,  of  fat  is  found  in  the  hepatic 
cells,  and  that  the  quantity  of  fat  present  seems  to  be  in- 
creased by  such  diets  as  naturally  increase  the  glycogen  in 
the  liver.  But  we  shall  have  occasion  to  point  out  that  the 
direct  conversion  of  carl)ohydrates  into  fat  is  at  least  dis- 
puted;  and  no  one  has  yet  been  alile  even  to  suggest  the 
wa}^  in  which  glycogen  could  be  converted  into  fat.  In  the 
absence  of  more  direct  and  exact  information,  the  discus- 
sion as  to  the  fate  of  the  hepatic  glycogen  has  been  made 
to  turn  chiefly  f)n  the  question,  whether  there  is  evidence  of 
tlie  reconversion  normally,  during  life,  of  the  glycogen  into 
sugar,  whether  the  blood  of  tlie  hepatic  vein  contains  in  life 
more  sugar  than  that  of  the  portal  vein.  Bernard,  both  in 
his  earlier  and  later^  researches,  maintained  that  the  lilood 
of  the  hepatic  vein  under  noimal  conditions  was  licher  in 
sugar  than  the  blood  of  the  portal  vein,  or,  indeed,  of  any 
other  part  of  the  vascular  system  ;  and  this  he  regarded  as 
an  indication  that  the  liver  is  always  engaged  in  discharg- 
ing a  certain  quantity  of  sugar  into  the  liepatic  veins.  Ber- 
nard's views  have  been  accepted  by  many  observers.  On 
the  other  hand,  Pavy  was  the  first  to  maintain  that  the  blood 
in  the  hepatic  vein,  if  care  be  taken  to  keep  tlie  animal  in  a 
l)erfectly  normal  condition,  contains  no  more  sugar  than 
does  the  blood  of  the  right  auricle  or  of  the  poi'tal  vein,  and, 
indeed,  that  the  Hver  itself,  if  examined  before  any  post- 
mc^rtem  changes  have  had  time  to  develop  themselves,  is 
absolutely  free  from  sugar;  in  this  he  has  been  supported 
by  Tscherinofl' and  others. 

Now  the  quantitative  determination  of  sugar  in  blood 
whichever  procedure  l)e  adopted  is  open  to  many  sources  of 
error.-'  And  when  the  quantity  of  blood  which  is  continu- 
ally (lowing  through  the  liver  is  taken  under  consideration, 
it  is  obvious  that  an  amount  of  sugar,  which  in  the  specimen 
of  blood  taken  for  examination  fell  within  the  limits  of  errors 
of  observation  might,  when  multiplied  b}^  the  whole  quan- 

^  Lefons  sur  le  Diabete,  1877. 

2  Cf.  Fliigge,  Zt.  f.  Biol.,  xiii,  p.  133. 


GLYCOGEN.  547 

tity  of  blood,  and  by  the  number  of  times  the  blood  passed 
through  the  liver  in  a  certain  time,  reach  dimensions  quite 
sufficient  to  account  for  the  conversion  into  sugar  of  the 
whole  of  the  glycogen  present  in  the  liver  at  any  given 
time.  Hence  we  may  safely  conclude  that  the  comparative 
analyses  of  hepatic  and  [)ortal  blood,  if  they  do  not  of  them- 
selves prove  that  the  liver  is  either  continually  or  at  intervals 
converting  some  of  its  glycogen  into  sugar  and  discharging 
this  sugar  into  tiie  general  system,  are  at  least  not  suffi- 
ciently trustworthy  to  dis[)rove  the  possibility  of  such  a  dis- 
charge of  sugar  being  one  of  the  normal  functions  of  the 
liver. 

Kormal  hepatic  blood  was  obtained  by  Pavy,  by  means  of  an 
ingenious  catheterization.  He  introduced  through  the  jugular 
vein,  into  the  superior,  and  so  into  the  inferior  vena  cava,  a  long 
catheter,  constructed  in  such  a  manner  that  he  could  at  pleasure 
plug  up  the  vena  cava  below  the  embouchement  of  the  hepatic 
veins,  and  draw  blood  exclusively  from  the  latter  ;  or  vice  versa. 

In  the  absence  of  positive  evidence  we  are  thrown  back 
upon  theoretical  considerations;  and  undoubtedly  there  are 
many  a  prioin  arguments  which  may  be  ui-ged  in  support  of 
the  view  that  the  glycog;en  is  deposited  in  the  liver  simply 
as  a  store  of  carbohydrate  material,  being  accumulated 
whenever  amylaceous  material  is  abundant  in  the  alimentary 
canal,  and  being  converted  into  sugar  and  so  drawn  upon 
by  the  body  at  large  to  meet  the  general  demands  for  carbo- 
hydrate material  during  the  intervals  when  food  is  not  being 
taken.  And  we  can  accept  this  view  without  being  able  to 
say  definitely  what  becomes  of  the  sugar  thus  thrown  into 
the  hepatic  blood.  i3eruarvl  believed  that  tliis  sugar  under- 
went an  immediate  and  direct  oxidation  ;  but  we  have  al- 
ready dwelt  (p.  4B6)  on  the  objections  to  such  a  view.  It  is 
surticient  for  us  at  the  present  to  admit  that  the  sugar  is 
made  use  of  in  some  way  or  other. 

Now,  many  cons^iderations  lead  us  to  believe  that  a  cer- 
tain average  composition  is  nece>'-snry  for  that  great  inter- 
nal medium  the  blood,  in  order  that  the  several  tissues 
may  tlirive  upon  it  to  tlie  best  advantage,  one  element  of 
that  composition  being  a  certain  percentage  of  sugar.  It 
would  ajjpear  that  all,  or  some  at  least,  of  the  tissues  are 
continually  drawing  upon  the  bjood  for  sugar,  and  that 
heiice  a  certain  supply  must  be  kept  up  to  meet  this  demand ; 


518      THE    METABOLIC    PHENOMENA    OF    THE    BODY. 

on  tlie  other  hand,  an  excess  of  sugar  in  the  blood  itself 
would  be  injurious  to  the  tissues.  And,  as  a  matter  of  fact, 
we  find  the  quantity  of  sugar  in  blood  is  small  but  constant; 
it  remains  about  the  same  when  food  is  beiug  taken  as  in 
the  interval  between  meals.  If  sugar  be  in  too  large  quan- 
tities, or  too  rapidly  injected  into  the  jugular  vein,  a  certain 
quantity  ai)i)ears  in  the  urine,  indicating  an  effort  of  the 
system  to  throw  off  the  excess  and  l)ring  back  the  blood  to 
its  average  condition.  Such  a  constant  percentage  of  sugar 
would  obviously  be  provided  for,  or  at  least  largely  assisted, 
by  the  liver  acting  as  a  structure  where  the  sugar  might  at 
once  and  without  much  labor  be  packed  away  in  the  form 
of  the  less  soluble  glycogen,  wiien,  as  during  an  amylaceous 
meal,  sugar  is  rapidly  passing  into  the  blood,  and  there  is 
a  danger  of  the  blood  becoming  loaded  with  far  more  sugar 
than  is  needed  for  the  time  being;  and  it  may  be  inciden- 
tally noted  that  a  larger  quantity  of  sugar  may  be  injected 
into  the  portal  than  into  the  jugular  vein  without  any  reap- 
}>earing  in  the  urine,  apparently  because  a  large  portion  of 
it  in  such  a  case  is  retained  in  the  liver  as  glycogen.  When, 
on  the  otiier  hand,  sugar  ceases  to  pass  into  the  blood  from 
the  alimentary  canal,  the  average  percentage  in  the  blood 
is  maintained  by  a  reconversion  into  sugar,  and  its  passage 
into  the  hepatic  blood  of  the  glycogen  })reviously  stored  u[). 
Moreover,  this  view,  that  the  glycogen  of  the  liver  is  a 
reserve  fund  of  carbohydrate  material,  is  strongly  supported 
by  the  analogy  of  the  migration  of  starch  in  the  vegetable 
kingdom.  We  know  that  the  starch  of  the  leaves  of  a  plant, 
whether  itself  having  previously  passed  through  a  glucose 
stage  or  not,  is  normally  converted  into  sugar,  and  carried 
down  to  the  roots  or  other  parts,  where  it  frequently  becomes 
once  more  changed  back  again  into  starch. 

A  similar  argument  may  be  drawn  from  the  relations  of  gly- 
cogen to  muscle.  So  frequently  is  glycogen  found  in  muscle  that 
it  may  be  regarded  as  an  ordinary  though  not  an  invariable  con- 
stituent of  that  tissue  ;  indeed,  it  may  almost  be  considered  as  a 
constituent  of  all  contractile  tissues.  According  to  Chandelon^ 
it  is  increased  in  quantity  when  tlie  nerve  of  the  muscle  is  divided, 
and  the  muscle  thus  brought  into  a  state  of  quiescence.  On  the 
other  hand,  it  diminishes  or  even  disappears  when  the  muscle 
has  been  tetanized  or  has  entered  into  rigor  mortis.'^  But  muscles 
may  be  fully  alive  and  contractile  from  which  glycogen  is  wholly 

1  Pfliiger's  Archiv,  xiii  (1^76),  p.  626. 

2  ^^asse,  Pfluger's  Archiv,  ii  (18G9),  p.  97;  xiv  (1877),  p.  484. 


GLYCOGEN.  549 


absents  From  this  we  may  infer,  not  that  ^jlyco^en  is  a  neces- 
sary chemical  factor  of  muscular  metabolisui,  but  that  it  can 
furnish  materials  for  that  metabolism,  and  hence  is  stored  up  in 
the  muscle  so  as  to  be  ready  at  hand  for  use.  The  ftict  observed 
by  Weiss^  that  in  starvimr  hens  glycogen  is  still  found  in  the  pec- 
toral muscles  after  it  has  disappeared  from  the  liver,  suggested 
that  this  secondar}^  and  special  store  in  the  muscle  was,  from  its 
functional  importance,  more  constant  than  what  may  be  consid- 
ered as  the  general  and  primary  store  in  the  liver  ;  but  Luch- 
singer^  states' that  this  is  a  special  feature  of  the  fowl's  pectoral 
muscles  ;  from  other  muscles  glycogen  may  disappear  long  before 
the  store  in  the  liver  has  been  exhausted. 

But  if  we  answer  the  question,  Wliat  becomes  of  the 
he[)atic  glycogen,  by  accepting  the  view  that  the  hepatic 
glycogen  is  simply  store  glycogen,  waiting  to  be  converted 
into  sugar  little  by  little  as  the  needs  of  the  economy  de- 
mand, and  not  glycogen  on  its  way  to  take  part,  through 
tlie  agency  of  the  hepatic  protoplasm,  in  the  formation  of 
some  more  complex  compound,  such  as  fat,  we  have  pre- 
pared the  way  for  an  answer  to  the  question  with  which  we 
started,  Jn  what  is  the  exact  origin  of  the  hepatic  glycogen? 
For  if  such  be  the  purpose  of  glycogen,  it  is  only  reasonable 
to  supj)ose  that  the  glycogen  which  makes  its  appearance  in 
the  liver  after  an  amylaceous  meal  arises  frotn  a  direct  con- 
version of  tlie  grape-sugar  carried  to  the  liver  by  the  por- 
tal vein,  the  sugar  becoming,  through  some  action  of  the 
hepatic  protoi>lasm.  dehydrated  into  starch,  by  a  process 
the  reverse  of  tliat  by  which  in  the  alimentar}'  canal  starch 
is  hydrated  into  sugar  through  the  action  of  the  salivary  and 
pancreatic  ferments.  Vegetable  i)rot()[)lasni  can  undcnibt- 
edly  convert  both  starch  into  sugar  and  sugar  into  starch  ; 
and  there  are  no  a  priori  arguments  or  positive  facts  which 
would  lead  us  to  suppose  that  the  activity  of  animal  proto- 
plasm cannot  accomplisli  the  latter  as  well  as  the  former  of 
these  changes.  At  tlie  same  time  it  must  l)e  remembered  that 
this  view  does  not  preclude  the  possibility  of  glycogen,  in 
the  absence  of  a  supply  of  sugar  from  tlie  portal  blood,  as 
for  instance  when  'glycogen  is  stored  up  in  the  liver  as  the 
result  of  purely  proteid  food,  being  formed  in  other  ways. 

It  has  been  stated*  that  glycerin,  introduced  into  the  alimen- 
tary canal,  gives  rise  to  an  increase  of  gl3-cogen  in  the  liver ;  and 

'  Luolisinger,  Pfliiger's  Archiv,  xviii  (1878),  p.  472. 
2  Wiener  Sitzungsbericht,  Bd.  04  (1871).  ^  Op.  cit. 

*  Weiss,' Wiener  Sitzungsberielit,  Bd.  67  (1873).     Luchsinger,  Pflii- 
ger's Archiv,  viii  (1874),  289. 


550      THE    METABOLIC    PHENOMENA    OF    THE    BODY. 


Liichsinger^  finds  that  in  an  animal,  the  liver  of  which  has  been 
proved  to  be  free  from  glycogen  by  the  examination  of  an  excised 
lobule,  glycogen  appears  in  the  liver  within  an  hour  of  the  glyc- 
erin being  given  ;  this  seems  undoubtedly  to  show  that  hepatic 
glycogen  may  be  formed  in  other  ways  than  by  the  direct  dehy- 
dration of  sugar.  It  is  difficult  to  suppose  that  glycerin  can  be 
directly  converted  into  glycogen  ;  and  it  has  been  urged  that  in 
this  case  the  glycerin,  by  becoming  oxidized,  causes  a  saving  in 
the  expenditure  of  carbohydrate  material,  and  thus  indirectly 
leads  to  an  accumulation  of  glycogen.  But  this  view  is  opposed 
by  the  fact  that  lactic  acid,  to  which  we  should  readily  turn  as 
being  eminently  oxidizable,  and  therefore  eminently  calculated 
to  save  carbohydrate  expenditure,  does  not  lead  to  any  similar 
storing  up  of  glycogen.  And  Luchsinger-  states  that  glycerin, 
injected  in  considerable  quantities  under  the  skin,  and  absorbed 
from  the  subcutaneous  tissue,  leads  to  no  increase  of  glycogen  ; 
so  that  the  glycogen  which  appears  in  the  liver  when  glycerin  is 
introduced  into  the  alimentary  canal  would  seem  to  come  from 
some  conversion  of  the  gh'cerin  either  in  the  alimentary  canal  or 
when  it  reaches  the  hepatic  cells  by  the  portal  blood,  ditiicult  as 
any  chemical  conception  of  that  conversion  may  be. 

The  statements  with  regard  to  the  glycogenic  intluence  of  gela- 
tin are  conflicting.^  The  balance  of  evidence  is  perhaps  in  favor 
of  glycogen  being  stored  up  in  the  liver  as  a  result  of  a  diet  of 
pure  gelatin.  This  would  indicate  a  transformation  into  gly- 
cogen of  the  non-nitrogenous  moiety  resulting  from  that  splitting 
up  of  gelatin  of  which  we  shall  have  to  speak  later  on. 

In  general,  glycogen,  having  as  far  as  we  know  in  all  cases  the 
same  characters,  appears  to  be  formed  in  varying  quantity  when 
any  of  the  following  substances  are  given  as  food  :  starch,  dex- 
trin, sugar  (cane,  grape,  fruit,  milk),  inulin,  lichenin,  arbutin, 
glycerin,  albumin,  fibrin,  casein,  gelatin.  It  appears  not  to  be 
formed  by  fat,  inosit,  quercite,  mannite,  erythrite. 

The  question  niay  be  asked.  How  is  it  [possible  for  the 
glycogen,  which  at  the  temperature  of  tlie  body  is  so  readil}' 
converted  into  sugar  by  the  action  of  ferments,  to  remain 

as   o-lvc'open   in  the  i)resence  of  the  ferment  which,  as  we 

^  *  .         .  .      . 

know  from  i)ost-mortem  changes,  exists  in  the  hepatic  tis- 
sue ?  We  can  only  answer  that  the  sohition  of  this  problem 
is  of  the  same  kind  as  tiiat  of  the  |roblems,  why  Idood  does 
not  clot  in  the  living  bloodvessels,  why  the  living  muscle 
does  not  become  rigid,  an<l  why  the  living  stomach  or  pan- 
creas does  not  digest  itself.     It  might  be  added,  hearing  in 

1  Pfliifrer's  Archiv,  xviii  (1878),  p.  472. 
^  Pfliiger's  Archiv,  viii  (1874),2S9. 

'  Bernard,  MacDonnel,  Luchsinger,  Mering,  oj).  cit.  Wolffberg,  Zt. 
f.  Biol.,  xii,  p.  266. 


DIABETES.  551 

mind  the  liistory  of  the  fibrin  ferment,  that  we  have  no 
proof  that  snch  an  amyiolytic  ferment  does  exist  in  the 
living  hepatic  cells.  It  is  possible  that  the  ferment  which 
can  be  extracted  after  death  only  makes  its  appearance  as 
the  resnlt  of  chancres  vvliich  have  taken  place  in  the  proto- 
[)lasm  of  the  hepatic  cells. 

If,  as  Seegen  states  (see  p.  556),  the  sugar  formed  by  the  liver 
is  true  grape-sugar,  while  that  produced  by  the  action  of  ordinary 
amyiolytic  ferments  is  another  though  allied  kind  of  sugar,  the 
formation  of  sugar  in  the  tirst  case  must  be  regarded  as  a  pecu- 
liar and  complex  process. 

It  is  clear  that  the  glycogen  is  contained  in  the  hepatic  cells.; 
but  it  is  by  no  means  certain  that  it  exists  there  in  what  may  be 
called  a  tree  state.  The  fact  that  under  the  microscope  the  he- 
patic cells  give  with  iodine  the  color  reaction  of  glycogen,  is  no 
proof  of  the  glj'cogen  being  free.  It  has  been  described  as  some- 
times occurring  in  granules;  but  this,  if  ever,  is  certainly  not 
always  its  condition.  It  is  worthy  of  notice  that  all  the  means 
adopted  to  extract  glycogen  from  a  tissue  are  such  as  wM)uld  read- 
ily decompose  unstable  complex  compounds.  If  we  advance  the 
view  that  the  glycogen  of  the  hepatic  protoplasm  does  not  exist 
as  an  independent  body,  simply  mixed  with  the  other  proto- 
plasmic constituents,  but  is  loosely  connected  with  other  (pos- 
sibly proteid)  substances  as  part  of  a  very  complex  compound, 
few  facts  would  be  found  opposing,  and  many  supporting,  such  a 
view\ 

Diabetes. — Natural  diabetes  is  a  disease  characterized  by 
the  ai)pearance  of  a  large  quantity  of  sugar  in  the  urine. 
Into  tiie  pathology  of  tiie  various  forms  of  this  disease  it  is 
impossible  to  enter  here  ;  but  a  temporar}'  diabetes,  the  ap- 
pearance for  awhile  of  a  large  quantity  of  sugar  in  the  urine, 
may  be  artificially  produced  in  animals  in  several  ways.  If 
the  medulla  oblongata  of  a  well  fed  rabbit  be  pur.ctured 
(Fig.  14(i)  in  the  region  which  we  have  previously  described 
(p.  278)  as  that  of  the  vaso-motor  centre  (tlie  area  marked 
out  by  Eckhard  as  the  diabetic  area  agreeing  very  closely 
with  that  defined  by  Owsjannikow  as  the  vasomotor  area), 
though  the  animal  need  not  necessarily  be  in  any  other  way 
obviously  affected  by  the  operation,  its  urine  will  be  found, 
in  an  hour  or  two,  or  even  less,  to  contain  a  considerable 
quantity  of  sugar,  and  to  be  increased  in  amount.  A  little 
later  the  quantity  of  sugar  will  have  reached  a  maximum, 
after  which  it  declines,  and  in  a  day  or  two,  or  even  less, 
the  urine  will  again  be  perfectly  normal.  The  better  fed 
the  animal^  or.  more  exactly,  the  richer  in  glycogen  the  liver 


552      THE    METABOLIC    PHENOMENA    OF    THE    BODY. 

at  the  time  of  the  operation,  tlie  greater  the  amount  of 
sugar.  If  the  animal  be  previously  starved  so  that  the  liver 
contains  little  or  no  glycogen,  the  urine  will  after  the  opera- 
tion contain  little  or  no  sugar.  It  is  clear  that  the  urinary 
sugar  of  this  form  of  artificial  dialietes  comes  from  the  gly- 
cogen of  the  liver.  The  puncture  of  the  medulla  causes 
such  a  change  in  the  liver  that  the  previously  stored-up 
glycogen   disappears  and  the  blood   becomes  loaded  with 

[Fig.  146. 


T  t  show  the  position  of  tli«  punctures  required  to  produce  glucosuria,  the  lobes  of 
the  cerebellum  are  separated;  below  are  seen  the  restiform  bodies,  the  divergence  of 
which  circuuiscribes  the  apex  of  the  calamus  scriptorins  and  the  fourth  ventricle. 
The  puncture/)'  produces  glycosuria,  the  puncture  p  glycosuria  with  polyuria,  and 
a  puncture  a  littlj  higher  up  thanp,  albuminuria.] 

sugar,  much  if  not  all  of  which  passes  away  by  the  urine.  In 
the  absence  of  any  proof  to  the  contrary,  we  may  assume 
that  in  this  form  of  artificial  diabetes  the  glycogen  pre- 
viously present  in  the  liver  becomes  converted  into  sugar, 
just  as  we  know  that  it  does  become  so  converted  by  post- 
mortem changes.  Tlie  glycogenic  function  of  the  liver  is 
therefore  sul»ject  to  the  influence  of  the  nervous  system,  and 
in  particular  to  the  influence  of  a  region  of  the  cerebro- 
spinal centre  which  we  already  know  as  the  vaso-motor 
centre,  or  at  least  of  a  part  of  that  region.  The  path  of  the 
influence  may  be  traced  along  the  cervical  spinal  cord  (and 
not  along  tlie  vagi,  though  the  roots  of  these  nerves  lie  so 
close  to  the  diabetic  spotj  as  far  down  as  (in  rabbits)  the 


DIABETES.  553 

level  of  the  third  or  fourth  dorsal  vertebra,^  or  even  a  little 
lower,  from  the  spinal  cord  to  tlie  first  tlioracic  glanglion, 
and  from  thence  to  the  liver  by  some  channel  or  channels  at 
present  undetei'mined.  We  cannot  at  present  define  clearly 
the  nature  of  tiiat  influence.  We  cannot  say  whether  the 
temporary  diabetes  is  a  simple  effect  of  dilation  of  the  he- 
patic arteries  which  accompanies  the  dial>etic  puncture  or 
of  some  direct  action  of  the  nerves  on  the  metabolic  activity 
of  the  hepatic  protoplasm. 

According  to  Eckhard-  the  phenomena  are  those  of  irritation, 
and  not  of  the  simple  withdrawal  of  any  accustomed  nervous  in- 
fluence. He  states  that  Avhile  mechanical  injury  of  the  first 
thoracic  ganglion  (see  Fig.  76)  will  produce  diabetes,  no  such 
eftect  is  produced  if  the  ganglion  be  carefully  removed,  or  if  its 
connections  with  the  spinal  cord  or  with  the  remainder  of  the 
thoracic  chain  be  completely  divided. 

Cyon  and  Aladoft^  on  the  contrary,  regard  the  whole  matter 
as  one  of  simple  loss  of  vascular  tone.  They  state  that  the  dia- 
betic puncture  produces  dilation  of  the  small  branches  of  the 
hepatic  artery,  from  injury  to  the  corresponding  portion  of  the 
general  vaso-motor  centre,  and  accordingly  find,  in  opposition  to 
Eckhard,  that  simple  division  of  the  nervous  path,  removal  of  the 
first  thoracic  ganglion,  or  division  of  certain  (variable)  nerves 
proceeding  from  it,  produces  diabetes  equally  well  as  irritation  of 
the  ganglion.  Eckhard  found  that  simple  section  of  the  splanch- 
nic nerves,  not  only  did  not  produce  diabetes  but  even  prevented 
its  occurrence  when  performed  previously  to  the  diabetic  punc- 
ture. On  the  hypothesis  that  the  phenomena  in  question  are 
those  of  irritation  and  not  of  paralysis,  this  fact  would  seem  to 
show  that  the  splanclmics  serve  as  the  channels  by  which  the 
impulses  set  up  in  the  medulla,  thoracic  ganglion,  etc.,  reach  the 
liver.  CVon  and  Aladofl",  however,  regard  the  absence  of  diabetes 
after  simple  section  of  the  splanchnics  as  a  proof  that  the  vaso- 
motor fibres  concerned  in  the  matter  pass  to  the  liver  by  some 
other  channel  than  the  splanchnics  ;  and  they  explain  the  pre- 
ventive influence  of  previous  section  of  the  splanchnics,  by  sup- 
posing that  this  operation,  b}"  withdrawing  a  large  quantity  of 
blood  into  the  abdominal  organs,  prevents  the  effects  of  the  dila- 
tion of  the  comparatively  small  hepatic  arter}'  from  manifesting 
themselves.  For,  according  to  them,  it  is  not  the  total  quantity 
of  blood,  but  the  relative  proportion  of  arterial  blood  reaching  the 
liver,  which  determines  the  appearance  of  the  sugar. 

■Simple  section  of  the  spinal  cord  (in  rabbits)  sometimes  does 
and  sometimes  does  not  produce  diabetes,  and  in  all  cases  the 

^  Eckhard,  Beitriige,  viii  (1S77),  p.  79. 

2  Beitnicre,  iv  (1869),  1  ;  vii,  1. 

=  Bull.  Acad.  Imp.  Sci.  St.  Petersb.,  xvi  (1871),  p.  308. 


TUE    METABOLIC    PHENOMENA    OF    THE    BODY. 


effect  appears  rapidly  and  soon  disappears.  Complete  section  of 
the  spinal  cord  at  any  height  down  to  the  level  of  the  third  or 
fourth  dorsal  vertehra  renders  the  diabetic  puncture  ineffectual,^ 
and  prevents  the  diabetes  of  morphia  poisoning  from  being  devel- 
oped. Section  of  the  vagi  may  produce  a  very  slight  and  passing 
diabetes,  but  stimulation  of  the  central  end  of  either  vagus  may 
give  rise,  apparently  by  reflex  excitation  of  the  medullary  centre, 
to  a  marked  quantity  of  sugar  in  the  urine.  The  diabetic  punc- 
ture is  in  no  way  interfered  with  by  previous  section  of  both  vagi. 

Artificial  diabetes  is  also  a  prominent  symptom  of  urari 
poisoning.  Tins  is  not  due  to  the  artificial  respiration, 
wiiich  is  had  recourse  to  in  order  to  keep  the  urarized  ani- 
mals alive;  because,  though  disturbance  of  the  respiratory 
functions  sufficient  to  interfere  with  the  hepatic  circulation 
n)ay  produce  sugar  in  the  urine,  artificial  respiration  may  he 
carried  on  without  any  sugar  making  its  appearance.  More- 
over, it  is  seen  in  frogs,  in  which  respiration  can  be  satis- 
factorily^ carried  on  without  any  pulmonar}^  respirator}^ 
movements. 

A  very  similar  diabetes  is  seen  in  carbonic  oxide  poison- 
ing; and  is  one  of  the  results  of  a  sufficient  dose  of  morphia 
or  of  amyl  nitrite. 

According  to  Dock ,2  sugar  appears  in  the  urine  of  urarized 
mammals,  even  when  they  are  starving  and  presumably  contain 
no  glycogen  in  their  livers.  If  this  be  so,  urari  diabetes  must 
have  quite  a  different  causation  from  puncture  diabetes ;  but 
Winogradoff  "^  found  no  sugar  in  the  urine  of  curarized  frogs  from 
which  the  livers  had  been  removed,  and  Saikowsky*  found  that 
in  mammals  after  arsenic  poisoning  urari  did  not  produce  dia- 
betes, showing  that  if  in  urari  poisoning  the  sugar  does  not  come 
from  the  liver  but  from  the  muscles,  arsenic  has  a  like  effect  in 
preventing  the  accumulation  of  glycogen  in  the  latter  as  in  the 
former. 

Eckhard^  found  that  morphia  diabetes  was,  like  the  puncture 
diabetes,  prevented  by  section  of  the  splanchnics  or  by  section  of 
the  spinal  cord  above  the  level  of  the  third  or  fourth  dorsal  ver- 
tebra. The  drug  appears,  therefore,  to  act  through  the  medul- 
lary diabetic  centre. 

The  subcutaneous  injection  of  glycerin  prevents  (but  not  in  all 
cases,  and  not  always  effectually)  the  appearance  of  diabetes  after 


^  Eckhard.  Beitriige,  viii,  p.  79. 

2  Pfliiger's  Archiv,  v  (1<S72),  p.  71. 

^  Virchow's  Archiv,  xxvii  (1863),  p.  533. 

*  Centrbt.  Med.  Wiss.,  1865,  p.  769.  «  Op.  cit. 


DIABETES.  555 


the  puncture^  or  after  morphia  poisonins:.  The  reason  of  this 
is  not  at  present  clear.  The  urine  at  the  same  time  becomes 
blood}'. 

The  injection  of  o:lycogen  in  sufficient  quantit}'  into  the  blood 
gives  rise  in  the  urine  not  only  to  sugar  but  to  a  much  larger 
quantity  of  a  substance  identical  apparently  with  Brlicke's  ach- 
roodextrin.- 

There  can  be  no  doul)t  tliat  in  diabetes,  arising  from  what- 
ever cause,  the  sugar  appears  in  the  urine  because  the  blood 
contains  more  sugar  than  usual.  The  system  can  only  dis- 
pose (either  by  oxidation,  or  as  seem.s  more  probalde  in 
other  ways)  of  a  certain  quantity  of  sugar  in  a  certain  time. 
Sugar  injected  into  the  jugular  vein  reappears  in  the  urine, 
whenever  the  injection  becomes  so  rapid  tliat  the  percentage 
of  sugar  in  the  blood  reaches  a  ceitain  (low)  limit.  Sugar 
in  the  urine  means  an  excess  of  sugar  in  the  blood.  How 
in  natural  diabetes  that  excess  arises,  we  have  at  present  no 
facts  to  sliow  ;  but  it  is  extremely  probable  that  the  sources 
of  tlie  excess  may  be  various,  and  hence  that  several  distinct 
varieties  of  diabetes  may  exist.  In  one  among  many  points, 
the  clinical  history  of  diabetes  tiirows  light  on  the  |)ossible 
sources  of  glycogen.  While  in  many,  especially  of  the  less 
severe  cases  of  diabetes,  withdrawal  of  all  amylaceous  food 
is  followed  by  a  disappearance  of  sugar  fi'om  the  urine,  in 
many  instances  the  sugar  continues  to  be  discharged  even 
though  the  diet  be  perfectly  free  from  carbohydrates  ;  and 
in  many  other  cases  the  sugar  in  the  urine  is  far  in  excess 
of  that  taken  as  food.  In  these  cases  the  sugar  must  have 
some  non-amylaceous  source  ;  Irom  this  we  infer  that  glyco- 
gen also  ma}'  have  a  similar  origin  ;  and  the  fact  that  the 
urea  is  increased  (and  that  too  in  some  cases  in  ratio  with 
the  sugar^)  in  diabetes,  suggests  that  the  sugar  may  arise 
from  proteids  which  have  been  split  up  into  a  nitrogenous 
(urea)  and  a  non-nitrogenous  moiety. 

It  has  been  shown  by  Wickham  Legg,  and  confirmed  by  Von 
Wittich,  that  ligature  of  the  bile-ducfs  causes  a  disappearance  of 
glycogen  from  the  liver,  and  that  (four  or  six  days)  after  the  lig- 
ature the  diabetic  puncture  produces  no  diabetes.  This  cannot 
be  explained  by  supposing,  as  Yon  Wittich  does  that  the  glyco- 
gen formed  previous  to  the  operation  is  rapidly  converted  into 


^   Luchsinger,  Pfliiger's  Archiv,  xi  (1875),  p.  502. 

-  Boehm  and  Ho.'fmann,  Archiv  Exp.  Path.,  vii  (1877),  p.  489. 

'  Ringer,, Med.-C'hir.  Trans.,  xliii. 


556      THE    METABOLIC    PHENOMENA    OF    THE    BODY. 


sugar  by  a  ferment  developed  in  the  stagnant  bile,  for  no  sugar 
appears  in  the  urine. ^  ■  We  are  rather  led  to  infer  that  the  forma- 
tion of  the  glycogen  is  prevented  by  interference  with  the  nutri- 
tive functions  of  the  hepatic  cells. 

According  to  Seegen''  the  sugar  which  is  formed  naturally  in 
the  liver  post-mortem  is  true  grape-sugar,  but  that  which  is  arti- 
ficially formed  out  of  glycogen  by  the  action  of  ferments  (sali- 
vary, pancreatic,  etc.),  like  the  sugar  similarly  formed  out  of 
starch,  is  not  true  grape-sugar  but  some  allied  form  (see  p.  308). 
It  is  possible  that  the  phenomena  of  some  kinds  of  diabetes  may 
depend  on  the  liver  forming  an  abnormal  kind  of  sugar,  which 
cannot  undergo  the  changes  which  are  undergone  by  the  normal 
kind  or  kindsusually  present  in  the  body.  Such  an  explanation 
of  diabetes  was  suggested  long  ago,  but  has  not  hitherto  been 
supported  by  suffici^nit  evidence,  and  further  investigation  is 
still  necessary  before  any  opinion  can  be  passed  as  to  its  value. 

Various  suggestions  have  been  made  with  reference  to  the 
chemical  ways  in  which  carbohydrate  material  might  make  its 
appearance  during  hepatic  metabolism.  It  has  been  pointed 
out,  for  instance,  "that  proteid  material  might  be  split  up  into 
glycogen  and  the  bile  acids,  or  that  glycin  might  be  split  up  into 
urea  and  glucose  (4C2H,NO,  =  2CH,N,0  +  C  JI,  A).  But  these 
views  must  at  present  be  considered  as  suggestions  only. 

The  Histonj  ofFat—Adipot^e  TisHue. 

Of  all  the  tissues  of  the  body  adipose  tissue  is  the  most 
fluctuating  in  bulk  ;  within  a  very  short  space  of  time  a. 
large  amount  of  adipose  tissue  may  disappear,  and  within 
an  almost  equally  short  time  the  quantity  present  in  a  itody 
may  be  several  times  multiplied.  Histological  inquiries 
teach  us  that  when  an  animal  is  fattening  the  minute  drops 
or  specks  of  fat  normally  present  in  certain  connective-tissue 
corpuscles  are  seen  to  increase  in  numlier,  the  protoplasm 
enlarging  at  the  same  time.  As  these  specks  increase  they 
coalesce  into  drops,  which  by  similar  coalescence  form  larger 
dnjps.  until,  the  protoplasm  first  ceasing  to  increase  and 
then  diminishing,  the  original  connective-tissue  coi-i)uscle  is 
transformed  into  a  fat-cell,  with  a  remnant  only  of  proto- 
plasm gathei'ed  round  the  nucleus  and  forming  an  im[)ei-rect 
envelope  round  the  enlai'ged  contents.  When,  on  the  con- 
trary, an  animal  is  fasting,  the  fat  seems  in  some  way  to 
escape  from  the  cell,  which  it  may  leave  as  an  empty  bag- 
collapsed  around  the  nucleus.     These  facts  point  to  the  con- 

'  Kiilz  and  E.  Frerichs,  Pfliiger's  Archiv,  xiii  (187G),  p.  460. 
^  Pfliiger's  Archiv,  xix  (1879),  p.  100. 


FAT.  557 

elusion  that  tlie  fat  of  adipose  tissue  is  not  simply  and 
mechanically  collected  in  the  cell,  but  is  formed  l\v  the  active 
agency  of  the  cell,  being:  apparently  the  result  of  a  breaking 
up  of  the  protoplasm  ;  when  formed,  however,  it  appears  to 
be  discharged  from  the  cell  in  a  more  or  less  mechanical 
manner,  as  the  needs  of  the  economy  demand.  vVnd  this 
view  is  supported  by  the  fact  that  protoi)lasm,  wherever 
occurring,  botli  during  life  and  after  death  (when  it  could 
not  possibly  be  supplied  with  fat  from  without),  is  subject 
to  fatty  degeneration,  in  which  the  fat  evidently  arises,  in 
large  part  at  least,  from  the  breaking  up  of  proteid  com- 
pounds. 

On  the  other  hand,  we  have  traced  the  fats  taken  as  food, 
and  found  tliat  they  pass  with  comparatively  little  change 
from  the  alimentary  canal  into  the  blood,  either  directly,  or 
through  the  intermediate  passage  of  the  chyle.  We  might 
infer  from  this  that  an  excess  of  fat  thus  entering  the  blood 
w^ould  naturally  be  simply  stored  up  in  the  available  adipose 
tissue,  without  any  further  change,  the  connective  tissue 
corpuscles  after  the  fashion  of  an  amoeba  eating  the  fat 
brought  to  them  but  not  digesting  it,  simply  keeping  it  in 
store  till  it  was  wanted  elsewhere. 

Which  of  these  views  is  the  true  one,  or  how  far  are  both 
these  operations  carried  on  in  the  animal  body  ?  In  the  first 
jilace,  it  is  evident  that  in  an  animal  fattened  on  ordinary 
fattening  food,  only  a  small  fraction  of  the  fat  stored  up  in 
the  body  can  possibly  come  direct  from  the  fat  of  the  food. 
Long  ago,  in  opposition  to  the  views  of  Dumas  and  his  school, 
who  taught  that  all  construction  of  organic  material,  that 
all  actual  manufacture  of  protoplasm  or  even  of  its  organic 
constituents,  was  confined  lo  vegetables  and  unknown  in 
animals,  Liebig  showed  that  the  butter  present  in  the  milk 
of  a  cow  was  much  greater  than  could  be  accounted  for  l)y 
the  scanty  fat  present  in  the  grass  or  other  fodder  she  con- 
sumed. He  also  urged,  as  an  argument  in  the  same  direc- 
tion, that  the  wax  produced  by  bees  is  out  of  all  proportion 
to  the  fat  contained  in  their  food,  consisting  as  this  does 
chiefly  of  sugar.  And  Lawes  and  Gilbert^  have  shown  by 
direct  analysis  that  for  every  100  parts  of  fat  in  the  food  of 
a  fattening  pig,  47-  parts  were  stored  up  as  fat  during  the 
fattening  period.  It  is  clear  that  fat  is  formed  in  the  body 
out  of  something  which  is  not  fat. 

'  Phil.  Trans.,  1860. 
47 


Carbon. 

Hyflrogpti. 

Oxv^Pii. 

Nitrogen. 

Urea,   . 

.       20.00 

6.66 

26.67 

46.67 

Proteid, 

.     53 

7.30 

23.04 

15.53 

558      THE    METABOLIC    PHENOMENA    OF    THE    BODY. 

There  are  two  possible  sources  of  this  manufactured  fat. 
In  treating  of  digeslion  (p.  398),  we  referred  to  the  possi- 
bility of  digested  carbohydrates  becoming  converted  into 
fats  by  the  butyric  acid  fermentation.  Analogous  ferment 
actions  may  similarly  elaborate  other  fats.  And  there  can  be 
no  doubt  that  a  carl)ohydrate  diet  is  most  etticacious  in  pro- 
ducing an  accumulation  of  fat  in  the  body.  Sugar  or  starch, 
in  some  form  or  other,  is  alwa^'s  a  large  constituent  of  ordi- 
nary fattening  foods. 

Another  source  of  fat  is  to  be  found  in  the  proteids.  We 
have  seen  that  the  urea  of  the  urine  practically  represents 
the  whole  of  the  nitrogen  which  passes  through  the  body. 
Now  in  any  given  quantity  of  urea  the  amount  of  carbon  is 
far  less  than  that  found  in  the  quantity  of  proteid  contain- 
ing the  same  amount  of  nitrogen.  Thus  the  percentage 
composition  of  the  two  being  respective!}'. 

Sulphur. 

1.13 

100  grams  of  urea  contain  about  as  much  nitrogen  as  300 
grams  ol' proteid  ;  but  the  300  grams  of  proteid  contain  139 
grams  (159-20)  more  carl)on  than  do  the  100  grams  urea. 
Hence  the  300  grams  of  proteid  in  passing  through  tiie  body 
and  giving  rise  to  100  grams  of  urea,  would  leave  behind 
139  grams  of  carbon,  in  some  combination  or  other;  and 
tliis  surplus  of  carbon,  if  the  needs  of  the  economy  did  not 
demand  that  it  should  be  immediately  converted  into  car- 
bonic acid  and  thrown  off  from  the  body,  might  be  deposited 
somewhere  in  the  form  of  fat.  We  have  already  seen,  in 
treating  of  the  action  of  the  pancreatic  juice  (p.  336),  tliat 
there  is  evidence  of  a  fatty  element  being  thrown  otf  from 
the  complex  proteid  compound  in  the  very  process  of  di- 
gestion. 

It  is  clear  that  a  construction  of  fat  does  occur  in  the 
body  somewhere.  What  limits  can  we  place  on  the  degree 
to  which  this  construction  is  carried?  In  reference  to  this 
pjoint  it  is  wortiiy  of  notice  that  the  composition  of  fat 
varies  in  different  animals.  Tlie  fat  of  a  man  differs  from 
the  fat  of  a  dog,  even  if*  both  feed  on  exactly  the  same  food, 
fatty  or  otherwise.  Were  tiie  fat  whicli  is  taken  as  food 
stored  up  as  adipose  tissue  directly  and  without  change, 
recourse  beintr  had  to  other  sources  of  food  for  the  construe- 


FAT.  559 

tion  of  fat  only  in  cases  where  the  fat  in  the  food  was  defi- 
cient, we  should  expect  to  find  that  the  constitution  of  the 
fat  of  the  bod_y  would  vary  greatly  with  the  food.  So  far 
from  this  being  the  case,  Subhotin/  finds  that  the  fat  of  the 
dog  is,  as  far  as  composition  is  concerned,  almost  entirely 
independent  of  the  food,  tiiat  the  normal  constituents  of  fat 
make  their  appearance  as  usual,  though  some  of  them  may 
wholly  be  absent  in  the  food,  and  that  alaiormal  fats  pre- 
sented as  food  are  not  to  be  found  in  the  fat  wliich  is  stored 
up  ill  the  body  as  a  consequence  of  a  large  supply  of  that 
food. 


Subbotin,  after  starving  a  dog  till  he  had  reason  to  think  all 
fat  had  disappeared  from  the  body,  fed  it  largely  on  palm-oil  (con- 
taining palmitin  and  olein,  but  no  stearin)  and  the  very  leanest 
meat.  The  composition  of  the  fat  which  w^as  stored  up  during 
this  diet  is  shown  in  column  2,  the  normal  constitution  of  the  fat 
of  a  dog  being  shown  in  column  1.  Another  dog,  after  a  similar 
removal  of  the  natural  fat  by  starvation,  was  fed  on  meat  and  a 
soap  composed  of  palmitic  and  stearic  acids.  The  animal  in  this 
case  received  no  olein.  Yet  the  composition  of  his  Iht  was  that 
given  in  column  3. 


1. 
A.             B. 

A. 

2.    - 

B. 

c. 

3. 

A.             B. 

Palmitin, 

Stearin, 

Olein, 

44.87    39.72 
19.23    32.48 
35.90     27.80 

50.80 

9.00 

40.20 

53.30 
13.20 
33.50 

55. 3G 
13.24 

30.80 

52.80    53.60 
13.20    13.40 
34.00    33.00 

A  signifies  the  subcutaneous,  b  the  mesenteric,  and  c  the  supra- 
renal adipose  tissue. 

Moreover,  when  a  dog  was  fed,  after  a  preliminary  starvation 
period,  with  1  kgm.  of  spermaceti,  of  wdiich  he  was  found  to 
absorb  at  least  800  grams,  nothing  more  than  a  trace  of  the  sper- 
maceti was  to  be  found  in  his  fat. 

Of  course  it  is  quite  possible  that  in  such  cases  as  these, 
though  the  stearin,  or  the  olein,  when  absent  from  the  food, 
was  in  some  way  or.other  constructed  anew,  yet  at  the  s;ime 
time  those  constituents  which  were  present  were  simply 
stored  up;  but  it  is  also  open  for  us  to  suppose  tliat  all 
the  fat  taken  as  food  was  in  some  way  or  other  disposed  of, 
and  that  all  the  new  fat  which  made  its  appearance  was 
constructed  anew.     And  the  latter  view  is  su})ported  by  the 

^  Zt.  f.  Biol.,  vi  (1870),  p.  73. 


5G0      THE    iMETABOLIC    PHENOMENA    OF    THE    BODY. 

liistorical  facts  mentioned  above  (p.  55fi),  as  well  as  hy  other 
considerations,  which  we  shall  presently  have  to  urj^e.  At 
the  present,  however,  we  may  be  content  with  the  following 
conclusions:  1.  Fat  is  formed  anew  in  the  animal  body.  2. 
The  carbon  elements  of  the  newly  formed  fat  may  be  sup- 
plied either  from  amylaceous  food,  or  from  the  carbon  sur- 
plus of  proteid  food,  or  from  fats  taken  as  food  which  are 
not  the  natural  constituents  of  the  body-fat.  3.  The  fat 
stored  up  appears  as  fat-granules  or  drops  deposited  in  the 
protoplasm  of  certain  cells,  and  the  increase  of  the  fat  in 
the  cells  is  accompanied  first  by  a  growth,  and  subsequently 
by  a  decay  of  the  jjrotoplasm  ;  but  there  is  no  complete  evi- 
dence to  show  vvhether  the  fat-j;ranules  which  appear  are 
simply  deposited  l>y  the  protoplasm  in  a  more  or  less  me- 
chanical manner,  without  their  forming  an  integral  portion 
of  it,  the  chief  stages  of  the  manufacture  of  the  fat  having 
been  gone  through  elsewhere,  or  whether  they  arise  from  a 
breaking  up,  a  functional  metabolism  of  the  protoplasm  of 
the  fat-cell  its(?lf 

The  question  touched  on  here  is  one  the  solution  of  which  is 
probably  still  far  distant.  We  know  that  protoplasm  such  as 
that  of  Penicillium'  can  build  itself  up  out  of  ammonium  tar- 
trate and  inorganic  salts,  and  can  by  a  decomposition  of  itself 
give  rise  to  fats  and  other  bodies  ;  and  we  have  every  reason  to 
suppose  that  this  constructive  power  belongs  naturally  to  all 
native  protoplasm  wherever  found.  At  the  same  time,  we  see 
that  even  in  Penicillium  it  is  of  advantage  to  offer  to  the  proto- 
plasm as  food,  substances  such  as  sugar  and  proteids  (peptone), 
which  are,  so  to  si)eak,  already  on  the  way  to  become  protoplasm  ; 
the  organism  is  thus  saved  much  constructive  labor.  And  we  may 
imagine  that  a  cell  would  always  take  and  assimilate  into  itself 
already  constructed  fats,  sugar,  proteids,  etc.,  rather  than  have 
the  preliminary  trouble  of  l)uilding  up  these  substances  out  of 
simpler  compounds.  But  when  we  consider  how  in  every  being, 
every  cell  and  every  part  of  a  cell  has  its  own  individual  charac- 
ters, stamped  on  it  by  long  hereditar}-  action,  we  see  a  reason 
why  every  bit  of  protoplasm,  especially  in  the  higher  more  difter- 
entiated  organisms,  should  be  made  anew^  And  the  energy  re- 
quired for  the  construction  is  always  at  hand.  The  food,  which, 
instead  of  being  directly  assimilated  without  loss  of  energy,  is 
reduced  to  simple  compounds,  sets  free  an  ent^rgy  which  remains 
available  f  >r  reconstruction.  Of  course  in  every  such  decompo- 
sition and  recompostion  there  will  be  an  irrecoverable  loss  in  the 
form  of  heat  which  escapes  ;  but,  as  we  know^,  the  whole  of  ani- 
mal life  is  arranged  with  a  view^  to  this  continual  loss     It  is  not, 

^  Huxley  and  Martin,  Elementary  Biology,  lesson  v. 


THE    MAMMARY    GLAND, 


561 


theivfore.  unreasonable  thoucrli  opposed  to  established  ideas  to 
suppose  that  the  animal  protoplasm  is  as  constructive  as  the 
vegetable  protoplasm,  the  difference  between  the  two  being  that 
the  former,  unlike  the  latter,  is  as  destructive  as  it  is  construc- 
tive, and  therefore  requires  to  be  continually  fed  with  ready  con- 
structed material. 


Tcnninaiion  of  portion  of 
Milk-duct  ill  a  cluster  of  fol- 
licles; from  a  mercurial  in- 
jection ;  enlarged  four  times. 


The  Mammary  Gland. 

[Physiological  Anatomy  of  the  Mammary  Gland. — The 
mammary  gland  is  a  compound  racemose  gland,  and,  like 
others  of  its  type,  consists  of  a  number  of  lobes,  composed 
of  smaller  divisions  or  lobules  ;  these 
lobules   in   turn   being    made  up   of  n..  i;;, 

smaller  divisions  or  follicles,  which 
form  a  cluster  on  one  of  tlie  terminal 
ducts.  (Fig.  147.)  They  are  com- 
posed of  a  basement  membrane 
which  is  lined  with  glandular  epi- 
thelium. Each  lobule  lias  a  common 
duct,  whicli,  uniting  with  the  ducts, 
from  other  lobules,  and  these  re- 
uniting, form  al)Out  fifteen  or  twenty 
larger  ducts,  which  are  called  the 
lactiferous  or  galactophoroas  ducts. 

These  ducts  converge  as  they  approach  the  nipple,  at  the 
base  of  which  they  become  expanded  into  saccular  dilatations, 
which  act  as  receptacles  for  milk  during  the  period  of  lacta- 
tion. (Fig.  148.)  From  these  receptacles  the  milk  is  con- 
veyed to  the  surface  of  the  nipple,  through  the  final  ducts. 
Near  the  base  of  the  nipple  are  numbers  of  sebaceous  glands 
which  secrete  an  unctuous  fluid,  which  acts  as  a  protection 
to  the  nipple  and  parts  immediately  surrounding  during  the 
act  of  sucking. 

The  ducts  consist  of  a  fibrous  coat,  which  is  composed  of 
fibrous,  elastic,  and  unstriated  muscular  tissue.  This  coat  is 
lined  with  a  mucous  membrane,  consisting  of  a  basement 
membrane  witli  pavement  or  spheroidal  epithelium. 

The  gland  is  invested  with  a  fibrous  tissue  wliich  pene- 
trates the  substance  of  the  organ  between  the  lobules.  This 
tissue  contains  the  nerves  and  vessels,  witli  a  very  large 
amount  of  fat.  The  capillaries  form  a  plexus  around  the 
follicles.] 

Since  milk  is  a  secretion,  and,  indeed,  an  excretion,  the 
mammary  gland  ought  not  to  be  classed  as  a  metabolic  tis- 
sue, in  the  limited  meanino;  we  are  now  attaching  to  those 


562      THE    METABOLIC    PHENOMENA    OF    THE    BODY. 

words.  Yet  the  metabolic  phenomena  giving  rise  to  the 
secretion  of  milk  are  so  marked  and  distinct,  and  have  so 
many  analogies  with  the  purely  metabolic  events  in  adipose 
tissue,  that  it  will  he  more  convenient  to  consider  the  matter 
here,  rather  than  in  any  other  connection. 

["Fig.  14S. 


Distribution  of  ilie  Milit-aucts  in  the  Mamma  of  the  Human  Female,  during 
Lactation;  the  ducts  injected  with  wax.] 

Human  milk  lias  a  specific  gravity  of  from  1.02S  to  1.034, 
and  when  ([uite  fresh  possesses  a  slightly  alkaline  reaction. 
It  speedily  becomes  acid,  and  cow's  milk,  even  when  quite 
fresh,  is  sometimes  slightly  acid,  the  change  of  reaction 
taking  place  during  the  stagnation  of  the  milk  in  the  mam- 
marv  ducts. 


The  constituents  of  milk  are : 


MILK.  563 

1.  Proteids,  viz.,  casein,  and  an  albumin,  agreeing  in  its 
general  features  with  ordinary  serum-'dhuniin.  Tlie  casein 
may  be  tlirovvn  down  by  tbe  careful  addition  of  acetic  acid; 
but  the  most  complete  precipitation  is  effected  by  first  adding 
to  tiie  milk  a  sliglit  quantity  of  acetic  acid,  and  then  pass- 
ing through  it  a  stream  of  carbonic  acid.  From  the  filtrate 
the  serum-all)umin,  which  is  present  in  small  and  variable 
quantities,  may  be  obtained  by  coagulation  with  heat,  or  by 
precipitation  with  i)otassium  ferrocyanide,  etc. 

2.  Fats.     These  are  palmitin,  stearin,  and  olein. 

There  are  present  also,  to  the  extent  of  about  2  per  cent,  of  the 
total  fat,  the  glycerides  of  butyric,  capronic,  caprylic,  and  my- 
ristinic acids. 

3.  Milk-sugar,  the  conversion  of  which  into  lactic  acid 
gives  rise  to  many  of  the  features  of  milk. 

4.  Extractives,  including,  according  to  some  observers, 
urea  and  salts.  The  last  consists  chiefiy  of  potassium  phos- 
phate, with  calcium  phosphate,  j)otassium  chloride,  small 
quantities  of  magnesium  phospliate,  and  traces  of  iron. 

The  following  is  the  c  imposition  of  1000  parts  of 


Casein,      .  .         .         , 

Albumin, 

Fat,  .  .         .         , 

fSugar,       .  . 

Salts,         .  '  . 

Total  solids,     . 

Water,      .... 

Milk  is  an  emulsion,  the  fats  existing  in  the  form  of  glob- 
ules of  various  but  minute  size,  each  protected  by  a  thin 
envelope  of  casein -or  albumin.  Jt  is  this  condition  of  the 
fat  which  gives  to  milk  its  peculiar  white  color.  (Fig.  149.) 
The  olostrum  or  secretion  of  the  mammary  gland  at  the 
beginning  of  lactation,  differs  from  milk  in  being  very  de- 
ficient in  casein,  and  proportionately  rich  in  all)umin.  It  is 
said  that  the  milk  at  the  end  of  a  long  lactation  again  be- 
comes poor  in  casein  and  rich  in  albumin.  Milk  on  stand- 
ing turns  sour  and  curdles.     This  is  due  to  the  milk-sugar 


IIuiiiRn  milk. 

Cow's  milk, 

.     39.24 

48.28 

. 

5.76 

.     26.6(3 

43.05 

.     43.64 

40.37 

.       1.38 

5.48 

.  110.92 

142.94 

.  889.08 

857.06 

5'')4      THE    METABOLIC    PHENOMENA    OF    THE    BODY. 

becominor  converted  by  a  fermentative  process  into  lactic 
acid,  which  in  tnrn  precipitates  the  casein.  The  change 
may  be  rapidly  lironght  about  by  means  of  a  ferment  con- 
tained in  the  gastric  membrane.     (See  p.  324.) 

Milk,  like  the  other  secretions  which  we  have  studied,  is 
the  result  of  the  activity  of  certain  protoplasmic  secreting 
cells  forming  tiie  epithelium  of  the  mammary  gland.  As 
far  as  the  fat  of  milk  is  concerned,  the  processes  taking 
place  in  the  gland  are  very  instructive,  since  the  fat  can  he 
seen  to  be  gathered  in  the  epithelium-cell,  in  the  same  way 
as  in  a  fat-cell  of  the  adipose  tissue,  and  to  be  discharged 
into  the  channels  of  the  gland,  either  by  a  breaking  up  of 
the  cells,  or  by  a  contractile  extrusion   very  similar  to  that 

[Fig.  149. 


Microscopic  appearance  of  Human  Milk,  with  au  intermixture  of  Colostric 
Corpuscles.] 

which  takes  place  when  an  amoeba  ejects  its  digested  food. 
All  the  evidence  we  possess  goes  to  prove  that  the  fat  is 
formed  in  the  cell  through  a  metabolism  of  the  protoplasm. 
The  microscopic  history  is  thoroughly  supported  by  other 
facts.  Thus  the  quantity  of  fat  present  in  milk  is  largely 
and  directly  increased  by  proteid,  but  not  increased,  on  the 
contrary  diminished,  by  fatty  food.'  This  is  quite  intelligi- 
ble when  we  know,  as  vvill  be  shown  in  a  succeeding  section, 
that  proteid  food  increases,  and   fatty  food  diminishes  the 


Subbotin  and  Kemmerich,  Cbl.  Med.  Wiss.,  1866,  p.  337. 


MILK.  565 

metabolism  of  the  body;  and  we  have  ab'eadv  discussed 
the  manner  in  wiiicli  proteid  material  may  give  rise  to  fat. 
A  bitch  fed  on  meat  for  a  given  period  gave  of!'  more  fat  in 
her  milk  than  she  could  po!-sil»ly  have  taken  in  her  food,  and 
that  too  while  she  was  gaining  in  weiglit,  so  that  siie  could 
not  have  supplied  tlie  mammary  gland  with  fat  at  the  ex- 
pense of  fjxt  previously  existing  in  her  body.  In  the  ''ripen- 
ing" of  ciieese  we  have  a  similar  conversic)n  of  proleids 
into  fat.  We  have  also  evidence  tiiat  the  casein  is.  like  tiie 
fat,  formed  in  the  gland  itself.  When  milk  is  kept  at  35^  C. 
out  of  the  body  the  casein  is  increased  at  the  expense  of  the 
albumin.  When  the  action  of  the  cell  is  imperfect,  as  at 
the  beginning  or  end  of  lactation,  the  albumin  is  in  excess 
of  the  casein  ;  but  as  long  as  the  cell  possesses  its  pr.)per 
activity'  the  formation  of  casein  becomes  prominent,  it  has 
been  suggested  that  the  casein  may  be  formed  by  a  splitting 
up  of  albumin  by  some  fermentative  process,  but  no  such 
ferment  has  yet  been  isolated.  That  the  milk-sugar  also  is 
formed  in  and  i)y  tiie  protoplasm  of  ti»e  cell,  is  indirated  by 
the  fact  that  the  sugar  is  not  dependent  on  carbohydrate 
food,  and  is  maintained  in  abundance  in  tiie  uiilk  of  carniv- 
ora  when  these  are  fed  exclusively  on  meat,  as  free  as  pos- 
sible from  any  kind  of  sugar  or  glycogen.  We  thus  have 
evidence  in  the  mammary  gland  of  the  formation,  by  the 
direct  metabolic  activity  of  the  secreting  cell,  of  the  repre- 
sentatives of  the  tliree  great  classes  of  food-stuffs,  proteids, 
fats,  and  carboliydrates,  out  of  the  comprehensive  substance 
protoplasm.  And  what  we  see  taking  i>lace  in  the  mammary 
cell  is  probably  a  picture  of  what  is  going  on  in  all  proto- 
plasmic bodies.  If  the  fat  of  the  milk  were  not  ejected 
from  the  mammary  cell,  the  mammary  gland  would  become 
a  mass  of  adipose  tissue,  especially  if,  \ty  a  slight  change  in 
the  metabolism,  the  production  of  fat  were  exalted  at  the 
expense  of  the  production  of  casein  or  milk-sugar.  If,  again, 
by  a  similar  slight  change  the  milk  sugar  were  accumulated 
rather  than  the  fat  or  proteid,  we  should  have  a  result  which, 
!)}•  an  easy  step,  woidd  l)ring  us  to  glycogenic  tissue.  And, 
lastly,  if  the  proteid  accumulation  were  greater  than  the 
fatt}'  or  the  saccharine,  these  being  carried  off  in  some  way 
or  other,  we  should  have  an  image  of  the  nutrition  of  an 
ordinary  nitrogenous  tissue. 

That  both  the  secretion  and  ejection  of  milk  are  under  the 
control  of  the  nervous  system  is  shown  by  common  experience, 

48 


566       THE    METABOLIC    PHENOMENA    OF    THE    BODY. 


but  the  exact  nervous  mechanism  has  not  yet  been  fully  worked 
out.  While  erection  of  the  nipple  ceases  when  the  spinal  nerves 
which  supply  the  breast  are  divided,  the  secretion  continues,  and 
is  not  arrested  even  when  the  sympathetic  as  well  as  the  spinal 
nerves  are  cut.^ 

The  SpleeM. 

[Physiological  Anatomy  of  the  Spleen. — The  spleen  is  a 
ductless  u'land.  It  is  covered  with  a  fihro-elastic  coat  or 
capsule,  which  is  reflected  inwards  at  the  hilum  as  a  sheath 

Fig.  150. 


Branch  of  Splenic  Artery,  the  ramifications  of  which  are  studded  with  Malpigliiau 

Corpuscles. 

for  the  bloodvessels.  From  the  whole  of  the  inner  surface 
of  the  capsule  numerous  prolongations  called  trabeculde  are 
continued  into  the  substance  of  the  organ,  and  these  unit- 
ing with  similar  trabeculse  given  off  from  the  sheaths  of 
the  vessels,  form  the  framework  or  ntroma.  The  trabeculne 
consist  of  yellow  and  white  elastic  tissue  containing  un- 
striated  muscular  fibres,  and  form  by  their  interlacements 


1  Eckhard,  Beitriige,  i  and  viii  (1877),  p.  117.     Rohrig,  Virchow's 
Archiv,  Ixvii  (1876),  p.  119. 


THE    SPLEEN. 


667 


numerous  irregular  spaces,  called  loculi^  which  contain  the 
splenic  subxtauce  ov  pulp.  This  pulp  is  of  a  reddish-brown 
color,  and  of  a  soft  granular  consistence;  containing  hlood 
disks  (some  of  which  have  undergone  retrograde  metamor- 
phosis), colorless  corpuscles,  nuclei,  nucleated  cells,  pig- 
ment cells,  and  extractions.  Running  through  this  pulp  is 
an  extremely  delicate  fibrous  network  containing  blood 
capillaries. 

Along  the  ramifications  of  the  splenic  artery  are  seen 
numerous  ovoid,  opaque  whitish  bodies,  which  are  called 
the  Malpighian  corpuaclea.  (Fig.  150.)  The}'  appear  upon 
the  vvalls  of  the  vessels  as  budding  processes,  each  of  them 

Fig.  151. 


liTalpi^chian  Corpuscle  from  the  Spleen  of  the  Hedj^ehog,  with  its  vascular  supply. 
b,  splenic  pulp,  with  the  intermediary  blood-passages  ;  c,  the  rootlets  of  the  veins. 

being  invested  by  a  capsule  which  is  formed  by  an  expan- 
sion of  the  sheath  of  tlie  vessel.  They  are  covered  with 
plexuses  of  capillaries,  which  send  loops  into  the  interior  of 
the  corpuscles.  The  substance  of  the  corpuscles  consist  of  a 
white  semifluid  all)uminous  material,  containing  nuclei,  nu- 
cleated cells  and  granular  matter,  which  are  supported  in  a 
stroma  of  filirillar^  tissue  and  capillary  loops.  The  veins 
arise  within  the  spleen  either  as  continuations  of  the  arte- 
rial capillaries,  as  intercellular  passages,  or  as  ca^'cal  pouches. 
The  capacity  of  the  veins  is  about  twice  that  of  the  arteries. 
The  nerves  are  derived  from  the  syra[)athetic  and  right 
pneumogastric] 

The  spleen  may  be  wholly  removed  from  an  animal  with- 
out an}^  obvious  changes  in  the  economy  taking  place ;  the 


i 

568      THE    METABOLIC    PHENOMENA    OF    THE    BODY. 

functions  of  the  rest  of  tlie  body  appear  to  2:0  on  unim- 
paired. We  are  ol)liged  to  assume  that  some  compensating 
actions  take  place;  but  wiiat  those  actions  are  we  do  not 
know,  and  we  are  left  at  present  by  these  experiments  al- 
most completely  in  the  dark  as  to  the  functions  of  the  spleen. 
Tiie  most  that  has  been  observed  is  a  slight  increase  in  the 
lymphatic  glands,  and  in  the  activity  of  the  medulla  of 
bones. 

Schiff'  maintains  that  after  extirpation  of  the  spleen,  pancre- 
atic juice  is  no  longer  able  to  digest  proteids.  He  believes  that 
the  spleen  during  its  turgescence  manufactures  a  substance, 
which  being  carried  to  the  pancreas,  gives  rise  by  a  kind  of  fer- 
ment action  of  its  own  to  the  pancreatic  proteolytic  ferment. 
Tn  the  language  of  Heidenhain's  results,  the  presence  of  the 
splenic  product  is  necessary  for  the  conversion  of  the  zymogen 
into  the  pancreatic  proteolytic  ferment.  Herzen-  further  states 
that  in  the  exceptional  cases  where  the  spleen  does  not  become 
turgid  during  digestion,  the  pancreatic  juice  is  inert  towards  pro- 
teids.  The  evidence  in  favor  of  this  action  of  the  spleen  is,  at 
present,  not  coirent,  and  Mosler-  denies  that  extirpation  of  the 
spleen  has  any  influence  whatever  over  either  gastric  or  pancre- 
atic digestion. 

After  a;  meal  the  spleen  increases  in  size,  reaching  its 
maximum  about  five  hours  after  the  taking  of  food  :  it  re- 
mains swollen  for  some  time,  and  then  returns  to  its  normal 
bulk.  In  certain  diseases,  such  as  in  the  pyrexia  attendant 
on  fevers  or  inflammations,  and  more  especially  in  ague,  a 
similar  temporary  enlargement  takes  place.  Jn  prolonged 
ague  a  permanent  hypertrophy  of  the  spleen,  the  so-called 
ague-cake,  occuis. 

The  turgescence  of  the  spleen  seems  to  be  due  to  a  relax- 
ation both  of  the  small  arteries  and  of  the  muscular  bands 
of  the  trabecuhtt;  to  be,  in  fact,  a  vaso-motor  dilation  ac- 
companied by  a  local  inhibition  of  the  tonic  contraction  of 
the  other  plain  muscular  fibres  entering  into  the  structure 
of  the  organ.  And  the  condition  of  the  spleen,  like  that  of 
other  vascular  areas,  appears  to  be  regulated  by  the  central 
nervous  system,  the  digestive  turgescence  being  altogether 
con)i)arable  to  the  flushed  condition  of  the  jiancreas  and  the 
gastric  membrane  during  their  phases  of  activit}'. 

'  Schweiz.  Zt.  f.  Heilk.,  i  (1862),  p.  209.  See  also  Lemons  sur  la  Di- 
gestion. 

2  Cbt.  f.  Med.  Wiss.,  1877,  p.  435. 

3  Cbt.  f.  Med.  Wiss.,  1871,  p.  290. 


THE    SPLEEN.  569 


According  to  Tnrcbanoff"'  section  of  the  splenic  nerves  causes 
a  turgescence  lasting  for  some  time,  but  disappearing  in  the  course 
of  a  few  days.  Stimulation  of  the  spinal  cord  causes  a  shrink- 
ing, which,  however,  fails  to  make  its  appearance  if  the  splanch- 
nic nerves  be  previousl}^  divided.  Tlie  shrinking  or  constiiction 
may  be  brought  about  in  a  reflex  manner  by  stimulation  of  the 
central  stump  of  the  sciatic  nerve.  The  effect,  however,  is  in  the 
case  of  this  nerve  slight,  whereas  if  the  central  stump  of  the  va- 
gus be  stimulated,  a  very  marked  shrinking  is  observed.  Local 
stimulation  causes  local  shrinking  ;  if  the  electrodes  of  an  inter- 
rupted current  be  drawn  across  a  turgid  spleen,  their  course  is 
marked  by  a  white  line  of  constriction  lasting  for  some  little 
time.  Contraction  of  the  spleen  is  also  caused  by  quinine  and 
strychnia. 

This  functional  intermittent  turgescenee.  so  clearly  re- 
lated to  the  ingestion  of  food,  may  be  connecled  with  that 
manufacture  of  white  corpuscles  and  destruction  of  red  cor- 
puscles of  the  blood  of  which  we  spoke  in  an  early  chapter 
(p.  57);  but  when  the  peculiar  arrangements  of  the  blood- 
vessels of  the  spleen,  with  their  large  open  venous  networks, 
are  borne  in  mind,  it  seems  in  the  highest  degree  prol)al)le 
that  metabolic  events  of  great  importance  (possibly  associ- 
ated in  some  way  with  the  metamorphosis  of  the  blood-cor- 
puscles) take  place  in  the  spleen,  though  at  present  we  are 
unable  to  follow  them.  And  this  view  is  supported  by  the 
som.ewhat  peculiar  chemical  characters  of  the  spleen-pulp, 
which,  in  spite  of  its  containing  a  very  large  number  of  blood- 
corpuscles,  differs  markedly  in  its  chemical  composition  from 
either  blood  or  serum.  Thusa  special  proteid  of  thenature 
of  alkali  albumin  seems  to  be  present,  holding  iron  in  some 
way  peculiarly  associated  with  it.  The  occurrence  of  this 
ferruginous  proteid,  accompanied  as  it  is  by  several  peculiar 
but  at  present  little  understood  pigments,  rich  in  carl)on, 
bears  out  the  histological  conclusions  concerning  the  disap- 
pearance of  the  red  corpuscles.  The»inorganic  salts  of  the 
spleen,  or  at  least  those  of  its  ash,  are  remarkable  for  the 
large  amount  of  both  soda  and  phosi)hates,  and  the  scanti- 
ness of  the  potash 'and  chlorides  which  they  contain,  thus 
differing  from  blood-corpuscles  on  the  one  hand,  and  from 
blood-serum  on  the  other.  But  perhaps  the  most  striking 
feature  of  the  spleen-pulp  is  its  richness  in  the  so  called  ex- 
tractives. Of  these  the  most  common  and  plentiful  are 
succinic,  formic,  acetic,  but3'ric  and  lactic  acids  (these  may 

1  Pfliiger's  Archiv,  viii  (1874),  p.  97. 


570       THE    METABOLIC    PHENOMENA    OF    THE    BODY. 

arise  in  part  from  tlie  decomposition  of  htemoolobin),  inosit, 
leucin.  xantliin,  hypoxanthin,  and  uric  acid.  Tyrosin  appar- 
ently is  not  present  in  the  perfectly  fresh  spleen,  though  leu- 
cin is  ;  both  are  found  when  decomposition  has  set  in.  The 
constant  presence  of  uric  acid  is  remarkaide,  especially  since 
it  has  been  found  even  in  the  Sj)leen  of  animals,  such  as  the 
herbivora,  vviiose  urine  contains  none.  No  less  suggestive 
is  the  fact  that  the  increase  of  uric  acid  in  the  urine  during 
ague,  and  during  ordinary  pyrexia,  seems  to  run  parallel  to 
the  turgescence,  and  therefore  presumably  to  the  activity,  of 
the  spleen.  But  these  facts  are  at  present  suggestive  only  ; 
they  point  to  an  active  metabolism  ai^sociated  with  digestion 
taking  place  in  the  spleen  ;  exact  information  as  to  the  natui-e 
of  the  metabolism  is  however  wanting.  The  thyroid  and 
thymus  bodies,  often  in  descriptions  associated  with  the 
spleen,  though  different  in  structure,  the  former  absolutely 
so,  resemble  the  spleen  somewhat,  as  far  as  their  extractives 
are  concerned.  The  thymus  contains  leucin,  xanthin,  and 
hypoxantiiin,  with  lactic  and  succinic  acids  ;  uric  acid  seems 
to  be  absent.  The  extractives  of  the  thyroid  are  scanty,  but 
apparently  of  tiie  same  nature. 

Sec.  2.    The  History  of  Urea  and  its  Allies. 

We  may  now  return  to  the  questions  which  we  left  un- 
answered at  p.  537.  Where  is  urea  formed  ?  What  are  its 
immediate  antecedents?  What  are  the  various  chemical 
links  between  it  and  the  proteid  material  of  wldch  it  is  the 
excretory  rejij^esentative  ? 

We  have  seen,  p.  100,  that  the  muscular  tissues  contain 
kreatin,  together  with  smaller  (piantities  of  allied  nitro- 
genous crystalline  l)0(lies,  such  as  xanthin,  hypoxanthin,. 
etc. ;  and  we  cannot  go  far  wrong  in  supposing  that  tiiese 
bodies  are  in  some  way  or  other  the  products  of  muscular 
metabolism.  We  do  not  know  in  what  quantities  they  are 
formed  ;  but  since  tiiey  are  such  bodies  as  would  readily  be 
carried  away  from  the  muscle  by  the  blood-stream,  and  yet 
are  always  to  be  found  in  the  muscle,  w^e  infer  that  they  are 
continually  being  formed,  and  as  continually  being  converted 
into  some  other  bodies  and  carried  away.  And  we  may 
further  say,  that  since  kreatin  exists  in  muscle  to  the  extent 
of  .2  or  .4  per  cent.,  and  since  muscle  forms  so  large  a  por- 
tion of  the  whole  body,  it  is  at  least  possible,  if  not  prob- 
able, that  a  considerable  amount  of  kreatin  passes  within 


UREA.  571 

twenty-four  hours  into  the  blood,  on  its  way  to  becojne 
transformed  by  other  tissues  into  urea,  or  into  some  stage 
nearer  to  urea  than  itself. 

The  urine  contains  a  certain  amount  (.9  gram  in  twenty-four 
hours)  of  kreatin,  or  kreatinin,  into  which  kreatin  is  easily  con- 
verted ;  but  neither  of  these  can  be  considered  as  the  normal  form 
in  which  the  kreatin  of  the  muscles  passes  out  of  the  body.  For 
the  urinary  kreatin  is  exceedingly  variable  in  quantit}',  vanishes 
during  starvation,  and,  though  not  at  all  increased  by  exercise,  is 
largely  augmented  by  a  tlesh-diet ;'  and  kreatin  injected  into  the 
biood,*^even  in  small  quantities,  reappears  unchanged  in  the  urine. 
Without  laying  too  much  stress  on  the  last  fact,  we  are  led  to 
conclude  that  the  kreatin  or  kreatinin  in  urine  has  an  origin  quite 
independent  of  that  which  is  present  in  the  muscles,  being  prob- 
ably derived  directly  from  the  food. 

AVith  regard  to  the  substances,  such  as  xanthin,  which  appear 
in  muscle  tn  small  quantities  only,  our  information  is  too  imper- 
fect to  allow  us  to  make  any  statement  whatever  about  them. 

While,  then,  we  have  some  reason  for  thinking  that  the 
kreatin  found,  and  presumably  formed,  in  muscle  is  a  more 
or  less  distant  antecedent  of  urea,  it  must  be  remembered 
that  this  is  simply  a  more  or  less  probable  view,  not  an 
ascertained  or  clearly  proven  fact. 

Of  the  metabolism  of  the  nervous  tissues  we  know  little; 
but  kreatin  is  found  in  the  brain,  in  some  cases  in  not  incon-. 
siderable  quantity.  Now  the  bodies  of  the  nerve-cells  are 
undoubtedly  comi)Osed  of  protoplasm  ;  the  axis-cylinders 
of  the  nerve-tibres  are  also  protoplasmic  in  nature,  and  it  is 
at  least  possible  that  much  of  the  peculiar  matrix  of  the 
cerebral  and  cerebellar  convolutions,  and  of  the  gray  matter 
generally,  is  also  in  reality  protoplasmic.  Hence  we  may, 
witii  a  certain  amount  of  reason,  suppose  that  the  nervous, 
like  the  muscular  tissues,  are  continually,  but  to  a  much 
less  extent,  supplying  an  antecedent  to  urea  in  the  form  of 
kreatin. 

Lastly,  the  spleen  contains  a  considerable  quantity  of 
kreatin,  as  well  as*  of  xanthin,  etc.;  and  these  are  present 
also  in  vai'ious  glandular  organs. 

We  thus  have  evidence  of  a  continual  formation  of  krea- 
tin. possibly  in  large  quantities,  in  various  parts  of  the  body. 
On  the  other  hand,  urea  is  certainly  not  present  in  muscle 

'  Volt,  Zt.  f.  Biol.,  iv,  p.  77. 


572      THE    METABOLIC    PHENOMENA    OF    THE    BODY. 

(save  in  certain  exceptional  cases),  and  its  ])resence  in 
nervous  tissue  is  extremely  doubtful.  It  is  absent  from  tiie 
spleen  (of  the  occurrence  of  urea  in  the  liver  we  shall 
speak  presently),  the  thymus,  and  thyroid  bodies,  and 
from  the  lymphatic  glands,  thoiigh  uric  acid,  as  we  have 
seen,  appears  to  be  a  normal  constituent  of  the  spleen.  It 
seems  very  tempting  to  jumj)  at  once  from  these  facts  to  the 
conclusion  that  kreatin  is  the  ^latural  antecedent  of  urea, 
and  that  as  far  as  nitrogenous  excretion  is  concerned  the 
labor  of  the  kidney  is  confined  to  the  simple  transformation 
of  kreatin  into  urea.  We  have  only  to  suppose  that  the 
kreatin  passes  from  these  several  tissues  into  the  blood,  in 
which  it  may  1)6  found,  and  while  circulating  in  the  blood 
is  seized  upon  by  the  renal  epithelium  and  converted  into 
urea.  And  there  are  some  facts  which  support  this  view. 
But  there  are  others  which  oppose  it;  and  while  it  cannot 
be  said  to  be  wholly  disproved,  it  cannot  at  piesent  be  ac- 
cepted as  sufficiently  satisfactoiy  to  serve  as  a  foundation 
for  other  arguments. 

In  the  first  place,  urea,  in  spite  of  its  absence  from  the  muscles 
and  other  tissues,  is  always  ])resent  in  the  blood,  and  has  also 
been  found  in  the  chyle,  in  the  serous  tluids,  and  in  saliva.  It 
might  be  urged,  of  course,  that  this  urea  is,  so  to  speak,  an  over- 
flow from  the  kidney,  that  owing  to  its  great  ditfusibility  it  has 
passed  back  from  the  renal  epithelium  where  it  was  manufac- 
tured into  the  blood-stream.  When,  how^ever,  we  reflect  how 
all  diffusion  is  overborne  by  the  natural  physiological  currents, 
as  shown  indeed  by  the  absence  of  urea  from  muscle,  in  spite  of 
its  presence  in  the  blood,  this  argument  loses  all  the  little  force 
it  had. 

In  certain  diseases  of  the  kidney,  the  excretion  of  urine  ceases. 
This  suppression  of  urine,  as  it  is  called,  is  followed  bv  an  accu- 
mulation of  urea  in  the  blood  and  all  parts  of  the  body,  and  is 
acL'ompanied  b}^  symptoms  known  as  those  of  ura?mic  poisoning, 
though  the  toxic  consequences  are  due  not  to  the  presence  in  the 
system  of  the  larije  quantity  of  urea,  but  of  other,  at  present  un- 
defined, substances  wiiich  have  at  the  same  time  ceased  to  be 
excreted.  Oppler'  and  Zalesky  stated  that  when  the  kidneys  of 
an  animal  were  extirpated,  or  the  renal  arteries  ligatured,  though 
ursemic  symptoms  set  in  as  usual,  there  was  no  accumulation  of 
urea  in  the  blood  or  tissues,  and  no  excess  of  carbonic  acid  or 
ammonium  carbonate,  such  as  might  have  arisen  from  a  rapid 
decomposition  of  urea.  There  was,  however,  a  marked  accumu- 
lation of  kreatin  or  of  kreatinin.     On  the  other  hand,  these  ob- 


'   \'irchow's  Arcliiv,  xxi,  p.  2t50. 


UREA.  573 


servPL-s  found  that  when  the  ureters  were  ligatured,  so  that  the 
blood  was  still  brought  uuder  the  influence  of  the  renal  epithe- 
lium, and  yet  the  products  of  the  activity  of  that  epithelium  not 
allowed  to  escape,  an  accumulation  of  urea  (in  birds  of  uric  acid) 
and  not  of  kreatin  was  observed.  These  results,  if  indisputable, 
would  indeed  aflbrd  strong  evidence  of  the  conversion  of  kreatin 
into  urea  by  the  agency  of  the  renal  epithelium.  They  have, 
however,  been  much  disputed.  Thus  Gr'hant,'  using  what  was 
probably  a  better  method  for  the  estimation  of  urea  (and  the  de- 
tection of  urea  in  complex  organic  fluids  is  subject  to  very  con- 
siderable errors),  came  to  the  conclusion  that  the  urea  in  the 
blood,  after  extirpation  of  both  kidneys,  rose  from  .0'2(5  and  from 
.088  to  .206  and  .270  per  cent,  in  24  and  27  hours  respec- 
tively. And  Gscheidlen-  has  come  to  a  similar  conclusion.  The 
results,  according  to  both  these  latter  observers,  are  the  same 
whether  the  kidneys  are  extirpated  or  the  ureters  tied  ;  in  the 
latter  case  the  distension  of  the  tubules  soon  renders  the  epithe- 
lium cells  incapable  of  performing  their  functions,  and  thus  an 
animal,  in  which  the  ureters  have  been  ligatured,  is  practically 
in  the  same  condition  as  one  from  which  the  kidneys  have  been 
removed.  Neither  Grehant  nor  Gscheidlen  makes  an}'  state- 
ment about  an  increase  of  kreatin.  And  it  may  be  worth  while 
to  notice  that  though  the  experiments  of  these  observers  prove 
that  all  the  urea  of  the  urine  is  certainly  not  formed  in  the  kid- 
ue)',  they  do  not  necessarily  oppose  the  view  that  some  of  it  may 
be  so  formed  out  of  kreatin  or  some  similar  antecedent.  Nor  fs 
there  anything  a  priori  to  contradict  the  supposition  that  the 
origin  of  urea  may  be  double,  part  being  formed  in  one  wa}'  and 
part  in  another.  Lastl}',  the  fact  that  urea  injected  into  the 
blood  causes  a  rapid  secretion  of  urine,  may  be  used  as  an  argu- 
ment that  the  habit  of  the  renal  epithelium  is  to  pick  out,  so  to 
speak,  the  urea  from  the  blood  and  to  carry  it  into  the  channels 
of  the  renal  tubules. 

There  is.  moreover,  another  possible  souice  of  urea  be- 
sides the  kreatin  formed  in  muscle  and  elsewhere.  We 
have  seen  that  one  result  of  I  lie  action  of  the  pancreatic 
juice  is  the  formation  of  considerable  quantities  of  leuein 
and  tyrosin.  In  dealing  with  tlie  statistics  of  nutrition,  our 
attention  will  be  drawn  to  the  fact  that  the  introduction  of 
proteid  matter  into  the  alimentary  canal  is  followed  by  a 
large  and  rapid  excretion  of  urea,  suggesting  the  idea  that 
a  certain  part  of  the  total  quantity  of  the  urea  normally 
secreted  comes  from  a  direct  metabolism  of  the  proteids  of 
the  food,  without  these  really  forming  a  part  of  the  tissues 

1  Cbt.  Med.  Wiss.,  1870,  p.  249. 

2  ^tudien  ii.  d.  Ursprnng  d.  Harnstofls,  Leipzig,  1871. 


574      THE    METABOLIC    PHENOMENA    OF    THE    BODY. 

of  the  body.  We  do  not  know  to  what  extent  normal  pan- 
creatic digestion  lias  for  its  product  leucin,and  its  compan- 
ion tyrosin  ;  but  if,  especially  when  a  meal  rich  in  proteids 
has  been  taken,  a  considerable  quantit}-  of  leucin  is  formed, 
we  can  perceive  an  eas}'  and  direct  source  of  urea,  provided 
that  the  metabolism  of  the  bod}'  is  capable  of  converting 
leucin  into  urea.  That  the  l)ody  can  effect  this  change  is 
shown  by  the  fact  that  leucin,  when  introduced  into  the  ali- 
mentar}'  canal  in  even  large  quantities,  does  reappear  in  the 
urine  as  urea;  that  is,  the  urine  contains  no  leucin,  but  its 
urea  is  proportionately  increased  ;  and  the  same  is  i)robably 
the  case  with  ty rosin,  though  this  is  disputed.  Now  the 
leucin  formed  in  the  alimentary  canal  is  probably  can-ied 
by  the  portal  blood  straigiit  to  the  liver ;  and  the  liver, 
unlike  other  glandular  organs,  does,  even  in  a  perfectly 
normal  state  of  things,  contain  urea.  We  are  thus  led  to 
the  view  that  among  the  numerous  metabolic  events  which 
occur  in  the  hepatic  cells, the  formation  of  urea  out  of  leucin 
or  of  other  antecedents  may  be  ranked  as  one.  Probable, 
however,  as  this  view  may  appear,  it  has  not  as  yet  been 
established  as  a  fact. 

Meissner'  found  a  large  quantity  of  urea  in  the  liver  of  mam- 
mals, and  of  urates  in  the  liver  of  birds.  Cyon"''  attempted  to 
demonstrate  the  formation  of  urea  in  the  liver  by  passing  a  stream 
of  fresh  blood  through  the  liver  of  an  animal  recently  killed,  and 
estimating  the  percentage  of  urea  in  the  blood  used  before  and 
after.  He  found  it  to  be  increased  from  .08  to  .176.  This,  how- 
ever, is  not  conclusive  ;  for,  as  Gscheidlen  has  urged, =^  the  in- 
creased quantity  in  the  blood  which  had  been  circulated  might 
have  been  sinq)ly  urea  which  had  been  washed  out  from  the 
liver,  where  it  had  previously  been  staying.  A  strong  presump- 
tion in  favor  of  urea  arising  through  the  hepatic  metabolism, 
from  leucin  as  an  antecedent,  is  afforded  by  the  fact  that  in  cases 
of  acute  atrophy  of  the  liver,  where  the  hepatic  cells  lose  their 
functional  activity,  the  urea  of  the  urine  is  replaced  by  leucin 
and  ty  rosin.  And,  lastly,  it  may  be  remarked  that  not  only  are 
leucin  and  tyrosin  found  in  nearly  all  the  tissues  after  death 
especially  in  the  glandular  tissues,  but  they  also  appear  with 
striking  readiness  in  almost  all  decompositions  of  proteid,  and, 
in  the  case  of  the  former,  of  gelatiniferous  substances. 

The  view  that  leucin  is  transformed  into  urea  lands  us,  how- 

'  Zt.  f.  rat.  Med.  (3j,  xxxi,  144. 

''  Cbt.  f.  Med.  Wiss.,  1870,  p.  580. 

'  Cf.  also  Mnnk,  PlUiger's  Arohiv,  xi  (1875),  p.  100. 


UREA.  575 


ever,  in  very  consideriible  difficulties.  Leucin,  as  we  know,  is 
amido-caproic  acid  ;  and,  with  our  present  chemical  knowledge, 
we  can  conceive  of  no  other  way  in  which  leucin  can  be  converted 
into  urea  than  by  the  complete  reduction  of  the  former  to  the 
ammonia  condition  (the  caproic  acid  residue  being  either  elabo- 
rated into  a  fat  or  oxidized  into  carbonic  acid),  and  l)y  a  recon- 
struction of  the  latter  out  of  the  ammonia  so  formed.  We  have 
a  somewhat  parallel  case  in  glycin.  This,  which  is  amido-acetic 
acid,  when  introduced  into  the  alimentary  canal,  also  reappears 
as  urea  ;  here,  too,  a  reconstruction  of  urea  out  of  an  ammonia 
phase  must  take  place.'  And  there  are  other  facts  which  point 
in  exactl}-  the  same  direction,  viz..  in  a  derivation  of  the  normal 
urea  of  the  urine  from  a  simple  ammonia  antecedent.  O.  Schult- 
zen-  finds  that  when  an  appropriate  quantity  of  sarcosin  is  given 
by  the  mouth,  urea  disappears  from  the  urine,  being  rejjlaced  b}' 
a  compound  of  sarcosin  and  carbamic  acid  (in  company  with  a 
compound  of  sarcosin  with  sulphamic  acid).  The  interpretation 
of  this  result  is  that  in  normal  metabolism  the  proteids  are  ulti- 
mately broken  down  to  carbamic  acid  and  ammonia,  which, 
uniting  and  becoming  subsequently  dehydrated,  form  urea  ;  thus 
CO.X.TI,;  ammonium  carbamate — R  0  =  CON  H^  urea  ;  but  the 
carbamic  acid,  having  a  greater  affinity  for  sarcosin  than  am- 
monia, seizes  the  former  in  preference  an  hen  it  is  at  hand,  and 
consequently  gives  rise  to  Schultzen's  compound. 

There  are,  however,  many  objections  to  Schultzen's  vievT  in 
respect  to  both  the  nature  and  the  mode  of  origin  of  the  com- 
pound described  by  him.-^  More  valid  is  the  argument  which 
may  be  drawn  from  the  fact  that  when  ammonium  chloride  is 
given  to  a  dog  a  very  large  portion  reappears  as  urea,  i.  e.,  there 
is  an  increase  in  the\irea  of  the  urine  corresponding  to  a  large 
portion  of  the  nitrogen  contained  in  the  ammonium  chloride.* 
But,  even  gi*anted  that  the  urea  of  the  urine  may  be  formed  out 
of  ammonia,  there  still  remains  the  question,  Is  the  urea  formed 
by  the  union  of  ammonia  with  carbonic  acid  and  subsequent  de- 
hydration, the  whole  of  the  nitrogen  of  the  urea  coming  into  it 
as  ammonia,  or  by  the  union  of  ammonia  with  carbamic  acid  with 
dehydration,  as  advocated  by  Schultzen,  or,  lastly,  by  the  union 
of  ammonia  with  some  cyanogen  body  V  Our  information  will 
not  at  present  allow  us  to  decide  this  point,  though  arguments 
have  been  adduced  in  tavor  of  the  latter  view.^ 

'  Cf.  Salkowski,  Zt.'f.  Physiolog.  Chem.,  i  (1877),  1.  SchmiedeLeig, 
Archiv  1".  Exp.  Path.,  viii  (1877),  p.  1. 

2  Ber.  Deut.  Chem,  Gesell,  1872,  p.  578. 

3  Cf.  Hoppe-Sevler  and  Baumann,  Ber.  d.  Deutsch.  Chem.  Gesell,  vii, 
p.  34. 

*  Van  Knieriem,  Zt.  f.  Biol,  x  (1874),  p.  263.  Salkowski,  Zt.  f. 
Phvsiol.  Chem.,  i  (1877),  p.  1.  Munk,  ibid.,  ii  (1878),  p.  29.  Haller- 
vorden,  Arch.  f.  Exp.  Path.,  x  (1878),  p   125. 

^  Cf.  Salkowski,  op.  cit.,  and  see  Appendix  sub  voce  Urea. 


576       THE    METABOLIC     PHENOMENA    OF    TH^    BODY. 

To  sum  up  our  imperfect  knowledge  concerning  the  his- 
tory of  urea.  We  have  evidence,  not  exactly  complete,  but 
fairly  satisfactory,  that  a  part  at  least  of  the  urea  is  simply 
withdrawn  from  the  hlood  by  the  renal  epithelium.  The 
activity  of  the  protoplasm  of  tiie  secreting  cells  must,  there- 
fore, as  far  as  this  part  of  the  urea  is  oncerned.  be  confined 
to  alisorbing  the  urea  from  the  renal  Idood,  and  to  passing 
it  on  into  the  cavities  of  tiie  renal  tubules.  The  mechanism 
by  which  this  is  effected  we  cannot  at  present  fathom,  but 
it  seems  more  comparable  to  a  selection  of  food  than  to 
anytiiing  else  ;  the  cells  appear  to  treal  urea  much  in  the 
same  way  as  they  treat  indigo-carmine  (p.  .533).  The  ante- 
cedents of  tlie  urea  in  the  blood  are,  we  may  at  present 
suppose,  partly  the  kreatin  formed  in  muscle  and  elsewhere, 
partly  tiie  leucin  and  other  like  bodies  formed  in  the  ali- 
mentary canal  as  well  as  in  various  tissues.  The  trans- 
formation of  these  bodies  into  urea  may  take  place  in  the 
liver,  and  possibly  in  the  spleen,  but  we  have  no  exact  proof 
of  this,  nor  can  we  say  exactly  in  what  vvay  the  transforma- 
tion is  effected.  There  is  no  proof  of  any  body  existing  in 
the  blood  capable  of  efiecting  this  transformation  ;  and  we 
may  probably  rest  assured  that  in  this,  as  in  other  nietabolic 
events,  the  activity  exercised  in  the  change  comes  from 
some  tissue,  and  cannot  be  manifested  by  simple  blood 
plasma. 

Lastly,  it  is  possible  that  the  kidney  may,  besides  the 
simpler  duty  of  withdrawing  ready-formed  urea  from  the 
blood,  l)e  exercised  in  transforming  various  nitrogenous 
crystalline  bodies  to  serve  as  part  of  the  supph'  of  urea 
which  passes  from  it. 

Uric  Acid. — This,  like  urea,  is  a  normal  constituent  of 
urine,  and,  like  urea,  has  been  found  in  the  blood,  and  in 
the  liver  and  spleen.  We  have  already,  p.  570,  referred  to 
its  relations  with  this  latter  organ.  In  some  animals,  such 
as  birds  and  most  reptiles,  it  takes  the  place  of  urea  In 
various  diseases  the  quantity^  in  the  urine  is  increased  ;  and 
at  times,  as  in  gout,  uric  acid  accumulates  in  the  blood,  and 
is  deposited  in  the  tissues.  By  oxidation  a  molecule  of  uric 
acid  can  be  s[jlit  up  into  two  mf)lecules  of  urea,  and  a  mole- 

1  It  need  hardly  be  pointed  out  that  an  increase  in  the  quantity  of 
uric  acid  in  the  urine  must  be  distinguished  from  an  increase  in  the 
'prominence  of  uric  acid  due  to  the  precipitation  of  its  alkaline  salts. 


nippuRic  ACID.  577 

cule  of  me?oxalic  acid.  It  may,  therefore,  be  spoken  of  as 
a  less  oxidized  product  of  proteid  metaliolism  tlian  urea; 
hut  tiiere  is  no  evidence  whatever  to  show  that  the  former 
is  a  necessary  antecedent  of  the  latter;  on  the  contrar}',  all 
the  facts  known  go  to  show  that  the  appearance  of  uric  acid 
is  the  result  of  a  metabolism  slightly  diverging  from  that 
leading  to  nrea.  And  we  have  no  evidence  to  prove  that 
the  cause  of  the  divergence  lies  in  an  insutlicient  sup})ly  of 
oxygen  to  the  organism  at  large;  on  the  contrary,  uric  acid 
occurs  in  the  rajjidly  breathing  birds,  as  well  as  in  the  more 
torpid  reptiles.  It  has  been  urged^  that  birds,  though  breath- 
ing vvith  great  energy,  yet  consume  oxygen  to  such  an  ex- 
tent that  in  spite  of  their  income  they  are  always  in  lack  of 
it;  but  of  this  there  is  no  proof,  while  the  richness  of  their 
blood  in  red  corpuscles  points  in  the  opposite  direction. 
Nor  can  the  fact  that  in  the  frog  urea  again  replaces  uric 
acid  be  explained  by  reference  to  that  animal  having  so 
large  a  cutaneous,  in  addition  to  its  pulmonai  y,  respiration. 
The  final  causes  of  the  divergence  are  to  be  sought  rather 
in  the  fact  that  urea  is  the  form  adapted  to  a  fluid,  and  uric 
acid  to  a  more  solid  excrement. 

Hippuric  Acid. — In  the  urine  of  herbivora  uric  acid  is  for 
the  most  part  absent,  being  replaced  by  hippuric  acid.  In 
the  urine  of  omnivorous  man,  both  acids  may  be  present 
together.  The  history  of  the  hippuric  acid  of  urine  is  very 
instructive  ;  for  though  at  first  sight  its  presence  might  ap- 
pear to  indicate  that  the  metabolism  of  the  herl)ivora  is  in 
some  points  fundamentalh*  ditferent  from  that  of  carnivora, 
there  can  be  little  doubt  that  the  hippuric  acid  which  ap- 
pears in  the  u.rine  of  beri)ivora  comes  directU'  from  the  in- 
gested food.  Hippuric  acid  is  a  compound  of,  or  rather  a 
result  of  the  union  or  co^^njugalion  of  benzoic  acid  and  gl3cin  ; 
and  when  benzoic  acid  is  introduced  into  the  stomach  of  an 
animal,  vvheflier  herbivorous  or  not,  it  reappears  not  as  ben- 
zoic, hut  as  hippuric  acid.  It  evidently  meets,  somewhere 
in  the  body,  with,  glycin ;  and  uniting  with  this  becomes 
hii)puric  acid,  in  which  form  it  passes  out  by  the  urine. 
Nitrobenzoic  acid  in  a  similar  way  becomes  nitrohippuric 
acid  ;  and  many  other  bodies  of  the  aromatic  class,  by  a  like 
assumption  of  glycin,  become  conjugated  in  their  passage 
through  the  body. 

^  Odling,  Lectures  ^:i  Animal  Chemistry,  p.  144. 


578       THE    METABOLIC    PHENOMENA    OF    THE    BODY. 

The  knowledge  of  the  fact  that  benzoic  acid  is  thus  con- 
verted into  hippiiric  acid  naturally  suo:gested  the  idea  that 
the  food  of  herl)ivora  might  contain  either  benzoic  acid  or 
some  allied  body,  and  that  the  presence  of  hii)pnric  acid  as 
a  normal  constituent  of  urine  might  be  thus  accounted  for. 
And  Meissner  and  Shepard^  have  shown  that  all  the  hip- 
piiric acid  of  herbivorous  urine  is  in  reality  due  to  the  pres- 
ence in  ordinary  fodder  (ha}')  of  a  particular  constituent 
containing  a  benzoic  residue;  when  this  constituent  is  with- 
drawn the  hippuric  acid  disappears  from  the  urine.  Tiiey 
regarded  this  substance  as  a  particular  form  of  cellulose  ;  but 
this  does  not  seem  certain.^ 

As  far  as  w^e  know,  glycln  does  not  exist  preformed  or  in  a  free 
state  in  any  tissue  of  the  body,  but  it  makes  its  appearance  during 
the  decomposition  of  proteids  and  of  gelatin,  and  may  be  formed 
by  various  reactions  from  those  bodies ;  and  the  presence  in  the 
bile  of  glycocholic  acid,  which  results  from  the  union  of  conjuga- 
tion of  glycin  and  cholalic  acid  (sec  p.  381),  shows  that,  in  the 
liver  at  all  events,  compounds  of  glycin  may  be  formed.  Kuhne 
and  Hallwachs''  observed  that  benzoic  acid  wdien  injected  into 
the  portal  vein  sufficiently  slowly  issued  by  the  urine  as  hippuric 
acid,  but  when  injected  into  the  jugular  vein,  especially  with  any 
rapidity,  passed  out  in  the  urine  as  unchanged  benzoic  acid; 
they  also  found  that  benzoic  acid  introduced  into  the  stomach, 
passed  out  as  benzoic  acid  wdien  the  liver  had  been  excised. 
Hence  they  concluded  that  the  transformation  of  benzoic  into 
hippuric  acid  took  place  in  the  liver,  the  former  acid  finding  in 
that  organ  the  glycin  necessary  for  the  transformation.  Meiss- 
ner and  Shepard,^  however,  maintained  that  the  transformation 
of  benzoic  into  hippuric  acid  took  place  not  so  much  in  the  liver 
as  in  the  kidney  ;  and  Bunge  and  Schmiedeberg^  have  brought 
forward  experimental  evidence  to  the  same  efltect. 

Of  the  meaning  of  the  appearance  in  the  tissues  of  such 
liodies  as  xanthin,  etc.,  and  of  the  e\act  nature  of  the  meta- 
bolism which  the}'  undergo,  we  know  nothing.  \Ye  cannot 
say  whether  they  are  simply  the  accidental  by-products  of 
nitrogenous  metabolism,  the  result  of  imperfect  chemical 
machinery  ;  or  whether  they,  though  small  in  quantity,  serve 
some  special  ends  in  the  economy. 

^  Die  Hippnrsaiire,  Hannover,  1866. 
2  Cf.  Weiske,  Zt.  f.  Biol.,  xii  (1876),  p.  241. 

^  Virchow's  Archiv,  xii  (1857),  380.  *  Op.  cit. 

5  Archiv  f.  Exp.  Pathol.,  xi  (1876),  p.  233.  Cf.  also  Kochs,  Pfluger's 
Archiv,  xx  (1879),  p.  64.  • 


THE    STATISTICAL    METHOD.  579 


Sec.  3.  Tee  Statistics  of  Xutrition. 

The  precediiioj  sections  liave  sliown  us  how  wholly  impos- 
sible it  is  at  present  to  master  the  metabolic  phenomena  of 
the  body  by  attempting  to  trace  out  forwards  or  liack wards 
the  several  ciianges  undergone  by  the  individual  constitu- 
ents of  the  food,  the  body,  or  the  waste  products.  Another 
method  is,  however,  open  to  us,  the  statistical  method.  We 
may  ascertain  the  total  income  and  the  total  expenditure  of 
the  body  during  a  given  period,  and  by  comparing  the  two 
may  be  able  to  draw  conclusions  concerning  the  changes 
which  must  have  taken  place  in  the  body  while  the  income 
was  being  converted  into  the  outcome.  Many  researches 
have  of  late  years  been  carried  out  by  this  method  ;  but 
valuable  as  are  the  results  which  have  been  therelw  gained, 
they  must  be  received  with  caution,  since  in  this  method  of 
inquiry  a  small  error  in  the  data  may.  in  the  process  of  cal- 
culation and  inference,  lead  to  most  wrong  conclusions. 
The  gi-eat  use  of  such  inquiries  is  to  suggest  ideas,  but  the 
views  to  which  they  give  rise  need  to  be  verified  in  other 
ways  before  they  can  acquire  real  worth. 

Composition  of  the  Animal  Body. — The  first  datum  we  re- 
quire is  a  knowledge  of  the  composition  of  the  body,  as  far 
as  the  relative  i)roportion  of  the  various  tissues  is  concerned. 
In  the  human  body,  according  to  E.  BischofF,^  the  chief  tis- 
sues are  found  in  the  following  proportions  by  weight: 


Adult 

mail 

New 

-born  baby 

(aged 

33). 

(boy). 

Skeleton, 

15.9  per  cent. 

17.7 

per  cent. 

Muscles, 

■41.8 

22.9 

tt 

Thoracic  viscera,     . 

1.7 

3.0 

a 

Abdominal  viscera. 

7.2 

11.5 

a 

Fat, 
Skin, 

18.2 
6.9 

20.0 

" 

Brain,      .         ... 

1.9 

15.8 

li 

An  analysis  of  a  cat  gave   Bidder  and  Schmidt-  the  fol- 
lowing: 

^  Quoted  by  Ranke,  Griindziige,  p.  143. 
^  Die  Verdauungssiifte,  p.  329. 


580       THE    METABOLIC     PHENOMENA    OF    THE    BODY. 


Muscles  and  tendons,         .         .         .  45.0  per  cent. 

Bones, 14.7  '' 

Skin, 12.0 

Mesentery  and  adipose  tissue,  .         .  :}.8  " 

Liver, 4.8  '' 

Blood  (escaping  at  death),         .         .  6.0  " 

Other  organs  and  tissues,  .         .13.7  " 

One  point  of  importance  to  he  noticed  in  these  analyses 
is  that  tlie  skeletal  muscles  form  nearly  half  the  hody  ;  and 
we  have  already  seen  (p.  (iO)  that  about  a  quarter  of  the  total 
blood  in  the  body  is  contained  in  them.  We  infer  from  this 
that  a  large  part  of  tlie  metabolism  of  the  l)ody  is  carried  on 
in  the  muscles.  Next  to  the  muscles  we  must  place  the  liver, 
for  though  far  less  in  bulk  than  them,  it  is  subject  to  a  very 
active  metabolistn,  as  sliown  by  tiie  fact  that  it  alone  holds 
about  a  quarter  of  the  whole  blood. 

The  Starving  Body. — Before  attemjUing  to  study  the  influ- 
ence of  food,  it  will  be  useful  to  ascertain  what  changes  occur 
in  a  body  when  all  food  is  withhekl.  Voit^  found  that  a  cat 
lost  in  a  hunger  pei'iod  of  lo  days  734  grams  of  solid  mate- 
rial,of  which  248.8  were  fat  and  118.2  muscle,  the  remainder 
being  derived  from  the  other  tissues.  Tlie  percentage  of 
di'y  solid  matter  lost  by  the  more  important  tissues  during 
the  period  was  as  follows : 


Adipose  tissue,    . 

.    97.0 

Spleen,         .         .         .         . 

.     63.1 

Liver,          .... 

.     56.6 

Muscles,      .... 

.     30.2 

Blood,          .         .         .         . 

.     17.6 

Brain  and  spinal  cord, 

.       0.0 

Tims  the  loss  during  starvation  fell  most  heavily  on  the 
fat,  indeed  nearly  the  whole  of  this  disappeared.  Next  to 
the  fat,  the  glandular  organs,  the  tissues  which  we  have  seen 
to  be  eminently  metabolic,  sutl'ered  most.  Then  come  the 
mus(,'les,  that  is  to  say,  the  skeletal  muscles,  for  the  loss  in 
the  heart  was  veiy  trifling;  obviously  this  organ,  on  account 
of  its  importance  in  carrying  on  the  work  of  the  economy, 
was  spared  as  much  as  })ossihle;  it  was  in  fact  fed  on  tiie 
rest  of  the  i)ody.     Tlie  same  remaik  api)Hes  to  the  brain  and 

^  Zt.  f.  Biol.,  ii  (1866j,  307. 


THE    STATISTICAL    METHOD.  581 

Spinal  cord  ;  in  order  that  life  might  be  prolonged  as  much 
as  possible,  these  important  organs  were  nourished  by  mate- 
rial drawn  from  less  nol)le  organs  and  tissues.  The  blood 
surt'ered  proportionally  to  the  general  body-waste,  becoming 
gradually  less  in  bulk  but  retaining  the  same  specific  grav- 
ity ;  of  the  total  dry  proteid  constituents  of  the  body  17.3 
per  cent,  was  lost,  which  agrees  very  closely  with  the  17.6 
per  cent,  lost  by  the  blood.  It  is  worthy  of  remark  that 
the  tissues  in  general  became  more  watery  than  in  health. 

We  might  infer  from  these  data  the  conclusions  that  metabol- 
ism is  most  active  first  in  the  adipose  tissue,  next  in  such  meta- 
bolic tissues  as  the  hepatic  cells  and  spleen-pulp,  then  in  the 
muscles,  and  so  on  ;  but  these  conclusions  must  be  guarded  by 
the  reflection  that  because  the  h.-is  of  cardiac  and  nervous  tissue 
was  so  small,  we  must  not  therefore  infer  that  their  meUiholism 
w^as  feeble  ;  they  may  have  undergone  rapid  metabolism,  and 
yet  have  been  preserved  from  loss  of  substance  by  their  drawing 
upon  other  tissues  for  their  material. 

During  this  starvation-period,  the  urine  contained  in  the 
form  of  urea  (for,  as  we  shall  see,  the  other  nitrogenous 
constituents  of  urine  may  for  the  most  part  be  disregarded), 
27.7  grams  of  nitrogen.  Now  the  amount  of  muscle  which 
was  lost  during  the  period  contained  al)Out  15.2  of  nitrogen. 
Thus,  more  than  half  the  nitrogen  of  the  outcome  during 
the  starvation-period  must  have  come  ultimately  from  the 
metabolism  of  muscular  tissue.  This  is  an  important  fact 
of  which  we  shall  be  able  to  make  use  hereafter.  Bidder 
and  Schmidt^  came  to  the  conclusion,  from  their  observa- 
tions on  a  starving  cat,  that  the  quantity  of  urea  excreted 
per  diem,  in  all  but  the  earlier  days  of  the  inanition-period, 
bore  a  fixed  ratio  to  the  body-weight.  In  the  first  two  or 
three  days  of  the  period,  the  daily  quantity  of  the  urea  was 
much  greater  than  this.  They  were  thus  led  to  distinguish 
two  sources  of  urea:  a  quantity  arising  fiom  the  functional 
activity  of  the  whole  body,  and  therefore  bearing  a  fixed 
ratio  to  the  body-weight,  and  continuing  until  near  the  close 
of  life  ;  and  a  quantity  arising  from  the  amount  of  surplus 
nitrogenous  or  proteid  material  which  happened  to  be  stored 
up  in   the   body  at  the  commencement  of  the  period,  and 

'   Die  Verdauungssafte,  1852. 
49 


582      THE    METABOLIC    PHENOMENA    OF    THE    BODY. 

which  was  rapidly  got  rid  of.  The  latter  they  regarded  as 
not  entering  distinctly  into  the  composition  of  the  tissues, 
but  as,  so  to  speak,  floating  capital,  upon  which  each  or  any 
of  the  tissues  could  draw.  They  spoke  of  its  direct  meta- 
bolism as  a  laxas  consumption.  Bischoff  and  Yoit,^  however, 
by  means  of  more  extended  observations,  concluded  that 
though  the  urea  of  the  first  two  or  three  days  much  exceeds 
that  of  the  subsequent  days  of  a  starvation-period,  no  such 
fixed  relation  of  urea  to  body-weight  as  that  suggested  by 
Bidder  and  Schmidt  obtains  ;  but  that  the  quantity  which 
is  passed  is  directly  dependent  on  the  amount  of  proteid 
material  present  in  the  food  during  the  days  antecedent  to 
the  commencement  of  the  starvation-period.  This  question 
of  a  luxus  consumption  is  one  to  which  we  shall  frequently 
have  to  refer. 

The  Normal  Diet. — What  is  the  proper  diet  for  a  given 
animal  under  given  circumstances,  can  only  be  determined 
when  the  laws  of  nutrition  are  known.  Meanwhile  it  is 
necessary  to  gain  an  ai)proximate  idea  of  what  may  be  con- 
sidered as  the  normal  diet  for  a  body  such  as  that  of  man 
under  ordinary  circumstances.  This  may  be  settled  either 
by  taking  a  very  large  average,  or  by  determining  exactly 
the  conditions  of  a  particular  case.  In  the  table  below  is 
given  both  the  average  result  obtained  by  Moleschott^  from 
a  large  number  of  public  diets,  and  the  diet  on  which  Ranke^ 
found  himself  in  good  health,  neither  losing  nor  gaining 
weiofht. 


Proteids,    . 

Fat,  .... 

Amyloids, 

Salts, 

Water, 

Of  these  two  diets,  which  agree  in  many  respects,  that  of 
Ranke  is  probably  the  better  one,  since  in  public  diets,  from 
which  Moleschott's  table  is  drawn,  the  cheaper  carbohj'- 
d rates  are  used  to  the  exclusion  of  the  dearer  fats. 


olesfhott. 

Kankti  (weight  74  ki 

30 

100 

84 

100 

404 

240 

80 

25 

2800 

2600 

^  Die  Gesetze  d.  Ernahrung  des  Fleischfressers,  1860. 

'^  Die  Nahrungsmittel,  p.  216. 

^  Tetanus,  p.  249 ;  Gnindziige,  p.  158. 


THE    STATISTICAL    METHOD.  583 


Compariaon  of  Income  and  Outcome. 

Method. — We  have  now  to  inquire  how  the  elements  of 
such  a  diet  are  distributed  in  tlie  excreta,  in  order  that, 
from  tlie  manner  of  the  distributi(5n,  we  ma>'  infer  the  na- 
ture of  the  inter uiediate  stages  which  take  place  within  the 
body.  By  comparing  the  ingesta  with  the  excreta,  we  shall 
learn  what  elements  have  been  retained  in  the  body,  and 
what  elements  appear  in  the  excreta  which  w^ere  not  present 
in  the  food  ;  from  these  we  may  infer  the  changes  which  the 
body  has  undergone  through  the  influence  of  the  food. 

In  the  first  place,  the  real  income  must  be  distinguished 
from  the  apparent  one  by  the  subtraction  of  the  faeces.  We 
have  seen  that  by  far  the  greater  part  of  the  fieces  is  undi- 
gested matter,  i.  (?.,  food  which,  though  placed  in  the  ali- 
mentary canal,  has  not  really  entered  into  the  body.  The 
share  in  the  fa'ces  taken  up  by  matter  which  has  been  ex- 
creted from  the  blood  by  the  alimentary  canal,  is  so  small 
that  it  may  be  neglected  :  certainly  with  regard  to  nitrogen, 
the  whole  quantity  of  this  element,  which  is  present  in  the 
f<eces,  may  be  regarded  as  indicating  simply  undigested 
nitrogenous  matter. 

In  comparing  the  income  and  outcome  of  a  given  period  great 
difficulty  is  often  found  in  determining  whether  the  fkces  passed 
in  the  early  days  of  the  period  belong  to  the  income  of  the  period, 
or  are  the  remains  of  food  taken  before.  The  ditfieulty,  however, 
is  frequently  lightened  when  the  diet  of  the  experimental  period 
differs  from' the  foregoing  diet.  Thus,  in  the  dog,  the  faeces  of  a 
bread  diet  ma}-  easily  bedistinguished  from  those  of  a  meat  diet. 

The  income,  thus  corrected,  will  consist  of  so  much  nitro- 
gen, carbon,  hydrogen,  oxygen,  sulphur,  phosphorus,  saline 
matters,  and  water,  contained  in  tlie  proteids,  fats,  carbo- 
hydrates, sails,  and  water  of  the  food,  together  with  the 
oxygen  absorbed  by  the  lungs,  skin,  and  alimentary  canal. 
The  outcome  may  be  regarded  as  consisting  of  ( 1)  the  respi- 
ratory products  of  the  lungs,  skin,  and  alimentary  canal, 
consisting  chiefly  of  carbonic  acid  and  water,  with  small 
quantities  of  hydrogen  and  carburetted  hydrogen,  these 
two  latter  coming  exclusively  from  the  alimentary  canal ; 
(2 )  of  perspiration,  consisting  chiefly  of  water  and  salts,  for 
the  dubious  excretion  (see  p.  512)  of  urea  by  the  skin  ma.y 
be  neglected,  and  the  other  organic  constituents  of  sweat 
amount  to  very  little  ;  and  ( 3 )  of  the  urine,  which  is  assumed 


584      THE    METABOLIC    PHENOMENA    OF    THE    BODY. 

to  contain  all  the  nitrogen  really  excreted  b}'  the  body,  be- 
sides a  large  quantity  of  saline  matters,  and  of  water. 
Where  greater  accuracy  is  required  the  total  nitrogen  of  the 
nrine  ought  to  be  determined;  it  is  maintained,  however, 
that  no  errors  of  serious  importance  arise  when  the  urea 
alone,  as  determined  by  Liebig's  method,  is  taken  as  the 
measure  of  the  total  quantity  of  nitrogen  in  the  urine. 

It  has  been,  and,  indeed,  still  is  debated  whether  the  body  may 
not  suffer  loss  of  nitrogen  by  other  channels  than  by  the  urine, 
whether  nitrogen  may  not  leave  the  body  by  the  skin,  or,  indeed, 
in  a  gaseous  state  by  the  lungs.  While  Boussingault,  Reguault, 
Reiset,  and  Barral  believed  that  such  was  the  case,  Bidder  and 
Schmidt,  Bischoff  and  Yoit,  llanke,  Henneberg,  and  others  have 
come  to  the  contrary  conclusion  that  all  the  nitrogen  of  the  in- 
gesta  passes  out  as  the  nitrogen  of  the  urine  and  feces,  a  view 
which  derives  its  strongest  support  from  the  observations  of  Voit 
on  a  pigeon.'  That  indefatigable  observer  fed  for  a  considerable 
time  a  pigeon  on  a  known  diet  (peas),  the  nicrogen  of  samples  of 
which  was  carefully  determined,  and  during  the  wdiole  period 
collected  and  determined  the  nitrogen  of  the  faeces  and  urine. 
At  the  end  of  the  period,  the  nitrogen  of  the  latter  was  found  to 
correspond  almost  exactly  to  the  nitrogen  of  the  food,  allowance 
being  made  for  a  retention  of  a  small  quantity  of  nitrogen  in  the 
body  to  supply  a  slight  gain  in  weight  which  was  assumed  to  be 
"■flesh."  Quite  recently  Seegen  and  Xowak-  have  revived  the 
older  views  of  the  French  physiologists,  since  they  find  an  actual 
increase  of  nitrogen  (4  to  9  m.  gram  per  hour  \k'1'  kilo  of  body- 
weight  of  animal)  in  the  air  of  a  contined  chamber  in  which  an 
animal  has  been  kept  for  several  hours,  the  air  being  continually 
supplied  with  oxygen,  and  the  carbonic  acid  and  other  products 
removed.  They  urge  against  Voit's  experiment  that  jieas  and 
other  articles  of  food  vary  so  much  in  their  nitrogen  that  in  cal- 
culating the  whole  nitrogen  of  the  ingesta  during  a  long  time 
from  the  determined  nitrogen  of  samples,  errors  are  introduced 
of  such  a  magnitude  as  to  render  the  data  almost  valueless. 

Of  lliese  elements  of  the  income  and  outcome,  the  nitro- 
gen, the  carbon,  and  the  free  oxygen  of  respiration  are  by 
far  the  most  in)portant.  Since  water  is  of  use  to  the  body 
for  merely  mechanical  purposes,  and  not  solely  as  food  in 
the  strict  sense  of  the  word,  the  hydrogen  element  becomes 
a  dubious  one;  the  sulphur  of  the  proteids,  and  the  phos- 
phorus of  the  fats,  are  insignilicant  in  amount;  while  the 


1  Ann.  Cheni.  Pharm.  SuppL,  ii,  1863. 

2  Pfluger's  Archiv,  xix  (1879),  p.  34. 


THE    STATISTICAL    METHOD.  585 

saline  matters  stand  on  a  wholly  different  footing  from  the 
other  parts  of  food,  inasmuch  as  they  are  not  sources  of  en- 
ergy, and  pass  through  the  bod}^  with  comparatively  little 
change.  The  body-weight  must,  of  course,  be  carefully  as- 
certained at  the  beginning  and  at  the  end  of  the  period, 
coirection  being  made  where  possible  for  the  fieces. 

it  will  be  seen  that  the  labor  of  such  inquiries  is  consid- 
erable. The  urine,  which  must  be  carefully  kept  separate 
from  the  faeces,  re(piires  daily  measurement  and  analysis. 
Any  loss  1)3'  the  skin,  either  in  the  form  of  sweat,  or,  in  the 
case  of  woolly  animals,  of  hair,  must  be  estimated  or  ac- 
counted for.  The  food  of  the  period  must  be  as  far  as  pos- 
sible uniform  in  character,  in  order  that  the  analyses  of 
specimens  may  serve  faithfully  for  calculations  involving 
the  whole  quantity  of  food  taken;  and  this  is  especially  the 
case  when  the  diet  is  a  meat  one,  since  portions  of  meat 
dilfer  so  much  from  each  other.  But  the  gi'eatest  ditliculty 
of  all  lies  in  the  estimation  of  the  carbonic  acid  produced 
and  the  oxygen  consumed.  In  the  earlier  researches,  such 
as  those  of  J^ischotf  and  Yoit.  this  element  was  neglected, 
and  the  variations  occurring  were  simpl}'  guessed  at,  through 
which  very  serious  errors  were  introduced.  No  comparison 
of  income  and  outcome  can  be  considered  satisfactory  unless 
the  carbonic  acid  produced  be  directly  measured  by  means 
of  a  respiration  chamber.  And  in  order  that  the  compari- 
son should  be  really  complete,  the  water  given  off  by  skin 
and  lungs  must  be  directly  measured  also;  but  this  seems 
to  be  more  difficult  than  the  determination  of  the  carbonic 
acid. 

Pettenkofer  and  Yoit^  were  the  first  to  make  use  on  a  large 
scale  of  this  means  of  inquiry.  Their  apparatus  consists  essen- 
tially of  a  large  air-tight  chamber,  ca}mble  of  holding  a  man 
comfortably.  I3y  means  of  a  steam-engine  a  current  of  pure  air, 
measured  by  a  gasometer,  is  drawn  through  the  chamber.  Meas- 
ured portions  of  the  outgoing  air  are  from  time  to  time  with- 
drawn and  analyzed  ;  and  from  the  data  aftbrded  by  these  anal- 
yzes the  amount  of  carbonic  acid  (and  other  gases)  and  water 
given  oft'  by  the  occupant  of  the  chamber  during  a  given  time  is 
determined.  The  apparatus  works  so  well  that  Pettenkofer  and 
Yoit  were  able  almost  exactly  to  recover  the  carbonic  acid  pro- 
duced b}^  the  burning  of  a  stearin  candle  in  the  chamber,  the 
error  not  amounting  to  more  than  .8  per  cent.  ;  the  recovery  of 

^  Ann.  Chem.  Pharm.  Suppl.,  ii,  1863. 


586      THE    METABOLIC    PHENOMENA    OF    THE    BODY. 


the  water  was  less  satisfactory,  the  discrepancies  being  very  con- 
siderable. 

If  the  total  amount  of  carbonic  acid  and  water  given  out 
by  the  lungs  and  skin  be  known,  as  well  as  the  amount  of 
urine  and  faeces,  then  the  quantity  of  oxygen  can  be  deter- 
mined by  a  simple  calculation.  For  evidently  the  differ- 
ence between  the  terminal  weight  plus  all  the  egesta  and 
the  initial  weight  plus  all  the  ingesta  can  be  nothing  else 
than  the  weight  of  the  ox3'gen  absorbed  during  the  period. 

Let  us  imagine,  then,  an  experiment  of  this  kind  to  have 
been  completely  carried  out,  that  the  animal's  initial  and 
terminal  weiglits  have  been  accurately  determined,  the 
composition  of  the  food  satisfactorily  known  to  consist  of 
so  much  proteid,  fat,  carbohydrates,  salts,  and  water,  and  to 
contain  so  much  nitrogen  and  carbon,  the  weight  of  the 
i'atces  and  the  nitrogen  they  contain  ascertained,  the  nitro- 
gen of  the  urine  determined,  the  carbonic  acid  and  water 
given  off'  by  the  whole  bod}^  carefully  measured,  and  the 
amount  of  oxygen  absorbed  calculated — what  interpretation 
can  be  placed  on  tlie  results? 

Let  us  suppose  that  the  animal  has  gained  w  in  weight 
during  the  period.  Of  what  does  w  consist?  Is  it  fat  or 
proteid  material  which  has  been  laid  on,  or  simply  water 
which  has  been  retained,  or  some  of  one  and  of  the  other? 
Let  us  further  suppose  that  the  nitrogen  of  the  urine  passed 
during  the  period  is  less,  say  by  j:  grams,  than  the  nitrogen 
in  the  food  taken,  of  course  after  deduction  of  the  nitrogen 
in  the  fyeces.  This  means  that  x  grams  of  nitrogen  have 
been  retained  in  the  body  ;  and  we  may  with  reason  infer 
that  they  have  been  retained  in  the  form  of  proteid  mate- 
rial. We  may  even  go  farther  and  sa}'  that  they  are  retained 
in  tlie  form  of  flesh,  i.  e.,  of  muscle.  In  this  inference  we 
are  going  somewhat  beyond  our  tether,  for  the  nitrogen 
might  be  stored  up  as  liepatic,  or  splenic,  or  any  other  form 
of  protoplasm.  Indeed  it  might  be  for  the  while  retained  in 
the  form  of  some  nitrogenous  crystalline  body  ;  but  this  last 
event  is  unlikely;  and  if  we  use  the  word  ''  flesh  "  to  mean 
protoplasm  of  any  kind,  contractile  or  metabolic,  or  of  any 
other  kind,  we  may,  without  fear  of  any  great  error,  reckon 
the  deficiency  of  ^  grams  nitrogen  as  indicating  the  storing 
up  of  a  grams  of  flesh.  There  still  remain  w  —  a  grams  of  in- 
crease to  be  accounted  for.  Let  us  suppose  that  the  total 
carbon  of  the  egesta  has  been  found  to  be  y  grams  less 


NITROGENOUS    METABOLISM.  587 

than  thai  of  the  iiii^esta;  in  other  words,  that  y  grams  of 
carbon  have  been  stored  up.  Some  carbon  has  been  stored 
up  in  th.e  flesh  with  the  nitrogen  just  considered;  this  we 
must  deduct  from  ?/,  and  we  shall  then  have  y'  grams  of 
carbon  to  account  for.  Xow  there  are  only  two  principal 
forms  in  which  carbon  can  be  stored  up  in  the  body  :  as 
gl^'cogen  or  as  fat..  The  former  is  even  in  most  favorable 
cases  inconsiderable,  and  we  therefore  cannot  err  greatly  if 
we  consider  the  retention  of  y'  grams  carbon  as  indicating 
the  laying  on  of  b  grams  fat.  If  a-Vh  are  found  equal  to 
w?,then  tiie  whole  change  in  the  economy  is  known  ;  if  zo  — 
(a  -\-b)  leaves  a  residue  c,  we  infer  that  in  addition  to  the 
laying  on  of  flesh  and  fat  some  water  has  been  retained  in 
the  system.  U  x  —  {a  +  b)  gives  a  negative  quantity,  then 
water  must  have  been  given  off  at  the  same  time  that  flesh 
ajid  fat  were  laid  on.  In  a  similar  way  the  nature  of  a  loss 
of  w^eight  can  be  ascertained,  whether  of  flesh,  or  fat,  or  of 
water,  and  to  what  extent  of  each.  The  careful  compari- 
son, the  debtor  and  creditor  account  of  income  and  out- 
come, enal)les  us,  witli  the  cautions  rendered  necessar}^  by 
the  assumptions  just  now  mentioned,  to  infer  the  nature  and 
extent  of  the  bodily  changes.  The  results  thus  gained 
ought  of  course,  if  an  account  is  kept  of  the  water,  to  agree 
with  the  amount  of  oxvgen  consumed, and  also  totally  with 
the  conclusions  arrived  at  concerning  the  retention  or  the 
reverse  of  water. 

Pettenkofer  and  Yoit  did  succeed  in  drawing  up  a  completely 
accurate  balance  sheet,  the  discrepancy  being  exceedingly  small ; 
but  it  has  been  justly  urged  that,  in  face  of  the  possible  sources 
of  error,  so  complete  an  accurac}'  is  in  itself  suspicious. 

Having  thus  studied  the  method  and  seen  its  weakness 
as  well  as  its  strength,  we  ma}'  briefly  review  the  results 
which  have  been  obtained  hy  its  means. 

Nitrogenous  Metabolism. — When  a  diet  of  lean  meat,  as 
free  as  possible  from  fat,  is  given  to  a  dog,  which  has  pre- 
viously been  deprived  of  food  for  some  time,  and  whose 
body,  therefore,  is  greatly  deficient  in  flesh,  it  migiit  be  ex- 
pected that  the  great  mass  of  food  would  be  at  once  stored 
up,  and  only  a  small  quantity  be  immediately  worked  oflf  as 
an  additional  quantity  of  urea,  occasioned  by  the  increased 
labor  thrown   on  the  econom}'  by  the  very  presence  of  the 


588       THE    METABOLIC    PHENOMENA    OF    THE    BODY. 

food.  This,  however,  is  not  the  case;  tlie  larger  portion 
passes  off'  as  urea  at  once,  and  only  a  comparatively  small 
(piantity  is  retained.  If  the  diet  be  continued,  and  we  are 
supposing  the  meals  given  to  be  ample  ones,  the  proportion 
of  the  nitrogen  which  is  given  off  in  the  form  of  urea  goes 
on  increasing  until  at  last  a  condition  is  estai)lished  in  which 
the  nitrogen  of  the  egesta  exactly  equals  that  of  the  iugesta. 
This  condition,  which  is  spoken  of  as  nitrogenous  equilib- 
rium, is  attained  in  dogs  with  an  exclusively  meat  diet  only 
when  large  quantities  of  food  are  given,  and  is  not  easily 
maintained  for  any  length  of  time.  The  exact  quantity 
of  meat  required  to  attain  nitrogenous  equilibrium  varies 
with  the  previous  condition  of  the  dog  ;  it  is  frequently 
seen  when  1500  or  1800  grams  of  meat  are  given  daily. 
Thus  the  most  striking  effect  of  a  purely  nitrogenous  diet  is 
large!}'  to  increase  the  nitrogenous  metabolism  of  the  body. 

Tliis  result  has  been  explained  b}-  supposing  tliat  with  the 
meat  diet  the  consumption  of  oxygen  is  largely  increased; 
in  other  words,  that  the  oxidizing  activity  of  the  body  is 
directly  augmented  by  a  meat  diet.  This  in  turn  may  be 
due  in  part  to  the  fact  that  proteid  food  largely  increases 
tile  number  of  the  red  corpuscles,  and  so  augments  the 
amount  of  oxygen  witli  wliich  the  tissues  are  su[)plied  ;  but 
as  we  liave  already  urged  more  than  once  the  oxidative  ac- 
tivity of  the  tissues  is  determined  by  the  tissues  themselves 
rather  than  by  the  mere  abundance  of  oxygen  at  their  dis- 
posal;  and  probabl}^  other  agencies  are  at  woik. 

When  nitrogenous  equilibrium  is  established,  it  does  not 
mean  that  a  body-equilibrium  is  established,  that  a  bod}'- 
weight  neither  increases  nor  diminishes.  On  the  contrary, 
when  the  meal  necessary  to  balance  tlie  nitrogen  is  a  large 
one,  the  body  may  gain  in  weiglit,  and  the  increase  is  proved, 
both  by  calculation  from  tlie  income  and  outcome,  and  by 
actual  examination  of  the  bodj^  to  be  due  to  the  laying  on 
of  fat.  The  amount  so  stored  up  may  be  far  greater  than 
can  possibly  be  accounted  for  b}^  any  fat  still  adhering  to 
the  meat  given  as  food.  We  are  therefore  driven  to  the 
conclusion  that  the  [)roteid  food  is  split  into  a  urea  moiety 
and  a  fatty  moiety,  that  the  urea  moiety  is  at  once  dis- 
charged, and  that  such  of  the  fat  as  is  not  made  use  of  di- 
rectly by  the  body  is  stored  up  as  adipose  tissue.  And 
this  disruption  of  the  proteid  food  at  the  same  time  explains 
why  the  meat  diet  so  largely  and  immediately  increases  the 
uiea  of  the  egesta.     We  have  already  pointed  out  that  pes- 


NITROGENOUS    METABOLISM.  589 

siMy  this  disruptive  metabolism  of  proteids  is  largely  car- 
ried on  in  the  alimentary  canal  itself  by  the  aid  of  tlic  pan- 
creatic juice  ;  whether  or  to  what  extent  other  organs  share 
in  the  action  we  do  not  at  present  know. 

Voit  and  others  with  him  speak  in  the  most  decided  waj'  of  the 
proteids  of  the  body  as  existing  in  tw^o  forms  :  organ  or  tissue 
proteid  and  circulating  or  blood  proteid.  They  regard  the  former 
as  entering  into  the  formation  of  the  tissties  and  undergoing  ftmc- 
tional  metabolism,  the  latter  as  simpl}-  tarrying  in  the  blood  and 
undergoing  a  direct  oxidative  metabolism.  It  is  of  course  the 
latter  alone  which  sutlers  the  luxus  consumption.  To  these  two 
Voit  has  been  led  to  add  a  third,  or  intermediate  proteid,  viz., 
store  or  surplus  proteid,  which  is  more  labile  than  tissue  proteid 
and  yet  more  stable  than  the  circulating  proteid.  We  have 
again  and  again  insisted  in  the  course  of  this  work  that  the  oxi- 
dations of  tile  body  take  place  not  in  the  blood  but  in  the  tissues  ; 
and  are  consequently  prepared  to  reject  Volt's  conclusions  unless 
evidence  of  a  strictly  po.^itive  character  can  be  offered  in  their  favor. 
No  such  evidence,  how^ever,  is  forthcoming  ;'  the  most  that  can 
be  said  in  favor  of  tliem  is  that  they  afford  an  easy  explanation 
of  the  phenomena  of  proteid  metabolism  ;  on  the  other  hand,  if 
we  admit  a  large  luxus  consumption  in  the  alimentarv  canal,  the 
remaining  phenomena  can  be  explained  without  throwing  on  the 
tissues  what  may  appear  too  heavy  a  metabolic  task.  And  in 
speaking  of  the  metabolism  of  any  tissue  it  must  be  remembered 
that  the  metabolic  changes  need  not  necessarily  involve  the  so- 
called  structural  elements.  A  fat-cell  may  probably  accumulate 
in  and  discharge  from  its  protoplasm  a  considerable  quantity  of 
fat  without  the  morphological  relations  of  the  cell  undergoing 
any  marked  ciiange  ;  and  w^e  can  readily  imagine  that  a  tissue 
may  suffer  partial  disintegration  and  reintegration  without  any 
interference  with  its  morphological  framework.  Our  knowledge, 
however,  of  this  matter,  is  very  imperfect;  w^e  know  that  wiien 
a  muscle  contracts  it  loses  some  of  its  substance,  but  we  do  not  at 
all  know  which  parts  of  the  fibre  bear  the  loss.  Bearing  this  in 
mind,  there  is  nothing  absolutely  to  forbid  the  idea  that  certain 
tissues  (possibly  the  liver)  may  serve,  within  hmits,  as  store- 
houses of  proteid  material  in  the  same  way  that  adipose  tissue 
serves  as  a  storehouse  of  fatty  and  the  liver  of  starchy  material. 
In  this  sense  Voit's  surplus  proteid  might  be  accepted  even  when 
his  circulating  proteid  is  rejected. 

The  characteristic  meta!)olic  effects  of  proteid  food  are 
shown  not  only  by  these  calculations  of  what  is  supposed 
to  take  place  in  the  bodj',  but  also  by  direct  analysis.    Lawes 

>  Cf.  Hoppe-Seyler,  Pfliiger's  Arehiv,  vii  (1873),  399. 
50 


590      THE    METABOLIC    PHENOMENA    OF    THE    BODY. 

and  Gilbert/  laboriously  analyzing  the  body  of  a  pig,  which 
had  been  fed  on  a  known  diet,  and  comparing  the  analysis 
with  that  of  another  pig  of  the  same  litter,  killed  at  the  time 
when  the  first  was  put  on  the  fixed  diet,  found  that  of  the 
dry  nitrogenous  material  of  the  food  only  7.84  per  cent,  was 
laid  up  as  dry  proteid  material  during  the  fattening  period, 
though  the  amount  of  proteid  food  was  low ;  in  the  sheep 
the  increase  was  only  4.14  per  cent. 

The  Effects  of  Fatty  and  of  Carbohydrate  Food.— Unlike 
those  of  proteid  food,  the  eflects  of  fats  and  carbohydrates 
cannot  be  studied  alone.  When  an  animal  is  fed  simply  on 
non-nitrogenous  food  death  soon  takes  place  ;  the  food  rap- 
idly ceases  to  be  digested,  and  starvation  ensues.  We  can, 
therefore,  only  study  the  dietetic  effects  of  these  substances 
when  taken  in  connection  with  proteid  material. 

When  a  small  quantity  of  fat  is  taken,  in  company  with 
a  fixed  moderate  quantity  of  proteid  material,  the  whole  of 
the  carbon  of  the  food  reappears  in.  the  egesta.  No  fat  is 
stored  up  ;  some  even  of  the  previously  existing  fat  of  the 
body  may  be  consumed.  As  the  fat  of  the  meal  is  increased, 
a  point  is  soon  reached  at  which  carbon  is  retained  in  the 
body  as  fat.  So  also  with  starch  or  sugar.  When  the  quan- 
tity of  this  is  small,  there  is  no  retention  of  carbon  ;  as  soon, 
however,  as  it  is  increased  beyond  a  certain  limit,  carbon 
is  stored  up  in  the  form  of  fat,  or,  to  a  smaller  extent,  as 
gl3'cogen.  Fats  and  carbohydrates,  therefore,  differ  essen- 
tially from  proteid  food  in  that  they  are  not  distinctly  provoc- 
ative of  metabolism.  This  is  exceedingly  well  shown  in 
the  results  of  Lawes  and  Gilbert,  for  in  the  pig  previously 
mentioned  472  parts  of  fat  were  stored  up  for  every  100 
parts  of  fat  in  the  food,  and  of  the  total  dry  non-nitroge- 
nous food  21.2  per  cent,  was  retained  in  the  body  as  fat. 
No  clearer  proof  than  this  could  be  afforded  that  fat  is 
formed  in  the  body  out  of  something  which  is  not  fat. 

Pettenkofer  and  Yoit^  came  to  the  conclusion  that,  marked  as 
was  the  difierence  between  proteid  and  non-nitrogenous  food  as 
regards  the  increase  of  metabolism,  fixt  did  nevertheless,  to  a 
certain  extent,  behave  like  proteids ;  when  an  excess  of  fat  was 
given  the  consumption  of  carbon  in  the  body  was  increased,  so 
that  only  a  portion  (though  a  large  portion)  of  the  excess  of  fat 
in  the  food  was  stored  up. 


1   Phil.  Trans.,  1859,  part  2.  ^  gt.  f.  Biol.,  ix. 


FATTY    AND    CARBOHYDRATE    FOOD.  591 

As  one  might  imagine,  the  presence  of  fat  or  carbohy- 
drates in  the  food  was  found  to  check  proteid  metaholism  ; 
nitrogenous  equilibrium  was  established  with  a  mnch  less 
expenditure  of  proteid  food.  For  instance,  with  a  diet  of 
800  grams  meat  and  150  grams  fat,  the  nitrogen  in  the  egesta 
became  equal  to  that  in  the  ingesta  in  a  dog,  in  whose  case 
1800  grams  meat  would  have  to  be  given  to  produce  the  same 
result  in  the  absence  of  fats  or  carbohydrates. 

On  the  other  hand,  it  was  found  that,  with  a  fixed  quan- 
tity of  fiitty  or  carbohydrate  food,  an  increase  of  the  ac- 
companying proteid  led  not  to  a  storing  up  of  the  surplus 
carbon  contained  in  the  extra  quantity  of  proteid,  but  to 
an  increase  in  the  consumption  of  carbon.  Proteid  food 
increases  not  onl}'  })roteid,  but  also  non-nitrogenous  meta- 
bolism. This  explains  how  an  excess  of  proteid  food  may, 
by  the  increase  of  metal»olism,  actually  reduce  the  fat  of  the 
body,  as  is  exemplified  in  the  dietetic  system  known  as  that 
of  Mr.  Banting. 

There  can  be  no  doubt,  then,  that  both  a  proteid  diet  and 
a  carbohydrate  diet  may  give  rise  to  the  formation  of  fat 
within  the  body.  And  the  question  which  we  have  already 
(p.  560)  partly  discussed  comes  again  before  us,  In  what 
vva\'  is  this  fat  so  formed  ?  Is  the  sugar,  arising  during 
diuestion  from  the  carbohydrate,  converted  by  a  series  of 
fermentative  changes  into  fat?  or  is  the  sugar  directly  con- 
sumed by  the  tissues  in  oxidative  changes,  by  which  means 
the  fatty  derivatives  of  the  metabolized  proteids  are  shel- 
tered from  oxidation  and  stored  up  as  fat  ?  What  light  does 
the  statistical  method  throw  on  this  vexed  question?  Weiske 
and  Wildt^  have  attempted  to  settle  it.  They  took  two  young 
pigs  of  the  same  litter;  one  the>'  killed  and  analyzed  as  a 
standard  of  comparison  ;  the  other  they  fed  for  six  months 
on  known  food  (chiefly  potatoes),  and  then  killed  and  an- 
alyzed it.  Supi)0sing  that  the  fattened  pig  had  to  start  with 
the  same  composition  as  the  other,  tliey  calcidated  that  it 
had  stored  up  5.5  kilos  of  fat.  During  the  six  inonths  it 
had  consumed  14.:^  kilos  of  proteid  material,  of  which  it  had 
stored  up  l.o  kilos  and  metabolized  13  kilos.  On  the  sup- 
position that  the  metabolism  of  this  13  kilos  consisted  in 
its  being  split  up  into  a  urea  and  a  fatt}^  moiety,  about  6 
kilos  of  iat  would  thus  have  been  produced.  In  other  words, 
more  than  the  fat  actually  stored  up  might  have  come  from  the 

1  Zt.  f.  Biol.,  X. 


592      THE    METABOLIC    PHENOMENA    OF    THE    BODY. 

proteid  of  the  food.  This  of  course  does  not  prove  tli.it  this 
vvMS  its  actual  source  ;  and,  on  the  otiier  hand,  Lawes  and 
Gilhert^  found  that  in  the  case  of  two  pigs  fed  ad  libitum  on 
Indian  corn  and  i)arley-meal  respectively,  as  much  as  40  per 
cent,  of  the  fat  produced  and  stored  up  in  the  body  could 
not  have  come  from  the  metaholized  proteids  of  tiie  food. 
In  spite  of  the  analogy  of  mammary  metabolism  (see  p. 
5()5),  we  may  conclude  that  some  fat  may  come  direct  from 
carbohydrate  food. 

Lawes  and  Gilbert  urge  very  justly  that  AVeiske  and  Wildt,  in 
the  experiment  just  quoted,  did  not  use  a  sufficiently  fattening  diet, 
and  in  another  experiment  used  too  much  nitrogen.  They  state 
that  if  a  pig  were  fed  on  a  rich  barley-meal  diet  so  that  it  doubled 
its  weight  in  about  eight  or  ten  weeks,  the  amount  of  proteid  meta- 
bolized, in  spite  of  the  diet  being  richer  in  proteid  material  than 
are  potatoes,  w^ould  probably  ])e  insufficient  to  account  for  the  fat 
stored  up.  This  question  is  from  a  dietetic  point  of  view  one  of 
extreme  im])ort;ince  ;  for  if  all  stored  fat  does  come  from  proteid 
food,  then  all  fattening  food  must  contain  a  due  proportion  of  it. 

We  have  at  present  no  exnct  information  concerning  the 
nutritive  differences  between  fats  and  carbohydrates,  l)eyond 
the  fact  that  in  the  final  combustion  of  the  two,  while  car- 
bohydrates require  surlicient  oxygen  only  to  combine  with 
tiieir  carbon,  and  there  being  already  sulTicient  oxygen  in 
the  carbohydrate  itself  to  form  water  with  the  hydrogen 
present,  fats  require  in  addition  oxygen  to  burn  off  some  of 
their  hydrogen.  Hence  in  herbivora  a  larger  portion  of  the 
oxygen  consumed  rea[)pears  in  the  carl)onic  acid  of  the 
egesta  than  in  carnivora,  where  more  of  it  leaves  the  body 
as  formed  water;  the  proportions  of  the  oxygen  in  tiie 
carbonic  acid  expired  to  the  oxygen  consumed  being  in 
an  average  1)0  per  cent,  in  the  former  and  60  per  cent. 
in  the  latter.  When  a  herbivorous  animal  starves,  it  feeds 
on  its  own  fat,  and  under  these  circumstances  the  oxy- 
gen proportion  in  the  expired  carbonic  acid  falls  to  the  car- 
nivorous standard.  The  carbohydrates  are  notably  more 
digestible  than  tiie  fats,  but  on  the  other  hand  the  fats  con- 
tain more  potential  energy  in  a  given  weight.  As  to  the 
dietetic  or  rather  metabolic  difference  between  starch  and 
sugar,  we  know    nothing   very  delinite.      Lawes   and   Gil- 

'  Sources  of  Fat  of  Animal  Body,  Phil.  Mag.,  Dec,  1866-  See  also 
Jonrn.  Anat.  and  Phys.,  xi  (1877),  p.  577. 


SALTS    AS    FOOD.  693 


bert^  found  that  cane-sugar  was  rather  more  fattening  than 
starch. 

The  Effacts  of  Gelatin  Food. — It  is  a  matter  of  common 
experience  that  gelatin  will  not  supply  the  place  of  proteids 
as  a  constituent  of  food.  Animals  fed  on  gelatin  with  fat 
or  carbohydrates  die  very  much  in  the  same  way  as  when 
they  are  fed  on  non-nitrogenous  material  alone.  Neverthe- 
less the  researches  of  Voif^  stiow,  as  might  be  expected,  that 
the  presence  of  gelatin  in  food  is  not  without  effect.  Ac- 
cording to  him  nitrogenous  equilil)rium  is  established  at  a 
lower  level  of  proteid  food  when  gelatin  is  added.  Thus  the 
nitrogen  of  the  ingesta  andegesta  became  equal  in  a  dog  on 
a  ration  of  400  grams  proteid  and  200  grams  gelatin.  A 
dog,  moreover,  uses  up  less  of  tiie  nitro<yen  of  the  body  on 
ft  diet  of  gelatin  and  fat,  than  on  a  diet  of  fat  alone  ;  and 
the  consumption  of  fat  also  seems  to  be  lessened  by  tiie 
presence  of  gelatin.  All  these  facts  become  intelligible  if 
we  suppose  that  gelatin  is  rapidly  split  up  into  a  urea  and  a 
fjit  moiety,  in  the  same  way  that  we  have  seen  a  certain 
quantity  of  pioteid  material  to  be.  It  is  this  direct  meta- 
bolism of  proteid  matter  which  gelatin  can  take  up;  it 
seems,  however,  unable  to  imitate  the  other  function  of  pro- 
teid matter,  and  to  take  part  in  the  formation  of  living  pro- 
toplasm. What  is  the  cause  of  this  difference  we  cannot  at 
present  say. 

The  Effects  of  Salts  as  Food. — All  food  contains,  besides 
the  potential  substances  which  we  have  just  studied,  certain 
saline  matters,  organic  and  inorganic,  having  in  themselves 
little  or  no  latent  energy,  but  yet  either  absolutely  neces- 
savy  or  highly  beneficial  to  the  body.  These  must  have 
important  functions  in  directing  the  metal)olism  of  the 
body:  the  striking  distribution  of  them  in  the  tissues,  the 
])reponderance  of  sodium  and  chlorides  in  blood-serum  and 
of  potassium  and  piiosphates  in  the  red  corpuscles,  for  in- 
stance, must  have- some  meaning;  but  at  present  we  are  in 
the  dark  concerning  it.  The  element  phosphorus  seems  no 
less  important  from  a  biological  point  of  view  than  carI>on 
or  nitrogen.  It  is  as  absolutel\'  essential  for  the  growth 
of  a  lowly  being  like  Penicillium.  as  for  man  himself.     We 


Brit.  Assoc.  Reports,  18o4. 
Zt.  f.  Biol.,  viii,  297. 


594       THE    METABOLIC    PHENOMENA    OF    THE    BODY. 

find  it  probtibly  playing  nn  imj)ortant  part  as  the  conspicn- 
ous  constituent  of  lecithin;  we  find  it  peculiarly  associated 
with  tlie  proteids,ai)parently  in  the  form  of  phosphates  ;  but 
we  cannot  explain  its  role.  The  element  sulphur,  again,  is 
only  second  to  phosphorus,  and  we  find  it  as  a  constituent 
of  nearl}'  all  proteids ;  but  we  cannot  tell  what  exactly 
would  happen  to  the  economy  if  all  the  sulphur  of  the  food 
were  withdrawn.  We  know  that  the  various  saline  matters 
are  essential  to  health,  that  when  they  are  not  present  in 
proper  proportions  nutrition  is  affected,  as  is  shown  by 
certain  forms  of  scurvy;  we  are  aware  of  the  peculiar  de- 
pendence of  proteid  qualities  on  the  presence  of  salts  ;  but 
beyond  this  we  know  vei-y  little. 


Sec.  4.   The  Energy  of  the  Body. 

Broadly  speaking,  the  animal  body  is  a  machine  for  con- 
verting potential  into  actual  energy.  The  potential  energy 
is  supplied  b}-  food  ;  this  the  metabolism  of  the  body  con- 
verts into  the  actual  energy  of  heat  and  mechanical  labor. 
We  have  in  the  present  section  to  stud}'  what  is  known  of 
the  laws  of  this  conversion,  and  of  the  distribution  of  the 
energy  set  free. 

The  Income  of  Energy. 

Neglecting  all  subsidiar}^  and  unimportant  sources  of 
energy,  we  may  say  that  the  income  of  animal  energy  con- 
sists in  the  oxidation  of  food  into  its  waste  products,  viz., 
the  oxidation  of  proteids  into  urea  and  carbonic  acid,  of 
fats  into  carbonic  acid  and  water,  and  of  carbohydi'ates  into 
carbonic  acid.  Taking  as  our  guide  the  principle  laid  down 
by  the  chemist,  that  the  potential  energy  of  any  body,  con- 
sidered in  relation  to  any  chemical  change  in  it,  is  the  same 
when  the  final  result  is  the  same,  whether  that  result  be 
gained  at  one  leap  or  by  a  series  of  steps — that,  for  in- 
stance, the  energy  set  free  by  the  oxidation  of  one  gram  of 
fat  into  carbonic  acid  and  water  is  the  same,  whatever  the 
changes  forwards  or  backwards  which  the  fat  undergoes  be- 
fore it  finally  reaches  the  stage  of  carbonic  acid  and  water; 
and  similarl}',  that  the  energy  available  for  the  body  in  one 
gram  of  dry  proteid  is  the  energy  given  out  by  the  complete 
combustion  of  that  one  gram,  less  the  energy  given  out  by 
the  complete  combustion  of  that  quantity  of  urea  to  which 


THE  EXPENDITURE  OF  ENERGY.        595 

the  one  gram  of  proteid  gives  rise  in  the  body — we  easily 
calculate  the  total  energy  of  any  diet.  Frankland^  has  sup- 
plied the  following  data,  given  both  in  gram-degree  C  units 
of  heat,  and  meter-kilogram  units  of  force. 

The  direct  oxidatiou  of  the  Gives  rise  to 

fullowini^,  dried  at  100°  C.  gram-deg.     met.-kilo. 

1  sjram  beef-fat, 9069  3841 

1  gram  butter, , 72(54  3077 

1  gram  arrowroot,          ....  3912  1057 

1  gram  beef-muscle  purified  with  ether,  5103  2101 

1  gram  urea, 2200  934 

Supposing  that  all  the  nitrogen  of  proteid  food  goes  out 
as  ui'ea,  1  gram  of  dry  proteid,  such  as  dried  beef-muscle, 
would  give  rise  to  about  ^  gram  of  urea;  hence 

Gram-deg.     M<>t.-kil(). 

1  gram  proteid,       .....     5103        2161 

less 
^  gram  urea,  .....       735  311 

would  give  as 

Available  energy  of  proteid,  .         .     4368        1850 

In  a  normal  diet,  such  as  Ranke's,  p.  582,  would  be  found  : 

Gram-deg.  Met.-kilo. 

100  grams  proteid,         .  .     436,800        185,000 

100  2 rams  fat,        .         .         .         .     906,900        384,100 
240  grams  starch,  .         .         .     938,880        397,680 


Total  income,       ....  2,281,580        966,780 
or  in  round  numbers,  one  million  meter-kilograms. 

The  Expendilure. 

There  are  only  -two  ways  in  which  energy  is  set  free  from 
the  body, — mechanical  labor  and  heat.  The  body  loses  energy 
in  producing  muscular  work,  as  in  locomotion,  in  all  kinds  of 
labor,  in  the  movements  of  the  air  in  respiration  and  speech, 
and,  though  to  a  hardly  recognizable  extent,  in  the  move- 
ments of  the  air  or  contiguous  bodies  by  the  pulsations  of 

1  Phil.  Mao-.,  xxxii.  d.  182. 


51)0       THE    METABOLIC    PHENOMENA    OF    THE    BODY. 

the  vascnlar  system.  The  body  loses  eneroy  in  the  form  of 
heat  by  conduction  and  radiation,  by  respiration  and  perspi- 
ration— in  fact,  by  the  warming  of  all  the  egesta.  All  the 
internal  work  of  the  body,  all  the  mechanical  labor  of  the 
internal  muscular  mechanisms  with  their  accompanying 
friction,  all  the  molecular  labor  of  tlie  nervous  and  other 
tissues  is  converted  into  heat  before  it  leaves  the  body.  The 
most  intense  mental  action,  unaccompanied  by  any  muscu- 
lar manifestations,  the  most  energetic  action  of  the  heart  or 
of  the  bowels,  wnth  the  slight  exceptions  mentioned  above, 
the  busiest  activity  of  the  secreting  or  metabolic  tissues,  all 
these  end  simply  in  augmenting  the  expenditure  of  income 
in  the  form  of  heat. 

A  normal  daily  expenditure  in  the  way  of  mechanical 
labor  can  be  easily  determined  by  ol'servation.  Whether 
the  work  take  on  t!ie  form  of  walking,  or  of  driving  a  ma- 
chine, or  of  an}'  kind  of  muscular  toil,  a  good  day's  work 
may  be  put  down  at  about  150,000  meter-kilograms.  The 
normal  daily  expenditure  in  the  way  of  iieat  cannot  be  so 
readily  determined.  Direct  calorimetric  observations  are 
attended  with  this  ditficulty, — that  the  body  while  within  the 
calorimeter  is  placed  in  abnormal  conditions,  which  produce 
an  abnormal  metal)olism.  Hence  results  arrived  at  by  this 
method  are  of  little  value  unless  they  be  accompanied  by  a 
comparison  of  the  egesta  and  ingesta,  so  that  the  rate  and 
nature  of  the  metabolism  going  on  may  be  known.  Many 
attempts  have  been  made  to  calculate  the  amount  in  an  in- 
direct manner.  As  trustworthy  as  any  is  the  plan  of  simply 
subtracting  the  normal  daily  mechanical  expenditure  from 
the  normal  daily  income.  Thus,  150,000  meter-kilograms 
subtracted  from  1,000,000  meter-kilograms  gives  850.000 
meter  kilograms  as  tiie  daily  expenditure  in  the  form  of  lieat; 
i.e.,  between  one-fifth  and  one-sixth  of  the  total  income  is 
ex[)ended  as  mechanical  labor,  the  remaining  four-fifths  or 
five-sixths  leaving  the  body  in  the  form  of  heat. 

The  Sources  of  Muscular  Energy. — Liebig.  satisfied  witii 
having  i)roved  that  the  animal  body  was  constructive  as  far 
as  the  foimation  of  fat  was  concerned,  held  to  the  distinc- 
tion between  nitrogenous  or  plastic  and  non  nitrogenous  or 
respiratory  food.  Put  broadly,  his  view  was  that  all  the 
nitrogenous  food  went  to  build  up  the  proteid  tissues,  the 
muscular  flesh,  and  other  forms  of  protoplasm,  and  that 
the  nitrogenous   egesta   arose   solely   from    the    functional 


THE  EXPENDITURE  OF  ENERGY.        597 

metaliolisin  of  these  tissues,  while  the  non-iiitrocrenons  food 
was  used  with  equal  exelusiveness  for  respiratory  or  calorific 
purposes,  being  either  directly  oxidized  in  the  blood,  or  if 
present  in  excess,  stored  up  as  fatty  tissue.  According  to 
him  the  two  classes  of  income  corresponded  exactly  to  the 
two  forms  of  expenditure.  We  have  already  urged  several 
objections  against  this  view.  We  have  seen  that  in  the  blood 
itself  very  little  oxidation  takes  place,  that  it  is  the  active 
tissue,  and  not  the  passive  blood-plasma,  which  is  the  seat 
of  oxidation.  We  have  further  seen  that  proteid  food  may 
undoubtedly  be  in  Liebig's  sense  respiratory,  and  inci- 
dentally give  rise  to  the  storing  up  of  fat.  One  division  of 
Liebig's  view  is  thereby  overthrown.  We  have  now  to  in- 
quire whether  the  other  division  holds  good,  whether  muscle 
or  other  protoplasm  is  fed  exclusiveh'  on  the  proteid  material 
of  food,  and  whether  muscular  enei"gy  comes  exclusively 
from  tiie  metabolism  of  the  proteid  constituents  of  muscle. 
We  have  already  seen  (p.  101 )  that  when  the  muscle  itself  is 
examined,  we  find  no  proof  of  nitrogenous  waste,  but,  on 
the  other  hand,  clear  evidence  of  the  production  of  non- 
nitrogenous  bodies,  such  as  carbonic  and  lactic  acid.  We 
have  now  to  ask  the  question  :  Does  muscular  exercise  in- 
crease the  urea  given  off  by  the  body  as  a  whole  ?  For  this, 
according  to  Liebig's  theory,  it  certainly  ought  to  do.  Con- 
flicting evidence  has  been  offered  on  this  point ;  but  by  far  the 
strongest  and  clearest  is  that  which  gives  a  negative  answer. 

In  addition  to  the  careful  observations  of  Lawes  and  Gilbert, 
Edward  -Smith,  lianke,  Yoit,  and  others,  the  long-continued  and 
admirable  inquiries  of  Parkes^  are  especially  deserving  of  atten- 
tion. This  observer  determined  both  the  total  nitrogen  of  the 
urine  and  of  the  faeces,  so  that  no  possible  source  of  error  could 
lie  in  this  direction  ;  and  examined  the  effect  of  exercise,  slight 
and  severe,  on  both  a  non-nitrogenous  and  on  a  mixed  nitrogen- 
ous diet.  He  found  no  marked  increase  in  the  urea,  but  often  a 
diminution,  during  the  exercise,  though  subsequently  a  slight 
increase  took  place.  This  after-increase  possibl}-  had  nothing  to 
do  with  the  muscles  in  particular,  but  was  the  result  of  the  ex- 
ercise on  the  body  at  large. 

The  results  of  Flint,-  gained  by  observations  on  a  celebrated 
pedestrian,  rather  illustrate  the  effects  of  protracted  exercise  on 
general  proteid  metabolism  under  a  rich  diet  than  contradict  the 
more  exact  inquiries  of  Parkes. 

'  Proc.  Roy.  Soc.  xv  (1SC7),  p.  339  ;  xvi,  p.  44 ;  xix,  p.  349  ;  xx,  p.  402. 
-  Journ.  Anat.  Plivs.,  vol.  xi  (1876) ;  xii  (1877).     Cf.  North.  Joirn. 
of  Phys.,'i  (1878),  p.' 171. 


598       THE    METABOLIC    PIlENOxMENA    OF    THE    BODY. 

More  than  tliis,  the  ex])erience  of  Fick  and  Wislicenns^ 
lands  ns  in  an  absurdity  if  we  suppose  the  whole  energy  of 
muscular  work  to  arise  from  proteid  metabolism.  They  per- 
formed a  certain  amount  of  work  (an  ascent  of  the  Faulhorn) 
on  a  non-nitrogenous  diet,  and  estimated  the  amount  of 
urea  passed  during  the  period.  Assuming  the  urea  to  rep- 
resent tlie  oxidation  of  so  much  proteid  matter,  which  oxi- 
dation represented  in  turn  so  much  energy  set  free,  they 
found  that  whereas  the  actual  work  done  amounted  to 
129.026  and  148,656  meter-kilos,  for  each  respectively,  the 
total  energy  available  from  proteid  metabolism  during  the 
period  was  in  the  case  of  the  first  68. G9,  and  of  the  second 
68.876  meter-kilos.  That  is  to  say,  the  energy  set  free  by 
the  proteid  metabolism  of  the  muscles  engaged  in  the  work 
was  at  the  most  far  less  than  that  necessary  to  accomplish 
the  work  actually  done.  Their  muscular  energy,  therefore, 
must  have  had  other  sources  than  proteid  metabolism. 

The  total  nitrogen  excreted  was  estimated  (A)  for  12  hours 
previous  to  the  commencement  of  the  labor,  (B)  for  the  period  of 
the  labor,  and  (C)  for  six  hours  succeeding  the  labor ;  the  latter 
in  order  that  there  might  be  no  possible  retention  within  the  body 
of  the  urea  formed  during  the  labor  period. 

The  tijtal  iiiti-ogen  excreted.  Fick.  TV^islicenus. 

A.  In  12  hours  before  the  labor,  .     6.91  grm.       6.68  grm. 

B.  In  3  hours^  labor,   ....     3.31  3.13 

C.  In  6  hours' rest  after  labor,     .        .     2.43  2.42 

B.  Corresponds  in  dry  proteid  sub- ]  ^^    90  98  20  89 

stance  consumed  into  urea     |        "  ' 

C.  Corresponds  in  dry  proteid  sub- ]  ,      -j^q  j|^g  16  11 

stance  consumed  into  urea     J 


The  total  proteid  consumed  there-  |       g-  -j^y  ^y  qq 

fore  during  and  after  labor  was  j 
The  oxidation  of  these  within  the  j 

body  to  urea,  would  produce  in  y       66.690  68.376 

meter-kilos,  .  .  .  .  j 
Whereas  the    actual  work    done  |     -^.^g  qqq  -j^^g  q^q 

was  also  in  meter-kilos,      .         .  j       "  ' 

The  argument  may  be  made  still  stronger  by  the  following  con- 
siderations A  large  internal  amount  of  muscular  energy,  that 
of  the  vascular  and  respiratory  mechanisms,  did  not  appear  in 
the  work  done,  being  transformed  into  heat  before  it  left  the  body. 
On  the  supposition  that  this  muscular  energy  also  arose  from  pro- 
teid metabolism,  we  must  add  to  the  above  estimate  of  work  done, 

1  Phil.  Mag.,  xxxi  (1866),  p.  485. 


THE  EXPENDITURE  OF  ENERGY.        599 


qimntities  calculated  to  have  been  in  the  case  of  Fick  30.5J:1,  of 
Wisliceniis  35.031  meter-kilos,  bringing  up  the  totals  to  1.59.637 
and  184.287  respective!}'.  But  even  this  is  not  all.  Supposing  that 
the  whole  energy  set  free  by  a  muscular  contraction  arises  from 
proteid  metabolism,  since  some  of  this  energy  goes  out  directly 
as  heat,  we  must  add  to  the  above  estimate  of  mechanical  work, 
the  Avork  which  might  have  been  done  by  the  heat  given  out  at 
the  same  time.  Ileidenhain  calculates  that  while  ^ths  of  the 
total  energy  of  the  body  takes  on  the  form  of  heat,  the  share  of 
the  energy  set  free  in  the  contraction  of  any  individual  muscle 
which  must  be  reckoned  as  heat  amounts  to  about  half.  Hence 
the  sums  given  above  must  be  doubled  ;  so  that  the  real  contrast 
is  between  319.274  and  3(38.574  meter-kilos  of  actual  energy  ex- 
pended on  the  one  hand  and  60.690  and  08.376  meter-kilos  of 
energ}-  available  tlu'ough  proteid  metabolism  on  the  other. 

That,  on  the  contrary,  the  production  of  carbonic  acid  is 
at  once  and  largely  increased  by  muscular  exercise  is  beyond 
all  doubt.  One  hour's  hard  labor  will  increase  fivefold  the 
quantity  of  carlmnic  acid  given  off  within  tiie  hour.  And 
Pettenkofer  and  Yoit  found  that  a  man  in  24  hours  con- 
sumed 954  grams  oxygen  and  produced  1284  grams  car- 
bonic acid  when  doing  work,  as  against  708  grams  oxygen 
consumed  and  911  grams  carbonic  acid  produced  when  re- 
maining at  rest,  the  quantity  of  urea  secreted  being  in  the 
first  case  37  grams,  in  tlie  second  37.2  grams. 

These  observers  found  that  the  production  of  carbonic  acid 
was  verv  distinctly  diminished,  and  the  consumption  of  oxygen 
increased,  during  the  night  as  compared  with  the  da}'.  Thus  the 
1284.2  grams  of  carbonic  acid  of  the  whole  period  of  24  hours 
Avas  furnished  by  884.6  grams  given  out  between  6  a.m.  and  6 
P.M.,  and  399.6  grams  between  0  p.m.  and  6  a.m.  Similarly,  of 
the  954.5  grams  oxygen  294.8  grams  were  taken  in  between  6  A.3I. 
and  0  P.M.,  and  659.7  grams  between  6  p.m.  and  0  A.3i.  These 
figures  very  strikingly  indicate  the  independence  of  muscular 
contraction  and  iminediate  oxidation.  During  the  day  when  the 
body  is  at  work,  or  at  least  manifesting  activity  in  one  direction 
or  another,  while  the  production  of  carbonic  acid  is  much  greater, 
the  consumption  of  oxygen  is  much  less  than  during  the  night 
when  the  body  is  a-t  rest  and  asleep. 

It  is  evident  that  the  conclusions  arrived  at  by  the  statis- 
tical method  entirely  corroborate  those  gained  by  an  exam- 
ination of  muscle  itself,  viz.,  that  during  muscular  contrac- 
tion an  explosive  decomposition  takes  place,  the  non-nitro- 
genous products  of  which  alone  escape  from  the  muscle  and 
from  the  body,  any  nitrogenous  products  which  result  being 
retained  within  the  muscle.     We  must  therefore  reject  the 


600       THE    iMETABOLTC    PHENOMENA    OF    THE    BODY. 

second  as  well  as  the  first  division  of  Liehig's  view,  tliat  tlie 
muscle  is  fed  exclusively  on  proteid  material,  and  tiiat  its 
energy  arises  from  proteid  metabolism. 

We  must,  however,  guard  ourselves  against  rushing  into  the 
extreme  opinion  that  a  muscle  is  simply  a  machine  for  getting 
work  out  of  the  oxidation  of  non-nitrogenous  food.  The  hypoth- 
esis advanced  at  p.  148  concerning  the  re-entrance  of  the  nitro- 
genous products  of  metabolism  into  the  composition  of  the 
nascent  contractile  sul)stance,  is  undoubtedly  a  very  rough  and 
provisional  idea.  But  if  it  means  anything  it  means  this,  that 
the  decomposition  which  gives  rise  to  the  carbonic  and  lactic 
acid,  is  a  decomposition  of  iha  whole  contractile  subdance  and  not 
of  an}'  non- nitrogenous  portion  of  it,  and  that  before  a  fresh  de- 
composition can  take  place  the  whole  complex  explosive  contrac- 
tile material  has  to  be  made  anew,  and  not  simply  a  non-nitro- 
genous gap  filled  up.  And  this  is  probal)ly  true,  not  of  muscular 
tissue  only,  but  of  all  forms  of  active  protoplasm  however  other- 
wise modified.  It  is,  as  we  have  seen,  not  in  the  case  of  muscle 
alone  that  the  oxygen  disappears  into  the  molecular  recesses  of 
the  tissue  to  reappear  again  in  oxidized  products  whose  oxida- 
tion does  not  take  place  at  the  moment  of  their  production.  We 
have  more  than  once  insisted  that  the  oxidations  of  the  body,  in 
general  at  least,  are  oxidations  by  the  tissues,  and  are  oxidations 
in  which  the  oxygen  is  first  absorbed  and  made  latent  by  the 
physiological  actions  of  the  protoplasm.  In  the  at  present  un- 
known molecular  actions,  by  which  the  raw  material  of  the  pro- 
toplasm is  united  with  the  absorbed  oxygen  in  the  manufacture 
of  the  explosive  material,  nitrogenous  compounds  evidently  play 
a  peculiar  part.  This  is  clearly  shown  by  the  metabolic  activity 
of  proteid  matters  illustrated  in  the  previous  section.  Indeed 
the  whole  secret  of  life  may  almost  be  said  to  be  wrapped  up  in 
the  occult  properties  of  certain  nitrogen  compounds  ;  and  Pflager' 
has  drawn  some  very  suggestive  comparisons  between  the  so- 
called  chemical  properties  of  the  c3'anogen  compounds  and  the 
so-called  vital  properties  of  protoplasm.  If  we  admit  that  the 
energy  of  muscular  contraction  (and  with  that  the  energy  of  all 
other  vital  manifestations)  arises  from  an  explosive  decomposi- 
tion of  a  complex  substance,  which  we  may  call  real  protoplasm, 
and  that  this  complex  protoplasm  is  capable  of  reconstruction 
within  limits  which,  as  we  urged  at  p.  560,  may  be  very  wide, 
we  acquire  a  conception  of  physiological  processes  which,  if  not 
precise  and  definite,  is  at  least  simple  and  consistent,  and  more- 
over a  first  step  towards  a  future  molecular  physiolog}'. 

The  Sources  and  Distribution  of  Heat. — We  have  already 
seen  that  the  conception  of  the  non-nitrogenous  portions  of 


'  Pfliiger's  Archiv,  x  (1875),  p.  251. 


ANIMAL    HEAT.  601 

food  being  solely  calorifacient  or  respiratory,  proves  to  be 
unfounded  when  we  attenipt  to  trace  the  history  of  the  food 
on  its  way  through  ti»e  body.  The  same  view  is  still  more 
strikingly  shown  to  be  inadequate  when  we  stud}'  the  man- 
ner in  which  the  heat  of  the  bod}-  is  i)rodnced.  We  may 
indeed  at  once  affirm  that  the  heat  of  tlie  body  is  generated 
by  the  oxidation,  not  of  any  particular  substances,  but  of 
the  tissues  at  large.  Wlierever  metabolism  of  protoplasm 
is  going  on,  heat  is  being  set  free.  In  growth  and  iu  repair, 
in  the  deposition  of  new  material,  in  the  transformation  of 
lifeless  pabulum  into  living  tissue,  in  the  constructive  meta- 
Ijolism  of  tlie  body,  heat  niay  be  undoubtedly  to  a  certain 
extent  absorbed  and  rendered  latent ;  the  energy  of  the 
construction  may  be,  in  part  at  least,  supplied  by  the  heat 
present.  But  all  this,  and  more  than  this,  viz  ,  the  heat 
present  in  a  potential  form  in  the  substances  so  built  up 
into  the  tissue,  is  lost  to  the  tissue  during  its  destructive 
metabolism  ;  so  that  the  wliole  metabolism,  the  whole  cycle 
of  ciianges  from  the  lifeless  pabulum  tlirough  the  living  tis- 
sue back  to  the  lifeless  products  of  vital  action  is  eminently 
a  source  of  heat. 

Of  all  tlie  tissues  of  the  body  the  muscles  not  only  from 
their  bulk,  forming  as  they  do  so  large  a  portion  of  the 
whole  frame,  but  also  from  the  characters  of  their  metabol- 
ism, must  be  regarded  as  the  ciiief  sources  of  heat.  Wlien- 
ever  a  muscle  contracts,  heat  is  given  out.  When  a  mercury 
thermometer  is  plunged  into  a  mass  of  muscles,  such  as 
those  of  the  thigh  of  the  dog.  a  rise  of  the  mercury  is  ob- 
served upon  the  muscles  being  thrown  into  a  prolonged 
contraction.  ]SIore  exact  results  however  are  obtained  b}- 
means  of  a  thermopile,  by  the  help  of  which  the  heat  given 
out  by  a  few  repeated  single  contractions,  or  indeed  by  a 
siugle  contraction,  may  be  observed  and  measured.  Fick^ 
found  that  the  greatest  heat  given  out  by  the  muscles  of  the 
thigh  of  a  frog  in  a  single  contraction  was  3.1  micro-units  of 
heal"  for  a  gram  of  muscle,  the  result  being  obtained  b}'- 
dividing  by  five  the.  total  amount  of  heat  given  out  in  five 
successive  single  contractions.  We  have  no  satisfactory 
quantitative  determinations  of  the  heat  given  out  by  the 
muscles  of  warm-blooded  animals,  but  there  can  be  no  doubt 

'  PHiiger's  Archiv,  xvi  (1877),  p.  58. 

^  The  micro-unit  being  a  milligram  of  water  raised  one  degree  Cen- 
tigrade. 


602      THE    METABOLIC    PHENOMENA    OF    THE    BODY. 


that  it  is  much  greater  than  that  given  out  b}-  the  muscles 
of  the  frog. 

The  thermopile  may  consist  either  of  a  single  junction  in  the 
form  of  a  needle  plunged  into  the  substance  of  the  muscle  or  of 
several  junctions  either  in  the  shape  of  a  flat  surface  carefully 
opposed"  to  the  surface  of  muscle  (Heidenhain^),  the  pile  being 
balanced  so  as  to  move  with  the  contracting  muscle, and  thus  to 
keep  the  contact  exact,  or  in  the  shape  of  a  thin  wedge  (Fick^), 
the  edge  of  which  comprising  the  actual  junctions  is  thrust  into 
a  mass  of  muscles  and  held  in  position  by  them.  In  all  cases 
the  fellow  junction  or  junctions  must  be  kept  at  a  constant  tem- 
perature. 

The  amount  of  heat  given  out  by  a  muscle  when  thrown 
into  contraction  by  the  application  of  a  stimulus  will  of 
course  depend  on  the  amount  of  energy  set  free  by  the  de- 
composition of  the  explosive  contractile  substance,  part  of 
this  energy  going  to  produce  movement,  and  part  being 
transformed  into  heat.  We  have  seen,  in  treating  of  muscle 
itself,  that  the  total  amount  of  energy  set  free  by  the  action 
of  a  stimulus  will  depend  not  only  on  the  strength  of  the 
stimulus,  but  also  on  a  variety  of  circumstances,  notably  on 
the  amount  of  resistance  against  which  the  muscle  has  to 
contract;  mere  extension  of  the  muscular  filire  increases 
the  metabolism  of  the  muscular  substance,  and  leads  to  a 
freer  expenditure  of  energy.  (See  p.  118.)  The  ratio  of  the 
expended  energy  going  out  as  heat  to  that  producing  move- 
ment appears  to  vary  with  circumstances,  and  according  to 
Fick^  increases  with  an  increase  of  the  resistance.  Hence 
muscles  contracting  against  a  great  resistance  economize, 
so  to  speak,  the  expenditure  of  their  substance,  inasmuch  as 
more  and  more  of  the  energy  set  free  is  devoted  to  the  spe- 
cific muscular  movement  instead  of  the  more  general  devel- 
opment of  heat,  which  latter  task  might  be  more  cheaply 
undertaken  b}'  less  specialized  tissues.  It  is  impossible  to 
say  at  present  what  are  the  exact  limits  of  the  i"atio  of  heat 
to  movement.  Fick  calculates  that  in  the  bloodless  muscles 
of  the  frog  the  amount  of  work  may  vary  from  one-fourth  to 
one-twenty-fifth  of  the  heat  given  out.  If  we  may  venture 
to  argue  from  the  muscles  of  a  frog  to  those  of  the  mammal, 
and  to   take  somewhat  below  the   mean  of  the   above  two 


^  Mechanische,  Leistung,  etc.,  1804.  ^  Op_  ^it.  ^  Op.  cit. 


ANIMAL    HEAT.  6U3 

limits,  say  one-tenth,  then,  upon  the  calculation  that  the 
total  external  work  of  tlie  body  is  ahont  one  fifth  of  the  total 
eneruT  set  free  in  the  body,  it  is  clear  that  the  heat  given 
ont  by  the  muscles,  at  those  times  only  when  they  are  con- 
tracting, must  form  a  very  large  part  of  the  total  heat  given 
ont  by  the  body.  But  the  skeletal  muscles,  though  fre- 
quently, are  not  continually  contracting  ;  they  have  i)eriods, 
at  times  long  periods,  of  rest,  and  during  these  periods  of 
rest,  metabolism,  of  a  subdued  kind  it  is  true,  but  still  a 
metabolism,  involving  an  expenditure  of  energy,  is  going 
on.  Tliis  quiescent  metabolism  must  also  give  rise  to  a 
certain  amount  of  heat;  and  if  we  add  this  amount,  which 
in  the  present  state  of  our  knowledge  we  cannot  exactly 
gauge,  to  that  given  out  during  the  movements  of  the  body, 
it  is  very  clear,  even  in  the  al)sence  of  exact  data,  that  the 
metabolism  of  the  muscles  must  supply  a  very  large  propor- 
tion of  the  total  heat  of  the  body.  They  are  par  excellence 
the  thermogenic  tissues. 

Xext  to  the  muscles  in  importance  come  the  various  se- 
creting inlands.  In  these  the  protoplasm,  at  the  j^eriods  of 
secretion  at  all  events,  is  in  a  state  of  metabolic  activity, 
which  activity,  as  elsewhere,  must  give  rise  to  heat.  In  the 
case  of  the  salivary  gland  of  the  dog  Ludwig  and  Spiess^ 
found  that  the  temperature  of  the  saliva  secreted  during 
stimulation  of  the  chorda  might  be  as  much  as  1°  or  1.5^ 
higher  than  that  of  the  blood  in  the  carotid  arter}'  at  the 
same  time,  and  in  all  probal)ility  the  investigation  of  other 
secreting  glands  would  lead  to  similar  results.  Of  all  these 
various  glands  the  liver  deserves  special  attention  on  ac- 
count of  its  size  and  large  supply  of  blood  and  because  it 
ai^pears  to  be  continually  at  work.  We  find,  indeed,  that 
the  l)lood  in  the  hepatic  veins  is  the  warmest  in  the  body. 
Heidenhain'-  observed  in  the  dog  a  temperature  of  40  73^  C. 
in  the  hepatic  vein,  while  that  of  the  vena  cava  inferior 
was  38.35''  to  39.58°,  and  that  of  .the  right  heart  37.7°. 
Bernard  previousl}'  had  found  the  blood  of  the  hepatic  vein 
warmer  than  thai  of  either  the  portal  vein  or  the  aorta, 
showing  that  the  increased  temperature  is  not  due  simply 
to  the  liver  being  far  removed  from  the  surface  of  the  body. 

The  brain,  too,  may  be  regarded  as  a  source  of  heat,  since 


^  Wien.  Sitzun2;sberichte,  Bd.  25  (1857). 
2  PHiiger's  Archiv,  iii  (1870),  p.  504. 


G04      THE    METABOLIC    PHENOMENA    OF    THE    BODY. 

its  temperature  is  higher  than  that  of  the  arterial  blood  with 
which  it  is  supplied  ;  thouiijh  from  the  smaller  quantity  of 
blood  passing  through  its  vessels  it  cannot  in  this  respect 
compare  with  either  the  liver  or  the  muscles  as  a  source  of 
heat  to  the  body. 

The  blood  itself  cannot  be  regarded  as  a  source  of  any- 
considerable  amount  of  heat,  since,  as  we  have  so  frequently 
urged,  the  oxidations  or  other  metabolic  changes  taiving 
place  in  it  are  comparatively  slight.  The  heat  evolved  by 
indillcrent  tissues,  such  as  lione,  cartilage  and  connective 
tissue,  may  be  passed  over  as  insigniticant ;  and  we  cnnnot 
even  regard  the  adipose  tissue  as  a  seat  of  the  [)roduction 
of  heat  since  the  fat  of  tiie  fat-cells  is  in  all  probability  not 
oxidized  in  situ  but  simply  carried  away  from  its  place  of 
stornge  to  the  tissue  which  stands  in  need  of  it,  and  it  is  in 
the  tissue  that  it  undergoes  the  metabolism  by  which  its 
latent  energy  is  set  free.  Some  amount  of  heat  is  also  pro- 
duced by  the  changes  which  the  food  undergoes  in  the  ali- 
mentary canal  before  it  really  enters  the  body. 

Hence  taking  a  survey  of  the  whole  body  we  may  con- 
clude that  since  metal)olism  is  going  on  to  a  greater  or  less 
extent  everywhei'e,  heat  is  everywhere  being  generated  ; 
but  that,  looked  at  from  a  quantitative  point  of  view,  the 
muscles  and  the  glandular  organs  must  be  I'egarded  as  the 
main  sources  of  the  heat  of  the  l»ody,  the  muscles  being  in 
all  probability  the  more  inip(.rtant  of  the  two. 

But  heat,  wiiile  being  thus  continually  produced,  is 
as  continually  being  lost,  by  the  skin,  the  lungs,  the  urine, 
and  the  faeces.  The  blood,  passing  Irom  one  part  of  the 
body  to  the  other,  and  carrying  warmth  from  the  tissues, 
where  lieat  is  being  rapidly  generated,  to  the  tissues  or 
organs  where  heat  is  being  lost  by  radiation,  conduction, 
or  evaporation,  tends  to  equabze  the  temperature  of  the 
various  parts,  and  tiius  maintains  a  "constant  bodily  tem- 
perature." 

When  the  production  of  heat  is  not  great  as  compared 
with  the  loss  there  is  no  great  accumulation  of  heat  within 
the  body,  tiie  temperature  of  whicii  consequently  is  but 
slightly  raised  above  that  of  surrounding  objects.  Thus 
tiie  temperature  of  the  frog,  for  instance,  is  rarely  more 
tlian  .04°  to  .05°  C.  above  that  of  the  atmosphere,  though 
in  the  breeding  season  the  dilference  may  amount  to  1°. 
Such  animals,  and  they  comprise  all  classes  except  birds 
and  mammals,  are  spoken  of  as  cold-blooded.     Exceptions 


ANIMAL    HEAT.  605 

among  them  are  not  uncommon.  Some  fish,  such  as  the 
tunwy.  are  warmer  than  the  water  in  which  they  live,  and 
in  a  species  of  P^'thon  (P.  bivi/tatus)  adirterence  of  as  much 
as  12°  C.  has  been  observed.  Hiiber  found  that  in  a  bee- 
hive the  temperature  rose  at  times  as  much  as  to  40°  C.  In 
the  so-called  warm-blooded  animals,  birds  and  mammals, 
the  loss  and  production  of  heat  are  so  l)alanced  that  the 
temperature  of  the  body  remains  constant  at,  in  ronnd  num- 
bers, 35°  or  40^  C,  whatever  be  the  temperature  of  the  air. 
The  temperature  of  man  is  about  37.6^  C. ;  in  some  birds 
it  is  as  high  as  44°  C.  (Hirundo),  and  in  the  wolf  it  is  said 
to  be  as  low  as  35.24°  C. 

This  temperature  is  with  slight  variations  maintained 
throughout  life.  After  death  the  generation  ot  heat  rapidly 
diminishes,  and  the  body  speedily  becomes  cold  ;  but  for 
some  sliort  time  immediately  following  upon  systemic 
death,  a  rise  of  temperature  may  be  observed,  due  to  the 
fact  that,  while  the  metaboHsm  of  the  tissues  is  still  going 
on,  the  loss  of  heat  is  somewhat  checked  by  the  cessation 
of  the  circulation.  The  onset  of  pronounced  rigor  mortis 
causes  a  marked  accession  of  heat,  and  when  occurring 
after  certain  diseases,  ma}-  give  rise  to  a  very  considerable 
elevation  of  temperature.  This  mean  bodily  temperature 
of  warm-blooded  animals  is,  during  health,  maintained,  with 
slight  variations,  of  which  we  shall  presently  speak,  within 
a  very  narrow  margin,  a  rise  or  indeed  a  fall  of  much  more 
than  a  degree  above  or  below  the  limit  given  above  being 
indicative  of  some  failure  in  the  organism,  or  of  some  unu- 
sual influence  being  at  work.  It  is  evident,  therefore,  that 
the  mechanisms  which  co-ordinate  the  loss  with  the  produc- 
tion of  heat  must  be  exceedingly  sensitive.  It  is  obvious, 
moreover,  that  these  mechanisms  may  act  when  the  bodil}' 
temperature  is  tending  to  rise,  b}^  either  checking  tlie  pro- 
duction or  by  augmenting  the  loss  of  heat;  and  wlien  tlie 
bodily  temperature  is  tending  to  fall,  by  either  increasing 
the  production  or  by  diminishing  the  loss  of  heat.  As  the 
I'egulation  of  temperature  by  variations  in  the  loss  of  heat 
is  far  better  known  than  regulation  by  variations  in  produc- 
tion, it  will  be  best  to  consider  this  first. 

Regulation  by  Variations  in  Loss. — Heat  is  lost  to  the 
body  by  the  warming  of  the  feces  and  of  the  urine,  by  the 
warming  of  the  expired  air,  by  the  evaporation  of  the  water 

51 


606      THE    METABOLIC    PHENOMENA    OF    THE    BODY. 


of  respiration,  by  conduction  and  radiation  from  the  skin, 
and  by  the  evaporation  of  the  water  of  perspiration.  Helm- 
holtz  has  calculated  that  the  relative  amounts  of  the  loss  by 
these  several  ciiannels  are  as  follows  :  In  warming  the  fjEces 
and  urine  2.G  per  cent.  In  warming  the  expired  air  5.2  per 
cent.  In  evaporating  the  water  of  respiration  14.7  percent. 
In  conduction  and  radiation  and  evaporation  by  the  skin 
775  per  cent. 

The  two  chief  means  of  loss  then,  which  are  at  all  suscep- 
tible of  any  great  amount  of  variation,  and  which  can  be 
used  to  regulate  the  temperature  of  the  bod}',  are  the  skin 
and  the  lungs. 

The  more  air  passes  in  and  out  of  the  lungs  in  a  given 
time  the  greater  will  be  the  loss  in  warming  the  expired  air, 
and  in  evaporating  the  v.^ater  of  respiration.  And  in  such 
animals  as  the  dog,  which  do  not  pers[)ire  freely  by  the  skin, 
respiration  is  a  most  important  means  of  regulating  the 
temperature.^ 

While  Bernard, 2  G.  Liebig,^  Heidenhain,  and  older  observers 
found  the  blood  of  the  right  heart  warmer  (from  .1^  to  .3^-')  than 
that  of  the  left,  Colin*  and  Jacobson  and  Bernhardt^  state  that 
the  left  heart  is  warmer  or  at  least  as  warm  as  the  right.  From 
the  latter  observations  it  might  be  inferred  that  the  loss  of  heat 
by  respiration  is  neutralized  by  chemical  changes  going  on  in  the 
lungs.  Heidenhain  and  Korner,^  however,  make  the  important 
observation  that  the  higher  temperature  of  the  right  ventricle  is 
independent  of  the  respiration,  and  they  attribute  the  diti"erence 
between  the  two  ventricles  solely  to  the  fact  that  the  right  ven- 
tricle lies  nearer  to  the  abdominal  viscera,  the  high  temperature 
of  which  has  already  been  mentioned.  And  they  argue  that  the 
loss  of  heat  from  the  body  to  the  air  has  been  already  achieved 
before  the  inspired  air  reaches  the  ptdmonary  alveoli,  the  evapo- 
ration of  water  taking  place  chiefly  in  the  nasal  and  bronchial 
passages. 

The  great  regulator  however  is  undoubtedly  the  skin. 
The  more  blood  passes  through  the  skin  the  greater  will  be 
the  loss  of  heat  by  conduction,  radiation,  and  evaporation. 

1  See  Kiegel,  Pfliiger's  Archiv,  v  (1872),  651. 

2  Lt-p.  de  Phys.  Exp.,  1855. 

^  Ueber  die  Temperatnrunterschiede  des  venosen  uiid  arteriellen 
Blutes.     Giessen,  1853. 

4  Compt.  Rend.,  Ixii  (1865),  p.  680. 

5  Cbt.  f.  Med.  Wiss.,  1868,  p.  643. 

6  Pfliiger's  Archiv,  iv  (1871),  558. 


ANIxMAL    HEAT.  607 

Hence,  any  action  of  the  vasomotor  nieclianism  wliich,  by 
causing  dilation  of  the  cutaneous  vascular  areas,  leads  to  a 
larger  flow  of  blood  through  the  skin,  will  tend  to  cool  the 
body  :  and  conversely,  any  vaso-raotor  action  which,  by  con- 
stricting the  cutaneous  vascular  areas,  or  by  dilating  the 
si)L'inclinic  vascular  areas,  causes  a  smaller  flow  through  the 
skin,  and  a  larger  flow  of  blood  through  the  ai)dominal  vis- 
cera, will  tend  to  heat  the  body.  Besides  this  the  special 
nerves  of  perspiration  will  act  directly  as  regulators  of  tem- 
perature, increasing  the  loss  of  iieat  when  they  promote, 
and  lessening  the  loss  when  they  cease  to  promote,  the 
secretion  of  the  skin.  The  working  of  this  heat-regulating 
mechanism  is  well  seen  in  the  case  of  exercise.  Since  every 
muscular  contraction  gives  rise  to  heat,  exercise  must  in- 
crease for  the  time  being  the  production  of  heat;  yet  the 
bodily  temperature  rarely  rises  so  much  as  a  degree  C,  if  at 
all.  By  the  exercise  the  respiration  is  quickened,  and  the 
loss  of  heat  by  the  lungs  increased.  The  circulation  of 
Mood  is  also  quickened,  and  the  cutaneous  vascular  areas 
becoming  dilated,  a  larger  amount  of  blood  passes  through 
the  skin.  Added  to  this,  the  skin  perspires  freely.  Thus 
a  large  amount  of  heat  is  lost  to  the  body,  sufficient  to  neu- 
tralize the  increase  caused  l)y  the  muscular  contraction,  tise 
increase  which  the  more  rapid  flow  of  blood  through  the 
abdominal  organs  might  tend  to  bring  about  leing  more 
than  snfliciently  counteracted  by  their  smaller  supply  for 
the  time.  The  sense  of  warmth  which  is  felt  during  exercise 
in  consequence  of  the  flushing  of  the  skin,  is  in  itself  a 
token  that  a  regulative  cooling  is  being  carried  on.  Jn  a 
similar  way  the  application  of  external  cold  or  heat,  either 
partially  or  completely,  defeats  its  own  ends.  Under  tiie 
influence  of  external  cold  the  cutaneous  vessels  are  con- 
stricted, and  the  splanchnic  vascular  areas  dilated,  so  that 
the  blood  is  withdrawn  from  the  colder  and  cooling  regions 
to  the  hotter  and  heat-producing  organs.  This  vascular 
change  may  be  used  to  explain  the  fact  that  stripping  naked 
in  a  cold  atmosphere  often  gives  rise  to  an  actual  increase 
in  the  mean  temperature  of  the  blood,  as  indicated  by  a 
tliermometer  placed  in  the  mouth,  though  possiblv  the  effect 
may  be  partly  due  to  an  actual  increase  of  the  production 
of  heat.  Under  the  influence  of  external  warmth,  on  the 
other  hand,  the  cutaneous  vessels  are  dilated,  a  rapid  dis- 
charge of  lieat  takes  place ;  and  if  the  circumstances  be 
such  that  the  bod\'  can  perspire  freely,  and  the  perspiration 


608       THE    METABOLIC    PHENOMENA    OF    THE    BODY. 

be  readily  evaporated,  the  temperature  of  the  body  may 
remain  very  near  to  the  normal,  even  in  an  excessively  hot 
atmosphere.  Thus,  more  than  a  century  ago,  Drs.  Fordyce 
and  Blagden^  were  able  to  remain  with  impunity  in  a  cham- 
ber heated  even  to  127^  (2G0°  P'ahr.),  and  with  ease  in  one 
so  hot  that  it  became  painful  for  them  to  touch  the  metal 
buttons  of  their  clothing.  It  is  unnecessary  to  give  any 
more  examples  of  this  regulation  of  temperature  by  varia- 
tions in  the  loss  of  heat ;  they  all  readily  explain  them- 
selves. 

Regulation  by  Variations  in  Production. — It  is  not,  how- 
ever, solely  by  variations  in  the  loss  of  heat  that  the  constant 
temperature  of  the  warm-blooded  animal  is  maintained. 
Variations  in  the  amount  of  heat  actually  generated  in  the 
bod_y  constitute  an  important  factor,  not  only  in  the  main- 
tenance of  the  normal  temperature,  but  also  probably  in 
the  production  of  the  abnormally  high  or  low  temperatures 
of  various  diseases.  Many  considerations  have  long  led 
physiologists  to  susi)ect  the  existence  of  a  nervous  mechan- 
ism by  wliich  afferent  impulses  arising  in  the  skin  or  else- 
where might  through  the  central  nervous  system  originate 
efferent  impulses  whose  effect  would  be  to  increase  or  dimin- 
ish the  metabolism  of  the  muscles  or  other  organs,  and  thus 
to  increase  or  diminish  the  amount  of  heat  generated  for  the 
time  being  in  the  body.  The  existence  in  fact  of  a  metabolic 
or  thermogenic  nervous  mechanism,  comparable  in  many 
respects  to  the  vaso-motor  mechanism,  or  to  the  various 
secreting  nervous  mechanisms,  seems  in  itself  probable. 
And  we  have  now  a  certain  amount  of  experimental  evi- 
dence that  such  a  mechanism  does  really  exist.  The  warm- 
blooded animal  is  distinguished  from  the  cold-blooded  animal 
by  the  fact  that  when  it  is  exi)osed  to  cold  or  heat,  it  does 
not  like  the  latter  become  colder  or  hotter,  as  the  case  may 
be,  but,  within  certain  limits,  maintains  its  normal  tempera- 
ture. If  the  temperature  of  the  warm-blooded  animal  during 
exposure  to  cold  is  maintained  by  means  of  an  increased 
production  of  heat,  and  not  sim[)Iy  by  a  diminished  loss,  we 
ought  to  find  evidence  of  an  increased  metabolism  durinor 
that  exposure.  We  ought  to  find,  under  these  circumstances, 
an  increased  production  of  carl)onic  acid  and  an  increased 
consumption  of  oxygen,  since  it  is  to  these  products,  rather 


1  Phil.  Trans.,  1775,  pp.  Ill,  484. 


ANIMAL    HEAT.  609 

than  to  the  nitrogenous  factors,  on  the  peculiarities  of  which, 
as  uncertain  signs  of  metabolism,  we  have  already  insisted, 
we  must  look  for  indications  of  the  rise  or  fall  of  metabolic 
activity.  Now  Pfliiger  and  his  pupils  have  shown  that  ex- 
posure to  cold  does  most  markedly  increase  the  production 
of  carbonic  acid  and  consumption  of  oxygen  in  a  warm- 
blooded animal  (rabbit,  guinea-pig),  whereas  in  a  cold- 
blooded animal  (frog)  the  metabolism,  as  measured  by  the 
amounts  of  the  same  products,  is  diminished  by  cold  and 
increased  b}^  heat  The  body  of  the  latter  behaves  in  this 
respect  like  a  mixture  of  dead  sulistances  in  a  chemist's 
retort;  heat  promotes  and  cold  retards  chemical  action  in 
both  cases.  In  the  body  of  the  warm-blooded  animal,  on 
the  other  hand,  there  is  a  mechanism  by  which  such  a  reac- 
tion is  brought  about  that  chemical  action  is  actually  in- 
creased by  tlie  application  of  cold.  And  Pdiiger  has  further 
shown  that  this  mechanism  is  of  a  nervous  nature,  since 
warm-blooded  animals,  in  which  the  action  of  the  nervous 
system  is  suspended  by  urari  poisoning,  section  of  the 
medulla  oblongata,  or  otherwise,  behave  like  cold-blooded 
animals  towards  heat  and  cold ;  their  metabolism  is  increased 
by  the  former  and  diminished  by  tlie  latter. 

We  may  regard  it,  then,  as  establislied  that  such  a  ther- 
motaxic  nervous  mechanism  does  exist,  and  the  imj)oitauce 
of  such  a  mechanism  in  explaining  not  only  the  maintenance 
of  the  normal  temperature,  but  tlie  almormal  variations  of 
temperature  in  disease,  can  hardh'  be  exaggerated.  Much, 
however,  still  requires  to  be  learnt  before  we  can  speak  with 
confidence  as  to  its  exact  nature  or  expound  the  details  of 
its  work. 

The  view  that  the  generation  of  heat  in  the  animal  body  is  regula- 
ted by  a  special  mechanism,  and  that  of  a  nervous  nature,  has  long 
seemed  probable,  though  much  of  the  evidence  brought  forward 
in  its  favor  was  imperfect  and  indecisive.  The  results  of  injuries 
to  and  diseases  of  the  nervous  system  seemed  to  point  in  this 
direction.  Thus  Brodie'  long  ago  called  attention  to  a  rise  of 
temperature  after  -injury  to  the  spinal  cord.  In  a  previous 
memoir-'  he  had  contended,  on  insufficient  grounds,  it  is  true,  for 
a  direct  generation  of  heat  l)y  means  of  the  nervous  system. 
Since  that  time  many  clinicaf  cases  have  been  observed  on  the 
one  hand  of  a  lowering,  and  on  the  other  hand  of  a  rise  of  tem- 
perature, as  the  result  of  injury  to,  or  disease  of,  the  spinal  cord, 

1  Med.-Chir.  Trans.,  vol.  xx  (1837),  p.  119. 

2  Phil.  Trans..  1811,  1812. 


610      THE    METABOLIC    PHENOMENA    OF    THE    BODY, 


or  other  parts  of  the  central  nervous  system.  A  certain  amount 
of  experimental  evidence  is  also  forthcoming.  Tscheschicliin^ 
observed  in  rabbits  a  fall  of  temperature  after  section  of  the  spinal 
cord,  but  a  marked  rise  of  temperature  after  a  section  carried 
through  the  juncture  of  the  medulla  oblongata  and  pons  Varolii. 
Naunyn  and  Quincke,^  on  the  contrarj^  found  that,  in  dogs,  sec- 
tion of  the  spinal  cord  was  followed  at  first  by  a  fall,  but  sub- 
sequently by  a  rise  of  temperature,  the  latter  being  the  more 
marked  the  higher  up  the  division  of  the  cord,  and  reaching  to 
as  .much  as  3^  or  4^.  The}"  explained  the  initial  fall  as  due  to 
an  increased  escape  of  heat,  due  to  the  vaso-motor  paralysis, 
which  the  section  caused,  allowing  a  large  portion  of  the  blood 
to  pass  through  the  cutaneous  vessels  ;  and  they  remarked  that 
the  fall  was  less  the  more  rapidly  after  the  operation  the  animal 
was  surrounded  by  cotton-wool,  or  like  bad  conductors  of  heat. 
The  subsequent  rise  of  temperature  they  attributed  to  an  actual 
increased  production,  which  in  time  overcame  the  increased  escape 
due  to  vaso-motor  paralysis.  They  thought  that  they  had  satis- 
fied themselves  that  the  rise  was  not  due  to  fever  occasioned  by 
the  mere  wound,  as  Schroff"^  has  since  concluded.  Parinaud'' 
finds  that  in  rabbits  section  of  the  spinal  cord  invariably  pro- 
duces a  continued  fall  of  temperature,  especially  of  the  deeper 
parts  of  the  body,  more  marked  in  the  paralyzed  than  in  the  non- 
paralyzed  parts.  Tscheschichin  attributed  the  rise  which  he 
observed  after  the  section  of  the  medulla  to  the  removal  of  some 
inhibitory  action  exerted  by  the  higher  parts  of  the  brain  on 
thermogenic  centres  lower  down. 

But  in  all  such  experiments  and  observations  it  is  obvious  that 
difficulties  arise  on  account  of  the  complications  introduced  by 
the  mechanisms  of  the  vaso-motor  system.  We  have  already 
seen,  in  treating  of  that  system,  how  intricate  is  its  working ; 
and  the  study  of  an  elaborate  inquiry  of  Heidenhain,^  in  which 
that  acute  and  careful  observer  discusses  in  a  particular  case  the 
possibility  of  a  direct  nervous  regulation  of  the  generation  of 
heat,  and  finally  rejects  it  in  favor  of  a  simple  vaso-motor  ex- 
planation of  the  phenomena  observed,  will  illustrate  very  clearly 
the  dangers  of  inferring  the  existence  of  a  distinct  thermogenic 
nervous  action,  in  the  absence  of  a  criterion  more  satisfactory 
than  a  mere  rise  or  fall  of  temperature  in  this  or  that  part.  The 
only  really  satisfactory  criterion  short  of  direct  calorimetric  ob- 
servations (which  as  we  have  seen  are  attended  with  the  greatest 
difficulties)  is  the  measurement  of  the  actual  metabolism  going 
on  by  a  quantitative  determination  of  the  carbonic  acid  produced 
and  oxygen  consumed. 

^  Du  Bois-Reymond's  Archiv,  1866,  p.  151. 

2  Du  Bois-Reymond's  Archiv,  1869,  pp.  174,  521. 

3  Wien.  Sitziingsherichte,  Ixxiii  (1876). 

*  Archives  de  Phvsiologie  fii),  iv  (1877),  pp.  73,  310. 
^  Plliiger's  Archiv,  iii  (1870),  504;  ibid.,  v  (1872),  77. 


ANIMAL    HEAT.  611 


Tho  phenomena  of  the  rise  of  temperature  (p3^rexia)  in  certain 
diseases  ahiioet  irresistibly  suggest  the  idea  of  an  actual  increase 
in  the  production  of  heat.  And  while  many  incidental  features, 
such  for  instance  as  the  fact  that  even  profuse  sweating  by  jabo- 
randi  has  comparatively  little  etfect  on  the  high  temperature  of 
the  cold  stage  of  ague,^  concur  in  indicating  that  the  rise  of 
temperature  cannot  be  due  to  a  mere  diminution  of  loss,  and  none 
speak  distinctly  in  favor  of  such  an  explanation,  here  also  as  in 
the  experiments  quoted  above  the  desideratum  is  a  direct  meas- 
urement either  of  the  amount  of  heat  given  out,  or  of  the  actual 
metabolism  as  shown  b}'  the  quantities  of  carbonic  acid  produced 
and  oxygen  consumed,  Leyden  and  Fraenkel'  find  the  excretion 
of  carbonic  acid  increased  in  the  dog  during  pyrexia ;  and  in  all 
probability  future  investigations  will  very  speedily  enlarge  our 
knowledge  in  this  direction. 

That  the  maintenance  of  the  temperature  of  the  warm-blooded 
mammal  during  exposure  to  cold  is  due  to  an  increased  metabolism 
is  shown  by  the  experiments  of  Colasanti,^  who,  under  Plluger's 
guidance,  found  that  in  guinea-pigs  cold  increases,  in  a  very  re- 
markable and  regular  manner,  both  the  production  of  carbonic 
acid  and  the  consumption  of  oxygen,  the  ratio  of  the  oxygen  con- 
sumed to  the  oxygen  contained  in  tlie  carbonic  acid  expired  re- 
maining constant  during  the  experiments.  Sanders-Ezn'  had 
previousl}^  found  that  in  rabbits  the  production  of  carbonic  acid 
was  increased  by  sudden  exposure  of  the  bodil}'  surface  to  cold, 
and  diminished  by  sudden  exposure  to  warmth,  and  R'^hrig  and 
Zuntz^  had  observed  in  rabbits  an  increase  in  both  the  carbonic 
acid  produced  and  in  the  oxygen  consumed  to  result  from  cold 
baths,  and  also,  though  to  a  less  extent,  from  saline  baths.  A 
strong  contrast  to  the  behavior  of  the  warm-blooded  guinea-pig, 
in  which  a  fall  of  30^  C.  in  the  surrounding  medium  actually 
doubled  the  amount  of  the  metabolism,  is  afforded  b}'  the  cold- 
blooded frog,  in  which,  according  to  Pfiiiger  and  Sdiuiz,''  repeat- 
ing the  earlier  experiments  of  Marchand  and  Moleschott,  cold 
depresses  and  heat  exalts  the  metabolic  activity  of  the  tissues. 

The  exact  nature  of  this  metabolic  mechanism  was  indicated 
by  the  experiments  of  Zuntz  and  E,<ihrig,'  who  found  that  in 
urari  poisoning  there  was  a  marked  diminution  of  the  bodily 
metabolism  as  shown  by  the  quantities  of  oxygen  consumed  and 
carbonic  acid  produced  :  these,  indeed,  miglit  fall  to  half  the 
normal.    At  the  same  time  the  bodily  temperature  fell  considera- 

'  Ringer,  Lancet,  Oct.  oth,  1878. 

2  Virchow's  Areiiiv,  Bd.  76  (1879),  p.  136.  See  also  the  references 
given  tJiere. 

^  Pfliiger's  Archiv,  xiv  (1877),  p.  92.  See  also  the  subsequent  con- 
troversy carried  on  in  that  and  tlie  following  volume. 

*  Ludwig's  Arbeiten,  1867.         ^  Pfliiger's  Archiv,  iv  (1871),  p.  57. 

^  Pfliiger's  Archiv,  xiv  (1877),  73. 

'  Op.  eit.,  and  Zuntz,  Pfliiger's  Archiv,  xii  (1876),  p  522. 


612      THE    METABOLIC    PHENOMENA    OF    THE    BODY. 


bly  ;  and  that  this  fall  was  the  effect  and  not  the  cause  of  the 
diminution  of  tlie  metabolism  was  shown  by  the  fact  that  the 
metabohsm  continued  to  diminish,  when  loss  of  heat  from  the 
body  was  prevented  by  wrappings  of  cotton-wool.  While  under 
urari,  too,  the  metabolic  activity  was  far  less  influenced  by  cold 
and  other  baths. 

Pfl'.lger  has  since,  in  an  elaborate  research,^  shown  (1)  that  in 
rabbits  poisoned  with  urari  there  is  a  large  decrease  of  metabolism, 
the  carbonic  acid  produced  diminishing  37.4  per  cent. ,  and  the 
oxygen  consumed  35.2  per  cent ;  the  normal  being  of  the  former 
570  cc,  of  the  latter  (373  cc.  per  kilo  per  hour,  while  the  urarized 
animal  gave  357  cc.  carbonic  acid  and  43(3  cc.  oxygen,  all  meas- 
ured at  0"^  C.  and  7G0  mm.  mercury  ;  (2)  that  in  the  urarized 
animal  increased  temperature  produces  an  increase  of  metabolism 
(an  increase  of  44  cc.  oxygen  consumed  per  1°  C.  per  kilo  per 
hour,  and  of  81.(3  cc.  carbonic  acid  produced  per  1^  C.  per  kilo  per 
hour), and  diminished  temperature  a  diminution  of  metabolism  ; 

(3)  that  elimination  of  nervous  action  by  section  of  the  medulla 
oblongata  gives  rise  to  similar  but  less  striking  results,  whereas 

(4)  in  the  normal  animal  cold  produces,  as  has  been  previously  ob- 
served, a  marked  rise  of  metabolism.  If  in  spite  of  the  increased 
metabolism  the  external  cold  succeeds  in  reducing  the  tempera- 
ture of  the  animal,  then,  as  the  temperature  falls,  a  point  is 
reached  at  which  the  reaction  of  the  nervous  system  is  powerless 
against  the  direct  depressing  action  of  the  low  temperature,  and 
metabolism  is  diminished.  rflUger  further  observed  that  in  the 
urarized  animal,  the  metabolism  is  not  directly  proportional  to 
the  temperature,  but  increases  with  enormous  rapidity  when  the 
temperature  rises  above  the  normal.  The  production  of  carbonic 
acid  and  consumption  of  oxygen  apparently  do  not  run  exactly 
parallel ;  with  a  rise  of  temperature  above  the  normal  the  pro- 
duction of  carbonic  acid  is  much  more  rapid  than  the  consump- 
tion of  oxygen,  and  conversely  when  the  temperature  sinks  below 
the  normal  the  production  of  carbonic  acid  diminishes  more  slowly 
than  the  consumption  of  oxygen  ;  but  on  the  latter  point  further 
and  more  extended  observations  are  needed. 

The  interpretation  which  may  naturally  be  put  on  the  results 
of  the  foregoing  experiments,  especially  of  those  with  urarized 
animals,  is  that  external  cold  acts  as  a  stimulus  to  the  skin, 
giving  rise  to  afferent  impulses  which,  reaching  some  central 
nervous  mechanism,  give  rise  to  efferent  impulses,  and  these  in 
turn  passing  to  the  muscles,  increase  the  metabolic  activity  of 
these  organs,  and  thus  give  rise  to  an  increased  production  of 
heat.  When  the  muscular  nerves  are  paralyzed  by  urari,  the 
efferent  impulses  can  no  longer  reach  the  muscles,  and  hence  no 
increase  of  metabolism  takes  place  in  them.  Pointing  in  the 
same  direction  are  the  experiments  of  Samuel,-  who  found  that 


Pfhigei-'s  Archiv,  xviii  (1878),  p.  247. 

Ueber  die  Enstehung  der  Eigenwarme,  etc.,  Leipzig,  1876. 


ANIMAL    HEAT.  613 


while  rabbits  in  a  normal  condition  will  bear  exposure  to  even 
severe  cold  without  any  great  change  in  their  bodily  temperature, 
this  sinks  rapidly,  and  death  ensues,  when  the  chief  muscular 
parts  of  the  body  are  eliminated  from  the  total  action  of  the  or- 
ganism b}'  ligature  of  all  four  arteries  of  the  limbs  or  by  section 
of  their  main  nerve-trunks  ;  the  wounds  necessary  for  the  opera- 
tion producing  of  themselves  only  a  slight  etlect.  And  we  have 
been  prepared  by  previous  considerations  to  look  to  the  muscles 
as  the  chief  source  of  heat  (p.  602). 

Although  in  the  above  experiments  the  diminution  of  meta- 
bolism and  of  the  production  of  heat  was  coincident  with  the  ab- 
sence of  muscular  contractions,  it  is  not  absolutely  necessary  to 
suppose  that  the  occurrence  of  contractions  is  essential  to  an  in- 
crease in  the  production  of  heat.  In  the  cases  where  the  meta- 
bolism was  even  largely  increased,  muscular  contractions  (at 
least  visible  muscular  contractions),  though  sometimes  observed, 
were  not  invariably  present.  And  indeed  there  is  no  a  priori 
reason  positively  contradicting  the  hypothesis  that  the  metabo- 
lism of  even  muscular  tissue  might  be  influenced  by  nervous  or 
by  other  agency  in  such  a  way  that  a  large  decomposition  of  the 
muscular  substance,  productive  of  much  heat,  might  take  place 
without  any  contraction  being  necessarily  caused.  If  wc  were 
to  permit  ourselves  to  suppose  that  the  contractile  material, 
whose  metabolism -when  resulting  in  a  contraction  gives  rise  to 
so  much  heat,  could  undergo  the  same  amount  of  metabolism,  in 
so  far  a  ditlerent  fashion,  that  all  the  energy  thereb}^  set  free  took 
on  the  form  of  heat,  variations  in  the  temperature  of  the  body, 
at  present  difficult  to  understand,  would  become  readily  intelli- 
gible. 

Although  the  experiments  of  Pd'igerhave  been  chietly  directed 
towards  the  thermotaxic  nervous  mechanism  by  which  external 
cold  is  made  to  increase  metabolism,  we  may  fairly  suppose  that 
a  complementary  mechanism  by  which  metabolism  may  be  dimin- 
ished also  exists,  a  sort  of  inhibitory  thermotaxic  mechanism. 
And  this  suggests  that  pyrexia  or  fever  is  the  result  of  a  paralysis 
or  suspension  of  this  mechanism,  the  metabolism  of  the  body 
running  riot,  so  to  speak,  in  the  absence  of  directive  and  re- 
straining nervous  influences.  Colasanti'  makes  the  interesting 
observation  that  in  a  guinea-pig  suffering  from  pyrexia  the  usual 
reaction  towards  external  cold  was  absent. 

Bernard-  felt  justified  in  speaking  most  distinctly  of  "-thermo- 
genic"' or  "'calorific"  and  of  "frigorific"  nerves,  in  complete 
analogy  with  vaso-dilator  and  vaso-constrictor  nerves.  He  states' 
that  after  division  of  one  cervical  sympathetic  the  temperature 
of  the  ear  of  the  side  operated  on  remains  considerably  higher 
than  that  of  the  other  side,  at  a  time  when  the  increased  vascu- 
larity has  nearly  disappeared,  thus  indicating  that  the  former  is 

^  Op.  cit.  '^  Chaleur  Animale  (1876),  passim. 

^  Op.  Cit.,  p.  283. 

52 


614      THE    METABOLIC    PHENOMENA    OF    THE    BODY 


not  wholly  dependent  on  the  latter  ;  and  Knock'  confirms  this. 
Bernard-  also  observed,  after  division  of  the  cervical  S3mpathetic 
on  one  side,  that  a  stimulation  of  the  central  end  of  the  divided 
auricular  nerve  sufficiently  intense  to  uiverise  to  pain,  occasioned 
on  the  one  side  in  which  the  sympathetic  was  intact,  a  fi\\\  (of  as 
much  as  2^  C.)  of  temjierature  in  the  ear,  unacconipanied  by  any 
jxillor^  while  on  the  side  on  wliich  the  sympathetic  had  been 
divided,  a  rise  of  temperature  was  at  the  same  time  observed. 
That  is  to  say,  the  sensation  of  pain  gave  rise,  by  retlex  action 
through  the  intact  cervical  sympathetic,  to  a  refrigeration  of  the 
ear,  without  any  vascular  change  in  the  ear  and  in  spite  of  an  in- 
creased temperature  of  other  i)arts  of  the  body.  In  the  submaxil- 
lary gland  he  found,  as  Ludwigand  Speiss  had  previously  shown 
(see  p.  603),  that  stimulation  of  the  chorda  tympani  produces  a  rise 
of  temperature,  and  he  states  that  the  rise  manifested  itself,  though 
to  a  less  degree  than  in  normal  circumstances,  even  when  all  the 
vessels  were  cut  or  when  the  veins  were  ligatured.  On  the  other 
hand  he  obtained  a  fall  of  temperature  when  the  sympathetic  was 
stimulated,  a  fall  moreover  which  he  asserted  to  be  still  recogniz- 
able after  division  of  the  bloodvessels  or  ligature  of  the  veins  of 
the  gland.  If  it  could  be  shown  that  under  stiuiulation  of  the 
sympathetic  a  fall  of  temperature  at  all  corresponding  to  the  rise 
obtained  by  Ludwig  and  Speiss,  manifested  itself,  B..n"nard's  view 
that  the  sympathetic  is  par  excellence  a  frigorific  nerve,  while  the 
cerebro-spinal  nerves  contain  all  tlie  calorifacient  libres,  would 
receive  a  striking  confirmation.  But  these  experiments  of  Ber- 
nard's need  repetition,  and  Heidenhain's''  observations,  as  far  as 
they  go,  point  to  a  slight  rise  rather  than  a  fall  of  temperature 
as  the  result  of  S3-mpatlietic  stimulation. 

By  regulative  mechanisms  of  this  kind  the  temperature 
of  the  warm  blooded  animal  is  maintained  within  very  nar- 
row limits.  In  ordinary  health  the  temperatu!-e  of  man 
varies  between  :J6^  and  38^,  the  narrower  limits  being  36.25° 
and  37.5°,  when  the  thermometer  is  placed  in  the  axilla. 
In  the  mouth  the  reading  of  the  thermometer  is  somewhat 
(.25°  to  1.5°)  higher;  in  the  rectum  it  is  still  higher  (about 
.9°  C)  than  in  the  mouth.  The  temperature  of  infants  and 
children  is  slightly  higher  and  much  more  stisceptible  of 
variation  than  that  of  adults,  and  after  40  years  of  age  tlie 
average  maximum  temperature  (of  healtli)  is  somewhat 
lower  than   before  that  epoch.     A  diurnal  variation,  inde- 

^  Quoted  by  Bernard  loc.  cit.  The  observations  of  Goltz,  see  p.  2o0, 
on  the  foot  of  the  do.s:,  woidd  seem  to  show  that  this  at  least  does  not 
hold  i^ood  for  the  sciatic  nerve. 

^  Op.  cit.,  p.  295.  2  Breslau.  Studien,  iv  (1868). 


ANIMAL    HEAT.  615 

pendent  of  food  or  otiier  circumstances,  has  been  observed,^ 
the  maximum  ranging  from  9  a.m.  to  6  p.m.  and  tlie  mini- 
ninni  from  11  p.m.  to  3  a.m.  Meals  cause  sometimes  a  slight 
elevation,  sometimes  a  slight  depression,  the  direction  of 
the  influence  depending  on  the  nature  of  the  food  ;  alcohol 
seems  always  to  jn-oduce  a  fall.  Exercise  and  variations  of 
exlernal  temperature,  within  ordinary  limits,  cause  very 
slight  change,  on  account  of  the  compensating  influences 
uhich  have  been  discussed  above.  The  ri.se  from  even  ac- 
tive exercise  does  not  amount  to  1°  C.  ;  wlien  labor  is  car- 
ried to  exhaustion  a  depression  of  teuiperature  may  be 
observed.  In  travelling  from  very  cold  to  very  hot  regions 
a  variation  of  less  than  a  degree  occurs,  and  the  temperature 
of  tropical  inhabitants  is  practically  the  s:ime  as  those  dwell- 
ing in  arctic  regions. 

When  external  cold  or  warmth  passes  certain  limits,  or 
when  during  the  application  of  these  agents  the  regulative 
mechanisms  are  interfered  with,  the  temperature  of  the  body 
maybe  lowered  or  raised  until  death  ensues.  When  tlie 
cold  or  warmtii  applied  is  not  very  great,  as  in  cold  and 
warm  baths,  it  has  been  noticed  that  the  temperature  is  more 
easily  raised  by  warmth  tiian  depressed  by  cold.  Death 
ensues  from  extreme  cold  by  a  depression  of  the  activities 
of  all  the  tissues,  more  especially  of  the  nervous;  aspliyxia 
is  produced  in  animals  when  the  fall  of  temperature  is  rapid. 
Puppies  can  be  recovered  alter  the  temperature  in  the  rec- 
tum has  fallen  to  about  4^  or  5°  C  ,  and  hibernating  mam- 
mals may  be  cooled  with  imjjunity  down  to  nearly  freezing- 
point.  Horvath- observed  when  external  warmth  is  brought 
to  bear  on  a  mammal  in  such  a  way  as  to  cause  a  rise  of 
temperature  in  the  body,  death  ensues  when  an  elevation  of 
al)Out  6'^  or  7^^  C.  above  the  normal  is  reached  ;  and  Bernard^ 
places  the  lethal  bodily  temperature  of  a  mammal  at  about 
46°.  The  exact  cause  of  the  death  has  not  been  as  yet  suf- 
flciently  explained.  It  cannot  he  due,  as  Bernard  suggests, 
to  the  muscles  entering  into  rigor  caloris,  for  the  animals 
frequently  succumb  before  this  takes  place.  A  high  tem- 
perature makes  the  heart  irregular,  and  Anally  stops  its  beat, 
but  probably  other  tissues  are  also  injuriously  atfected,  so 


^  Einijer,  Proc.  Eov.  Soc,  xvii,  p.  2S7  ;  ibid.,  xxvi  (1877),  p.  186. 
2  Cbt.^'f.  Med.  Wiss.,  1871,  p.  513. 
^  I^eg.  sur  la  Chaleur  Animale,  1876. 


616       THE    METABOLIC    PHENOMENA    OF    THE    BODY. 

tliat  death  cannot  be  attributed  to  the  stoppage  of  the  heart 
alone. 

One  of  the  most  marked  phenomena  of  starvation  is  tlie 
fall  of  temperature,  which  becomes  very  rapid  during  the 
last  days  of  life.  Indeed  the  low  temperature  of  the  body 
is  a  powerful  factor  in  bringing  about  death,  for  life  may  be 
much  prolonged  by  wrapping  a  starving  animal  in  some  bad 
conductor  so  as  to  economize  the  bodily  heat.^ 


Sec.  5.   The  Influence  of  the  Nervous  System  on 
Nutrition. 

In  the  preceding  sections  we  had  more  than  once  to  refer 
to  the  possibility  of  the  nervous  system  having  the  power 
of  directly  affecting  the  metabolic  actions  of  the  body,  apart 
from  au}^  irrital»le,  contractile,  or  secretory  manifestations. 
Thus  the  phenomena  of  dialietes  cannot,  at  present  at  all 
events,  be  satisfactorily  explained  as  a  .purely  vaso-motor 
effect,  and  the  production  of  heat  is,  as  we  have  seen,  under 
the  sjjecial  guidance  of  the  nervous  system.  In  treating  of 
the  salivary  glands  we  met  witii  the  striking  fact  that  when 
all  the  nerves  of  the  gland  have  been  divided,  and  a  ''  par- 
alytic "  secretion  set  up,  the  tissue  of  tlie  gland  may  ulti- 
mately degenerate.  This  result  differs  from  the  wasting  of 
a  muscle  which  follows  upon  severance  of  its  motor  nerve, 
since  this  may  be,  partly  at  all  events,  explained  by  the  fact 
that  the  muscle  is  no  longer  functional ;  and  indeed,  if  the 
muscle  is  rendered  functional,  if  it  is  directly  stimulated  for 
instance  from  time  to  time  with  a  galvanic  current,  the 
atrophy  may  be  postponed  or  even  altogether  prevented. 
But  the  salivary  gland  in  the  case  in  question  is  functional, 
it  does  go  on  secreting ;  nevertheless  in  the  absence  of  its 
usual  nervous  guidance  its  nutrition  becomes  profoundly 
affected.  We  are  not  justified  in  saying  that  in  this  case 
the  nutrition  of  the  salivary  cell  is  directly  dependent  on 
the  nervous  system,  because  all  biological  studies  teach  us 
that  the  growth,  repair,  and  reproduction  of  protoplasm 
may  go  on  quite  independently'  of  any  nervous  system,  and 
the  nutrition  of  the  nervous  system  itself  cannot  be  depend- 
ent on  the  action  of  that  sj'stem  on  itself;  but  we  may  go 

^  Chossat,  Eech.  Exp.  sur  I'lnanition,  Paris,  1843. 


TROPHIC    NERVES.  617 

SO  far  as  to  infer  that  the  nutrition  of  the  salivary  cell  is  in 
the  complex  animal  body  so  arranged  to  meet  the  constantl}^ 
recurring  influences  brought  to  bear  on  it  by  the  nervous 
system,  that,  when  those  influences  are  permanentlj'  with- 
drawn, it  is  thrown  out  of  equilibrium  ;  its  molecular  pro- 
cesses, so  to  speak,  run  loose,  since  the  bit  has  been  removed 
from  their  mouths.  And  we  might  expect  that  similar  in- 
stances would  be  met  with  where  nutrition  became  abnormal 
after  the  removal  of  wonted  nervous  influences.  Such  in- 
stances indeed  are  not  uncommon  ;  the  most  familiar  being 
perhaps  the  rapid  occurrence  of  bedsores,  in  consequence 
of  injuries  to  or  of  disease  of  the  spinal  cord  or  brain. 
And  there  are  many  pathological  phenomena,  inflammation 
itself  to  liegin  with,  which  seem  inexplicable,  except  when 
regarded  as  the  result  of  nervous  action.  In  all  these  cases, 
iiowever.  there  are  many  attendant  circumstances  to  be  con- 
sideied  before  we  can  feel  justified  in  s})eaking  of  any  direct 
influence  of  the  nervous  system  on  nutrition,  of  any  specific 
action  of  what  have  been  called  "•  trophic  "  nerves.  Perhaps 
the  instance  which  has  lieen  best  worked  out  is  the  connec- 
tion of  the  nutrition  of  the  eye  and  face  with  the  fifth  or 
trigeminal  neive.  AVhen  in  a  rabbit  the  trigeminus  is  di- 
vided in  the  skull  tliere  is  loss  of  sensation  in  those  parts  of 
the  face  of  wliich  it  is  the  sensory  nerve.  Very  soon,  within 
twent3-four  hours,  the  cornea  becomes  cloudy  ;  and  this  is 
the  precursor  of  an  inflammation  which  may  involve  tlie 
whole  eye  and  end  in  its  total  disorganization.  At  the  same 
time  the  nasal  chambers  of  tlie  same  side  are  inflamed,  and 
very  frequently  ulcers  make  their  ai)pearance  on  the  lips 
and  gums.  Seeing  how  delicate  a  structure  the  eye  is,  and 
how  carefully  it  is  protected  b}-  the  mechanisms  of  the  eye- 
lids and  tears,  it  seems  reasonable  to  suppose  that  the  in- 
flammation in  question  might  simply  be  the  result  of  the 
irritation  caused  l)y  dust  and  contact  witii  foreign  bodies, 
to  which  tlie  eye,  no  longer  guided  and  protected  by  sensa- 
tions, these  being  destroyed  b}-  the  section  of  the  nerve, 
became  subject.  In  the  same  way  the  ulcers  on  the  lips  and 
gums  might  be  explained  as  injuries  inflicted  by  the  teetli 
on  tiiose  structures  in  their  insensitive  condition.  And 
Snellen  found  that  the  inflammation  of  the  eye  might  be 
greatly  lessened  or  altogether  prevented  if  the  organ  were 
carefully  covered  up  and  in  all  possible  ways  protected  from 
the  irritating  influences  of  foreign  bodies.  Otlier  observers 
however  have  failed  to  prevent  the  inflammation  in  spite  of 


G18   THE  METABOLIC  PHENOMENA  OF  THE  BODY. 

eveiy  care.  This  negative  result  is  in  itself  no  strong  ar- 
gument, l)ut  the  question  cannot  yet  be  considered  as  en- 
tirely cleared  up. 

Sinitzen  found  that  after  removal  of  tiie  superior  cervical  sym- 
pathetic ganglion,  the  intiammatory  effects  of  section  of  the  tri- 
geminus were  very  much  lessened.  Sinitzen's  explanation,  that 
the  tissues  of  the  face  become  less  irritable  after  removal  of  the 
ganglion,  seems,  however,  hardly  satisfactory.  According  to 
Merkel'  the  intiammatory  phenomena  depend  on  a  particular 
portion  of  the  nerve  being  divided.  He  states  that  if  a  certain 
tract  along  the  inner  border  of  the  nerve  be  alone  cut,  there  is 
no  loss  of  sensation  either  in  the  cornea  or  other  parts  of  the  face, 
but  3^et  intlammation  comes  on  as  usual ;  if,  on  the  other  hand, 
the  whole  nerve  with  the  exception  of  this  tract  be  care f idly  di- 
vided, no  intlammation  ensues  though  sensation  is  lost.  Merkel 
traces  the  tibres  forming  the  inner  border  to  a  deep  origin,  difier- 
ent  from  that  of  the  rest  of  the  nerve.  If  these  results  be  cor- 
roborated, the  trigeminus  must  be  held  to  contain  "trophic" 
fibres. 

In  a  mammal  division  of  both  vagi  is  followed  by  pneumonia 
(intiammation  of  the  lungs),  ending  in  death.  This  has  been  ad- 
duced as  an  instance  of  the  trophic  action  on  the  pulmonary  tis- 
sues of  certain  tibres  of  the  vagi ;  but  the  real  explanation  seems 
to  be  that,  owing  to  a  paralysis  of  the  (esophagus  and  larynx 
caused  by  section  of  the  vagi,  food  accumulating  in  the  pharynx 
passes  into  the  air-passages  and  so  sets  up  the  pneumonia  ^  In 
birds  death  follows,  sometimes  from  pneumonia  of  a  similar 
causation,  but  more  frequently  from  inanition  on  account  of  the 
food  not  being  able  to  enter  the  stomach.  The  immediate  cause 
of  death,  however,  is  in  many  cases  at  all  events  a  paralysis  of 
the  heart,  and  according  to  Eichhorst, '  the  histological  changes 
(acute  fatty  degeneration)  in  the  cardiac  muscle  are  of  such  a 
character  as  to  suggest  a  trophic  action  of  the  vagus  tibres  on  that 
tissue  ;  he  also  tinds  similar  changes  in  the  hearts  of  rabbits. 
The  matter  however  requires  further  elucidation. 

Such  instances  of  nerves  manifesting  even  a  doubtful 
trophic  action  are  rare  ;  yet  there  seems  to  be  no  reason 
why  the  fifth  nerve  or  the  vagus  should  lie  conspicuous  in 
possessing  trophic  fibres.  When  the  sciatic  nerve  of  the 
frog  is  divided,  no  nutritive  alterations  beyond  those  expli- 

^  Untersuch.  Anat.  Inst.  Rostock,  p.  1. 

2  Cf.  Steiner,  Arch.  f.  Anat.  u.  Phys.,  1878  (Phys.  Abtli.),p.  218,  and 
references  tiiere  given. 

^  Die  trophischen  Bezieliungen  der  Nervi  vagi  znm  Herzmuskel  (Ber- 
lin, 1879).     Cf.  also  Zander,  Pfliiger's  Archiv,xix  (1879),  p.  263. 


DIETETICS.  619 

ealile  as  the  result  of  loss  of  function  are  observed  ;  and 
indeed  the  nsajority  of  the  effects  on  growth  and  nutrition 
resulting  from  the  section  of  nerves,  or  from  paralysis,  can 
be  referred  to  the  absence  of  the  usual  functional  activity, 
accompanied  in  some  cases  with  an  altered  vascular  sup})ly. 
jSevertheless  the  numerous  piienomena  of  disease,  joined  to 
the  facts  mentioned  above,  turn  the  balance  of  evidence  in 
favor  of  tiie  view  that  some  more  or  less  direct  influence  of 
the  nervous  system  on  metabolic  actions,  and  so  on  nutri- 
tion, will  be  established  by  future  inquiries. 

The  influence  which  Hoht  acting  on  the  retina  appears  to  exer- 
cise on  the  metabolism  of  the  body  may  be  quoted  as  an  illustra- 
tion of  the  statement  just  made.' 

Among  the  pathological  facts  which  may  be  quoted  as  sugges- 
tive of  trophic  action  are  the  occurrence  of  certain  eruptions, 
such  as  lichen,  zon:i,  ecthyma,  etc.,  in  various  spinal  or  cerebral 
diseases,  frequently  accompanied,  as  in  maladies  aflecting  the 
posterior  cornua,  with  intermittent  pains  ;  the  rapid  and  pecu- 
liar degeneration  of  and  loss  of  contractility  in  the  skeletal  mus- 
cles in  certain  aftectious  of  the  spinal  cord,  the  changes  in  the 
muscles  being  more  rapid  and  profound  than  in  the  nerves  ;  the 
so-called  acute  bedsores  of  cerebral  apoplexy  ;  some  at  least  of 
the  cases  of  vesical  affections  attendant  on  spinal  or  cerebral  dis- 
eases or  injuries  ;  the  more  rapid  atrophy  and  loss  of  contractility 
which  is  seen  in  muscles  after  contusions  than  after  sections  of 
nerves  ;  and  indeed  the  general  phenomena,  and  especially  the 
topography  of  the  eruption  of  a  large  number  of  cutaneous  dis- 
eases. The  pathological  evidence  of  "trophic"  action,  though' 
indirect,  affords,  by  its  abundance  and  prominence,  a  striking 
contrast  to  the  scanty  and  uncertain  indications  of  experimen- 
tal inquiry. 

Sec.  6.    Dietetics. 

We  may  sum  up  the  main  results  of  the  i^revious  sections 
somewhat  in  the  following  way  :  Although  the  body  consists, 
like  the  food,  of  proleids,  fats,  and  carbohydrates,  yet  the 
conversion  of  the  one  into  the  other  is  not  direct.  Assimi- 
lation does  not  proceed  in  such  a  way  that  the  proteids  of 
the  food  all  become  tlie  proteids  of  the  body,  the  fats  of  the 
food  the  fats  of  the  body,  and  the  starch  and  sugar  of  the 
food  tiie  glycogen,  dextrin,  and  sugar  of  the  body,  ^^'e 
cannot  even  say  that  the  n(m-nitrogenous  food  supplies  alone 

'  Cf.  Pfliiccer  and  Von  Phiten,  I^fiiiger's  Archiv,  xi  (1875),  pp.  263, 
272.     Fubini,  Molescliott's  Untersuch!,  xi  (1870),  p.  488. 


620      THE    METABOLIC    THENOMENA    OF    THE    BODY. 

the  non-nitrogenoiis  parts  of  the  body,  while  the  nitre genous 
food  remains  as  the  sole  source  of  the  nitrogenous  tissues. 
We  have  seen  that,  under  all  circumstances,  a  certain  quan- 
tity of  proteid  food  is  immediately  metabolized,  probably 
while  still  within  the  alimentary  canal,  and  that  when  an 
excess  of  proteid  food  is  taken  a  luxus  consumption  leads 
to  the  accumulation  of  bodily  fat.  On  the  other  hand,  we 
find  that  a  large  proportion  of  the  carbonic  acid  of  the 
egesta  comes  fn.m  the  metabolism  of  nitrogenous  tissues, 
such  as  muscle  :  and  we  have  had  proof  that  the  energy  set 
free  by  muscular  contraction  may  be  far  greater  than  could 
be  su[)plied  by  the  proteid  food  taken,  and  that  therefoi'e 
the  non-nitrogenous  factors  of  the  metabolism  which  set  free 
the  energy  must  have  ultimatfly  come  from  non-nitrogenous 
food.  We  have  abundant  evidence  that  the  various  food- 
stuflls  become  more  or  less  metabolized,  and  their  elements 
m.ore  or  less  rearranged  and  mixed  before  they  appear  as 
constituents  of  the  bodily  tissues. 

AYe  have  seen  that  the  oxidations  of  the  body  are,  as  in 
the  case  of  muscle,  of  a  peculiar  character,  and  carried  on 
b}^  the  tissues  tliemselves.  While  at  i)resent  we  should  be 
hardly  justified  in  denying  that  any  oxidations  at  all  take 
place  in  the  blood-plasma,  such  as  do  occur  must  be  slight 
in  amount  as  compared  with  those  going  on  in  the  tissues. 
We  might  also  say  that  one  Ijod}'  only,  viz.,  lactic  acid,  pre- 
sents itself  as  a  substance  likely  to  be  directly  oxidized  in 
tiie  blood  itself;  and  even  with  regard  to  this  the  evidence 
is  as  much  against  as  for  any  such  direct  oxidation  taking 
place.  The  great  mass  of  the  oxidation  of  the  body  is  of 
an  indirect  kind,  determined  by  the  activity  of  the  several 
tissues.  The  blood  serves  as  an  oxygen  carrier  for  the  tis- 
sues;  and  it  is  not  itself  the  large  combustible  agent  it  was 
once  thought  to  be.  Tlie  tendency  of  ail  recent  inquiries 
is  to  show  that  the  body  cannot  be  compared,  either  as  a 
whole  or  in  its  parts,  to  a  furnace  for  the  direct  combustion 
of  combustible  food.  On  the  contrary,  we  are  driven  neai'er 
and  nearer  to  the  conclusion  that  all  food  which  has  become 
absorbed  into  the  blood  must  become  tissue  before  it  be- 
comes waste  product,  and  only  boccjmes  waste  product 
through  a  metabolism  of  the  tissue.  When  we  say  ''be- 
come tissue"  we  must  leave  it  at  present  wholly  undecided 
how  far  the  constant  metabolism  which  this  view  demands 
affects  the  so-called  structural  elements  of  the  more  highly 
organized  tissues  :  it  is  quite  open,  however,  for  us  to  im- 


DIETETICS.  621 

agine  that  in  muscle,  for  instance,  there  is  a  framework  of 
more  stable  material,  giving  to  the  muscular  fibre  its  his- 
tological features,  and  undergoing  a  comparatively^  slight 
and  slow  metabolism,  while  the  energy  given  out  b^'  muscle 
is  supplied  at  the  expense  of  more  fluctuating  molecules, 
which  fill  up,  so  to  speak,  the  interstices  of  the  more  durable 
framework,  and  metabolism  of  which  alone  is  large  and 
rapid. 

The  characteristic  feature  of  proteid  food  is  that  it  in- 
creases the  oxidative,  metabolic  activity  of  the  tissues, 
leading  to  a  rapid  consumption,  not  only  of  itself,  but  of 
non-nitrogenous  food  as  well.  Where,  therefore,  a  rapid 
renewal  of  the  tissues  is  sought  for,  an  excess  of  proteid 
food  may  be  desiral)le.  But  it  must  be  borne  in  mind  that, 
by  the  very  nature  of  its  rai)id  metabolism,  proteid  food 
must  tend  to  load  the  body  with  the  so-called  extractives, 
i.  e.,  with  nitrogenous  crystalline  bodies.  How  far  these  are 
of  use  to  the  body,  and  what  part  tlie}'  play,  is  at  present 
unknown  to  us.  That  they  are  of  some  use  is  suggested  by 
the  beneficial  effects  of  the  extroctum  carnU^  when  taken 
as  food  in  conjunction  with  non-nitrogenous  material,  though 
it  is  possible  that  the  dietetic  value  of  tiiis  preparation  may 
be  due  to  the  small  amount  of  non-crystalline  extractives 
which  it  contains.  That  when  in  excess  these  nitrogenous 
products  may  be  highly  injurious  is  indicated  by  the  little 
we  know  of  the  connection  between  the  symptoms  of  gout 
and  the  presence  of  uric  acid.  A  large  meal  of  proteid  ma- 
terial must  tax  the  system  to  the  utmost  in  getting  rid  of  or 
stowing  away  the  nitrogenous  crystalline  bodies  arising 
through  the  luxus  consumption,  either  in  the  alimentary 
canal  or  in  the  liver. 

One  value  of  fats  and  carbohydrates  lies  in  their  being 
sources  of  energy,  more  than  three-fourths  of  the  normal 
income  of  potential  energ}'  coming  from  them  (p.  594); 
and.  as  we  have  seen,  the}-  are  ultimate  sources  of  muscular 
energy  as  well  as  of  heat.  But  their  great  characteristic  is 
that  the}-  do  not,. like  proteid  food,  excite  the  metabcjlic 
activity  of  the  body.  Hence,  to  a  far  gi-eater  extent  than 
is  the  case  with  proteid  food,  they  can  be  retained  and 
stored  up  in  the  body  with  comparative  ease.  The  digested 
elements  of  fatty  or  carl^ohydrate  food,  which  go  to  form 
the  protoplasm  of  adipose  tissue,  become  part  and  parcel 
of  a  substance  wliicli  can  perform  its  metabolism  without 
any  explosive  expenditure  of  energy,  and  which,  therefore, 


622       TEIE    METABOLIC    PHENOMENA    OF    THE    BODY. 

instead  of  iii\  ing  rise  to  bodies  demandinor  immediate  ex- 
cretion from  ti)e  system,  can  deposit  its  metabolic  products 
as  apparently  little,  but  as  we  have  seen  in  reality  greatly, 
changed  fat.  In  this  way  the  non-nitrogenous  food  of  to- 
day is  rendered  available  for  future,  and  even  far  distant, 
wants. 

In  comparing  fats  with  carbohydrates  we  can  only  point 
to  the  much  greater  potential  energy  of  the  former  than  of 
the  latter,  weight  Un'  weight  (see  p.  51)5). 

A  diet  maybe  chosen  either  for  the  simple  maintenance 
of  health,  or  for  the  sake  of  muscular  energy,  or  for  fatten- 
ing purposes.  For  the  lirst  purpose  there  is.  we  may  sup- 
pose, a  normal  diet;  and,  in  the  case  of  man,  instinct  and 
experience  have  probably  not  erred  far  in  choosing  some 
such  proportions  as  those  given  on  p.  582.  If,  as  we  have 
urged,  all  food  becomes  tissue  before  it  leaves  the  body  as 
waste  [)roduct,  the  dominant  principle  of  all  nutrition,  and 
the  ultimate  tribunal  of  all  questions  of  diet,  must  be  the 
individual  character  of  the  tissue,  the  idiosyncrasy  of  the 
body.  The  same  mysterious  qualities  which  cause  the  same 
blood-plasma  to  become  here  a  muscle  and  there  a  secreting 
cell,  convert  the  same  food  into  the  body  of  a  man  or  of  a 
sheep.  All  the  simpler  and  more  geneial  laws  of  metabol- 
ism are  made  subservient  to  more  intricate  and  special  laws 
of  piotoplasmic  construction.  We  can  only  speak  of  a 
normal  diet  in  the  same  way  that  we  speak  of  the  average 
intelligence  of  man. 

In  seeking  to  supply  such  a  normal  diet  out  of  ordinary 
articles  of  food,  we  must  bear  in  mind  that  the  nutritive 
value  of  any  substance,  estimated  in  terms  of  the  potential 
energy  of  the  jn-oteids.  fals,  or  carbohydrates  it  contains, 
must,  of  course,  be  corrected  by  its  digestibility.  One  gram 
of  cheese  has,  as  far  as  potential  energy  is  concerned,  an 
exceedingly  high  value;  but  the  indigestibility  of  cheese 
brings  its  nutiitive  value  to  a  very  low  level.  Here  too  the 
factor  of  idiosyncrasy  makes  itself  exceedingly  felt. 

In  feeding  for  fattening  purposes  the  comi)aratively  cheap 
carbohydrates  are,  of  course,  chiefly  depended  on.  If  the 
view  mentioned  on  p.  591  be  correct,  that  the  fat  really 
stored  up  all  comes  from  proteid  metabolism,  an  equivalent 
of  this  food-stutf  must  always  be  given.  If,  as  seems 
probable,  this  view  is  a  too  hurried  generalization,  there 
still  remains  the  possibility  that  for  economical  fattening, 
with  the  least  waste,  a  certain  proportion  between  the  nitre- 


DIETETICS.  623 

genons  and  non-nitrogenous  foods  must  always  be  main- 
tained. 

From  what  lias  been  previously  said  it  is  evident  tiiat 
proteid  food  is  not  the  only  foo(i-stuff  to  be  regarded  in 
selecting  a  diet  for  muscular  labor.  We  should,  howeA^er, 
equally  err  in  the  opposite  direction  if  we  selected  exclu- 
sively non-nitrogenous  food  on  which  to  do  work,  since,  as 
we  have  seen,  tliere  is  no  evidence  that  the  fats  or  carbo- 
hydrates are  the  direct^  though  they  njay  be  in  part  the 
vUiinate  source  of  muscular  energy.  Considering  how  com- 
plex a  thing  strength  is,  how  much  it  depends  on  the  vigor 
of  parts  of  the  body  other  than  the  muscles,  a  normal  diet, 
calculated  to  develop  equally  all  parts  of  the  l)ody,  is  proba- 
bly the  liest  diet  for  active  labor.  It  is  possible,  however, 
that  an  excels  of  proteid  food,  by  reason  of  the  renewal  of 
tissue  caused  by  its  metabolic  activity,  njay  be,  in  such  cases, 
of  service. 

Lastly,  the  several  saline  matters,  including  the  extrac- 
tives of  animal  and  vegetable  food,  are  no  less  essential  ele- 
ments of  a  diet  than  proteids,  fats,  or  carbohydrates.  Of 
use.  not  for  the  energy  they  themselves  possess,  but  by 
reason  of  their  regulating  the  energ}'  of  the  food-stuffs  more 
strictly  so  called,  they  are  necessary  to  life;  the  bod}'  in 
their  absence  fails  to  carry  out  its  usual  metabolism,  and 
disease  if  not  death  follows. 


The  dietetic  superiority  of  fresh  meat  and  vegetables  depends  in 
part  on  their  still  retaining;  these  various  saline  and  extractive 
matters.  A  diet  from  which  phosphorus  (or  even  possibly  phos- 
phates), or  chlorides,  or  potash,  or  soda  salts  are  absent  is,  as 
soon  as  the  store  of  the  substance  in  the  body  is  exhausted,  use- 
less for  nutritive  purposes.  Calcium  and  magnesium  may,  to  a 
certain  extent,  be  replaced  by  bases  closely  allied  to  them  ;  but 
the  metabolic  ro'e  of  phosphorus  or  of  sulphur  cannot  be  taken 
up  by  an  analogous  body  ;  and,  as  is  illustrated  by  their  distribu- 
tion in  the  body,  the  physiological  functions  of  potash  and  soda 
are  widely  ditfeVent  if  ii')t  antagonistic,  closely  allied  as  are  these 
two  alkalies  when  regarded  from  a  chemical  point  of  view\  Like 
medicines  and  poisons— and.  indeed,  they  are  in  a  manner  natural 
medicines— the  action  of  these  bodies  depends  in  part  on  their 
dose.  Indispensable  as  are  potash  salts  to  the  economy,  a  large 
dose  of  them  is  injurious  ;  and  a  dog  fed  on  nothing  but  Liebig's 
extract  dies  sooner  than  a  dog  not  fed  at  all,  on  account  of  the 
potash  salts  of  the  extract  exerting  their  deleterious  influence  in 
the  absence  of  the  food  whose  metabolism  their  function  is  to 
direct. 


624      THE    METABOLIC    PHENOMENA    OF    THE    BODY. 


The  physiology  of  nutrition  may  be  said  to  have  been  founded 
by  Liebig,  when  he  proved  the  formation  of  fat  in  the  animal 
body,  and  published  his  views  on  the  nature  and  use  of  food. 
The  labors  of  liegnault  and  Reiset'  added  much  to  our  knowledge 
of  the  Statistics  of  Respiration.  The  first  elaborate  inquiry  into 
the  Statistics  of  Metabolism  in  general  was  that  of  Bidder  and 
Schmidt ;"-  this  was  followed  by  the  investigations  of  the  Munich 
school,  viz.,  Bischoff,  Bischoff  and  Voit,^  Yoit,  and  Pettenkofer 
and  Voit.*  -Although  we  have  had  occasion  to  combat  some  of 
the  views  of  this  school,  it  must  be  admitted  that  their  extended 
and  laborious  researches  have  been  the  means  of  an  immense  ad- 
vance in  our  knowledge.  Their  method  has  been  largely  adopted, 
with  excellent  results,  by  the  various  agricultural  stations  in 
Germany  :  and  in  this  country  the  inquiries  of  Lawes  and  Gil- 
bert^ have  given  us  information  of  peculiarly  valuable  character, 
inasmuch  as  it  is  chietiy  based  on  direct  analysis  and  observation, 
and,  therefore,  free  from  the  possibilities  of  error  attaching  to 
mere  calculations.  If,  however,  one  discovery  can  be  pointed  to 
as  influencing  our  views  of  the  nature  and  laws  of  animal  meta- 
bolism more  than  any  other,  it  is  that  by  Bernard''  of  the  forma- 
tion of  glycogen  by  tlie  liver. 

'   Ann.  Ch.  Phys.  (1849)  (3),  xxvi,  32.  ^  Qp.  dt. 

^  Op.  cit. 

*  Op.  cit.,  and  many  subsequent  memoirs  in  the  Zt.  fiir  Biol. 
^  Op.  cit.  '  6  Op.  cit. 


BOOK  III. 

THE  CENTRAL  NERTOUS   SYSTEM  AND   ITS 
INSTRUMENTS. 


CHAPTER     I. 

[General  Arrangement  of  the  Nervous  Sydem. 

The  nervous  system  consists  of  two  secondary  divisions  : 
the  cerebrospinal  and  the  Hynipafhetic  or  ganglionic. 

The  cerebrospinal  system  embraces  a  centilil  system, 
which  inchides  the  brain  and  spinal  cord,  and  a  periph- 
eral system  consisting  of  the  cranial  and  spinal  nerves  and 
tlieir  ganglia.  The  central  system  is  known  as  the  cerebro- 
spinal axis  (Fig.  152),  and  it  comprises  all  the  organs  pre- 
siding over  the  functions  which  are  cliaracteristic  oi'  animal 
life,  such  as  volition,  special  sensation,  etc.  The  cranial 
and  spinal  nerves  serve  as  a  means  of  intercommunication 
between  the  central  nervous  system  and  the  peripheries  by 
conducting  impulses  to  and  from  the  centres. 

The  brain  is  composed  of  the  cerebrum  and  cerebellum 
and  the  ganglia  forming  part  of  the  former  ;  and  the  medulla 
oblongata  and  pons. Varolii,  by  wiiich  they  are  connected  to 
the  spinal  cord.  The  spinal  cord  is  that  portion  of  the 
cerebrospinal  axis  which  is  situated  within  the  spinal  canal 
between  the  foramen  mngnum  and  the  second  lumbar  ver- 
tebra. Abovia,  it  is  continuous  with  the  medulla  oblongata; 
below,  it  terminates  in  an  extremity^  of  gra}'  matter,  which 
is  teru^sed  the  Jilum  terminate. 

The  cranial  nerves  arise  from  the  under  surface  of  the 
cerebrum  and  medulla  oblonsata  and  make  their  exit  throuijh 


626 


THE    NERVOUS    SYSTExM. 
Fig.  ]o2. 


Uiuler  Surface  or  Base  of  the  Cerebrum,  and  Cerebellum,  and  of  the  Pons  Varolii 
and  Medulla  Oblongata. also  the  aiiteriorsurface  of  theSpinal  Cord,  to  show  the  mode 
of  origin  of  the  Spinal  Nerves  from  the.-pinal  Cord,  and  the  Cranial  Nerves  from  the 
base  of  the  Brain,  a,  a,  cerebral  hemisjiheres;  b,  rigiit  half  of  cerebellum  ;  m,  me- 
dulla oblongata;  above  this  is  a  transverse  white  mass,  the  pons  Varolii;  c,c',  the 


ANATOMY    OF    THE    NERVE-TISSUES.  627 

spinal  cord,  showing  its  cervical  and  lumbar  enlargements,  and  its  pointed  termina- 
tion ;  e,  the  cauda  equina,  formed  by  the  elongated  roots  of  the  lumbar  and  sacral 
nerves;  1  to 9,  the  several  cranial  nerves,  arising  from  the  base  of  the  brain  and  the 
sides  of  the  medulla  oblongata.  Below  these,  on  each  side,  are  the  roots  or  origins 
of  the  spina!  nerves,  cervical,  dorsal,  lumbar,  and  sacral.  In  some  of  these  the  dou- 
ble root  can  be  seen,  and  the  swelling  or  ganglion  on  the  posterior  root.  a.  x,  the 
axilh\ry  or  brachial  pU'Xus,  formed  by  the  four  lower  cervical  and  lirst  dorsal  spinal 
nerves:  I,  the  lumbar  plexus  ;  s,  the  sacral  plexus,  formed  by  the  last  lumbar  nerve 
and  first  four  sacral  nerves  ;  t,  shows  a  piece  of  the  sheath  of  the  cord  cut  open,  and 
with  it  a  portion  of  the  ligamentum  denticulatum  which  supports  the  cord. 

Fig.  61.—^,  a  transverse  section  through  the  cord,  to  show  the  form  of  the  gray 
cornua  or  horns,  in  the  midst  of  the  white  substance.  B,  shows  the  same  parts,  and 
also  the  membranes  of  the  cord  ;  and  the  anterior  and  posterior  roots  of  a  pair  of 
spinal  nerves  springing  from  its  sides. 

the  foramina  in  the  ba.se  of  the  cranial  vault.  The  spinal 
nerves  arise  by  two  roots,  anterior  and  posterior,  from  the 
sides  of  the  spinal  cord,  and  make  their  exit  through  the 
intervertebral  foramina.  On  the  posterior  root  is  a  ganglion. 
The  ganglionic  or  i<ym'pa(hetic  system  consists  of  a  double 
chain  of  ganglia,  which  extends  from  tiie  base  of  the  brain 
to  the  pelvic  cavity.  Each  chain  is  situated  to  the  front 
and  side  of  the  vertebral  column.  The  ganglia  are  inti- 
mately connected  with  the  adjacent  ganglia  and  with  the 
cerebro-spinal  axis  by  means  of  nervous  cords.  The  nerves 
given  off"  from  the  ganglionic  system  are  principally  distrib- 
uted to  the  viscera  of  the  thoracic,  abdominal,  and  pelvic 
cavities,  and  hence  are  more  intimately  connected  with  the 
functions  of  organic  life,  such  as  are  manifested  in  growth 
and  nutrition.  The  ganglionic  system  has,  therefore,  been 
termed  the  system  of  organic  life. 

The  Physiological  Anatomy  of  the  yerve-tissues. 

The  nervous  system  is  composed  of  two  elementary  ner- 
vous structures  :  the  vesicular  matter,  and  ihe  fibrous  matter. 
The  vesicular  matter  is  distinguished  from  the  fibrous  matter 
by  its  characteristic  reddish-gray  color,  its  vesicular  struc- 
ture, its  softer  consistency,  and  greater  vascularity.  It  con- 
sists of  an  aggregation  of  vesicles  which  are  called  the  gan- 
glionic or  nerve  corpuscles,  and  is  never  found  in  the  nerves. 
These  corpuscles  are  composed  of  a  delicate  wall,  which 
incloses  granular  pigmented  contents,  with  an  eccentric  nu- 
cleus, and  a  variaUe  numV»er  of  nucleoli. 

The  nerve  cells  are  found  in  aggregated  masses,  imbedded 
in  a  graiudar  material,  and  having  intermingled  and  con- 
nected with  them  some  fibrous  matter.     In  this  condition 


628 


THE    NERVOUS    SYSTEM. 


the_y  form  the  gnno^Ua  and  the  great  centres  of  gray  matter 
found  in  tlie  brain  and  spinal  cord.  The  vesicular  matter 
alone  is  supposed  to  he  capable  of  generating  nerve  force, 
and  of  dis[;osing  of  impressions  received  from  the  periph- 
ery. They  are  of  very  irregular  and  diverse  forms  (Fig. 
153),  and  generally  possess  one  or  more  caudate  processes 
or  poles  ;  hence  they  have  been  termed  unipolar,  bipolar, 
and  multipolar  cells.  The  processes  intercommunicate  with 
the  processes  of  neighboring  cells, or  are  continuous  with  the 
axis-cylinders  (Fig.  159)  of  nerve-fibi-es.  The  apolar  cells 
are    probably   undeveloped    cells.       The    bipolar    cells    are 


Various  forms  of  Ganglionic  Vesicles:  a,  b,  large  stellate  cells,  with  their  prolonga- 
tions, from  the  anterior  horn  of  the  gray  matter  of  the  spinal  cord;  c,  nerve-cell 
with  its  connected  tibre,  from  the  anastomosis  of  the  facial  and  auditory  nerves  iu 
the  meatus  aiiditorins  internus  of  the  ox  ;  a,  cell-wall ;  b,  cell-contents  ;  c,  pigments  ; 
d,  nucleus  ;  e,  prolongation  forming  the  sheath  of  the  fibre  ;  /,  nerve-fibre  ;  d,  nerve- 
cell  from  the  substantia  ferruginea  of  man  ;  e,  smaller  cell  from  the  spinal  cord, 
magnified  350  diameters. 

found  in  the  sympathetic  ganglia,  and  in  the  ganglia  of  the 
posterior  roots  of  the  spinal  nerves.  Dr.  Beale  and  other 
investigators  found  in  the  sympathetic  ganglia  of  the  frog 
very  complex  pyriform  nerve-cells  (Fig.  154),  vvhich  have 
two  fibres  arising  from  their  pointed  extremity.  One  of  the 
fibres  (a)  runs  in  almost  a  straight  course  to  the  cell  ;  the 
other  fibre  (b)  arises  from  the  exterior  of  the  cell,  frequently 
as  two  filaments,  which  form  several  spiral  turns  around 
the  axial  fibre  (^o,),  and  finallj^  emerges  from  the  capsule  as 


ANATOMY    OF    THE    NERVE-TISSUES, 


629 


a  single  fibre.  Otlier  investigators  state  that  the  straight 
filire  (Fig.  154,  B,  a  is  continued  into  tlie  nucleus,  and  that 
the  spiral  fibre  (b)  forms  a  plexus  on  the  exterior  of  the  cell, 
and  may  be  traced  to  the  nucleolus.  The  multipolar  cells  are 
found  in  all  the  ganglia,  but  are  most  numerous  in  the  gray 
matter  of  the  cerebro-spinal  centres.  In  the  anterior  cornna 
of  the  spinal  cord  tiiey  possess  sometimes  as  many  as  twelve 
processes.  The  processes  of  some  of  the  cells  divide  and 
subdivide  so  rapidly  into  smaller  filaments  that  they  form  a 
close  radiating  plexus  in  the  interstitial  vesicular  matter 
adjoining  the  cell  (Fig.  155). 

Fig.  154.  Fig.  1.^5. 


Fig.  154. — Structure  of  a  pyrit'orm  ganglionic  nerve  cell.  A,  according  toBeale; 
B,  according  to  Arnold. 

Fig.  155— Stellate  Nerve-cell,  from  the  Nucleus  Cervicis  Cornu  (posterior  vesicular 
column)  of  a  Foetus  of  six  months  X  420. — After  Beale. 

The  K7r//p  or  //6ro?/.s'7?ia/fp?' compose  the  nerve-fibres  forming 
the  cranial  anclsi)inal  nerves  and  the  white  strands  of  nervous 
matter  which  are  found  in  the  cerebro-spinal  axis.  The  nerves 
are  composed  of  bundles  of  fibres,  which  are  called  fuinc2ih\ 
and  are  inclosed  in  a  fibrous  sheath,  the  perineurium ;  the 
funiculi  being  separated  from  each  other  by  an  investing 
fibrous  membrane  formed  by  reflections  inwards  of  the  peri- 
neuriutn.  Kach  funiculus  is  formed  of  a  number  of  bundles 
of  Jibre.^  or  tubulef<,  which,  according  to  Ranvier,  are  inclosed 
in  a  layer  of  fiat  epithelium  cells  (Fig.  156)  ;  this  is,  however, 
contradicted  by  some  observers  who  deem  the  cells  a  lining 
of  lymphatic  spaces.  If  these  tubules  are  separated  and  indi- 
vidually examined  during  life  they  will  appear  to  consist  of  a 
simple  homogeneous  transparent  investment,  which  incloses 
a  soft  transparent  structureless  substance.    Each  tubule  has 

53 


630 


THE    NERVOUS    SYSTEM. 


a  well-accentuated  dark  outline  (Fig.  158,  A).  But  after  re- 
moval from  the  bod>',  the  lowered  temperature  or  other  in- 
fluences causes  the  contents  of  the  tubule  to  coagulate,  and 
a  double  contour  appears  (Fig.  158,  B),  which  indicates 
that  the  tubules  aie  not  of  a  simple  structure,  but  that  they 
are  composed  of  several  elements.  These  are  seeu  to  be  an 
external  or  white  poition  and  an  internal  or  gray  centre. 
When  these  changes  are  farther  advanced,  or  if  pressure 
has  been  made,  they  assume  a  varicose  appearance  (Fig.  158 
C),  which  is  caused  by  the  breaking  down  of  the  white  mat- 
ter into  small  segments  or  drops,  and  its  collection  in  cer 
tain  spots,  thereby  causing  tiie  tubule  to  swell.     Further 


Fig. 156. 


Fig.  157. 


ULi..  -ai^i 


ItluiLJ 


Fig.  156. — Funiculus  of  a  Mouse  after  impregnation  with  Nitrate  of  Silver.  Large 
flat  epithelial  cells  are  seen  covering  its  surface.  The  explanation  of  the  small 
crosses  is  seen  by  reference  to  the  next  figure.— After  Ranvier. 

Fig.  157. — Nerve-fibre  from  the  Sciatic  Nerve  of  the  Rabbit  after  the  action  of  Ni- 
trate of  Silver,  a,  ring  formed  by  thickened  membrane  of  Schwann  ;  m,  white  sub- 
stance of  Schwann  rendered  transparent  by  glycerin  ;  Cy,  axis-cylinder,  which  just 
above  and  below  the  level  of  the  annular  constriction  presents  the  strise  of  Fromniann. 

changes  are  afterwards  observed  when  the  substance  of  the 
interior  will  be  seen  to  be  collected  in  distinct  masses.  (Fig. 
158,  D.)  Tlie  dark  outline  in  B,  Fig.  158.  indicates  the  tube- 
sheath  or  neurilemma^  which  incloses  the  medullary  sub- 
stance or  ivhite  substance  of  Schwann,  the  inner  boundary  of 
which  is  indicated  by  the  inner  line.  In  the  central  portion 
of  the  medullary  substance,  corresponding  to  the  axis,  is  a 
gray,  flattened,  threadlike  filament,  which  is  termed  the  axis- 
cylinder.  (Fig.  159.)    The  fibres  thus  constructed  are  called 


ANATOxMY    OF    THE    NERVE-TISSUES. 


631 


the  mrduUated  nerve-fiiires,  in  contradistinction  to  other 
fibres  which  possess  no  medulhir}"  substance,  and  hence  are 
called  the  noa-meduUated  fibres. 


FiCx.  158. 

.4  n  c 


Primitive  Nerve-tubules,  a,  a  perfectly  frL-sli  tubule  with  a  simple  ilaik  outline. 
B,  a  tubule  or  fil)re  with  a  double  contour  from  coniniencing  post-inorteiu  change, 
c,  the  chauges  further  advanced,  producing  a  varicose  or  beaded  appearance.  D, 
a  tubule  or  fibre,  the  central  part  of  which,  in  consequence  of  still  further  changes, 
has  accumulated  in  separate  portions  of  the  sheath.— (After  Wagnek.) 

At  intervals  along  the  course  of  the  tubule,  annular  con- 
strictions are  seen  i  P^ig.  157).  These  appear  to 
be  due  to  a  thickening  of  the  neurilemma  at  the 
constricted  point.  The  axis-cylinder  passes 
through  these  constricted  portions  uninterrupt- 
edly, and  at  tliis  position  is  marked  by  a  numl)er 
of  transverse  lines  called  the  striae  of  Froramann. 
Between  each  of  these  constricted  points  a  nu- 
cleus is  found,  which  lies  between  the  white  sub- 
stance of  Schwann  and  the  neurilemma.  The 
axis-cylinder  in  the  ganglion  cells,  and  in  the 
ultimate  termination  of  the  olfactory  and  optic 
nerves  and  some  of  tlie  sympathetic,  have  been 
observed  to  be  composed  of  a  number  of  ex- 
tremely attenuated  varicose  fiitres,  which  are 
termed  the  primitive  nerve-fibrils  (Fig.  160). 

The  non-medullated  fibres  (gelatinous  fibres  of  Remak) 


1/ 

Diagram  of 
Structure  of 
Nerve-libre. 

1,  neurilem- 
ma ;  2,  white 
substance  of 
Schwann  ;  3, 
axis  cylinder. 


632 


THE    NERVOUS    SYSTEM. 


differ  from  the  niediilkted,  by  the  absence  of  the  annular 
constrictions  and  of  the  double  contour;  by  their  smaller 
size,  the  greater  number  of  nuclei  found  in  their  course,  and 
by  tlieir  grayish  color.  The  non-medullated  fibres  constitute 
the  entire  portion  of  the  olfactory  and  of  some  of  the  sympa- 
thetic nerves,  and  are  found  in  variable  quantity  with  tlie 
medullated  fibres  in  the  nerves  of  the  cerebro  spinal  system. 
Jn  the  cerebro-spinal  nerves,  especially  at  their  central  and 
peripheral  extremities,  other  non-medullated  fibres  are  found 
which  are  probably  nothing  more  than  the  axis-cylinders  of 
medullated  tubules. 

Fig. IGO. 


rriinitive  Nerve-fibrils,  a,  from  the  nervous  fibre-layer  of  the  retina;  b,  from  the 
?xiernal  granular  layer  of  the  retina,  showing  at  x  a  larger  varicosity  resulting  from 
imbibition  ;  c,  from  the  olfactory  nerve  of  the  pike,  showing  a  thick  nerve  inclosed 
in  a  sheath  breaking  up  into  fibrilia.-. 

The  nerve-fibres  serve  as  a  means  of  intercommunication 
between  the  centres  or  portions  of  them,  and  }>etween  the 
centres  and  peripheries.  Each  fibre  is  a  continuous  one  be- 
tween the  periphery  and  centre,  and  although  they  may  in- 
osculate, they  never  form  anastomoses.  Each  fibre,  therefore, 
consists  of  a  central  and  a  peripheral  extremity;  the  central 
extremity  may  properly  be  considered  as  the  root :  the  periph- 
eral extremity  as  the  peripheral  termination.     Fibres  which 


SENSORY    NERVES.  633 

convey  impressions  from  the  centre  to  tlie  periphery  are 
called  efferent  or  motor  fibres  ;  those  conveying  impressions 
from  the  peripherj'  to  the  centre,  aff'erent  or  ,sensori/  fibres. 

Tlie  nerves  terminate  in  x2)ecial  and  general  modes.  As 
special  modes  they  terminate  in  the  tactile  corpuscles 
(Fig.  134)  :  the  Pacinian  corpuscles  (Fig.  135)  ;  the  terminal 
bulbs  of  Krause  (Fig.  133);  and  in  other  terminal  organs 
concerned  in  special  sensation,  which  wll  be  hereafter  no- 
ticed. In  the  voluntary  muscles  they  terminate  in  the  end- 
plates  (Fig.  21 ).  The  mode  of  termination  of  the  nerves  in 
the  involuntar}'  muscles  is  as, yet  wrapped  in  obscurity;  re- 
cent investigations,  however,  indicate  that  the  fibres  form 
plexuses,  and  finally  terminate  in  the  nuclei  of  the  cells. 
In  the  glands,  according  to  Pfliiger,  the  axis-cylinder  is  con- 
tinued into  the  gland-cell. 

The  general  mode  of  termination  is  by  the  formation  of 
extremely  delicate  plexuses,  tiie  filaments  of  whicii  cannot  be 
traced  to  any  definite  terminal  point.  The  nerve-fibres  are 
devoid  of  tlie  white  substance  of  Schwann  at  their  ultimate 
terminations.] 

SEXSORY  NERVES. 

In  studying  the  phenomena  of  motor  nerves  we  are  greatly 
assisted  by  two  facts:  First,  that  the  muscular  contraction 
by  which  we  judge  of  what  is  going  on  in  the  muscle,  is  a 
comparatively  simple  thing,  one  contraction  difiering  from 
another  onl}'  b}-  such  features  as  amount,  rapidity,  and  fre- 
quency of  repetition,  and  all  such  difierences  being  capable 
of  exact  measurement.  Secondly,  that  when  we  applj'  a 
stimulus  directly  to  the  nerve  itself,  the  effects  difier  in  de- 
gree only  from  those  which  result  when  the  nerve  is  set  in 
action  by  natural  stimuli,  such  as  the  will.  When  we  come, 
on  the  other  hand,  to  investigate  the  phenomena  of  afi'erent 
nerves,  our  labors  are  for  the  time  rendered  heavier,  but  in 
the  end  more  fruitful,  by  the  facts  :  First,  that  we  can  only 
judge  of  what  is  going  on  in  an  afferent  nerve  by  the  effects 
it  produces  in  some  central  nervous  organ,  in  the  way  of 
exciting  or  modifying  reflex  action,  or  modifying  automatic 
action,  or  affecting  consciousness  ;  and  we  are  consequentl}'^ 
met  on  the  very  threshold  of  every  inquiry  by  the  difficulty 
of  clearly  distinguishing  the  events  which  belong  exclusivel}'- 
to  the  afferent  nerve  from  those  which  belong  to  the  central 
organ.  Secondly,  that  the  effects  of  apphing  a  stimulus  to 
the  peripheral  end-organ  of  an  afferent  nerve  are  very  differ- 
ent from  those  of  applj'ingthe  same  stimulus  directly  to  the 


634  SENSORY    NERVES. 

nerve-trunk.  This  may  be  shown  by  the  simple  experience 
of  comparing  the  sensation  caused  by  the  contact  with  any 
sharp  body  of  a  nerve  laid  Imre  by  a  wound  with  that  caused 
by  contact  of  an  intact  skin  vvith  the  same  body.  These 
differences  reveal  to  us  a  complexity  of  impulses,  of  which  the 
phenomena  of  motornerves  gave  us  not  so  much  as  a  hint;  but 
for  the  time  being  tiiey  increase  the  difficulties  of  our  stud3^ 

An  afferent  impulse  passing  along  an  afferent  nerve  may 
in  certain  cases  simply  produce  a  change  in  our  conscious- 
ness unaccompanied  by  any  visible  bodily  movements  ;  in 
other  cases  it  may  give  rise  ta  reflex  movements,  or  modify 
existing  reflex  or  automatic  actions  without  causing  any 
change  in  consciousness  ;  in  still  other  cases  it  may  bring 
about  both  results  at  the  same  time.  An  atterent  nerve  the 
stimulation  of  which  gives  rise  to  a  sensation,  and  so  leads 
to  a  modification  of  consciousness,  may  be  more  closely 
defined  as  a  "  sensory  "  nerve.  There  is  however  no  distinct 
proof,  having  regard  to  the  difficulties  just  mentioned,  that 
the  afferent  fibres  which  in  the  body  are  commonly  used  to 
cause  or  affect  reflex  action  differ  at  all  in  kind  from  those 
whose  function  it  is  to  modif}^  consciousness.  On  the  con- 
trary, such  evidence  as  we  have  goes  to  show  tliat  an  appro- 
priate stimulus  of  the  same  fibre  may  give  rise  to  one  or 
other  or  both  events  ;  and  that  whether  tlie  one  or  the  other, 
or  both,  ev^ents  occur  depends  on  the  condition  of  the  cen- 
tral organ,  and  on  the  relation  of  its  several  parts  to  the 
afferent  nerve.  The  stimulation  of  the  same  nerve  (and 
there  are  no  positive  facts  which  would  j)reclude  us  from 
saying  ''of  the  same  fibre")  may  under  certain  circum- 
stances, as  for  instance  when  the  brain  has  been  removed, 
simply  cause  a  reflex  action,  and  under  other  circumstances 
give  rise  merely  to  a  sensation.  Hence  an  afferent  nerve  is 
frequently  spoken  of  as  a  sensory  nerve  even  under  circum- 
stances where  there  is  no  evidence  of  consciousness  being 
actually  affected,  because  by  a  slight  change  of  circumstances 
the  same  stimulation  of  the  same  nerve  might  give  rise  to 
a  distinct  sensation  ;  the  substitution  of  the  specific  for  the 
general  term  being  justified  by  the  convenience  of  the  former. 

All  the  spinal  nerves  are  mixed  nerves,  composed  of  effer- 
ent and  afferent,  of  motor  and  sensory  fibres.  When  a 
spinal  nerve  is  divided,  stimulation  of  the  peripheral  portion 
causes  muscular  contraction,  of  the  central  portion  a  sen- 
sation (or  a  reflex  action).  At  the  junction  of  the  nerve 
with  the  spinal  cord  the  sensory  fibres  are  gathered  into  the 


SENSORY    NERVES.  635 


posterior  and  the  motor  fibres  into  the  anterior  root.  The 
proof  of  this,  which  was  first  made  known  by  Charles  Bell 
and  Magendie,  their  discoveries  forming  the  foundation  of 
modern  nervous  physiology,  is  simply  as  follows  : 

When  the  anterior  root  is  divided,  the  muscles  supplied 
by  the  nerve  cease  to  be  thrown  into  contractions,  either  by 
the  will  or  by  refiex  action,  while  the  structures  to  which 
the  nerve  is  distributed  retain  their  sensiiulit}'.  During  the 
section  of  the  root,  or  when  the  proximal  stump,  that  con- 
nected witli  the  sjiinal  cord,  is  stimulated,  no  sensory  effects 
are  produced.  When  the  distal  stump  is  stimulated,  the 
muscles  supplied  l)y  the  nerve  are  thrown  into  contractions. 
When  the  posterior  root  is  divided,  the  muscles  supplied  by 
the  nerve  continue  to  be  thrown  into  action  by  an  exercise 
of  the  will,  or  as  part  of  a  reflex  action,  but  tiie  structures 
to  which  the  nerve  is  distributed  lose  the  sensibility  which 
they  previously  possessed.  During  the  section  of  the  root, 
and  when  the  proximal  stump  is  stimulated,  sensory  effects 
are  produced.  When  the  distal  stump  is  stimuhated  no 
movements  are  called  forth.  These  facts  demonstrate  that 
sensory  impulses  pass  exclusively  by  the  posterior  root  from 
the  peripheral  to  the  central  organs,  and  that  motor  impulses 
pass  exclusively  b}-  the  anterior  root  from  the  central  to  the 
peripheral  organs. 

An  exception  must  be  made  to  the  above  general  statement,  on 
account  of  the  so-called  recurrent  sensibility  which  is  witnessed 
in  conscious  mammals  under  favorable  circumstances.  It  often 
happens  that,  when  the  peripheral  stump  of  the  divided  anterior 
root  is  stimulated,  signs  of  pain  are  witnessed.  These  are  not 
caused  b}-  the  concurrent  muscular  contractions  or  cramp  wdiich 
the  stimulation  occasions;  for  they  remain,  if  the  whole  trunk  of 
the  nerve  be  divided,  some  little  wa}'  below  the  union  of  the  roots, 
above  the  origins  of  the  muscular  branches,  so  that  no  contrac- 
tions take  place.  They  disappear  if  the  posterior  root  be  also 
cut,  and  the}'  are  not  seen  if  the  mixed  nerve-trunk  be  divided 
close  to  the  union  of  the  roots.  The  phenomena  are  probably 
due  to  the  fact  that  bundles  of  sensory  fibres  of  the  posterior  root, 
after  running  a  short  distance  dow^n  the  mixed  trunk,  turn  back 
and  run  upwards  in  the  anterior  root,  and  b\^  this  recurrent  course 
give  rise  to  the  recurrent  sensibility.  When  the  anterior  root  is 
divided  some  few  fibres  in  it  do  not,  like  the  rest,  degenerate, 
and,  when  the  posterior  root  is  divided,  a  few  fibres  in  the  ante- 
rior root  are  seen  to  degenerate  like  those  of  the  posterior  root. 

Concerning  the   ganglion  on  the  posterior  root,  we  may 
sa}'  definitely  that  it   is  neither  a  centre  of  reflex   nor  of 


636  SENSORY    NERVES. 

automatic  action.  Our  knowlerlg^e  concerning  its  function 
is  almost  limited  to  the  fact  that  it  is  in  some  way  inti- 
mately connected  with  the  nutrition  of  the  nerve.  Wiien  a 
mixed  nerve-trunk  is  divided,  tl»e  peripheral  portion  degen- 
erates from  the  point  of  section  downwards  towards  the 
periphery.  The  central  portion  does  not  so  degenerate,  and, 
if  the  length  of  nerve  removed  be  not  too  great,  the  central 
portion  uniting  with  the  degenerating  peripheral  portion 
may  grow  downwards,  and  thus  regenerate  the  nerve.  This 
degeneration  is  observed  when  the  mixed  trunk  is  divided 
in  any  part  of  its  course  from  the  periphery  to  close  u[)  to 
the  ganglion.  When  the  i)osterior  root  is  divided  between 
the  ganglion  and  the  spinal  cord,  the  portion  attached  to 
the  spinal  cord  degenerates,  but  tliat  attached  to  the  gan- 
glion remains  intact.  When  the  anterior  root  is  divided, 
the  proximal  portion  in  connection  with  the  spinal  cord 
remains  intact,  but  the  distal  i)ortion  between  the  section 
and  the  junction  with  the  other  root  degenerates  ;  and  in  the 
mixed  nerve-trunk  many  degenerated  fibres  are  seen,  which, 
if  they  be  carefully  traced  out,  are  found  to  be  motor  fibres. 
If  the  posterior  root  be  divided  carefully  between  the  gan- 
glion and  the  junction  with  the  anterior  root,  the  posterior 
root  above  the  section  remains  intact,  but  in  the  mixed 
nerve-trunk  are  seen  numerous  degenerated  fibres,  which, 
when  exatnined,  ai'e  found  to  have  the  distribution  of  sen-, 
sor}'  fibres.  Lastly,  if  the  posterior  ganglion  be  excised, 
the  whole  posterior  root  degenerates,  as  do  also  the  sensory 
fibres  of  the  mixed  nerve-trunk.  Putting  all  these  facts 
together,  it  would  seem  that  the  growth  of  the  motor  and 
sensory  fibres  takes  place  in  opposite  directions,  and  starts 
from  different  nutritive  or  "trophic"  centres.  'J' he  sensory 
fibres  grow  away  from  the  ganglion  either  towards  the 
periphery  or  towards  the  spinal  cord.  The  motor  fil)res 
grow  outwards  fr«;m  the  spinal  coy(\  towards  the  perii)hery. 
This  difference  in  their  mode  of  nutrition  is  frequently  of 
great  help  in  investigating  the  relative  distrioution  of  motor 
and  sensory  fil)res.  When  a  posterior  root  is  cut  beyond 
the  ganglion,  or  the  ganglion  excised,  all  the  sensory  nerves 
degenerate,  and  the  sensory  fibres,  by  their  altered  condi- 
tion, can  readily  be  traced  in  the  mixed  nerve-branches. 
Conversely,  when  the  anterior  roots  are  cut,  the  motor  fibres 
alone  degenerate,  and  can  be  similarly  diagnosed  in  a  mixed 
nerve-tract.  Thus  also  in  a  mixed  nerve,  like  the  vagus,  the 
fibres  which  spring  from  the  real  vagus  root  may  be  distin- 
guished from  those   proceeding  from  the  spinal  accessory, 


ROOTS    OF    SPINAL    NERVES.  637 

by  section  of  the  vagus  and  spinal  afcessory  roots  respec- 
tively; and  in  the  mixed  vagosympathetic  trunk,  met  with 
in  many  animals,  tlse  vagus  fihres  may  be  distinguished 
from  the  sympathetic,  since,  alter  a  section  of  the  mixed 
trunk,  the  former  degenerate  from  above  downwards,  whereas 
the  latter  degeuerate  in  an  upward  direction  from  tlie  in- 
ferior cervical  ganglion  below  to  the  superior  cervical  gan- 
glion above,  for  the  ganglia  of  the  sympathetic  behave  in 
tliis  respect  like  the  spinal  ganglia  of  the  posterior  roots. 
This  method  in  diagnosis  is  often  spoken  of  as  the  Waller- 
ian  method,  after  A.  Waller,^  to  whom  we  are  indebted  for 
the  discovery  of  most  of  these  facts. 

According  to  Wundt-  afferent  impulses  suffer  a  delay  in  pass- 
ing through  the  spinal  ganglia,  retlex  acts  bavins;  a  markedly 
shorter  latent  period  when  they  are  initiated  by  a  stimulus  ap- 
plied to  the  posterior  root  than  when  the  stimulus  is  applied  to 
the  mixed  nerve-trunk  just  below  the  ganglion.  Exner,''  how- 
ever, finds  that  the  nei^ative  variation  travels  at  the  same  rate 
through  a  spinal  ganglion  as  along  an  ordinary  nerve-trunk. 

In  the  cranial  nerves  the  motor  and  sensory  tracts  are  far 
lei-s  mixed  than  in  the  spinal  nerves.  The  olfactory,  optic, 
and  acoustic  nerves  are  purely  sensory  nerves.  The  fifth, 
glosso-pharyngeal,  and  vagus  are  mixed  nerves  ;  and  Steiner* 
finds  that  in  the  dog  the  afferent  and  etferent  fibres  are 
gathered  into  two  bundles  so  distinct  that  they  may  be 
separated  by  tiie  knife,  the  afferent  bundle  lying  to  the  out- 
side of  the  ert'erent  bundle. 

The  facial  and  hypoglossal  are  for  the  most  part  motor 
(efferent)  nerves,  but  contain  sensory  (atferent)  tihres.  The 
third,  fourth,  sixth,  and  spinal  accessory  are  exclusively 
motor  (efferent)  nerves.  These  statements  refer  to  what 
are  commonly  looked  upon  as  the  trunks  of  the  respective 
nerves.  More  exactly  speaking,  the  sensory  fil ns  of  the 
facial  come  from  the  fifth,  pneumogastric,  and  glosso-pharyn- 
geal nerves,  so  that  the  facial  proper  is  in  reality  a  purely 
motor  nerve.  So  likewise  is  the  hyi)oglossMl.  its  sensory 
fibres  coming  from  the  fifth,  pneumogastric,  and  three  upper 
cervical  nerves.     The  fifth  is  a  mixed  nerve  entirely  on  the 

1  Mtiller's  Archiv,  1852,  p.  392. 

2  Mechanik  der  Nerven  (1876),  2te  Abth.,  p.  45. 

^  Arch.  f.  Anat.  iind  Phvs.,  1877,  Phvs.  Abth.,  p.  567. 
"  Arch.  f.  Anat.  und  Phvs.,  1878,  Phvs.  Ahth.,  p.  218. 

54 


638  SENSORY    NERVES. 

plan  of*  a  si)inal  nerve,  having  distinct  motor  and  sensory 
roots.  Tlie  glosso-pharvngeal  seems  also  to  be  essentially 
a  sensory  nerve,  its  motor  fibiments  springing  from  the  fifth 
and  facial  nerves.  Concerning  the  vagns  some  have  main- 
tained that  tlie  pneiimogastric  root  proper  is  entirely  sen- 
sory (afferent),  and  that  all  the  efferent  functions  of  the 
vagus  are  dependent  on  the  fibres  of  the  spinal  accessory 
which  join  it.  To  this  point  we  shall  return  when  we  come 
to  consider  briefl}'  the  special  functions  of  these  several 
nerves. 

We  have  already  stated  (p.  158)  that  isolated  pieces  of 
motor  and  of  sensory  nerves  behave  exactly  alike  as  far  as 
all  the  physical  manifestations  attendant  on  the  passage  of 
a  nervous  impulse  are  concerned  ;  the  negative  variation 
makes  its  appearance  in  the  same  way,  and  seems  to  have 
the  same  ciiaracters  in  both  kinds  of  nerves.  Tlie  same  is 
also  true,  as  far  as  we  know,  of  nerves  within  the  body. 

Moreover,  the  rate  at  which  nervous  impul&es  travel  ap- 
pears to  be  about  tlie  same  in  motor  and  sensory  nerves  ;  at 
least  we  have  no  evidence  of  any  fundamental  difference  in 
this  respect  between  the  two.  We  have  seen  that  the  ve- 
locity of  a  nervous  impulse  in  the  motor  nerve  of  a  frog  is 
about  28  meters  per  second.  The  velocity  of  a  motor 
impulse  in  man,  as  judged  by  the  difference  of  the  latent 
period  of  the  contraction  of  the  thumb-muscles  when  stimu- 
lation is  l)rought  to  bear  on  the  motor  nerve  at  the  wrist,  or 
high  up  in  the  arm,  is  about  33  meters  per  second.  In 
warm-blooded  animals,  how-ever,  the  rate  of  transmission 
of  motor  im[)ulses  is  very  variable,  being  in  particular  closely 
dependent  on  temperature,  and  probal>ly  also  on  other  cir- 
cumstances Thus,  Helmholtz  and  Baxt^  obtained  a  range 
from  as  low  as  30  ni.  when  the  arm  was  cooled  to  as  high  as 
89.4  m.  when  the  arm  was  heated.  The  velocity  of  a  sensory 
impulse  is  estimated  by  measuring  the  time  taken  between 
a  stimulus  being  brought  to  bear  on  some  sentient  surface, 
as  the  skin,  and  the  making  of  a  signal  by  the  individual 
experimented  on  at  the  instant  that  he  feels  the  stimulus. 
The  time  taken  up  in  the  sensory  impulse  becoming  con- 
verted into  a  sensation  after  reaching  the  nervous  central 
organs,  in  the  mental  operation  of  determining  to  make  the 
signal,  and  in  the  beginning  to  make  the  signal,  corresponds 
in  a  way  to  tlie  purely  muscular  portion  of  the  latent  period 


^   Berlin.  Monatsbericht,  1870. 


AFFERENT  AND  EFFERENT  NER-VE-FIBRES.   639 

in  tl\e  experiment  for  determining  the  velocity  of  a  motor 
impulse.  The  application  of  the  stimulus  and  the  making 
of  tlie  signal  (ex  gr.,  closino-  a  galvanic  circuit)  being  both 
recorde<l  on  a  rapidly  travelling  surface,  the  time  taken  up 
in  the  whole  operation  can  be  easily  measured  ;  and  the  dif- 
ference between  the  time  taken  when  the  stimulus  is  applied 
to  some  spot  separated  from  the  central  nervous  system  by 
a  short  piece  of  nerve,  ex.  gr.,  the  top  of  the  thigh,  and  that 
taken  wlicn  a  long  piece  of  nerve  intervenes,  e.r.  gr.^  when 
the  stimulus  is  aj^plied  to  the  toe,  will  give  the  time  required 
for  the  sensory  impulse  to  pass  along  a  piece  of  sensory 
nerve  as  long  as  the  difference  of  length  between  the  alwve 
two  nerves  ;  from  which  the  velocity  can  be  calculated.  Ob- 
servations carried  on  in  this  way  led  to  most  discordant 
results,  varying  from  20  meters  to  94  meters,  or  even  more, 
per  second.  The  ditference  here  is  far  too  great  to  allow 
any  value  to  be  attached  to  an  averai^e.  Wlien  it  is  remem- 
bered how  complex  are  all  the  central  nervous  operations  in 
these  instances,  as  compared  with  the  changes  going  on  in  a 
muscle  during  the  latent  period  of  its  contraction,  and  how 
these  central  operations  might  vary,  according  as  one  or 
other  spot  of  skin  was  stimulated,  quite  independently  of 
the  length  of  nerve  between  the  centre  and  the  spot  stimu- 
lated, these  discrepancies  will  not  be  wondered  at;  and  it 
ma}"  fairly  be  concluded  that  the  vehicity  of  a  sensory  im- 
pulse does  not  materially  differ  from  that  of  a  motor  impulse. 
There  are,  however,  certain  phenoujena  which  might  at 
first  sight  be  interpreted  as  indicating  that  afferent  and 
efferent  nerve-fibres  behave  differently  towards  stimuli.  We 
have  already  (p.  124)  stated  that,  according  to  most  observers, 
when  an  ordinary  motor  nerve,  such  as  a  nerve  supplying  a 
muscle,  is  heated,  no  indications  of  the  generation  of  ner- 
vous impulses,  no  contractions  of  the  muscle,  for  instance, 
are  observed.  The  heat  does  not  act  as  a  stimulus  ;  it  may 
increase  the  irritability  of  the  nerve  for  the  time  being,  but 
apparently  cannot  originate  the  explosive  discharge  which 
we  call  an  impulse.'  AVe  have  also  seen  that  during  the  pas- 
sage of  a  constant  current  along  the  nerve  of  a  muscle-nerve 
prepaiation  no  contractions  are  visible,  no  impulses,  save  in 
certain  particular  cases,  are  generated,  so  long  as  the  cur- 
rent is  not  suddenly  varied  in  strength.  But  Griitzner^ 
finds  that  when  afferent  nerve-fibres,  such  as  those  in   the 

1  Pfliiger's  Ardiiv,  xvii  (1878),  p.  215. 


640  SENSORY    NERVES. 

central  stump  of  the  divided  sciatic,  or  in  the  central  stump 
of  the  vagus,  aie  heated  to  45^  or  50^,  events  occur,  clearly 
proving  that  impulses  are  generated  in  the  ati'erent  til)i'es  by 
the  elevation  of  temperature.  In  the  case  of  tiie  sciatic  the 
animal  shows  signs  of  pain,  the  blood  pressure  is  afiected, 
etc. ;  and  in  tlie  case  of  the  vagus  the  heart  is  slowed  by 
reflex  inhibitory  impulses  passing  down  the  other,  intact, 
vagus,  tiiough  lieating  tlie  peripheral  instead  of  tiie  central 
stump  of  the  divided  vagus,  has  no  effect  wiiatever  on  the 
heart.  Similarly,  when  tlie  same  nerves  or  otiier  nerves  con- 
taining afferent  fibres  are  submitted  to  the  action  of  the 
constant  current,  there  are  like  evidences  of  the  continued 
generation  of  nervous  impulses  during  the  whole  time  of 
the  passage  of  the  current,  even  though  it  be  kept  as  uni- 
form in  strength  as  possil)le.  On  the  other  hand  mau}^ 
ciiemical  substances  which  act  as  powerful  stimuli  to  motor 
nerves  are  ineffectual  towards  aderent  fil)res.  These  results, 
however,  until  the  contrary  is  proved  by  further  inquiries 
into  the  phenomena  attending  the  generation  and  transmis- 
sion of  nervous  impulses,  may  be  taken  as  indicating  not  so 
much  tliat  the  afferent  and  efferent  fibres  are  themselves 
acted  upon  in  a  different  way  by  heat,  or  by  the  constant 
current,  as  that  the  molecular  disturliances  generated  in  l)oth 
cases  iiave  different  effects,  according  as  they  iuipinge  upon 
a  central  or  a  peripheral  meciianism.  We  can  readily  im- 
agine that  jnolecular  disturbances  which  would  l)e  in)i)otent 
to  stir  the  sluggish  muscular  substance  to  a  contraction, 
and  thus,  so  to  speak,  be  lost  ui)on  the  muscle,  might  pro- 
duce a  very  great  effect  on  the  more  sensitive  and  m()l)ile 
material  of  the  centrnl  nervous  system.  We  may  for  the 
present,  therefoie,  conclude  that  there  is  no  distinct  proof 
of  an  absolute  difference  between  afferent  and  eflerent  Hl>res, 
but  we  must  at  the  same  time  be  cautious  not  to  consider 
tiie  grosser  phenomena,  presented  l)y  a  muscle-nerve  prepa- 
ration, as  a  satisfactory  test  of  all  the  changes  which  may 
take  place  in  a  nerve-fiore.  The  necessity-  of  this  caution 
will  be  almost  immediately  illustrated  from  another  point  of 
view. 

The  apparent  identity  in  function  between  aiTerent  and 
efferent  fibres,  taken  into  consideration  with  the  facts  just 
mentioned  concerning  tiie  regeneration  of  nerves,  suggests 
the  inquiry  wiiether  by  a  change  of  the  peripheral  or  cen- 
tral organs  a  motor  ner\e  can  be  converted  into  a  sensor}^ 
nerve,  or  vice  veraa.     Experiments  made  with  a  view  of  ob- 


AFFERENT    AND    EFFERENT    NERVE-FIBRES.       641 

taining  a  fuiu-lional  union  between  i)urely  motor  and  sen- 
sory nerves  have,  in  tlie  hands  of  most  observeis  (Flourens, 
Bidder,  Schifi",  etc.)  failed  ;  and  thoutrh  Pliilipeaux  and  Vul- 
pian^  were  so  far  more  successful,  that  they  obtained  an 
apparent  union  between  a  sensory  and  a  motor  nerve-trunk, 
their  results  do  not  prove  that  a  filne,  which  is  ordinaril}-  a 
purely  sensory,  may  act  as  a  motor  fibre,  and  vice,  cevi^a. 

These  observers,  having  in  young  dogs  divided  the  hypoglossal 
nerve  and  removed  its  central  portion  as  completely  as  possible, 
united  by  fine  sutures  its  peripheral  end  "with  the  central  portion 
of  the  lingual  of  the  same  side,  having  similarly  removed  from 
this  the  peripheral  portion.  Thus  the  central  lingual  was  united 
with  the  peripheral  hypoglossal.  Complete  union  took  place,  and 
it  was  found  that,  after  some  weeks,  the  portion  of  nerve  between 
the  tongue  and  the  point  of  union,  i.  e.,  the  part  which  had  pre- 
viously been  the  peripheral  hypoglossal,  was  in  a  sound  and 
healthy  condition.  .Stimulation  of  the  lingual  nerve  above  the 
point  of  union  produced  contractions  in  the  tongue  of  that  side, 
whether  the  stimulus  were  electrical  or  mechanical  ;  and  the  con- 
tractions were  still  visible  when  the  lingual,  in  order  to  preclude 
any  reflex  action,  was  divided  high'np  previous  to  stimulation. 
Here  the  sensory  lingual  was  apparently  the  means  of  causing 
motor  ertects.  It  must  be  remembered,  however,  that  this  is  not 
a  case  of  the  union  of  motor  and  sensory  fibres.  The  peripheral 
portion  of  the  hypoglossal  in  reality  became  wholly  degenerated, 
and  the  portion  of  nerve  which  apparently  Avas  hypoglossal 
nerve,  was  in  truth  new  nerve  produced  by  a  downward  growth 
of  the  lingual.  If  any  real  union  took  place  it  must  have  been 
between  the  lingual  fibres  and  the  end-plates  of  the  glossal  mus- 
cular fibres.  The  force  of  this  experiment  is  moreover  lessened 
by  the  fact  observed  by  ^"^ulpian^  himself,  that  \vhen  the  hypo- 
glossal is  simply  removed,  or  a  large  piece  of  the  nerve  cut  out, 
so  that  the  peripheral  portions  degenerate,  stimulation  of  the 
lingual  nerve  of  the  same  side  causes  movements  of  the  tongue, 
though  when  the  In'poglossal  is  intact,  stimulation  of  the  lingual 
produces  no  such  elfect.  The  motor  eflects  thus  seen  are  due  to 
the  chorda  fibres  present  in  the  lingual,  and  Yulpian  finds  that 
the  movements  olDtained  on  stimulating  the  lingual  nerve  after 
the  apparent  union  of  the  lingual  and  hypoglossal,  do  not  occur 
if  the  chorda  fibres  iii  the  lingual  be  brought  into  a  state  of  de- 
generation by  previous  section  of  the  chorda  nerve.  Schiff^  has 
observed  after  section  of  the  hypoglossal,  spontaneous  contrac- 
tions of  the  glossal  muscular  fibres,  contractions  which  are  at 

^  Yulpian,  Lee.  Svstenie  Xerv.,  274. 

'  Ct.  Rd.,  t.  US,  p."l46  (1873). 

3  R.  Accad.  dei  Lineei  (3j,  i  (1877). 


642  SENSORY    NERVES. 


first  inhibited,  but  at  a  later  period  increased,  by  stimulation  of 
the  (chorda  fibres  in  the)  lingual,  and  that  to  such  an  extent  as 
to  move  the  tongue  up  and  down  ;  this  curious  fact  helps  to  ex- 
plain Avhy  the  section  of  the  hypoglossal  seems  necessary  to  de- 
velop the  motor  effects  of  stimulating  the  lingual.  Vulpian  and 
Philipeaux  also  made  experiments  on  the  union  of  the  vagus  and 
hypoglossal,  but  the  results  were  even  less  satisfactory  than  those 
with  the  lingual  and  hypoglossal,  and  Yulpian  himself  admits 
that  the  functional  union  of  motor  and  sensory  fibres  is  as  3'et 
unproved . 

We  have  already  seen  (p.  15G)  that  a  sensory  nerve  in  its 
simplest  form  may  be  regarded  as  a  strand  of  eminently 
irritable  protoplasm,  forming  a  link  between  a  superficial  cell 
which  alone  is  subject  to  extrinsic  stimuli,  and  a  central 
(reflex  or  automatic)  cell  which  receives  stimuli,  chiefly  in 
the  form  of  nervous  impulses  proceeding  fiom  the  former 
along;  the  connecting'  strand.  In  tlie  earliest  stashes  of  the 
development  of  a  sensory  nervous  system,  the  superficial 
sensory  cell  is  susceptible  of  stimuli  of  all  kinds,  provided 
they  are  sufficiently  stroiig ;  and  probaldy  all  the  impulses 
which  it  transmits  to  the  central  cell  resemble  each  other 
very  closely,  difi'ering-  only  in  degree.  It  is  obvious,  how- 
ever, that  the  economy  would  gain  by  a  furtiier  division  of 
labor,  by  a  diflferentiation  of  the  simple  uniform  superficial 
cell  into  a  number  of  cells,  each  of  which  was  more  sus- 
ceptible to  particular  stimuli  tiian  its  fellows.  Tluis  one 
cell,  or  rather  one  group  of  cells,  would  become  eminently 
susceptible  to  the  influence  of  light;  in  tliem  the  impact 
rays  of  light  would  give  rise  to  nervous  impulses  more 
readily  than  in  the  other  groups;  another  gioup  would  de- 
velop a  sensitiveness  to  waves  of  sound,  and  so  on.  In  this 
way  the  primary  homogeneous  bodily  surface  would  be  dif- 
ferentiated into  a  series  of  aenae-organH^  disposed  and 
arranged  among  ectodermic  cells,  the  purpose  of  the  latter 
being  simply  protective  and,  therefore,  not  demanding  the 
existence  of  any  direct  connection  with  tiie  central  nervous 
system.  Similar  l)ut  less  highly  marked  differentiations 
would  be  established  in  the  endings  of  the  afferent  nerves 
connecting  the  central  nervous  system  with  the  internal  sur- 
faces and  parts  of  the  body. 

Moreover  it  is  obvious  tiiat  the  sensory  impulses  trans- 
mitted to  the  central  nervous  system  by  these  differentiated 
sense-organs  woidd  be  themselves  liirgely  differentiated. 
Just  as  the  impulses  which  pass  along  a  motor  nerve  differ 


SPECIAL    SENSES.  643 

according  to  the  nature  of  the  stimulus  which  is  applied  to 
the  nerve  (wliether,  for  instance,  the  stimnhis  be  a  single 
induction-shock,  or  several  shocks  repeated  slowly,  or  sev- 
eral shocks  repeated  rapidly,  and  so  on,  the  effect  on  the 
muscle  being  in  each  case  a  different  one\  so  to  a  much 
greater  degree  the  impulses  generated  liy  light  in  a  visual 
sense-organ  must  naturally  ditfer  from  tli(  se  generated  by 
simple  pressure  in  a  tactile  sense-organ. 

And  since  these  various  sensory  impulses  have  much 
work  to  perform  on  arriving  at  the  central  nervous  system, 
in  the  way  of  influencing  the  multitudinous  molecular 
operations  going  on  in  the  central  cells,  and  of  affecting 
consciousness,  this  differentiation  of  sensory  organs  and 
sensory  impulses  will  naturally  be  accompanied  by  a  cor- 
responding diflerentiation  of  those  nervous  cells  which  the 
impulses  are  the  first  to  reach  on  arriving  at  the  central 
organ.  Those  cells,  for  instance,  of  the  central  nervous 
system,  which  first  receive  the  particular  nervous  impulses 
coming  from  the  visual  sense-organs,  will  be  set  apart  for 
the  tai^k  of  so  modifying  and  preparing  those  impulses  as  to 
adapt  them  in  the  best  possible  way  for  the  work  which 
they  have  to  do.  Hence  each  peripheral  sense-organ  will 
be  united  by  means  of  its  nerve  with  a  corres{)onding  cev- 
tral  sense-organ,  the  former  being  altle  to  affect  other  parts 
of  the  cential  nervous  system  only  through  the  medium  of 
the  latter.  This,  at  least,  we  know  to  be  the  CMse  as  far  as 
relates  to  all  tlie  central  nervous  operations  in  which  con- 
sciousness is  concerned;  for  of  the  total  characters  which 
belong  to  an  afitction  of  consciousness  by  means  of  any 
of  the  sense  oigaus,  i.  e.,  which  belong  to  any  particular 
sensations,  while  some  are  gained  durins^  the  rise  of  the 
sensory  impulses  in  the  peripheral  sense-organ,  others  first 
appear  in  the  central  sense-organ  in  the  course  of  the  changes 
through  which  the  impulses  give  rise  to  a  sensation.  Tims 
a  stimulus  of  any  kind  applied  to  the  optic  nerve  along  any 
part  of  its  course  gives  rise  to  a  sensation  of  light,  and  pre- 
cisely the  same  stimulus  applied  to  the  acoustic  nerve  along 
any  part  of  its  course  gives  rise  to  a  sensation  of  sound,  and 
so  on.  All  the  evidence  we  possess  goes  against  the  view 
that  an  isolated  piece  of  optic  nerve  differs  in  function  from 
a  similarly  isolated  piece  of  acoustic  nerve  ;  such  facts  as 
are  within  our  knowledge  go  to  show  that  tlie  disturbances 
generated  in  a  piece  of  optic  nerve  by  a  galvanic  cm  rent 
are  the  same  as  those  generated  in  a  piece  of  acoustic  nerve. 


644  ANATOMY    OF    THE    EYE. 

We  are,  therefore,  driven  to  the  conclusion  that  the  differ- 
ence in  this  case  arises  in  tlie  central  oro;ans. 

In  all  these  differentiated  senst^ry  mechanisms,  or  special 
senses  as  they  are  called,  we  iiave  then  to  deal  with  two  ele- 
ments :  the  peripheral  sense-organ,  in  which  we  have  to 
study  how  the  special  pliysical  agent  gives  rise  to  special 
sensory  imi)nlsts ;  and  tiie  central  sense  organs,  in  which 
our  study  is  confined  to  tiie  manner  in  whicii  these  special 
impulses  modify  the  operations  of  the  central  nervous  sys- 
tem. Inasmuch  as  in  a  normal  body  the  peripheral  organ 
remains  in  connection  with  the  central  organ,  and  our  study 
of  the  special  senses  is  carried  on  chiefly  h}'  sul»jective  oi»- 
servations  in  which  we  make  use  of  our  own  consciousness, 
it  frequently  becomes  very  difficult  to  distinguish  in  any 
given  sensation  tlie  peripheral  form  of  the  central  element. 
The  two  become  more  distinct  the  more  complex  the  sense 
and  the  more  highly  organized  the  sense-organs.  For  this 
reason  it  will  be  most  convenient  to  commence  our  study  of 
the  special  senses  with  the  sense  of  vision. 


CHAPTER  II. 

[Phy. biological  Anatomy  of  (he  Bye. 

The  eyeball  is  of  a  spheroidal  siiape.  It  consists  of  two 
segments  of  different-sized  spheres.  The  larger  segment  is 
situated  posteriorly,  and  constitutes  about  five-sixths  of  the 
walls  of  the  eyel>all.  From  its  free  margin  projects  the 
smaller  segment,  which  is  tiiat  of  a  smaller  sphere.  The 
posterior  segment  is  composed  of  a  wliitish,  opaque,  firm 
wall,  consisting  of  three  coaLs  or  tunics  :  the  sclerotic^  the 
choroid^  and  retina.     The   anterior  segment  is  continuous 


ANATOMY    OF    THE     EYE. 


645 


with  the  sclerotic  coat.  (Fiof.  161.)  It  is  a  transparent, 
elastic,  convex  orj^an,  called  the  cornea.  The  cornea  con- 
sists of  three  layers:  an  anterior  anil  posterior  elastic  lam- 
ina, having  between  them  a  layer  which  is  the  proper  tissne 
of  the  organ.     This  middle  layer  is  composed  of  about  sixty 


Fig.  161. 


Diagram  of  a  Horizontal  Section  of  the  Eyeball. 

a,  outer  or  sclerotic  coat,  and  d,  the  cornea;  6,  niidile  or  clioroidalcoat;  ni,  ciliary 
ligament;  s,  ciliary  process;  e,  ciliary  muscle,  and  /,  iris;  c,  iirner  coat  of  retina, 
continuous  with  the  optic  nerve  behind,  with  a  dark  layer  outside  it;  g,  lens;  t,  sjis- 
pensory  ligament  of  the  lens;  A,  vitreous  body;  n,  hyaloid  membrane;  t,  posterior 
chamber;  o,  canal  of  Petit;  r,  sinus  circularis  iiidis;  /,  optic  nerve.  The  dotted 
line  through  the  centre  is  the  longitudinal  axis  of  the  ball. 


superimposed  laminte  of  fusiform  fibrous  cells.  In  the  in- 
terstices between  the  lamiiuti  are  found  tubular  spaces,  which 
contain  a  transparent  fluid.  The  anterior  and  posterior 
elastic  lamiiife  are  structureless  and  highly  elastic.  When 
separated  from  the  proper  corneal  tissue  they  have  a  great 
tendencv  to  curl   up.     Tliis  fact  suggests   that  these   two 


em 


ANATOMY    OF    THE    EYE. 


Fig.  162. 


lamin.ie  are  active  agents  in  the  retention  of  a  proper  curva- 
ture of  the  cornea.  The  cornea  is  covered  on  its  anterior 
surface  l)>tiie  conjunctival  mucous  mem- 
])rane,  which  consists  of  three  or  four 
layers  of  pavement  epithelium  cells;  the 
deeper  la>ers  of  cells  are  oblong,  and 
placed  perpendicularly.  (Fig.  162.)  The 
conjunctiva  has  no  perceptible  basement 
membrane.  The  posterior  surface  of  the 
cornea  is  covered  by  a  transparent  se- 
rous membrane,  which  consists  of  a  sim- 
ple layer  of  polygonal  pavement  epithe- 
lium cells  resting  on  an  elastic  mem- 
brane. This  is  called  the  membrane  of 
Demours,  The  cornea  has  no  blood- 
vessels, and  therefore  derives  its  nutri- 
ment by  diffusion. 

The  sclerotic  coat  is  so  named  on  ac- 
count of  the  firmness  of  its  texture  and 
hardness.  It  forms  the  outer  tunic  of 
the  posterior  segment.  It  is  whitish, 
opaque,  smooth,  excepting  at  the  points 
of  attachment  of  the  muscles  of  the  eye- 
ball. It  is  composed  of  white,  fil)r()us 
tissue,  arranged  more  or  less  in  bundles, 
which  interlace  each  other  in  various 
directions.  Anteriorly  the  interlace- 
ments are  in  a  general  transverse  direc- 
tion ;  posteriorly  the  direction  is  longi- 
tudinal. Tins  coat  also  contains  yellow 
elastic  fibres  and  fusiform  nucleated  cells. 
It  is  continuous  anteriorly  with  the  cor- 


Vertical  Section  of  the 

Cornea. 
A,  proper  tissue  of  (he 
cornea;  B,  anterior  elas- 
tic lamina  of  cornea,  with 
D,  the  conjunctival  epi- 
theliiHU  on  it  ;  C,  oblique  ,  •       i  •    i      i 

fibres  from  it  to  the  lay-  i^ea.aud  posteriorly  With  the  perineurium 
ers  of  the  cornea;  E,  pos-  of  the  optic  nerve.  At  the  internal  border 
of  the  junction  with  the  cornea  is  a 
venous  sinus  called  the  sinus  circidoris 
iridis^  or  canal  of  Schlemm.  The  optic 
nerve  pieices  it  about  2.6  mm.  internal 
to  the  anterc-posterior  axis  of  the  e3'e- 
ball.  At  this  point  the  coat  is  perforated 
by  minute  openings  for  the  passage  of  the  nerve-filaments. 
One  of  these  openings,  wliich  is  relatively  large,  gives  pas- 
sage to  the  arteria  centralis  retinse.  Surrounding  this  point 
of  entrance  of  the  optic  nerve  are  many  small  openings  for 


terior  elastic  lamina,  with 

F,  epithelium  on  it  of  the 
membrane   of   Demours  ; 

G,  surface  view  of  the  epi- 
thelium of  the  membrane 
of  Demours. 


ANATOMY    OF    THE    EYE. 


647 


the  passage  of  tlie  ciliary  nerves  and  vessels.  The  internal 
surface  of  the  sclera  contains  some  pignient-grannles.  It 
is  separated  from  the  choroid  coat  by  a  delicate  flocculent 
cellular  tissue,  called  the  lamina  fiisca. 

The  choroid  coat  is  a  vascular  membrane  containing  some 
pigment-granules.  The  external  portion  is  composed  prin- 
cipally of  bloodvessels  and  nerves.  Between  the  vessels 
are  found  numerous  stellate  pigment- cells,  which  form  a 
fibrous  network.  The  internal  surface,  where  it  is  adjoined 
to  the  pigment  layer  of  the  retina,  also  contains  pigment- 
cells.  Posteriorly  it  is  pierced  by  the  optic  nerve;  ante- 
riorly it  is  continuous  with  the  ciliary  processes,  and  is 
separated  from  the  sclerotic  coat  by  the  ciliary  m  uncle. 

The  ciliary  processes  are  arranged  in  the  form  of  a  ring. 
They  consist  of  about  sixty  to  eighty  somewhat  conical- 

Fio   163. 


Inner  View  of  the  Front  of  the  Choroid  Coat  with  its  Ciliary  Processes,  and  the 
Back  of  tlie  Iris,  a,  anterior  piece  of  the  choroid  coat;  b,  ciliary  processes;  c,  iri.-<; 
rf,  sphincter  of  the  pupil ;  e,  bundles  of  fibres  of  the  dilator  of  the  pupil. 


shaped  bodies,  situated  with  their  bases  internally'.  (Fig. 
IHo.)  They  are  placed  posterior  to  the  iris.,  and  are  at- 
tached by  their  thickened  or  internal  extremities  to  the 
suspensory  ligament  of  the  lens. 

The  ciliary  muscle  arises  from  the  point  of  junction  of 
the  sclerotic  coat  and  the  coinea.  It  consists  of  two  por- 
tions: a  radiating  or  meridional,  and  a  circular  layer.  The 
radiating  fasciculi  are  situated  externally,  and  have  a  me- 


648 


ANATOMY    OF    THE    EYE. 


ridional  direction.  (Fig.  104.)  From  this  layer  numerous 
fasciculi  interlace  between  the  fasciculi  of  the  circular  layer, 
which  occupies  an  internal  position  to  the  radiating  layer. 
The  ciliary  muscle  is  inserted  into  the  external  surface  of 
the  anterior  portion  of  the  choroid  coat,  tlie  fibres  extending 
somewhat  posterior  to  the  anterior  margin   of  the  retina. 

Fig.  164. 


Section  of  the  Ciliary  Region  of  the  Eye  in  Man.  o,  meridional  muscular  fasciculi 
of  the  iiiosculus  ciliaris  ;  b,  deeper-seated  radiating  fasciculi ;  c,  c,  c,  annular  plexus  ; 
d,  annular  muscle  of  Miiller;  /,  muscular  lamina  on  the  posterior  surface  of  the  iris  ; 
g,  muscular  plexus  at  the  ciliary  border  of  the  iris;  e,  annular  tendon  of  the  musculus 
ciliaris;  h,  ligameutum  pectinatum. 


This  muscle  is  a  very  important  factor  in  the  mechanism  of 
accommodation  (see  p.  6(i5). 

The  ?'?'/«  is  a  fibro-muscular  curtain  which  is  suspended 
between  the  cornea  and  the  crystalline  lens.  It  is  attaclied 
1)3'  its  circumference  to  the  internal  wall  of  the  sinus  c.  iridis. 
In  its  centre  is  a  round  i)erforation  called  the  pupil,  which 
is  susceptible  of  consideral)le  variations  in  size.  This  mem- 
brane is  composed  of  a  fibro-connective  tissue  having  a 
general  radiating  direction  from  the  pupillary  border.  Within 
this  tissue  are  found  pigment-cells  and  unstriated  muscular 
tissue.  The  muscular  tissue  element  consists  of  radiating 
and  circular  fasciculi.  (Fig.  1(55.)  The  circular  fasciculi 
form  a  sphincter  at  the  pupillary  margin  ;  the  radiating 
fasciculi  radiate  from  the  sphincter  to  the  circumference. 
At  the  circumference  of  the  iris  the  membrane  lining  the 
anterior  ciiamber  forms  fibrous  processes,  wliicli  are  termed 
the  ligameutum  iridis  j^f'ctinatum.     The  posterior  surface 


ANATOMY    OF    THE    EYE. 


649 


is  covered  with  a  pigmeiitaiT  layer,  which  is  a  continuation 
of  the  pio:raent  layer  of  the  retina. 

The  retina  or  third  coat  consists  of  two  portions:  tlie 
pigmentary  membrane  and  the  terminal  elements  of  the  optic 
nerve.  The  pigmentary  membrane  or  ejrternal  layer,  which 
has  been  called  the  system  of  the  uvea,  covers  the  whole  of  the 
internal  surface  of  the  ciliary  processes,  the  iris  and  the  cho- 
roid. It  consists  of  a  single  layer  of  hexagonal  nucleated 
pigment-cells  (Fig.  16(1)  of  a  dark-brown  colcr.  From  the 
inteinal  surface  of  this  meml'rane  delicate  tibres  are  con- 
tinued between  the  cellular  elements  of  the  nervous  layer. 


Fig.  165. 


"i 


Muscular  Structure  of  the  Iris  of  a  White  Ral>bit.     71,  sphincter  of  the  pupil  ;  b,  h, 
radiating  fa.«ciculi  of  dilator  nuiscle  :  c.  c,  connecting  tissue  with  its  corpuscles. 


It  is  frequently  dissected  with  the  choroid  coat,  and  spoken 
of  as  one  of  its  InuMiitie.  The  color  of  the  iris  in  different 
individuals  is  dependent  npon  the  density  of  the  fibro-con- 
nective  tissue  anteri^  r  to  the  urea,  and  to  the  amount  of 
pigment-granules  in  it.  In  persons  with  dark  eyes  the  pig- 
ment in  thi.s  tissue  is  relatively  more  abundant. 

The  internal  or  nervous  layer  of  the  retina  is  composed 
essentially  of  the  terminal  nerve  elements  of  the  optic  nerve. 
Externally,  it  is  covered  with  the  pigmentary  layer  ;  inter- 


650 


ANATOMY    OF    THE    EYE. 


nally,  it  is  lined  I)}'  a  homogeneous  transparent  structure 
called  the  hyaloid  membrane.  The  structure  of  the  retina  is 
one  of  oreat  conii)lexity.  It  consists  of  nine  distinct  layers, 
seven  of  which  are  layers  of  nerve  eleuients.  All  of  these 
layers  are  bound  together  and  supported  by  a  connective 
tissue  which  contains  bloodvessels.  This  layer  extends 
from  the  entrance  of  the  optic  nerve  to  a  point  where  the 
annular  fasciculi  of  the  ciliary  muscle  are  found  ;  at  this 
poiut  the  nervous  elements  cease  to  exist,  and  the  layer  has 
an  irregular  dentated  margin  called  the  ora  serraia.   13eyond 


Fig.  166. 


Pigment-cells  of  the  Eyeball  (Kolliker).     a,  ramified  pigment-cells  of  the  cho- 
roid coat;  B,  front  view  of  the  hexagoual-eells  of  the  pigmentary  membrane. 


this,  the  nervous  layer  is  continued  as  a  mere  fibrous  ex- 
tenuation. 

The  optic  nerve  pierces  the  sclerotic  and  the  choroid 
coats,  and  the  pigmentary  membrane  of  tlie  retina,  when  it 
rapidly  divides  into  vast  numbers  of  fibres,  which  consist 
alone  of  the  axis-cylinders  or  their  ultimate  fibrilLne.  This 
layer  of  fibres  is  continuous  over  nearly  the  whole  of  the 
internal  surface,  and  is  called  the  second  or  optic  nerve-fibre 
Layer.  On  its  internal  surface,  between  it  and  the  hyaloid 
membrane,  is  a  delicate  structure  called  the  fir.-^t  layer,  or 
membrana  limitaiis  interna.     The  third  or  ganglion  layer  is 


ANATOMY    OF    THE    EYE. 


651 


composed  of  iniiltipolar  ganglion  cells,  similar  to  those  found 
in  the  cerebral  substance.     In  the  posterior  portion  of  the 


Fig.  167 


Fig.  168. 


rs' 


Fig.  167. — Diagrammatic  Representation  of  the  Connections  of  the  Nerve-fibres 
in  the  Retina.  1,  membrana  limitans  interna  ;  2,  oiitic  nerve-fibre  layer ;  3,  layer  of 
ganglion  cells  ;  4,  internal  granulated  or  molecular  layer ;  5,  internal  granule-layer; 
6,  external  granulated  or  molecular  layer;  7,  external  granule-layer;  8,  membrana 
limitans  exterior;  9,  bacillary  layer,  or  layer  of  rods  and  cones. 

Fig.  168. — Rod  and  Cone/rom  the  Retina  of  Man  preserved  in  a  two  per  cent,  so- 
lution of  Perosmic  Acid,  to  show  the  fine  fibres  of  the  surface,  and  the  diflFereut 
lengths  of  the  internal  segment.  The  outer  segment  of  the  cone  is  broken  up  into 
disks,  which,  however,  are  still  adherent  to  one  another;  at  the  base  of  the  cone  are 
seen  a  few  fine  hair§  (X  1000  diameter). 

Fig.  169. — Diagrammatic  Representation  of  the  Connective  Tissue  of  the  Retina 
as  seen  near  the  Ora  Serrata.  The  numbers  correspond  to  those  of  the  several  layers 
of  the  retina  shown  in  Fig.  167. 


652  ANATOMY    OF    THE    EYE. 

retina  these  sfnn^lion  cells  are  in  several  layers ;  at  tlie 
macula  lulea.  there  are  as  many  as  eight,  and  at  the  anterior 
portion  of  the  relina  there  is  \n\t  a  single  layer.  From  each 
of  these  cells  fil>res  are  continned  to  the  fifth  or  internal 
granule  layer,  which  consists  of  granular  cells  with  nuclei. 
Between  the  third  and  fifth  layers  is  a  layer  of  vesicular 
matter  containing  nerve-fil>rils  of  extremie  minuteness.  This 
layer  is  i\\(i  fourtkov  internal  granulated  or  molecular  layer. 
The  iii.Tth  or  external  granulated  or  molecular  layer  consists 
of  parallel  interlaced  fibres,  containing  nuclei  and  stnooth 
cells.  The  seventh  or  e.rlernal  granule  layer  is  very  similar 
to  the  ffth.  The  eighth  layer  consists  of  a  delicate 
membrane  of  connective  tissue,  called  the  membrana  limi- 
tans  externa.  The  ninth  or  bacillary  laye7\  or  layer  of 
rodn  and  cones,  or  Jacob\'i  membrane^  is  composed  of  two 
elements,  the  rod.-i  and  cones.  The  rods  are  cylindrical 
bodies,  which  end  externally  in  a  truncated,  flattened  ex- 
tremity', and  internally  as  an  attenuated  fibre,  which  proba- 
l)ly  communicates  with  the  deeper  layer  of  ganglion  cells. 
The  cones,  as  their  names  indicate,  are  conical  shaped  bodies. 
Each  consists  of  two  })ortions,  a  conical  bod}-  having  pro- 
jecting from  its  apex  a  rodlike  segment,  which  appeals  in  all 
respects  like  the  rods.  This  segment  is  called  the  cone  rod. 
The  terminal  extremit}'  of  the  cone  rods  do  not  extend  as 
far  externally  as  the  extremities  of  the  rods.  The  rods  and 
cones  have  been  demonstrated  to  consist  of  two  segments 
or  limbs,  which  are  composed  of  filaments,  granular  matter, 
and  nuclei. 

The  optic  nerve,  where  it  pierces  the  coats  of  the  eye, 
projects  somewhat  beyond  the  surf{\ce  of  the  retina,  as  a 
papilla ;  here  the  essential  nerve-elements  of  the  retina  are 
absent,  and  luminous  rays  are  unperceived  ;  hence  it  is  called 
the  blind  spot  (see  p.  (>77).  About  2.B  mm.  external  to  the 
point  of  entrance  of  the  optic  nerve,  and  in  the  exact  centre 
of  the  retinal  surface  corresponding  to  the  antero-i)osterior 
axis  of  the  eye,  is  the  ''^-ellow  spot  of  .Sommerring  "  or 
macula  lutea  (Fig.  170.)  It  is  an  elliptical-shaped  spot, 
having  its  long  diameter  transverse.  In  the  centre  of  the 
macula  lutea  is  a  depression  called  the/bo^a  centralis.  At 
this  point  the  nervous  layer  of  the  retina  is  very  much  modi- 
fied in  c')mi)osition  of  the  different  layers.  At  the  macula 
lutea  the  nervous  layer  is  much  tliicker  than  at  any  other 
part  of  the  membrane.     The  ganglion  {third)  and  the  ex- 


ANATOMY    OF    THE    EYE. 


653 


tornal  gramilatecl  (s'?'.rM)are  the  most  thickened.  The  gan- 
glion layer  consists  of  six  or  eight  laniincTe  of  cells.  The 
rods  of  the  ninth  layer  are  absent,  and  are  replaced  by 
rones.  In  ihc  fovea  cenfj^alis  the  internal  granulated  {fourth  ), 
the  internal  granule  {fifth)^  and  the  optic  uerve-fil)re 
{Hecond )  are  wanting.  The  ganglion  cell  ( third)^  the  external 
granulated  {i^ixUv^  and  th^  external  granule  {aevenfh)  layers 
are  increased  in  thickness.  The  ganglion  la3'er  of  cells  in 
the  fovea  consist  of  three  laminae.  In  all  portions  of  the 
nervous  layer  the  rods  greatly  predominate  in  number  over 
the  cones,  excepting  in  the  macula  lutea,  where  they  are 
entirely  absent.  The  retina  is  much  thicker  posteriorly,  be- 
coming thinner  as  it  extends  forwards;  the  nervous  layer 
gradually  disappearing  in  the  anterior  portion  of  the  mem- 
brane. 


FiCx.  170. 


FKt.  171. 


Fig.  170.— Objects  on  the  Inner  Surface  of  the  Retina.  In  the  centre  of  tl»e  ball  is 
the  yellow  linibus  luteus,  here  represented  by  shading;  and  in  its  middle  the  dark 
spot.    To  the  inner  side  is  the  nerve,  with  its  accompanying  artery.— After  Sosi- 

MERRIXG. 

Fig.  171.— Magnified  Vertical  Section  of  the  Retina  (altered  from  Kolliker.).  k, 
microscopic  ajjpearanceof  the  outer  surface  of  the  retina  over  the  yellow  spot,  where 
there  are  only  cones;  I,  appearance  of  the  retina  near  the  yellow  spot — a  single 
circle  of  rods  surrounding  each  cone  ;  m,  appearance  of  the  middle  of  the  retina,  a 
large  number  of  the  rods  surrounding  each  cone.  In  all  three  figures  the  larger 
rings  represent  the  cones,  and  the  smaller  ones  the  rods  seen  endwise. — After  Ellis. 


The  interior  of  the  eyeball  is  divided  into  two  portions  by 
the  crystalline  lens  and  its  suspensory  ligament.  The  an- 
terior portion  contains  the  aqueous  humor,  the  posterior 
contains  the  vitreous  bod//. 

The  crystalline  lens  measures  about  7  mm.  in  transverse  di- 


654 


ANATOMY    OF    THE    EYE. 


A  Represenlation  of  the  Laminfe 
in  a  Hardened  Lens,  a,  the  nucleus; 
b,  superficial  lamiute. 


ameter,  and  about  4  mm.  antero-posterior  diameter.     It  is  a 
transparent  bi-convex  body,  somewhat  flattened  anteriorly-. 

It  consists  of  a  nnmber  of  seoj- 
^''''•^'■-  ments    wliicli   radiate   from    the 

centre,  similar  to  the  segments 
of  an  orange.  These  segments 
are  composed  of  superimposed 
laminae  of  varying  density.  The 
most  superficial  are  soft  and  gelat- 
inons;  tiie  deeper  are  relatively 
hard,  so  that  they  form  a  kernel 
or  nucleus.  The  lamime  are  made 
up  of  parallel  fibres,  with  an  un- 
dulating course,  the  convexities 
and  concavities  of  the  adjoining 
fibres  fitting  accuratel}'  into  each 
other.  The  lens  is  covered  with 
a  capsule  consisting  of  a  transparent,  elastic,  fragile  mem- 
brane, which  has  a  tendency  to  curl  up,  with  its  external 
surface  innermost. 

The  suspeni^ory  ligament  of  the  lens  is  formed  by  a  con- 
tinuation of  the  hyaloid  membrane  which  lines  the  vitreous 
body.  The  hyaloid  membrane  is  a  delicate  transparent 
structure  situated  between  the  vitreous  bod}'  and  mem- 
brana  limitans  interna  of  the  retina.  It  is  continued  in  front 
to  the  ora  serrata^  where  it  divides  into  two  layers.  Tiie 
posterior  is  attached  to  the  posterior  portion  of  the  capsule 
of  the  lens;  the  anterior  portion  gradually  becomes  thicker 
as  it  extends  forwards  behind  the  ciliary  processes,  and  is 
attached  to  the  anterior  surface  of  the  capsule.  This  tiiick- 
ened  portion  of  the  membrane,  which  is  corrugated  where  it 
has  attached  the  ciliary  processes,  is  called  the  zone  of  Zinn. 
These  two  layers  constitute  the  suspensory  ligament.  Be- 
tween them  is  a  triangular  canal,  with  its  base  correspond- 
ing to  tiie  crystalline  lens.  This  is  called  the  canal  of  Petit. 
The  vitreous  body  is  contained  within  the  cavity  formed 
by  the  hyaloid  membrane  and  the  posterior  surface  of  the 
lens.  It  consists  of  a  clear,  colorless  albuminous  fluid,  hav- 
ing nn  extremely  delicate  interlacement  of  fibres  extending 
in  all  directions  throuofli  it.  These  fibres  are  not  discerni- 
ble  in  the  adult,  but  can  readily  be  seen  in  the  foetus. 

The  aqueous  humo?^  is  contained  within  the  space  formed 
by  the  posterior  surface  of  the  cornea  and  tiie  anterior  sur- 
face of  the  lens.  The  space,  which  is  divided  into  two 
chambers  by  the  iris,  is  filled  with  a  clear,  colorless,  limpid 


FORMATION    OF    THE    IMAGE.  600 

fluid  containing  saline  and  proteid  substances  in  solution. 
This  fluid  constitutes  the  aqueous  humor. 

The  anterior  external  portion  of  the  eyeball  comprising 
the  surface  of  the  cornea  and  about  6  or  8  mm.  of  the 
sclerotic  coat  is  covered  by  the  conjunctival  mucous  mem- 
brane.] 

SIGHT. 

A  ra}'  of  light  falling  on  the  retina  gives  rise  to  what  we 
call  a  sensation  of  light:  but  in  order  that  distinct  vision  of 
any  object  ma}^  be  gained,  an  image  of  the  object  must  be 
formed  on  the  retina,  and  the  better  defined  the  image  the 
more  distinct  will  be  the  vision.  Hence  in  studying  the 
physiology  of  vision,  our  first  duty  is  to  examine  into  the 
arrangements  by  which  the  formation  of  a  satisfactory  image 
on  the  retina  is  effected  ;  these  we  may  call  briefly  the  diop- 
tric mechanisms.  We  shall  then  have  to  inquire  into  the 
laws  according  to  which  rays  of  light  impinging  on  the 
retina  give  rise  to  sensory  impulses,  and  those  according  to 
which  the  impulses  thus  generated  give  rise  in  turn  to  sen- 
sations. Here  we  shall  come  upon  the  difficulty  of  distin- 
guishing between  the  unconscious  or  physical  and  the  con- 
scious or  psychical  factors.  And  we  shall  find  our  diffi- 
culties increased  by  th.e  fact,  that  in  appealing  to  our  own 
consciousness  we  are  apt  to  fall  into  error  by  confounding 
primary  and  direct  sensations  with  states  of  consciousness 
which  are  produced  by  the  weaving  of  these  primary  sensa- 
tions with  other  operations  of  the  central  nervous  system, 
or,  in  familiar  language,  by  confounding  what  we  see  with 
what  we  think  we  see.  These  two  things  we  will  brieflv  dis- 
tinguish as  visual  sensations  and  visual  judgments  ;  and  we 
shall  find  that  both  in  vision  with  one  eye,  but  more  espe- 
ciall}'  in  binocular  vision,  visual  judgments  form  a  verj-  large 
part  of  what  we  frequently  speak  of  as  our  sight. 

Sec.  1..  Dioptric  Mechanisms. 
The  Formation  of  the  Image. 

The  eye  is  a  camera,  consisting  of  a  series  of  lenses  and 
media  arranged  in  a  dark  chamber,  the  iris  serving  as  a  dia- 
phragm ;  and  the  object  of  the  apparatus  is  to  form  on  the 
retina  a  distinct  image  of  external  objects.     That  a  distinct 


656  SKJHT. 

image  is  formed  on  the  retina,  may  he  ascertained  by  re- 
moving tiie  sclerotic  from  the  back  of  an  eye,  and  looking 
at  the  hinder  snrface  of  the  transparent  retina  while  rays  of 
light  proceeding  from  any  external  object  are  allowed  to  fall 
on  the  cornea. 

A  dioptric  apparatns  in  its  simplest  form  consists  of  two 
media  separated  by  a  (spherical)  snrface;  and  the  optical 
properties  of  such  an  apparatns  depend  npon  (1)  the  cnrva- 
tnre  of  the  surface,  (2)  the  relative  refractive  power  of  the 
media.  The  eye  consists  of  several  media,  bonnded  by 
surfaces  which  are  ai)proximately  spherical  hut  of  ditlerent 
curvature.  The  surfaces  are  all  centred  on  a  line  called 
the  optic  axii^^  which  meets  the  retina  at  a  point  somewhat 
above  and  to  the  inner  (nasalj  side  of  the  fovea  centralis. 
In  passing  from  the  outer  surface  of  the  cornea  to  the  retina 
the  rays  of  light  traverse  in  succession  the  cornea,  the  acpie- 
ous  humor,  the  lens,  and  the  viti"eons  humor.  Refraction 
takes  place  at  all  the  surfaces  bounding  these  several  media, 
but  particularly  at  the  anterior  siirlace  of  the  cornea,  and 
at  both  the  anterior  and  posterior  surfaces  of  the  lens. 
Since  the  anterior  and  posterior  surfaces  of  the  cornea  are 
parallel,  or  very  nearly  so,  the  rays  of  light  would  suffer 
little  or  no  change  of  direction  in  passing  throuijh  the  cor- 
nea, if  it  were  bounded  on  both  sides  by  the  same  medium. 
The  direction  of  the  rays  of  light  in  the  aqueous  humor 
would  therefore  remain  the  same  if  the  cornea  were  made 
exceedingly  thin,  if  in  fact  its  two  surfaces  were  made  into 
one,  forming  a  single  anterior  surface  to  the  aqueous  humor  ; 
or,  which  comes  to  the  same  thing  in  the  end,  since  the 
refractive  power  of  the  substance  of  the  cornea  is  almost 
exacth'  the  same  as  that  of  the  aqueous  humor,  the  refrac- 
tion at  the  posterior  snrface  of  the  cornea  may  be  neglected 
altogether.  Thus  the  two  surfaces  of  the  cornea  are  prac- 
tically reduced  to  one.  The  lens  varies  in  density  in  differ- 
ent parts,  the  refractive  power  of  the  central  portions  being 
greater  than  that  of  the  external  la3'ers  ;  but  tiie  refractive 
power  of  the  whole  may,  without  any  serious  error,  be 
assumed  to  be  uniform,  a  mean  being  taken  between  the 
refractive  powers  of  the  several  parts.  The  refractive  power 
of  the  vitreous  humor  is  almost  exactly  the  satne  as  that  of 
the  aqueous  humor. 

Thus  the  apparently  complicated  natural  e3'e  may  be  sim- 
plified into  a  "  diagrammatic  eye."  in  which  the  refracting 
surfaces  are  reduced  to  three,  viz.,  (1)  the  anterior  surface 


ACCOMMODATION.  657 

of  tlie  cornea.  (2)  the  anterior  surface  of  the  lens  separating 
the  lens  from  the  aqueous  humor,  and  (3)  the  posterior  sur- 
face of  tlie  lens  separating  the  lens  from  the  vitreous  hutnor. 
The  media  will  similarly  be  reduced  to  two ;  the  mean  sub- 
stance of  the  lens,  and  the  aqueous  or  vitreous  humor.  This 
"diagrammatic  eye''  is  of  great  use  in  the  various  calcula- 
tions which  become  necessary  in  studying  physiological 
optics  ;  for  the  magnitudes  which  are  derived  b}-  calculation 
from  it  represent  the  corresponding  magnitudes  in  an  aver- 
age natural  eye  with  sufficient  accuracy  to  serve  for  all 
practical  purposes.  The  values  adopted  by  Listing  for  the 
constants  of  this  ''diagrammatic  eye,"  and  to  him  we  are 
indebted  for  the  introduction  of  it,  are  as  follows: 

Radius  of  curvature  of  cornea,       ....  8  mm. 
"             "              of  anterior  surface  of  lens,    .10     " 
"            "              of  posterior         "         "           .  6     " 
Refractive  index  of  aqueous  or  vitreous  humor,     .  V'/ 
Mean  refractive  index  of  lens,         .         .         .         •  ji" 
Distance  from  anterior  surface  of  cornea  to  ante- 
rior surface  of  lens, 4  mm. 

Thickness  of  lens, 4     '' 

The  calculated  position  of  the  principal  poderior  focus^ 
i.  e.,  the  point  at  which  all  rays  falling  on  the  cornea  parallel 
to  the  optic  axis  are  brought  to  a  focus,  is  in  the  diagram- 
matic eye  14.(i470  mm.  behind  the  posterior  surface  of  the 
lens,  or  22.6470  mm.  beiiind  the  anterior  surface  of  the 
cornea.  That  is  to  say,  the  fovea  centralis  must  occupy 
this  position  in  order  tiiat  a  distinct  image  of  a  distinct 
object  may  be  formed  upon  it.  It  must  be  understood  that 
these  values  refer  to  the  eye  when  at  rest,  i.  e.,  when  it  is 
not  undergoing  any  strain  of  accommodation. 


AccommodaMon. 

When  an  object,  a  lens,  and  a  screen  to  receive  the  image 
are  so  arranged  in*  reference  to  each  other  ihat  the  image 
falls  upon  the  screen  in  exact  focus,  the  rays  of  light  pro- 
ceeding from  each  luminous  point  of  the  object  are  brought 
into  focus  on  the  screen  in  a  point  of  the  image  correspond- 
ing to  the  point  of  the  object.  If  the  object  be  then  re- 
moved farther  away  from  the  lens,  the  rays  proceeding  in  a 
pencil  from  each   luminous  point  will  be  brought  to  a  focus 


658  SIGHT. 


at  a  point  in  front  of  the  screen,  and,  subsequently  diverg- 
ing, will  fall  upon  the  screen  as  a  circular  patch  composed 
of  a  series  of  circles,  the  so-called  diff^uHion  cij^clei^^  arranged 
concentrically  round  the  principal  ray  of  the  pencil.  If  the 
oltject  1)6  removed,  not  farther,  hut  nearer  the  lens,  the  pen- 
cil of  rays  will  meet  the  screen  before  they  have  been  brought 
to  focus  in  a  point,  and  consequently  will  in  this  case  also 
give  rise  to  diffusion  circles.  When  an  ol»ject  is  placed 
before  the  eye,  so  that  the  image  falls  into  exact  focus  on 
the  retina,  and  the  pencils  of  rays  proceeding  from  each 
luminous  point  of  the  object  are  brought  into  focus  in  points 
on  the  retina,  the  sensation  called  forth  is  that  of  a  distinct 
image.  When  on  the  contrary  the  object  is  too  far  away, 
so  that  the  focus  lies  in  front  of  the  retina,  or  too  near,  so 
that  the  focus  lies  behind  the  retina,  and  the  [)encils  fall  on 
the  retina  not  as  points,  but  as  systems  of  diffusion  circles, 
the  image  produced  is  indistinct  and  blurred.  In  order  that 
ol'jects  both  near  and  distant  may  be  seen  with  equal  dis- 
tinctness b}'  the  same  dioptric  apparatus,  the  focal  arrange- 
ments of  the  apparatus  must  be  accommodated  to  the  dis- 
tance of  the  object,  either  by  changing  the  refractive  power 
of  the  lens,  or  by  altering  the  distance  between  the  lens  and 
the  screen. 

That  the  eye  does  possess  such  a  power  of  accommoda- 
tion is  shown  by  e very-day  experience.  If  two  needles  be 
fixed  upright  some  two  feet  or  so  apart,  into  a  long  piece  of 
wood,  and  tlie  wood  be  held  before  the  eye,  so  that  the 
needles  are  nearly  in  a  line,  it  will  be  found  that  if  attention 
be  directed  to  the  far  needle,  the  near  one  appears  blurred 
and  indistinct,  and  that,  converselv,  when  the  near  one  is 
distinct,  the  far  one  appears  blurred.  B3'  an  effort  of  the 
will  we  can  at  pleasure  make  either  the  far  one  or  the  near 
one  distinct ;  but  not  both  at  the  same  time.  When  the  eye 
is  arranged  so  that  the  far  needle  ap[)ears  distinct,  the  image 
of  that  needle  falls  exactlj'  on  the  retina,  and  each  pencil 
from  each  luminous  point  of  the  needle  unites  in  a  point 
ui)on  the  retina;  but  when  this  is  the  case,  the  focus  of  the 
near  needle  lies  behind  the  retina,  and  each  pencil  from  each 
luminous  point  of  this  needle  falls  upon  the  retina  in  a 
series  of  diffusion  circles.  Similarly,  when  the  eye  is  ar- 
ranged so  that  the  near  needle  is  distinct,  the  image  of  that 
needle  falls  upon  the  retina  in  such  a  vvay,  that  each  pencil 
of  rays  from  each  luminous  point  of  the  needle  unites  in  a 
point  on  tiie  retina,  while  each  pencil  from  each  luminous 


ACCOMMODATION.  659 

point  of  tlie  far  needle  unites  at  a  point  in  front  of  the  ret- 
ina, and  then  divergino;  ngain  falls  on  the  retina  in  a  series 
of  diffusion  circles.  If  the  near  needle  he  gradually  brought 
nearer  and  nearer  to  the  eve,  it  will  be  found  that  greater 
and  greater  effort  is  required  to  see  it  distinctly,  and  at  last 
a  point  is  reached  at  which  no  effort  can  make  the  image  of 
the  needle  appear  anything  but  blurred.  The  distance  of 
this  point  from  the  eye  marks  the  limit  of  accommodation 
for  near  objects  Similarly,  if  the  person  be  short-sighted, 
the  far  needle  may  be  moved  away  from  the  eye,  until  a 
point  is  renched  at  which  it  ceases  to  be  seen  distinctly,  and 
appears  blurred.  In  the  one  case,  the  eye,  with  all  its 
power,  is  unable  to  bring  the  image  of  the  needle  suf- 
ficiently forward  to  fall  on  the  retina;  the  focus  lies  perma- 
nently behind  the  retina.  In  the  other  the  eye  cannot 
bring  the  image  siitticieiitly  backward  to  fall  on  the  retina; 
the  focus  lies  permanently  in  front  of  the  retina.  In  both 
cases  the  pencils  of  rays  from  the  needles  strike  the  retina 
in  diffusion  circles. 

The  same  phenomena  may  be  shown  with  greater  nicety 
by  what  is  called  Scheiner's  experiment.^  If  two  smooth 
holes  be  pricked  in  a  card,  at  a  distance  from  each  other 
less  than  the  diameter  of  t!ie  pupil,  and  the  card  be  held 
up  before  one  eye,  with  the  holes  horizontal,  and  a  needle 
placed  vertically  be  looked  at  through  the  holes,  the  follow- 
ing facts  may  be  observed.  When  attention  is  directed  to 
the  needle  itself,  the  image  of  the  needle  appears  single. 
Whenever  the  gaze  is  directed  to  a  more  distant  object,  so 
that  the  eye  is  no  longer  accommodated  for  the  needle,  the 
image  appears  double  and  at  the  same  time  blurred.  It 
also  appears  double  and  blurred  when  the  eye  is  accommo- 
dated for  a  distance  nearer  than  that  of  the  needle.  When 
only  one  needle  is  seen,  and  the  eye.  therefore,  is  properly 
accommodated  for  the  distance  of  the  needle,  no  effect  is 
produced  by  blocking  up  one  hole  of  the  card,  except  that 
the  whole  field  of  vision  seems  dimmer.  When,  however, 
the  image  is  doul)le  on  account  of  the  eye  being  accommo- 
dated for  a  distance  greater  than  that  of  the  needle,  blocking 
the  left-hand  hole  causes  a  disappearance  of  the  right-hand 
or  opposite  image,  and  blocking  the  right-hand  hole  causes 
the  left-hand  image  to  disappear.  When  the  eye  is  accom- 
modated  for  a  distance  nearer  than   that  of  the  needle, 

^  Scheiner,  Oculus.     Innsbruck,  1619. 


660 


SIGHT. 


blocking  eitlier  hole  causes  the  imaore  on  tlie  satne  side  to 
vanish.  The  following  diagram  will  explain  how  these  re- 
sults are  l)rouoht  about. 

Let  a  (Fig.  173)  be  a  luminous  point  in  the  needle,  and 
ae,  af  the  extreme  right-hand  and  left- 
hand  rays  of  the  pencil  of  rays  proceeding 
from  it,  and  passing  resijectiveiy  through 
the  right-hand,  e,  and  left-hand,/,  holes 
in  the  card.  (The  figure  is  supposed  to 
be  a  horizontal  section  of  the  eye.) 
When  the  eye  is  accommodated  for  rt, 
the  rays  e  and  /  meet  together  in  the 
point  c,  the  retina  occui)ying  the  posi- 
tion of  plane  v  n  ;  the  luminous  point 
appears  as  one  point,  and  the  needle  will 
appear  as  one  needle.  Wlien  the  eye  is 
accommodated  for  a  distance  lieyond  a, 
tlie  retina  may  be  considered  to  lie^  no 
longer  at  n  n,  but  nearer  the  lens,  at  m  m, 
for  example:  the  rays  o.e  will  cut  this 
l)lane  at  p,  and  the  rays  a/ at  q;  hence 
the  luminous  point  will  no  longer  appear 
single,  but  will  be  seen  as  two  points,  or 
rather  as  two  systems  of  diffusion  cir- 
cles, and  the  single  needle  will  appear 
as  two  l)lurred  needles.  The  rays  pass- 
ing through  the  right-hand  hole  e  will 
cut  the  retina  at  p,  i.  e.,  on  the  right- 
hand  side  of  the  optic  axis  ;  but,  as  we 
shall  see  in  speaking  of  the  judgments 
pertaining  to  the  vision,  the  image  on 
the  right-hand  side  of  the  retina  is  re- 
ferred  by  the  mind  to  an  ol»ject  on  the 
left-hand  side  of  the  person  ;  hence  the 
affection  of  the  retina  at  ;j.  produced  by 
the  rays  ae  falling  on  it  there,  gives  rise 
to  an  image  of  the  spot  a  at  P,  and  sim- 
ilarly the  left-hand  spot  q  corresponds  to  the  right-liand  Q. 
Blocking  the  left-hand  hole,  therefore,  causes  a  disappear- 
ance of  the  right-hand  image  and  vice  versa.    Similarly  when 


Diagram  of  Scheiuer's 
Experiment. 


^  Of  course,  in  the  actual  eye,  as  we  shall  see,  accommodation  is  effected 
by  a  change  in  the  lens,  and  not  by  an  alteration  in  the  position  of  the 
retina ;  but,  for  convenience  sake,  we  may  here  suppose  the  retina  to  be 
moved. 


ACCOMMODATION.  661 


the  eye  is  accommodated  for  a  distance  nearer  than  the 
needle,  the  retina  may  be  supposed  to  be  removed  to  //,and 
tiie  right-liand  o  e  and  left-hand  af  rays,  after  uniting  at  c, 
will  diverge  again  and  strike  the  retina  at  j)'  and  q' .  The 
blocking  of  the  hole  e  will  now  cause  the  disappearance  of 
the  image  ^' on  the  left  hand  side  of  the  retina,  and  this  will 
be  referred  by  the  mind  to  the  right-hand  side,  so  that  Q 
will  seem  to  vanish 

If  the  needle  be  brought  graduall}'  nearer  and  nearer  to 
the  eye,  a  point  will  be  reached  within  which  the  image  is 
always  double.  This  point  marks  with  considerable  exact- 
itude the  near  limit  of  accommodation.  With  short-sighted 
persons,  if  the  needle  be  removed  farther  and  farther  away, 
a  point  is  reached  beyond  which  the  image  is  always  double  ; 
this  marks  the  far  limit  of  accommodation. 

The  experiment  may  also  be  porfoi'med  with  the  needle  placed 
horizontally,  in  which  case  the  holes  in  the  card  should  bever- 
tical.  The  adjustment  for  the  eye  for  near  or  far  distances  may 
be  assisted  by  using  two  needlts,  one  near  and  one  far.  In  this 
case  one  needle  should  be  vertical  and  the  other  horizontal,  and 
the  card  turned  round  so  that  the  holes  lie  horizontally  or  ver- 
tically, according  to  whether  the  vertical  or  horizontal  needle  is 
being  made  to  appear  double. 

In  what  may  be  regarded  as  the  normal  eye,  the  so-called 
emmetropic  eye,  the  near  limit  of  accommodation  is  about 
10  or  12  cm.,  and  the  far  limit  may  be  put  for  practical 
purposes  at  an  infinite  distance.  The  "  range  of  distinct 
vision,"  therefore,  for  the  emmetropic  eye  is  very  great.  In 
the  myopic^  or  short-sighted  eye,  the  near  limit  is  brought 
much  closer  (5  or  6  cm.)  to  the  cornea  ;  and  the  far  limit  is  at 
a  variable,  but  not  very  great  distance,  so  that  the  rays  of 

[Fig.  174. 


Myopic  Eye.] 

light  proceeding  from  an  object  not  man}'  feet  away  are 
brought  to  a  focus,  not  on  the  retina,  but  in  the  vitreous 
humor  (Fig.  174).     The  range  of  distinct  vision  is,  there- 

56 


662 


SIGHT, 


fore,  in  the  myopic  e^^e  very  limited.  In  the  hypermetropic^ 
or  long-sighted  e^^e,  the  rays  of  liglit  coming  from  even  an 
infinite  distance  are,  in  the  passive  state  of  the  eye,  l>ronght 
to  a  focns  heyond  the  retina  (Fig.  175).  Tlie  near  limit  of 
accommodation  is  at  some  distance  off,  and  a  far  limit  of 
accommodation  does  not  exist.  The  preahyopic  eve,  or  the 
long-sight  of  old  peo[)le,  resembles  the  hypermetropic  eye 
in  the  distance  of  the  near  point  of  accommodation,  hut 
differs  from  it,  inasmuch  as  tlic  former  is  an  esentiall}'  de- 


Hypermetropic  Eye.] 

fective  condition  of  tlie  accommodation  mechanism,  whereas 
in  tlie  latter  the  power  of  accommodation  ma}^  be  good,  and 
yet,  from  the  internal  arrangements  of  the  eye,  be  unai)le  to 
bring  the  image  of  a  near  object  on  to  the  retina.  When  a 
normal  eye  becomes  presbyopic,  the  far  limit  may  remain 
the  same  ;  but  since  the  power  of  accommodating  for  near 
objects  is  weakened  or  lost,  the  change  is  distinctly  a  reduc- 
tion of  the  range  of  distinct  vision.  In  the  normal  emme- 
tropic eye,  when  no  effort  of  accommodation  is  made,  the 
principal  focns  of  the  eye  lies  on  the  retina  (Fig.  176),  in 


[Fig.  176. 
A 


Eintnt'tropic  Eye.    Parallel  rays  focussetl  on  the  retina.] 


the  myopic  eye  in  front  of  it,  and  in  the  hypermetroi)ic  eye 
behind  it. 


ACCOMMODATION.  663 


Mechanism  of  Accommodation. — In  directing  our  attention 
from  a  far  to  a  very  near  object,  we  are  conscious  of  a  dis- 
tinct effort,  and  feel  that  some  change  has  taken  place  in  the 
eye.  When  we  turn  from  a  very  near  to  a  far  object,  if  we 
are  conscious  of  any  ciiange  in  the  eye,  it  is  one  of  a  differ- 
ent kind.  The  former  is  the  sense  of  an  active  accommoda- 
tion for  near  objects  ;  the  latter,  when  it  is  felt,  is  tiie  sense 
of  relaxation  after  exertion. 

Since  the  far  limit  of  an  emmetropic  eye  is  at  an  infinite  dis- 
tance, no  such  thing  as  active  accommodation  for  far  distances 
need  exist.  The  only  change  that  will  take  place  in  the  eye  in 
turning  from  near  to  far  objects  will  be  a  mere  passive  undoing 
of  the  accommodation  previously  made  for  the  near  object.  And 
that  no  such  active  accommodation  for  far  distances  takes  place 
is  shown  by  the  facts,  that  the  eye,  when  opened  after  being  closed 
for  some  time,  is  found  not  in  medium  state,  but  adjusted  for  dis- 
tance ;  that,  when  the  accommodation  mechanism  of  the  eye  is 
paralyzed  by  atropin  or  nervous  disease,  the  accommodation  for 
distant  objects  is  unaffected  ;  and  that  we  are  conscious  of  no 
effort  in  turning  from  moderately  distant  to  far  distant  objects. 
The  sense  of  effort  often  spoken  of  by  myopic  persons  as  being  felt 
Avhen  they  attempt  to  see  things  at  or  beyond  the  far  limit  of  their 
range  seems  to  arise  from  a  movement  of  the  eyelids,  and  not 
from  any  internal  change  taking  place  in  the  eye. 

What,  then,  are  the  changes  which  take  place  in  the  eye 
when  we  accommodate  for  near  objects  ?  It  might  be  thought, 
and  indeed  once  was  thought,  that  the  curvature  of  the  cornea 
was  changed,  becoming  more  convex,  with  a  shorter  radius 
of  curvature,  for  near,objects.  Young,  however,  showed  that 
accommodation  took  place  as  usual  when  the  eye  (and  head) 
is  immersed  m  water.  Since  the  refractive  powers  of  aqueous 
humor  and  water  are  very  nearly  alike,  the  cornea,  with  its 
parallel  surfaces,  placed  between  these  two  fluids,  can  have 
little  or  no  effect  on  the  direction  of  the  rays  passing  through 
it  when  the  eye  is  immersed  in  water.  And  accurate  meas- 
urements of  the  dimensions  of  an  image  on  the  cornea  have 
shown  that  these  undergo  no  change  during  accommodation, 
and  that  therefore  the  curvature  of  the  cornea  is  not  altered. 
Nor  is  there  any  change  in  the  form  of  the  bulb  :  for  any 
variation  in  this  would  necessarily  produce  an  alteration  in 
the  curvature  of  the  cornea,  and  pressure  on  the  bulb  would 
act  injuriousl}^  hj-  rendering  the  retina  anaemic,  and  so  less 
sensitive.    In  fact  there  are  onl\-  two  changes  of  importance 


664  SIGHT. 


which  can  be  ascertained  to  take  place  in  the  eye  during 
accommodation  for  near  objects. 

One  is  that  the  pupil  contracts.  When  we  look  at  near 
objects,  tile  pupil  becomes  s>nall ;  when  we  turn  to  distant 
objects,  it  dilates.  This,  however,  cannot  have  more  tlian 
an  indirect  intlnence  on  the  formation  of  the  image;  the 
chief  use  of  the  contraction  of  the  pupil  in  accommodation 
for  near  objects  is  to  cut  otf  tiie  more  divergent  circumfer- 
ential rays  of  light. 

Tiie  other  and  really  efficient  change  is  that  the  anterior 
surface  of  the  lens  becomes  more  convex.  (Fig.  177.)  If  a 
light  be  held  before  the  eye,  three  reflected  images  ma^'  be 

[Fig.  177. 


Eminctro.  ic  Eye.    The  doited  lines  showing  how  aecoininodatiou  for  the  diverging 
r;iys  of  ncai-  ohj.  cts  is  effected.] 

seen  by  a  bystander:  one  a  very  briglit  one  caused  by  the 
anterior  surface  of  the  cornea,  a  second  less  bright,  by  the 
anterior  suiface  of  the  lens,  and  a  third  very  dim,  by  the 
posterior  surface  of  the  lens.  Wlien  the  eye  is  accommo- 
dated for  near  ol>jects,  no  change  is  observed  in  eitiier  the 
first  or  the  third  of  these  images  ;  but  the  second,  that  from 
the  anterior  surface  of  the  lens,  is  seen  to  become  distinctly 
smaller,  showing  that  the  surface  has  liecome  more  convex. 
When,  on  the  contrary,  vision  is  directed  from  near  to  far 
objects,  the  image  from  the  anterior  surface  of  the  lens 
grows  lai'ger,  indicating  that  the  convexity  of  the  surface 
has  diminished,  while  no  change  takes  place  in  the  curva- 
ture either  of  the  cornea  or  of  the  posterior  surface  of  the 
lens.  And  accurate  measurements  of  the  size  of  the  image 
from  the  anterior  surface  of  the  lens  have  shown  tiiat  the 
variations  in  curvature  which  do  take  i)lace,are  sufficient  to 
account  for  the  power  of  accommodation  which  the  eye  pos- 
sesses. 

The  observation  of  these  reflected  images  is  facilitated  by  the 
simple  instrument  introduced  by  Helmholtz  and  called  a  Phako- 
scope.     It  consists  of  a  small  dark  chamber,  with  apertures  for 


ACCOMMODATION.  605 


the  observed  and  observins;  eyes  ;  a  needle  is  fixed  at  a  sbort  dis- 
tance in  front  of  the  former,  to  serve  as  a  near  object,  for  which 
accommodation  has  to  be  made  ;  and  by  means  of  two  prisms  the 
imaire  from  each  of  the  three  surfaces  of  the  observed  eye  is  made 
double  instead  of  single.  When  the  anterior  surface  of  the  lens 
becomes  more  convex  the  two  images  reflected  from  that  surface 
approach  each  other,  when  it  becomes  less  convex  they  retire 
from  each  other.  The  approach  and  retirement  are  more  readily 
appreciated  than  is  a  simple  change  of  size. 

These  obsei'vations  leave  no  doubt  that  the  essential 
change  by  which  accommodation  is  effected  is  an  alteration 
of  the  convexity  of  the  anterior  surface  of  the  lens.  And 
that  the  lens  is  the  agent  of  accommodation  is  shown  by 
the  fact  that  after  removal  of  the  lens,  as  in  the  operation  for 
cataract,  the  power  of  accommodation  is  lost. 

In  the  cases  which  have  been  recorded,  where  eyes  from  which 
the  lens  had  been  removed  seemed  still  to  possess  some  accommo- 
dation, we  must  suppose  that  no  real  accommodation  took  place, 
but  that  the  pupil  contracted  when  a  near  object  was  looked  at, 
and  so  assisted  in  making  vision  more  distinct. 

Concerning  the  nature  of  the  mechanism  by  which  this 
increase  of  the  convexity  of  the  lens  is  effected,  the  view 
most  generally  adopted  is  as  follows :  In  the  passive  condi- 
tion of  the  eye,  when  it  is  adjusted  for  far  objects  the  sus- 
pensory ligament  keeps  the  lens  tense  with  its  anterior  sur- 
face somewluit  flattened.  Accommodation  for  near  objects 
consists  essentially  in  a  contraction  of  the  ciliary  muscle, 
which,  by  pulling  forward  the  choroid  coat  and  tlie  ciliary 
processes,  slackens  the  suspensory  ligament,  and  allows  tlie 
lens  to  bulge  forward  by  virtue  of  its  elasticity,  and  so  to 
increase  the  convexity  of  its  anterior  surface. 

Though  all  the  parts  surrounding  the  lens  are  highh' vascular, 
the  change  in  the  lens  cannot  be  considered  as  the  result  of  any 
vaso-motor  action,  since  accommodation  may  be  effected  in  a 
practically  bloodless  eye  by  artificial  stimulation  with  an  inter- 
rupted current,  or  by  other  means.  Again,  the  fact  that  accom- 
modation may  take  place  in  eyes  from  which  the  iris  is  congeni- 
tally  absent,  disproves  the  suggestion  that  the  change  in  the  lens 
is  caused  either  by  the  compression  of  the  circumference  of  the 
lens,  or  in  an\^  other  way  by  contraction  of  the  iris.  On  the 
other  hand,  the  observations  of  Hensen  and  Ycilckers,'  who  saw 

'  Mechanisnius  d.  Accommod.,  Kiel,  1868.  Abst.  in  Cbt.  f.  Med. 
Wiss.,  1868,  p.  455. 


Q66  SIGHT. 


the  choroid  drawn  forward  durhig-  accommodation  (brouglit 
about  by  stimulation  of  the  ciHary  gans^diou),  and  satisfied  them- 
selves that  the  cornea  served  as  a  functional  tixed  attachment  for 
the  ciliary  muscle,  offer  a  strong  support  to  the  generally  accepted 
explanation.  To  which  it  may  be  added  that  the  lens  is  certainly 
elastic,  and,  moreover,  that  its  natural  convexity  appears  to  be 
diminished  by  the  action  of  the  suspensory  ligament,  since  after 
removal  from  the  body  its  anterior  surface  is"  found  to  be  more 
convex  than  when  in  the  natural  position  in  the  body.  Hock^ 
has  carefully  repeated  Hensen  and  V^iilckers's  experiment  on  the 
dog,  stimulating  the  radix  brevis  of  the  ganglion  instead  of  the 
ganglion  itself.  He  fully  confirms  their  results,  and  especially 
insists  that  the  choroid  is  pulled  forward  by  the  ciliary  muscles 
(longitudinal  fibres)  and  not  b}'  muscular  fibres  present  in  the 
choroid  itself. 

Accommodation  is  a  voluntary  act  ;  since,  however,  the 
change  in  the  lens  is  always  accompanied  by  movements  in 
the  iris,  it  will  be  convenient  to  consider  the  latter  before 
we  discuss  the  nervous  mechanism  of  the  whole  act. 

Movements  of  the  Pupil.— Thougii  b}^  making  the  efforts 
required  for  accommodation  we  cnn  at  pleasure  contract  or 
dilate  the  pupil,  it  is  not  in  our  power  to  bring  the  will  to 
act  directly  on  the  iris  by  itself.  This  fact  ahjne  indicates 
that  the  nervous  mechanism  of  the  pupil  is  of  a  peculiar 
character,  and  such  indeed  we  find  it  to  be.  The  pupil  is 
contracted  (1)  when  the  i-etina  (or  optic  nerve)  is  stimulated, 
as  when  light  falls  on  the  retina,  the  blighter  the  light  the 
greater  being  the  contraction  ;  (2)  when  we  accommodate 
for  near  objects.  The  pupil  is  also  contracted  when  the 
eyeball  is  turned  inwards,  when  the  a(pieous  humor  is  defi- 
cient, in  the  eaily  stages  of"  poisoning  by  chloroform,  alco- 
liol,  etc.,  in  nearly  all  stages  of  poisoning  by  ?norphia, 
physosf igmin,  and  some  other  drugs,  and  in  deep  slumber. 
The  pupil  is  dilated  (1)  when  stimulation  of  the  retina  (or 
optic  nerve)  is  arrested  or  diminished;  hence  the  pupil 
dilates  in  passing  into  a  dim  light,  (2)  when  the  eye  is  ad- 
justed for  far  objects.  Dilation  also  occurs  wiien  there  is 
an  excess  of  aqueous  humor,  during  dyspnoea,  during  violent 
muscular  efforts,  as  the  result  of  a  strong  stimulation  of 
sensory  nerves,  as  an  effect  of  emotions,  in  the  later  stages 
of  poisoning  by  chloroform,  etc.,  and  in  all  stages  of  poison- 
ing by  atropin  and  some  other  drugs.     Contraction  of  the 

'  Cbt.  f.  ^[od.  Wiss.,  1878,  p.  7()9. 


MOVEMENTS    OF    THE    PUPIL.  667 

pnpil  is  caused  by  contraction  of  the  circular  fibres  or 
sphincter  of  the  iris.  Dilation  is  caused  b}^  contraction  of 
the  I'adial  fibres  of  the  iris. 

The  existence  of  radial  fibres  has  been  denied  bj^  many  ob- 
servers, but  the  preponderance  of  evidence  is  clearly  in  favor  of 
their  being  really  present. 

Contraction  of  the  pnpil,  brought  about  by  light  falling 
on  the  retina,  is  a  reflex  act,  of  which  the  optic  is  the  affer- 
ent nerve,  the  third  or  oculo-motor  the  efferent  nerve,  and 
the  centre  some  portion  of  the  brain  lying  below  the  corpora 
quadrigemina  in  the  floor  of  the  aqueduct  of  Sylvius.  This 
is  proved  by  the  following  facts:  When  the  optic  nerve  is 
divided,  the  falling  of  light  on  the  retina  no  long,  r  causes 
a  contraction  of  the  pupil.  AVhen  the  third  nerve  is  divi- 
ded, stimulation  of  the  retina  or  of  the  o[)tic  nerve  no  longer 
causes  contraction  ;  but  direct  stimulation  of  the  peripheral 
portion  of  the  divided  third  nerve  causes  extreme  contrac- 
tion of  the  pupil.  After  removal  of  the  region  of  the  brain 
spoken  of  above,  stimulation  of  the  retina  is  similarly  inef- 
fectual. But  if  the  same  region  of  the  brain  and  its  con- 
nections with  the  optic  nei-ve  and  third  nerve  be  left  intact, 
contraction  of  the  jKipil  will  occur  as  a  rL-sult  of  light  fall- 
ing on  the  retina,  though  all  other  nervous  parts  be  re- 
moved. 

Certain  reservations  must  however  be  made  to  the  above  state- 
ments, since  in  the  excised  eye  of  the  eel  or  frog  the  pupil  will 
still  contract  on  exposure  to  light  though  the  nervous  centre  is 
absent. •  Holmgren  and  Edgren' find  that  in  the  frog  this  con- 
traction of  the  pupil  of  the  excised  eye  on  exposure  to  light  dis- 
appears when  the  retina  is  destroyed  ;  there  seems  therefore  to 
be  n-ithin  the  hidb  some  nervous  connection  between  the  retina 
and  iris. 

The  nervous  centre  is  not  a  double  centre  with  two  com- 
pletely independent  halves,  one  for  each  eye  ;  there  is  a 
certain  amount  of  fimctional  communion  between  the  two 
sides,  so  that  when  one  retina  is  stimulated  both  pupils 
contract.  It  might  be  imagined  that  this  cerebral  centre 
acted  as  a  tonic  centre,  whose  action  was  simply  increased 

^  Bro\Yn-Sequard,  Corapt.  Rend.,  xxv  (1847),  482,  508  ;  Proc.  Rov. 
Soc,  viii  (1856),  p.  233. 

2  Hofmaun  and  vSchwalbe's  Bericht,  v  {187G\  p.  103. 


668  SIGHT. 

not  originated  b}'  tlie  stimulation  of  the  retina  ;  but  this  is 
disproved  b}^  the  fact  that,  if  the  optic  nerve  be  divided, 
subsequent  section  of  the  third  nerve  produces  no  further 
dihition. 

In  considei'ing  tlie  movements  of  the  pupil,  however,  we 
have  to  deal  not  only  witii  contraction  but  with  active  dila- 
tion ;  and  this  renders  the  whole  matter  much  more  complex 
tlian  might  be  supposed  to  be  the  case  from  the  simple  state- 
ment just  made. 

The  iris  is  supplied,  in  common  with  the  ciliary  muscle 
and  choroid,  by  the  short  ciliary  nerves  coming  from  the 
opiithalmic  or  lenticular  (ciliary)  ganglion,  which  is  con- 
nected by  its  roots  with  the  third  nerve,  the  cervical  sympa- 
thetic nerve,  and  with  tlie  nasal  branch  of  the  ophthalmic 
division  of  the  fifth  nerve.  The  short  ciliary  nerves  are, 
moreover,  accompanied  by  the  long  ciliary  nerves  coming 
from  the  same  nasal  branch  of  the  ophthalmic  division  of 
the  fifth  nerve.  What  are  the  uses  of  these  several  nerves 
in  relation  to  the  pui)il  ? 

If  the  cervical  sympathetic  in  the  neck  be  divided,  all 
other  portions  of  the  nervous  mechanism  being  intact,  a 
contraction  of  the  pupil  (not  always  very  well  marked)  takes 
place,  and  if  the  peripheral  portion  (?'.  ^.,  the  upper  portion 
still  connected  with  the  eye)  be  stimulated,  a  well-developed 
dilation  is  the  result.  The  sympathetic  has,  it  will  be  ob- 
served, an  effect  on  the  iris,  the  opposite  of  that  which  it 
exercises  on  the  l)loodvessels  ;  when  it  is  stimulated  the 
pupils  are  dilated  while  the  bloodvessels  are  constricted. 
This  dilating  intiuence  of  the  sympathetic  may,  as  in  the 
case  of  the  vaso-motor  acticm  of  the  same  nerve,  be  traced 
back  down  the  neck,  along  the  rami  communicantes  and 
roots  of  the  last  cervical  and  first  dorsal  or  two  first  dorsal 
spinal  nerves,  to  a  region  in  the  lower  cervical  and  upper 
dorsal  cord  (called  by  Budge^  tlie  centrum  ciliospinale  in- 
ferius).  diwd  from  thence  up  through  the  medulla  oblongata 
to  a  centre,  which,  according  to  Hensen  and  Yolckers.'  lies 
in  the  floor  of  the  front  part  of  the  acpieduct  of  Sylvius. 

Considering  how  vascular  the  iris  is,  it  does  not  seem  unrea- 
sonable to  interpret  some  of  the  variations  in  the  condition  of  the 
pupil  as  the  results  of  simple  vascular  turgescenee  or  depletion 

^  Ueber  die  Bewegung  der  Iris,  1 855. 
2  Archly  f.  Ophthalmol.,  xxiv  (lS78j. 


MOVEMENTS    OF    THE    PUPIL.  669 


brouirht  about  by  vaso-motor  action  or  otberwise,  tbe  small  or 
contracted  pupil  correspondins:  to  the  dilated  and  tilled,  and  the 
large  or  dilated  pupil  to  constricted  and  emptied  condition  of  the 
bloodvessels.^  Thus  slight  oscillations  of  the  pupil  ma}'  be  ob- 
served S3'nchronous  with  the  heart-ljeat  and  others  synchronous 
with  the  respiratory  movements.  But  the  variations  in  the  pupil 
seem  too  marked  to  be  merely  the  eftects  of  vascular  changes, 
and  indeed  that  constriction  of  the  pnpil  cannot  be  wholly  the 
result  of  turgescence,  nor  dilation  wholly  the  result  of  depletion 
of  the  vessels  of  the  iris,  is  shown  by  the  fact  that  both  these 
events  may  be  witnessed  in  a  perfectly  bloodless  e3'e,  and  more- 
over when  the  cervical  sympathetic  is  stimulated  the  dilation  of 
the  pupil  begins  before  the  contraction  of  the  bloodvessels,  and 
maybe  over  beibre  this  has  arrived  at  its  maximum.  Hence  we 
are  driven  to  conclude  that  the  dilating  sympathetic  fibres  do  not 
end  in  bloodvessels,  but  are  connected  either  directly  or  indi- 
rectly with  the  muscular  fibres  of  the  dilator. 

The  pupil,  then,  seems  to  be  under  the  dominion  of  two 
antagonistic  mechanisms  ;  one  a  contracting  mechanism, 
refiex  in  nature,  the  third  nerve  serving  as  the  etferent,  and 
the  optic  as  the  afferent  tract ;  the  other  a  dilating  mechan- 
ism, tonic  in  nature,  of  which  the  cervical  sympathetic  is 
the  efferent  channel.  Hence,  when  the  third  or  optic  nerve 
is  divided,  not  only  does  contraction  of  the  pupil  cease  to 
be  manifest,  but  active  dilation  occurs,  on  account  of  the 
tonic  dilating  influence  of  the  sympathetic  being  left  free  to 
work.  When,  on  the  other  hand,  the  sympathetic  is  divided, 
tliis  tonic  dilating  influence  falls  away,  and  contraction  re- 
sults. When  the  optic  or  third  nerve  is  stimulated,  the 
dilating  ellect  of  the  sym[)athetic  is  overcome,  and  contrac- 
tion rc-sults  :  and,  when  the  sympathetic  is  stimulated,  the 
C(intracting  influence  of  the  third  is  overcome,  and  dilation 
ensues. 

But  there  are  considerations  which  show  that  the  matter  is 
still  more  complex  than  this.  A  small  quantity  of  atropin  intro- 
duced into  the  eye  or  into  the  S3'stem  causes  a  dilation  of  the 
pupil.  This  might  be  attributed  to  a  paralysis  of  the  third  nerve, 
and  indeed  it  is  fou-nd  that  after  atropin  the  falling  of  light  on 
the  retina  no  longer  causes  contraction  of  the  pupil.  A  ditiiculty, 
however,  is  introduced  by  the  fact  that  when  the  third  nerve  is 
divided,  and  when,  therefore,  the  contracting  efiects  of  stimula- 
tion of  the  retina  are  placed  entirely  on  one  side,  and  there  is 
nothing  to  prevent  the  sympathetic  producing  its  dilating  efiects 

^  Cf.  Mosso,  Sui  movimeiiti  idraulici  dell'  iride.     Turin,  1875. 


670    .  SIGHT. 


to  the  utmost,  dilation  is  still  further  increased  by  atropin.  When 
physostigmin  is  introduced  into  the  eye  or  system  contraction  of 
the  pupil  is  caused,  whether  the  third  nerve  be  divided  or  not ; 
and  when  the  dose  is  sufficiently  strong  the  contraction  is  so  great 
that  it  cannot  be  overcome  b}'  stimulation  of  the  S3'mpathetic. 
The  dilation  which  is  caused  by  a  sufficient  dose  of  atropin  is 
greater  than  that  which  can  ordinarily  be  produced  by  stimula- 
tion of  the  sympathetic,  and  the  contraction  caused  by  a  suffi- 
cient dose  of  physostigmin  is  greater  than  that  which  is  ordinarily 
produced  in  a  I'eflex  manner  by  stimulation  of  the  optic  nerve, 
or  even  than  that  produced  by  direct  stimulation  of  the  third 
nerve.  Evidently  these  drugs  act  on  some  local  mechanism,  the 
one  in  such  a  way  as  to  cause  dilation,  the  other  in  such  a  way 
as  to  cause  contraction.  Such  a  local  mechanism  cannot,  how- 
ever, lie  in  the  ophthalmic  ganglion,  for  both  drugs  produce  these 
ettects  in  a  most  marked  degree  after  the  ganglion  has  been  ex- 
cised. We  must  suppose,  therefore,  that  the  mechanism  is  sit- 
uated in  the  iris  itself  or  in  the  choroid,  where,  indeed,  ganglionic 
nerve-cells  are  abundant.  But  if  we  admit  the  existence  of  such 
a  local  mechanism,  it  is  at  least  probable  that  both  the  sympa- 
thetic and  the  third  nerve  act  not  directly  on  either  the  sphincter 
or  dilator  pupillse,  but  indirectly  through  means  of  the  local 
nervous  mechanism. 

The  share  of  the  fifth  nerve  in  the  work  of  the  iris  seems  to  be 
in  part  a  sensory  one  ;  the  iris  is  sensitive,  and  the  sensory  im- 
pulses which  are  generated  in  it  pass  from  it  along  the  fibres  of 
the  fifth  nerve. 

Though  the  ophthalmic  ganglion  does  receive  fibres  directly 
from  the  cavernous  plexus  of  the  sympathetic,  the  dilating  action 
of  the  sympathetic  would  seem  to  be  carried  out  not  by  these 
fibres,  but  by  fibres  joining  the  ophthalmic  branch  of  the  fifth 
nerve  higher  up  in  its  course,  and  passing  to  the  iris  apparently 
by  the  long  ciliary  nerves.  According  to  Oehl,^  when  these 
fibres,  which  appear  to  run  alongside  the  ophthalmic  branch, 
ratlier  than  actually  to  become  part  of  the  nerve,  are  destroyed, 
stimulation  of  the  sympathetic  in  the  neck  produces  no  dilation 
of  the  pupil  whatever.  Section  of  the  ophthalmic  branch  itself 
causes  contraction,  and  stimulation  of  the  peripheral  end  dila- 
tion of  the  pupil ;  and  the  effects  are  still  seen  after  the  sympa- 
thetic fibres  have  become  degenerated  in  consequence  of  the  re- 
moval of  the  superior  cervical  ganglion.  From  these  fects  Oehl 
infers  that  the  fifth  nerve  itself  contains  dilating  fibres,  and  he 
believes  that  these  take  their  origin  from  the  Gasseriai"!  ganglion. 
Oehl's  results,  independently  arrived  at  by  Rosenthal,^  were  con- 
ducted on  dogs  and  rabbits."^  Guttmann^  came  to  a  similar  con- 
clusion as  regards  frogs  ;  he  found  the  dilator  fibres  of  the  cer- 

^  Plenle  and  Meissner's  Bericht,  1862,  p.  506. 

^  See  Guttmann,  Centralblatt  f.  med.  Wiss.,  1864,  p.  598. 

3  Op.  cit. 


MOVEMENTS    OF    THE    PUPIL.  671 


vical  S3'mpathetic  passed  throuoh  the  Gasserian  ganglion,  and 
were  there  reinforced  by  fibres  taking  origin  in  the  ganglion  itself. 
Hensen  and  Yiilckers^  also  found  in  the  dog  dilating  fibres  in  the 
fifth  nerve,  and  Ynlpian-  has  observed  retiex  dilation  of  the  pupil 
after  section  of  both  cervical  and  thoracic  sympathetic,  and  re- 
moval of  both  the  upper  and  lower  cervical  ganglia.  These  dilat- 
ing fibres  of  the  fifth  nerve  have,  however,  been  thought  by  some 
to  be  vaso-motorial  in  nature,  producing  changes  in  the  pupil  in 
an  indirect  Avay  by  affecting  its  blood-supph'. 

When  atropin  is  applied  locally  so  as  to  affect  the  pupil  of  one 
eye  only,  the  large  amount  of  light  entering  through  the  dilated 
pupil  may  cause  a  contraction  of  the  pupil  of  the  other  eye. 

The  movements  of  the  pupil  may  be  brought  about  through 
reflex  action  by  sensory  impulses  other  than  those  arising  in  the 
retina  or  optic  nerve.  Holmgren-^  finds  that  in  rabbits,  after  sec- 
tion of  the  optic  nerve,  dilation  of  the  pupil  follows  upon  the 
liearing  a  noise,  and  indeed  upon  any  sufficiently  acute  sensation. 

We  have  already  stated  that  when  we  accommodate  for 
near  objects  the  pupil  is  contracted  ;  the  one  movement  is 
"  associated  ■'  with  the  other ;  that  is  to  say,  the  special  cen- 
tral nervous  mechanism  emplo3ed  in  carrying  out  the  one 
act  is  so  connected  by  nervous  ties  of  some  kind  or  other 
with  that  employed  in  carrying  out  the  other,  that  when  we 
set  the  one  mechanism  in  action  we  unintentionally  set  the 
other  in  action  also.  A  similar  associated  contraction  of 
tlie  pupil  occurs  when  the  eye  is  directed  inward.  Con- 
versely, the  drugs  which  liave  a  special  action  on  the  pupil, 
such  as  atropin  and  calabar  bean,  also  affect  the  mechanism 
of  accommodation.  Atropin  paialyzes  it  so  that  the  eye 
remains  adjusted  for  far  objects  ;  and  physostigmin  throws 
the  eye  into  a  condition  of  forced  accommodation  for  near 
objects.  The  latter  effect  may  be  explained,  on  the  view 
stated  above,  by  supposing  that  the  calabar  bean  throws  the 
ciliary  muscle  into  a  state  of  tetanic  contraction  in  the  same 
way  that  it  does  the  sphincter  pupilU^. 

According  to  Hensen  and  Yolckers*  the  nervous  centre  of  ac- 
commodation lies  in  dogs  in  the  hind  part  of  the  floor  of  the  third 
ventricle,  and  is  connected  with  the  most  anterior  bundles  of  the 
roots  of  the  third  nerve.  Immediately  behind  this  accommoda- 
tion centre,  in  the  front  part  of  the  floor  of  the  aqueduct  of  Syl- 
vius, comes  the  centre  for  the  contraction  of  the  pupils,  and  in 
spite  of  the  association  of  the  two  centres  in  their  ordinar}^  func- 

'  Op.  eit.  2  ct.  Kd.,  t.  86  (1878),  p.  1436.  ^  j^o^.  cit. 

*  Archiv  f.  OphUiamol.,  xxiv  (1878). 


672  SIGHT. 


tional  activity,  Hensenand  Yiilckers  find  that  accommodation  may 
be  brought  about  by  carefully  stimulating  the  accommodation 
centre  by  means  of  the  interrupted  current  without  any  accom- 
panying change  in  the  iris,  except  a  passive  bulging  forward 
caused  by  the  increase  in  the  curvature  of  the  lens.  The  same 
observers  state  that  dilation  of  the  pupil  results  when  the  floor 
of  the  aqueduct  of  Sylvius  is  stimulated,  not  in  the  median  line, 
but  more  to  the  side  ;  and  that  the  muscles  of  the  eyeball  sup- 
plied by  the  third  nerve  have  their  nervous  centres  placed  also  in 
the  floor  of  the  aqueduct  of  Sylvias,  but  behind  that  for  the  con- 
traction of  the  pupil. 

We  can  accommodate  at  will ;  but  few  persons  can  effect 
the  necessary  change  in  the  eye  unless  tliey  direct  tiieir  at- 
tention to  some  near  or  far  ooject,  as  the  case  may  be,  and 
thus  assist  tlieir  will  by  visual  sensations.  By  practice, 
however,  tiie  aid  of  exterual  objects  ma}'  be  dispensed  with  ; 
and  it  is  when  tiiis  is  achieved  that  the  pupil  may  seem  to 
be  made  to  dilate  or  contract  at  pleasure,  accommodation 
being  elhcted  without  the  eye  being  turned  to  any  particu- 
lar object. 


Impe7^fcctioris  in  the  Dioptric  Ajipar^atus. 

The  emmetropic  eye  may  be  taken  as  the  normal  eye. 
The  myopic  and  hypermetropic  eyes  may  be  considered  as 
imperfect  eyes,  though  the  former  possesses  certain  ad- 
vantages over  the  normal  eye.  An  eye  might  be  myopic 
from  too  great  a  convexity  of  the  cornea,  or  of  the  anterior 
surface  of  the  lens,  or  from  permanent  spasm  of  tiie  accom- 
modation-mechanism, or  from  too  great  a  length  of  the  long 
axis  of  the  eyeball.  According  to  Donders  tlie  last  is  the 
usual  cause.  Similaily,  most  hyi)ermetro[)ic  eyes  possess  too 
short  a  bulb.  The  presbyopic  eye  is,  as  we  have  seen,  an 
eye  normally  constituted  in  which  the  power  of  accommo- 
dation has  been  lost  or  is  tailing. 

According  to  Iw^anoft^'  and  v.  Arlt^  in  the  strongly  marked  my- 
opic eye  there  is  hypertrophy  of  the  longitudinal  (meridional) 
fibres  of  the  ciliary  muscle  and  atrophy  or  absence  of  the  circu- 
lar fibres  ;  in  the  hypermetropic  eye,  on  the  other  hand,  the 
circular  fibres  are  w^ell  developed,  and  the  meridional  fibres  scanty. 

'  Archiv  f.  Ophthalm.,  xv,  p.  284. 

'^  U.  d.  Ursachen,  etc.,  der  Kurzsichtigkeit,  1876. 


DIOPTRIC    IMPERFECTIONS.  673 

Spherical  Aberration. — In  a  spherical  lens  the  ray?,  which 
impinge  on  tlie  circumlerence  are  brought  to  a  focns  sooner 
than  those  which  pass  nearer  tlie  centre,  and  tlie  focus  of  a 
luminous  point,  ceasing  to  be  a  point,  is  spread  over  a  sur- 
face. Hence,  when  rays  are  allowed  to  fall  on  tiie  whole  of 
the  lens,  the  image  formed  on  a  screen  placed  in  the  focus 
of  the  more  central  rays  is  blurjcd  by  the  diffusion  circles 
caused  by  the  circumferential  rays  which  have  been  brought 
to  a  premature  focus.  In  an  ordinary  optical  instrument 
spherical  aberration  is  obviated  by  a  diaphragm  which  shuts 
off  tlie  more  circumferential  rays.  In  the  e^-e  tiie  iris  is  an 
adjustable  diaphragm  ;  and  when  the  pupil  contracts  in  near 
vision  the  moie  diveigent  rays  proceeding  from  a  near  ob- 
ject, wliich  tend  to  fail  on  tlie  circumferential  parts  of  the 
lens,  are  cut  off'.  As,  however,  the  refractive  power  of  the 
lens  does  not  increase  regularly  and  progressively  from 
the  centre  to  the  circumference,  but  varies  most  irregularly, 
tlie  puipose  of  tiie  narrowing  of  tiie  pupil  cannot  be  simply 
to  obviate  spherical  aberration ;  and,  indeed,  the  otlier 
o})tical  imperfections  of  the  eye  are  so  great  that  such 
spherical  al)errations  as  are  caused  b}-  the  lens  produce  no 
obvious  effect  on  vision. 

Astigmatism. — We  have  hitherto  treated  the  eye  as  if  its 
dioptric  surfaces  were  all  parts  of  perfect  spiierical  surfaces. 
In  reality  this  is  rarely  the  case,  either  with  the  lens  or  with 
the  cornea.  Slight  deviations  do  not  produce  any  marked 
effect,  but  there  is  one  deviation  which  is  present  to  a  cer- 
tain extent  in  most  eyes,  and  is  ver}^  largely  developed  in 
some,  known  as  regular  astigmatism.  This  exists  wlieii  the 
dioptric  surface  is  not  spherical  but  more  convex  along  one 
meridian  tlian  another,  more  convex,  for  instance,  along  the 
vertical  than  along  the  liorizontal  meridian.  When  this  is 
the  case  the  rays  proceeding  from  a  luminous  point  are  not 
brought  to  a  single  focus  at  a  point,  but  possess  two  linear 
foci,  one  nearer  than  tlie  normal  focus  and  corresponding  to 
the  more  convex  surface,  the  other  farther  that  the  normal 
and  corresponding  to  the  less  convex  surface.  If  the  ver- 
tical meridians  of  the  surface  be  more  convex  than  the  hori- 
zontal, tlien  tiie  nearer  linear  focus  will  be  horizontal  and 
the  farther  linear  focus  will  be  vertical,  and  rice  i"f^r.s«. 
(This  can  l)e  sliown  much  more  effectually  on  a  model  tlian 
in  a  diagram  in  wliich  we  are  liuiited  to  two  dimensions.) 
Xow,  in  order  to  see  a  vertical  line  distiiictlj',  it  is   much 


674  SIGHT. 


more  important  that  tlie  ra3'S  which  diverge  from  the  line  in 
the  series  of  horizontal  planes  shonld  be  brought  to  a  focus 
properly  than  those  which  diverge  in  the  vertical  plane  of 
the  line  itself;  and  similarly',  in  order  to  see  a  horizontal 
line  distinctly  it  is  much  more  important  that  the  rays  which 
diverge  from  the  line  in  the  series  of  vertical  planes  should 
be  brought  to  a  focus  properly  than  those  which  diverge  in 
the  horizontal  plane  of  the  line  itself.  Plence  a  horizontal 
line  held  before  an  astigmatic  dioptric  sui-face,  most  convex 
in  the  vertical  meridians,  will  give  rise  to  the  image  of  a 
horizontal  line  at  the  nearer  focus,  the  vertical  rays  diverg- 
ing from  the  line  being  here  brought  to  a  linear  horizontal 
focus.  Similarly,  a  vertical  line  held  before  the  same  sur- 
face will  give  rise  to  an  image  of  a  vertical  line  at  the  farther 
focus,  the  horizontal  rays  diverging  from  the  vertical  line 
being  here  brought  to  a  linear  vertical  focus.  In  other 
words,  with  a  dioptric  surface  jnost  convex  in  the  vertical 
meridians,  horizontal  lines  are  brought  to  a  focus  sooner 
than  are  vertical  lines. 

Most  eyes  are  thus  more  or  less  astigmatic,  and  generally 
with  a  greater  convexity  along  the  vertical  meridians.  If 
a  set  of  horizontal  or  vertical  lines  be  looked  at,  or  if  the 
near  point  of  accommodation  be  determined  by  Scheiner's 
experiment  (p.  659),  for  the  needle  placed  first  horizontally 
and  then  vertically,  the  horizontal  lines  or  needle  will  be 
distinctly  visible  at  a  shorter  distance  from  the  eye  than  tlie 
vertical  lines  or  needle.  Similarly,  the  vertical  line  must  be 
farther  from  the  eye  than  a  horizontal  one,  if  both  are  to  be 
seen  distinctly  at  the  same  time.  The  cause  of  astigmatism 
is,  in  the  great  niajority  of  cases,  the  unequal  curvature  of 
the  cornea;  but  sometimes  the  fault  lies  in  the  lens,  as  was 
the  case  with  Young. 

When  the  curvature  of  the  cornea  or  lens  differs  not  in  two 
meridians  gnly  but  in  several,  irregular  astigmatism  is  the  re- 
sult. A  certain  amount  of  irregular  astigmatism  exists  inmost 
lenses,  thus  causing  the  image  of  a  bright  point,  such  as  a  star, 
to  be  not  a  circle  but  a  radiate  figure. 

Chromatic  Aberration. — Tlie  diff'erent  rays  of  the  spec- 
trum are  of  difi'erent  refiangibility,  those  towards  the  violet 
end  of  the  spectrum  being  brought  to  a  focus  sooner  than 
those  near  the  red  end.  This  in  optical  instruments  is  ob- 
viated by  using  compound  lenses  made  up  of  various  kinds 


DIOPTRIC    IMPERFECTIONS. 


675 


of  glass.  In  the  eye  we  have  no  evidence  tliat  the  lens  is 
so  constituted  as  to  correct  tliis  fault;  still  the  total  dis- 
persive power  of  the  instrument  is  so  small,  that  such  amount 
of  chromatic  aberration  as  does  exist  attracts  little  notice. 
Nevertheless  some  slight  aberration  ma>'  be  detected  by 
careful  observation.  When  tiie  spectrum  is  observed  at  some 
distance  the  violet  end  will  not  be  seen  in  focus  at  the  same 
time  as  the  red.  If  a  luminous  point  be  looked  at  through 
a  narrow  orifice  covered  by  a  piece  of  violet  glass,  which 
while  shutting  out  the  yellow  and  green  allows  the  red  and 
blue  rays  to  pass  through,  there  will  be  seen  alternately  an 
image  having  a  blue  centre  with  a  red  fringe,  or  a  red  centre 
with  a  blue  fringe,  according  as  the  image  of  the  point 
looked  at  is  thrown  on  one  side  or  other  of  the  true  focus. 
Tiius  supposing /(Fig.  178)  to  be  the  plane  of  the  mean 
focus  of  A^  the  violet  ra^'s  will  be  brought  to  a  focus  in  the 
plane   V,  and  the  red  rays  in  the  plane  7? ;  if  the  rays  be 


F 

IG.  178. 

1 

r 

7» 

1 

^ 

^ 

:> 

^^ 

Diagram  Illustratiag  Cliroiuatic  Aberration. 

hk  is  the  dioptiic  surface,  At'  represents  the  blue,  and  hr  the  red  rays;  Fis  the  focal 
plane  of  the  blue,  R  of  the  red  rays. 

supposed  to  fall  on  the  retina  between  Fand/,  the  diverg- 
ing or  blue  rays  will  form  a  centre  surrounded  by  the  still 
converging  red  rays  ;  whereas  if  the  rays  fall  on  the  retina 
between /and  i?,  the  converging  red  rays  will  form  a  centre 
with  the  still  diverging  blue  rays  forming  a  fringe  round 
them  ;  when  the  object  is  in  focus  at/,  the  two  kinds  of  rays 
will  be  mixed  together. 


Entoptic  Phenomena. — The  various  media  of  the  eye  are 
not  uniformly  transparent  ;  the  rays  of  light  in  passing 
through  them  undergo  local  absorption  and  refraction,  and 
thus  various  shadows  are  thrown  on  the  retina,  of  which  we 
become  conscious  as  imperfections  in  the  field  of  vision, 
especially  when  the  eye  is  directed  to  a  uniformly  illumi- 


676  SIGHT. 

natecl  surface.    These  are  spoken  of  as  entoptic  phenomena, 
and  are  very  varied,  many  forms  having  been  descrihed. 

The  most  common  are  those  caused  by  the  |)resence  of 
floating  bodies  in  the  vitreous  humor,  the  so  called  muHcse 
volitaiiten.  These  are  readily  seen  when  the  eye  is  turned 
towards  a  uniform  surface,  and  are  frequently  very  trouble- 
some in  looking  through  a  microscope.  They  assume  the 
form  of  rows  and  groups  of  beads,  of  single  beads,  of  streaks, 
patches,  and  granules,  and  may  be  recognized  by  their  almost 
continual  movement,  esj)ecially  when  the  head  or  eye  is 
moved  up  and  down.  Wlien  an  attempt  is  made  to  (ix  the 
vision  upon  them,  they  immediately  float  away.  Tears  on 
the  cornea,  temporar}'  unevenness  on  the  anterior  surface 
of  the  cornea  after  tlie  eyelid  has  been  pressed  on  it,  and 
imperfections  in  the  lens  or  its  capsule,  also  give  rise  to 
visual  images.  Not  unfrequently  a  radiate  figure  corre- 
sponding to  the  arrangement  of  the  fibres  of  the  lens  makes 
its  appearance. 

Imperfections  in  the  margin  of  the  pupil  appear  in  the  shadow 
of  the  iris  which  bounds  the  field  of  vision  ;  and  the  movements 
of  the  iris  in  one  eye  may  be  rendered  visible  b}'  alternately  clos- 
ing and  opening  the  other  ;  the  field  of  the  first  may  be  observed 
to  contract  when  light  enters,  and  to  expand  when  the  light  is 
shut  off"  from  the  second.  The  media  of  the  eye  are  fluorescent ; 
a  condition  which  favors  the  perception  of  the  ultra-violet  rays. 
If  a  white  sheet  or  wdiite  cloud  be  looked  at  in  daylight  through 
a  Nicol's  prism,  a  somewdiat  bright  double  ccme  or  double  tuft, 
with  the  apices  touching,  of  a  taint  blue  color,  is  seen  in  the 
centre  of  the  field  of  vision,  crossed  by  a  similar  double  cone  of 
a  somewhat  3-ellow  darker  color.  These  are  spoken  of  as  Haid- 
inger's  brushes  ;  they  rotate  as  the  prism  is  rotated,  and  are  sup- 
posed to  be  due  to  the  unequal  absorption  of  the  polarized  light 
in  the  yellow  si)ot.  The  prism  must  be  frequently  rotated,  as 
when  the  prism  remains  at  rest  the  phenomena  fade.  Lastly, 
according  to  Helmholtz,  the  optical  arrangements  have  a  further 
imperfection  in  that  the  dioptric  surfaces  are  not  truly  centred 
on  the  optic  axis. 


Sec.  2.  Visual  Sensations. 

Light  falling  on  the  retina  excites  nenxory  impuli<e>i^  and 
these  passing  up  the  optic  nerve  to  certain  parts  of  the  brain, 
})roduce  changes  in  certain  cerebral  structures,  and  thus 
jj-ive  rise  to  what  we   call  a  sensation.     In  a  sensation  we 


VISUAL    SENSATIONS.  677 

ought  to  be  able  to  distinguish  between  tlie  events  tlirough 
which  the  impact  of  tlie  rays  of  liglit  on  the  retina  is  en- 
abled to  generate  sensory  impulses,  and  the  events,  or  ratiier 
series  of  events,  through  which  tiiese  sensory  impulses  (for, 
judging  by  the  analogy  of  motor  nerves,  we  have  no  reason 
to  think  that  they  undergo  any  fundamental  changes  in 
passing  along  the  optic  nerve),  by  the  agency  of  the  cerebral 
arrangements,  develop  into  a  sensation.  Such  an  analysis, 
however,  is  at  present  at  least,  in  most  particulars,  quite 
beyond  our  power;  and  we  must  therefore  treat  of  the  sen- 
sations as  a  whole,  distinguishing  i)etvveen  the  peripheral 
and  central  phenomena,  on  the  rare  occasions  when  we  are 
able  to  do  so. 

The  Origin  of  Visual  ImpuUes. 

Of  primary  importance  to  the  understanding  of  the  way 
in  which  luminous  undulations  give  rise  to  those  nervous 
changes  which  pass  along  the  optic  nerve  as  visual  impulses, 
is  tlie  fact  that  the  rays  of  light  produce  their  effect  by  act- 
ing not  on  tlie  optic  nerve  itself  but  on  its  terminal  organs 
(see  pp.  042-4^.  They  pass  through  the  anterior  layers 
of  the  retina  apparently  without  inducing  any  effect;  it  is 
not  till  they  have  reached  the  region  of  the  rods  and  cones 
that  they  set  n[)the  changes  concerned  in  the  generation  of 
visual  impulses ;  and  the  impulses  here  generated  travel 
back  to  tlie  layer  of  fibres  in  the  anterior  surface  of  the 
retina  and  thence  pass  along  the  optic  nerve.  That  the 
optic  fibres  are  themselves  insensible  to  light  and  that  visual 
impulses  begin  in  the  region  of  rods  and  cones  is  shown  by 
the  phenomena  of  the  blind  spot  and  of  Purkinje's  figures 
respectivel}'. 

Blind  Spot. — There  is  one  part  of  the  retina  on  which  rays 
of  light  falling  give  rise  to  no  sensations  ;  this  is  the  en- 
trajice  of  the  optic  nerve,  and  the  corresponding  area  in  the 
field  of  vision  is  called  the  blind  spot.  If  the  visual  axis 
of  one  eye,  the  righc.  for  instance,  the  other  being  closed, 
be  fixed  on  a  black  spot  in  a  white  sheet  of  paper,  and  a 
small  black  object,  such  as  the  point  of  a  quill  pen  dipped 
in  ink,  be  moved  gradually  sideways  over  the  paper  awa}^ 
to  the  outside  of  the  field  of  vision,  at  a  certain  distance 
the  black  point  of  the  quill  will  disappear  from  view\  On 
continuing  the  movement  still  farther  outward  the  point  will 
again  come  into  view  and  continue  in  sight  until  it  is  lost  in 


678  SIGHT. 

the  periphery  of  the  field  of  vision  (Fio^.  179).    If  the  pen  he 
used  to  make  a  mark  on  the  paper  at  the  moment  when  it 

[Fig.  179, 

•  + 

Fix  the  visual  axis  of  the  right  eye  on  the  black  spot,  keeping  the  left  eye  closed. 
Hold  the  page  about  five  inches  from  the  eye,  and  both  the  spot  and  cross  will  be 
seen.  If  now,  while  ihe  right  eye  is  steadily  fixed  on  the  spot,  the  page  is  moved 
slowly  outwards,  the  cross  will  disappear  entirely,  and  again  xvappear  if  the  move- 
ment is  continued.! 


is  lost  to  view,  and  at  the  moment  when  it  comes  into  sight 
again  ;  and  if  similar  marks  be  made  along  the  other  meri- 
dians as  well  as  the  horizontal,  an  irregular  ontline  will  he 
drawn  circuuiscribing  an  area  of  the  field  of  vision  within 
which  rays  of  light  {)rodnce  no  visual  sensation.  This  is 
the  blind  spot.  The  dimensions  of  the  figure  drawn  vary 
of  course  with  the  distance  of  the  paper  from  the  eye.  If 
this  distance  be  known,  the  size  as  well  as  the  position  of 
the  area  of  the  retina  corresponding  to  the  blind  spot  may 
be  calculated  from  the  diagrammatic  eye  (p.  657).  The 
position  exactly  coincides  with  the  entrar.ce  of  the  optic 
nerve,  and  tiie  dimensions  (al>out  1.5  mm.  diameter)  also 
correspond.  While  drawing  the  outline  as  a!)ove  directed 
the  indications  of  the  large  branches  of  the  retinal  vessels 
as  they  diverge  from  the  entrance  of  the  nerve  can  fre- 
quently be  recognized.  The  existence  of  the  blind  spot  is 
also  shown  by  the  fact  that  an  image  of  light,  sutficiently 
small,  thrown  upon  the  optic  nerve  by  means  of  the  oi)hthal- 
moscope,  gives  rise  to  no  sensations. 

The  existence  of  the  blind  spot  proves  that  the  optic 
fibres  themselves  are  insensible  to  light;  it  is  only  through 
the  agency  of  the  retinal  expansion  that  they  can  be  stim- 
ulated by  luminous  vibrations. 

Purkinje's  Figures — If  one  enters  a  dark  room  with  a 
candle,  and  while  looking  at  a  plain  (not  [larti-colored  )  wall, 
moves  the  candle  up  and  down,  holding  it  on  a  level  with 
the  eyes  by  the  side  of  the  head,  there  will  appear  in  the 
field  of  vision  of  the  eye  of  the  same  side,  projected  on  the 
wall,  an  image  of  the  retinal  vessels,  quite  similar  to  that 
seen  on  looking  into  an  eye  with  the  ophthalmoscope.  The 
field  of  vision  is  illuminated  with  a  glare,  and  on  this  the 
branched  retinal  vessels  appear  as  shadows.  In  this  mode 
of  experimenting  the  light  enters  the  eye  through  the  cor- 


VISUAL    SENSATIONS.  679 

nea,  and  an  image  of  the  candle  is  formed  on  the  nasal  side 
of  the  retina  ;  and  it  is  the  light  emanating  from  this  image 
which  throws  shadows  of  the  retinal  vessels  on  to  the  rest 
of  the  retina.  A  far  better  method  is  for  a  second  person 
to  concentrate  the  rays  of  light,  with  a  lens  of  low  power, 
on  to  the  outside  of  the  sclerotic  jnst  behind  the  cornea  ; 
the  light  in  this  case  emanates  from  the  illuminated  spot  on 
the  sclerotic  and  passing  straight  through  the  vitreous  iiu- 
mor  tlirows  a  direct  shadow  of  the  vessels  on  to  the  retina. 
Thus  the  rays  passing  through  the  sclerotic  at  b.  Fig.  180, 
in  the  direction  h  v,  will  thi'ow  a  shadow  of  the  vessel  v  on 
to  the  retina  at  ii  ;  this  will  appear  as  a  dark  line  at  B  in 
the  glare  of  the  field  of  vision.  This  proves  that  the  struc- 
tures in  which  visual  impulses  originate  must  lie  behind  the 
retinal  vessels,  otherwise  the  shadows  of  these  could  not  be 
perceived. 

If  the  light  be  moved  from  h  to  r/,  the  shadow  on  the  retina 
will  move  from  ,3  to  «,  and  the  dark  line  in  the  tield  of  vision  will 
move  from  B  to  A.  If  the  distance  B  A  be  measured  when  the 
wdiole  image  is  projected  at  a  known  distance,  A- B  from  the  e3'e, 
A*  being  the  optical  centre,'  then,  knowing  the  distance  h  ,i  in  the 
diagrammatic  eye,  the  distance  .i  a  can  be  calculated.  But  if  the 
disfance  3 a  be  thus  estimated,  and  the  distance  ha  be  directly 
measured,  the  distances  ^i-,  a  ; ,  h  /•,  a  r  can  be  calculated,  and  if  the 
appearance  in  the  field  of  vision  is  really  caused  by  the  shadow  of 
V  falling  on  i,  these  distances  ought  to  correspond  to  the  dis- 
tances of  the  retinal  vessels  i  from  the  sclerotic  h  on  the  one  hand, 
and  from  that  part  of  the  retina  3  where  visual  impressions  begin, 
on  the  other.  II.  Mliller  found  that  the  distance  h-  thus  calcu- 
lated corresponded  to  the  distance  of  the  retinal  vessels  from  the 
layer  of  rods  and  cones.  Thus  Purkinje's  figures  prove,  in  the 
first  place  that  the  sensory  impulses  which  form  the  commence- 
ment of  visual  sensations  originate  in  some  part  of  the  retina 
behind  the  retinal  vessels,  i.  e. ,  somewhere  between  them  and 
the  choroid  coat ;  and  H.  Midler's  calculations  go  far  to  show 
that  they  originate  at  the  most  posterior  or  external  part  of  the 
retina,  viz.,  the  layer  of  rods  and  cones.  It  must  be  admitted, 
however,  that  H.  Muller-s  results  were  not  sutficiently  exact  to 
allow  any  great  stress  to  be  placed  on  this  argument. 

^  For  the  properties  of  the  optical  centre,  we  must  refer  the  reader 
to  the  various  treatises  on  optics.  The  optical  centre  of  a  lens  is  the 
point  through  which  all  the  principal  rays,  of  the  various  pencils  of  rays 
falling  on  the  lens,  pass.  Tlie  diagrammatic  eye  of  Listing  (p.  657)  has 
two  optical  centres,  but  these  may,  without  serious  error,  be  farther  re- 
duced for  practical  purposes  to  one  lying  in  the  lens  near  its  posterior 
surface,  at  about  15  mm.  distance  fi-om  the  retina. 


6S0 


SIGHT. 


It  is  desirable  in  tliese  cases  to  move  the  light  to  and  fro, 
especially  in  {he  first  method,  as  the  retina  soon  becomes 
tired,  and  the  image  fades  away.  Some  observers  can  recog- 
nize in  the  axis  of  vision  a  faint  shadow  corresponding  to 
the  edge  of  the  depression  of  the  fovea  centralis. 


Fig.  181. 


Fl«.  180. — Diagram  Illustrating  the  Formation  of  Purkinje's  Figures,  when  the 
ilhiniiuation  is  directtd  through  the  Sclerotic. 

Fig.  181. — Diagram  Illustrating  the  Formation  of  Purkinje'.s  Figures,  wheu  the 
illumination  is  directed  through  the  Cornea. 


In  the  second  method  of  experimenting,  the  image  always 
moves  in  the  same  direction  as  the  light,  as  it  obviously  must 
do.  In  the  first  method,  where  the  light  enters  through  the  cor- 
nea, the  image  moves  in  the  same  direction  as  the  light  when  the 
light  is  moved  from  right  to  left,  provided  the  movement  does 
not  extend  beyond  the  middle  of  the  cornea,  but  in  the  opposite 
direction  to  the  light  when  the  latter  is  moved  up  and  down.  In 
Fig.  181,  which  represents  a  horizontal  section  of  an  eye,  if  a 
be  moved  to  a,  b  will  move  to  :J,  the  shadow  on  the  retina  c  to  y, 
and  the  image  d  to  <).  If,  on  the  other  hand,  a  be  supposed  to 
move  above  the  plane  of  the  paper,  b  will  move  below,  in  conse- 
quence c  will  move  above,  and  d  will  appear  to  move  below,  i.  e., 
d  will  sink  as  a  rises. 

The  retinal  vessels  may  also  be  rendered  visible  by  looking 
through  a  small  orifice  at  a  bright  field,  such  as  the  sky,  and 
moving  the  orifice  very  rapidly  from  side  to  side  or  up  and  down. 
If  the  movement  be  from  side  to  side,  the  vessels  wdiich  run  ver- 


VISUAL    SENSATIONS.  681 

tical  will  be  seen  ;  if  up  and  down,  the  horizontal  vessels.  The 
tine  capillary  vessels  are  seen  more  easily  in  this  way  than  by 
Purkinje's  method.  The  same  appearan  ces  may  also  be  produced 
by  looking  through  a  microscope  from  which  the  objective  has 
been  removed,  and  the  ej'e-piece  only  left  (or  in  which  at  least 
there  is  no  object  distinctly  in  focus  in  the  field),  and  moving  the 
head  rapidly  from  side  to  side  or  backwards  and  forwards.  Or 
the  microscope  itself  may  be  moved  ;  a  circular  movement  of  the 
field  will  then  bring  both  the  vertical  and  horizontally  directed 
vessels  into  view  at  the  same  time. 

The  Photochemistry  of  the  Retina. — In  seeking  to  under- 
stand how  it  is  that  rays  of  light  falling  upon,  the  region  of 
the  rods  and  cones  can  give  rise  to  visual  impulses  in  tiie 
optic  nerve  we  naturally  turn  to  a  chemical  explanation. 
We  are  familiar  with  the  fact  that  rays  of  light  are  able  to 
bring  about  the  decomposition  of  very  many  chemical  sub- 
stances ;  and  we  accordingly  speak  of  these  substances  as 
being  sensitive  to  light.  All  the  facts  dwelt  on  in  this  hook 
illustrate  the  great  complexity  and  corresj)onding  insta- 
bility of  the  composition  of  i)rotoplasm.  And  we  might 
reasonably  suppose  tliat  protoplasm  itself  would  be  sensitive 
to  iiglit ;  that  is  to  sa}'  that  rays  of  light  falling  on  even 
undirterentiated  protoplasm  might  set  up  a  decomposition 
of  that  protoplasm  and  so  inaugurate  a  molecular  disturb- 
ance;  in  other  words,  that  light  might  act  as  a  direct 
stimulus  to  protoplasm.  As  a  matter  of  fact,  however,  such 
evidence  as  we  at  present  possess  goes  to  show  that  native 
undifferentiated  protoplasm  is  not  sensitive  to  light  (that  is, 
to  those  particular  waves  which  when  the}'  fall  on  our  retina 
give  rise  in  us  to  tiie  sensation  of  light),  though  in  at  least 
one  instance  a  lowly  organism,  whose  protoplasm  exhibits 
very  little  differentiation  and  in  particular  contains  no 
pigment,  does  not  manifest  a  sensitiveness  to  light.'  Xor 
can  we  be  surprised  at  this  indifference  to  protoplasm  when 
we  reflect  that  what  we  may  call  pure  protoplasm  is  remark- 
able for  its  transparency,  that  is  to  say  the  rays  of  light  pass 
through  it  with  the  slightest  possible  absorption.  But  in 
order  that  light  ma:y  j)ruduce  chemical  effects,  it  must  be 
absorbed  ;  it  must  be  spent  in  doing  the  chemical  work. 
Accordingly  the  first  step  towards  the  formation  of  an 
organ  of  vision  is  the  differentiation  of  a  portion  of  proto- 
plasm  into  a  pigment  at  once  capable  of  absorbing  light, 

^  Engeliuann,  Pfliiger's  Archiv,  xix  (1879),  p.  1. 


682  SIGHT. 

and  sensitive  to  light,  i.  e.,  undergoing  decomposition 
upon  exposure  to  light.  An  organisnfi,  a  portion  of  whose 
protoplasm  had  thus  become  ditlerentiated  into  such  a 
l)igment  would  he  nl)le  to  react  towards  light.  The  light 
falling  on  the  organism  would  be  in  part  absorbed  by  the 
pigment,  and  the  rays  thus  absorbed  would  produce  a 
chemical  action  and  set  free  chemical  substances  which  be- 
fore were  not  present.  We  have  only  to  suppose  that  the 
chemical  substances  are  of  such  a  nature  as  to  act  as  a 
stimulus  to  the  protoplasm  of  other  parts  of  the  organism 
(and  we  have  manifold  evidence  of  the  exquisite  sensiveness 
of  protoplasm  in  general  to  cheniical  stimuli),  in  order  to  see 
how  rays  of  light  falling  on  the  organism  might  excite 
movements  in  it,  or  modify  movements  which  were  being 
carried  on,  or  might  otherwise  affect  the  organism  in  whole 
or  in  part/ 

Such  considerations  as  the  foregoing  may  be  applied  to 
even  the  complex  organ  of  vision  of  the  higher  animals. 
If  we  suppose  that  the  actual  terminations  of  the  optic 
nerve  are  surrounded  by  substances  sensitive  to  light,  then 
it  becomes  easy  to  imagine  how  light  falling  on  these  sensi- 
tive substances  sliould  set  free  chemical  bodies  possessed 
of  the  property  of  acting  as  stimuli  to  tlie  actual  nerve- 
endings  and  thus  give  rise  to  visual  impulses  in  the  optic, 
fibres.  We  say  "easy  to  imagine,"  but  we  are,  at  present, 
far  from  being  able  to  give  definite  proofs  that  such  an  ex- 
planation of  tlie  origin  of  visual  impulses  is  the  true  one, 
prolmble  and  enticing  as  it  may  appear.  One  of  the  most 
striking  features  in  the  structure  of  the  retina  is  the  abun- 
dance of  pigment  in  the  retinal  oi"  as  it  is  sometimes  called 
choroidal  epithelium.  It  is  diflicult  to  suppose  that  the  sole 
function  of  this  i:)igment  is  to  ai)sorh  tlie  superfluous  rays 
of  light,  and  tliat  the  rays  thus  absorbed  are  put  to  no  use 
but  simply  wasted  ;  and  Kiiline'^  indeed  lias  shown  that  the 
pigment  is  sensitive  to  light ;  but  the  changes  in  it  induced 
by  light  are  excessively  slow,  and  vision  is  not  only  possi- 
ble but  fairly  distinct  with  albinos  in  which  this  pigment  is 
absent. 

Then  again,  in  the  vast  majority  of  vertebrate  animals, 
the  outer  limbs  of  the  rods  are  suffused  with  a  purplish-red 
pigment,  the  so-called  visual  purple,  wliich  is  so  eminently 

*  Cf.  Kiihne,  Zur  Photochemie  der  Netzhaut. 
2  Journal  of  Physiology,  i  (1878),  pp.  109,  189. 


VISUAL    SENSATIONS.  G83 

sensitive  to  light  tliat  images  of  external  objects  may  by 
ai)propriate  means  be  photographed  in  it  on  the  retina. 
Am\  npon  the  first  discovery  of  this  visual  purple  we  seemed 
to  have  found  tlie  substance  of  wliich  we  are  in  searcli. 
But  unfortunately  this  pigment  is  absent  from  the  cones, 
and  from  the  fo\ea  centralis,  which  as  we  shall  see  is  the 
region  of  distinct  vision  ;  it  is  further  entirely  wanting  in 
some  animals  wiiich  undoubtedly  see  very  well,  and  lastly 
animals,  such  as  the  frog,  naturally  possessing  the  pigment, 
continue  to  see  very  well  when  it  has  been  absolutely 
bleached,  as  it  may  be  by  prolonged  exposure  of  the  eyes 
to  strong  light.  We  cannot  therefore  at  present  at  least 
explain  the  origin  of  visual  impulses  by  the  help  of  visual 
purple.  But  at  the  same  time  it  must  be  remembered  that 
the  dist-overy  of  its  existence  is  a  step  in  tlie  desired  direc- 
tion ;  though  it  has  failed  us  now,  it  gives  promise  of  suc- 
cess in  the  future. 

That  in  the  retina  there  does  exist  a  substance  or  do  exist  sub- 
stances, presumably  of  the  sensitive  nature  which  we  have  indi- 
cated, which  are  used  up  in  vision,  has  been  urged  by  Exner'  to 
be  proved  by  the  following  experiment : 

It  is  well  known  that  when  pressure  is  forcibly  ai)pUed  to  the 
eyeball,  the  retina  speedily  becomes  insensible  to  liglit.  If  a 
sheet  of  paper,  one-half  of  wdiich  is  white,  and  the  other  black, 
but  having  in  its  middle  a  white  patch  covered  temporarih"  Avith 
black,  be  held  before  the  e^'es.  and  if  while  looking  at  the  sheet, 
tiie  eyeball  be  pressed  till  the  white  half  is  no  longer  visible,  and 
then  \he  cover  of  the  wdiite  patch  in  the  black  half  be  suddenly 
withdrawn,  the  wiiite  patch  is  recognized  for  awhile  though  the 
white  half  is  invisible  ;  very  soon  however  the  wdiite  patch  fades 
away  too.  Exner-s  argument  is  that  the  blindness  due  to  pres- 
sure*^ must  be  caused  not  by  a  mere  loss  of  conductivity  of  the 
nervous  structures,  but  by  a  consumption  of  visual  substance 
which,  owing  to  the  pressure  checking  the  nutritive  supply,  can- 
not be  furnished  rapidly  enough.  Thus  in  the  retina  corre- 
sjionding  to  the  white  half  of  the  sheet  looked  at  this  visual  sub- 
stance is  being  used  up,  wiiile  in  that  part  wiiich  corresponds  to 
the  wiiite  patch,  there  is  no  consumption  as  long  as  the  black 
cover  is  kept  on.  WJien  the  black  cover  is  removed,  the  rays 
irom  the  wiiite  patch  accordingly  nnd  some  visual  substance  to 
work  upon,  and  hence  the  patch  is  visible  until  the  supply  of 
visual  substance  here  also  is  in  turn  exhausted.  Kiiline^  how- 
ever, urges  that  Exner's  interpretation  is  not  valid  and  that  the 

'  Pfliiger's  Archiv,  xvi  (1878),  p.  407. 

2  Untersuch.  Physiol.  Inst.  Heidel.,  Bd.  ii  (1878),  p.  40, 


684  SIGHT. 


phenomena  may  be  explained  on  tlie  Law  of  Contrast,  of  whicli 
we  shall  treat  presently,  manifested  in  a  not  wholly  exhausted 
retina. 

But  even  admitting  as  probable  the  existence  of  sensitive 
visual  substances,  the  products  of  whose  decomposition  act 
as  stimuli  to  the  real  endings  of  tlie  retinal  nervous  meciian- 
ism,  we  cannot  at  present  state  anything  definite  concerning 
those  nerve-endings  or  the  manner  of  tlieir  stimulation.  It 
may  be  that  even  the  outer  limbs  of  the  rods  and  cones  in 
spite  of  the  apparent  break  of  continuity  between  the  outer 
and  inner  limbs,  are  really  nervous  in  nature.  It  may  be 
on  the  other  hand  that  the  outer  limbs  are  either  purely 
dioptric  in  function  or  are  in  some  way  associated  with  the 
sensitive  visual  substances,  so  that  the  nervous  structures 
must  be  considered  as  extending  at  least  no  further  tlian 
the  inner  limbs.  We  cannot  as  yet  make  an}-  definite  state- 
ment in  tlie  one  direction  or  the  other. 

Visual  Purple. — As  long  ago  as  1839  Krohn  called  attention 
to  the  rose  color  of  the  retinas  of  cephalopods  ;  but  though  his 
observations  were  confirmed  by  Max  Schultze  and  others,  and 
though  some  years  afterwards  H.  MdUer,  and  Leydig  and  Max 
Schultze,  Ibund  a  similar  coloration  in  the  retinas  of  frogs  and 
other  vertebrates,  the  matter  did  not  attract  any  srreat  interest 
until  Boll'  discovered  that  this  color  was  in  the  living  animal 
susceptible  to  light,  being  bleached  when  the  animal  was  exposed 
to  light  but  returning  again  when  the  animal  was  kept  in  the 
dark.  He  found  that  when  the  eye  of  a  frog  which  had  been 
kept  for  some  time  in  the  dark  was  rapidly  opened,  the  outer 
limbs  of  the  rods  of  the  retina  presented  a  very  beautiful  purple, 
or  (as  he  afterwards  preferred  to  call  it)  red  color,  which  after  a 
few  seconds  changed  into  a  yellow  and  finally  disappeared,  leav- 
ing the  rods  colorless.  Scattered  among  these  red  or  purple  rods 
were  a  number  of  bright-green  rods,  the  color  of  which  also  faded 
on  exposure  to  light.  If  the  frog  had  previously  been  exposed 
for  some  time  to  a  bright  light,  the  retina,  even  with  the  most 
rapid  manipulation,  was  found  to  be  colorless.  And  by  examin- 
ing at  intervals  the  eyes  of  a  series  of  frogs  which  after  being 
kept  in  the  dark  had  l:een  exposed  to  light  for  variable  periods, 
and  conversely  of  frogs  which,  after  an  exposure  to  bright  light, 
had  been  kept  in  the  dark  for  variable  periods,  Bo'll  was  enabled 
to  satisfy  himself  that,  in  the  living  eye  the  color  of  the  rods  was 
destroyed  by  exposure  to  light  and  restored  by  rest  in  the  dark. 

^  Berlin.  Sitzungsberichte,  1876,  Sitzung,  Nov.  12;  1877,  Sitzung, 
Jan.  11.     Dii  Bois-Eeymond's  Archiv,  1877,  p.  4. 


VISUAL    SENSATIONS.  685 


Using  under  similar  circumstances  monochromatic  instead  of 
white  huht,  he  came  to  the  conclusion  that  under  exposure  to 
green  Hght  the  retina  hecame  first  purple,  then  violet,  and  tinally 
colorless  ;  under  blue  and  violet  light,  it  tirst  suffered  a  change 
to  violet  and  finally  lost  all  color  ;  while  under  red  light  it  be- 
came a  deeper  red,  under  yellow  light  a  brighter  red,  and  when 
exposed  to  the  ultra-violet  rays  underwent  very  little  change. 
He  found  this  visual  purple  or  visual  red  in  the  outer  limbs  of 
the  rods  not  only  of  the  frog,  but  of  all  other  vertebrates,  includ- 
ing mammalia,  whose  retinas  contain  sufiiciently  conspicuous 
rods.  He  concluded  that  the  color  must  be  largely  concerned  in 
the  act  of  vision. 

Kahne^  taking  up  and  largely  extending  Boll's  discovery  has 
been  led  to  the  following  results  : 

The  color  of  the  rods  is  susceptible  to  light  not  onl}^  during 
life  but  also  after  death,  the  fading  which  occurs  after  the  re- 
moval and  opening  of  an  eve  being  due  not  to  post-mortem 
changes  but  to  the  action  of  light. 

The  color  of  the  rods  is  due  to  the  presence  of  a  distinct  pig- 
ment, the  visual  purple,  which  may  be  extracted  from  the  sub- 
stance of  the  rods  b^-  dissolving  these  in  an  aqueous  solution  of 
bile  salts.  A  clear  purple  solution  is  thus  obtained,  which  is 
capable  of  being  bleached  by  the  action  of  light,  and  in  its  gen- 
eral features  and  behavior  is  similar  to  the  pigment  as  it  natu- 
rally exists  in  the  retina. 

Visual  purple  is  found  exclusively  in  the  outer  limbs  of  the 
rods ;  it  has  never  yet  been  found  in  the  cones,  and  it  is  accord- 
ingh^  absent  from  the  retinas  of  animals  (such  as  those  of  snakes) 
which  are  composed  of  cones  only,  and  from  the  macula  lutea 
and  fovea  centralis  of  the  retinas  of  man  and  the  ape.  The  in- 
tensity of  the  coloration  varies  in  different  animals,  and  the  reti- 
nas even  of  some  animals  possessing  rods  (bat.  dove,  hen)  seem 
to  be  wholl}'  devoid  of  the  visual  purple  ;  it  is  generalh'  well 
marked  in  retinas  in  which  the  outer  limbs  of  the  rods  are  well 
developed.  Its  absence  or  presence  is  not  dependent  on  noctur- 
nal habits,  since  the  intense  color  of  the  retina  of  the  owl  is  in 
strong  contrast  to  the  absence  of  color  in  the  bat.  It  has  been 
found  in  the  retina  of  a  sheep's  embryo.  As  a  general  rule  the 
amount  of  pigment  present  ma}'  be  said  to  be  in  inverse  ratio  to 
the  development  of  colored  ''globules  "  or  "  lenses  "  in  the  rods 
and  cones ;  but  it  would  be  premature  to  insist  on  an}-  exact  re- 
lation. 

The  visual  purple  is  bleached  not  only  liy  white  but  also  by 
monochromatic  hght  ;  the  change  however  in  the  latter  is  slower 
tiian  in  the  former.     Of  the  various  prismatic  rays  the  most  ac- 

^  Zur  Photochemie  der  Xetzhaut.  "  Ueberden  Sehpnrpur,"  Verhandl. 
d.  naturhistorisclinied.  Vereins  in  Heidellera:,  Bd.  i,  1877.  "Sehen 
ohne  Pju-pur,"'  Untersnch.  physiol.  Instit.  Heidelberg,  Bd.  i,  1877. 
Ewald  and  Kiihne,  "  Ueber  den  Sehpurpur,"  ibid, 

58 


6S6  SIGHT. 


tive  are  the  greenish -yellow  rays,  those  to  the  blue  side  of  these 
coming  next,  the  least  active  being  the  red.  Now  it  is  precisely 
the  greenish-yellow  rays  which  arc  most  readily  absorbed  by  the 
color  itself.  A  natural  colored  retina  or  a  solution  of  visual  pur- 
ple iiives  a  diffuse  spectrum  without  an}-  defined  absorption  bands, 
and  according  to  the  amount  of  coloring  material  through  which 
the  light  passes,  absorption  is  seen  either  to  be  limited  to  the 
greenish-yellow  part  of  the  spectrum  or  to  spread  thence  to- 
wards the  blue  and  to  a  much  less  extent  towards  the  red.  Thus 
the  various  prismatic  rays  produce  a  photochemical  effect  on  the 
visual  purple  in  proportion  as  they  are  absorbed  by  it.  Under 
the  action  of  light  the  visual  purple,  whether  in  solution  or  in 
its  natural  condition  in  the  rods,  passes  through  what  Krdme 
calls  a  chamois  color  (?.  e.,  the  purplish-orange  seen  on  the  cha- 
mois) to  a  yellow,  and  finally  becomes  colorless  ;  and  Klihne  be- 
lieves that  he  is  justified  in  speaking  of  a  visual  yellow  and  vis- 
ual white  as  products  of  the  photochemical  changes  undergone 
by  tlie  visual  purple. 

For  the  restoration  of  the  visual  purple,  after  it  has  been  de- 
stroyed by  light,  the  maintenance  of  the  circulation  of  the  blood 
through  the  tissues  of  the  eye  is  not  essential.  The  choroidal 
epithelium  has  by  itself,  provided  that  it  still  retains  its  tissue 
life,  the  power  of  regenerating  the  purple.  If  a  portion  of  the 
retina  of  an  excised  eye  be  raised  from  its  epithelial  bed,  bleached, 
and  then  carefully  restored  to  its  natural  position,  the  purple  will 
return  if  the  eye  be  kept  in  the  dark.  The  choroidal  epithelium 
ma}^  in  fact  be  spoken  of  as  a  "  purpurogenous  "  membrane. 

If  an  excised  eye,  a  portion  of  the  retina  of  which  has  been 
bleached  by  light,  be  treated  with  a  4  per  cent,  solution  of  potash 
alum  before  the  choroidal  epithelium  has  had  time  to  obliterate 
the  bleaching  effects,  the  retina  may  remain  permanently  in  that 
condition,  the  photochemical  effect  may,  as  the  photographers  say, 
be  fixed.  In  this  way  KUhne  succeeded  in  obtaining  promising 
"•  optograms  " 

The  above  facts  leave  no  room  for  doubt  that  the  visual  purple 
is  in  some  way  concerned  in  vision,  but  it  is  impossible  at  present 
to  say  what  is  its  exact  function.  Its  conspicuous  absence  from 
the  cones,  and  especiall}^  its  absence  from  the  fovea  centralis  of 
man,  show  that  vision,  indeed  the  best  and  most  exact  vision, 
may  take  place  without  it ;  and  Krihne  has  satisfied  himself  that 
frogs  whose  retinas  have  been  wholly  and  thoroughly  bleached 
by  exposure  to  light  can  see  perfectly  well.  It  is  ver}^  tempting 
to  connect  the  purple  in  some  way  with  color  vision,  but  we  know 
that  our  color  vision  is  most  exact  in  the  fovea  centralis,  and  the 
frogs  just  spoken  of  seemed  to  be  as  susceptible  to  color  as  normal 
frogs. 

Krdine  and  Ewald^  have  called  attention  to  the  remarkable 
changes  which  the  cells  of  the  retinal  pigment  epithelium  undergo 

'  Untersuch.  Physiol.  Inst.  Heidel.,  Bd.  i,  1877-8. 


VISUAL    SENSATIONS.  687 


under  the  influence  of  light.  When  an  ej-e  has  been  shut  ofl:' 
from  all  light  for  some  little  time  the  pigment  is  concentrated  in 
the  body  of  the  cells,  and  the  remarkable  fringes  of  filamentous 
processes  of  the  cells,  with  the  pigment  granules  or  crystals  which 
these  carry,  extend  a  slight  distance  only  between  the  limbs  of 
the  rods  and  cones  (about  one-third  down  the  length  of  the  outer 
limbs  of  the  rods).  Under  the  influence  of  light  these  processes 
loaded  with  pigment  thrust  themselves  a  much  longer  way  down 
towards  the  external  limiting  membrane  ;  in  consequence  a  con- 
siderable quantit}'  of  pigment  is  found  massed  between  the  outer, 
and  even  the  inner  limbs  of  the  rods  and  cones  ;  indeed,  the  outer 
limbs  of  the  rods  swelling  at  the  same  time  become  jammed  as  it 
were  between  the  masses  of  pigment,  causing  the  epithelial  layer 
to  adhere  ver}'  closely  to  the  la3'er  of  rods  and  cones. 

Retinal  Currer.ts. — Holmgren^  and  Dewar  and  McKendrick^ 
have  shown  that  an  electrical  change  takes  place  in  the  retina 
and  optic  nerve  whenever  the  former  is  affected  by  light.  When 
the  electrodes  of  a  galvanometer  are  placed  one  on  the  cornea  and 
the  other  on  the  posterior  surface  of  the  ej'eball,  or  on  the  trans- 
verse section  of  the  optic  nerve,  the  galvanometer  indicates  the 
existence  of  a  current  corresponding  to  the  so-called  natural  nerve- 
currents,  the  cornea  being  positive  ;  and  this  current  undergoes 
a  variation  when  light  falls  upon  or  is  withdrawn  from  the  eye. 
To  eliminate  currents  proceeding  from  the  iris,  the  front  half  of 
the  bulb  may  be  cut  awa}'  and  the  electrodes  placed  one  on  the 
retina  and  the  other  on  the  hinder  surface  of  the  e^'eball  or  on 
the  optic  nerve  or  on  the  surface  of  the  brain  ;  in  this  case  also 
the  incidence  or  withdrawal  of  light  produces  variations  in  the 
"  natural  "  currents  ;  and  Dewar  and  McKendrick  find  that  these 
variations  due  to  the  action  of  light  may  be  shown  in  the  intact 
body,  by  simply  placing  one  electrode  on  the  cornea  and  the  other 
on  some  portion  of  the  surface  of  the  body.  The  variations  ob- 
served are  sometimes  positive,  sometimes  negative,  or,  according  to 
Dewar  and  ]StcKendrick,  always  positive  at  first,  becoming  nega- 
tive as  the  action  of  light  continues  (exhaustion),  with  a  positive 
rebound  upon  the  withdrawal  of  the  light.  Currents  maybe  ob- 
served between  the  sclerotic  and  optic  nerve  after  the  removal  of 
the  retina,  but  these  are  wholly  unaflected  by  light  ;  and  the 
variations  just  described  as  brought  about  by  light  appear  to  be 
in  proportion  to  the  functional  activity  of  the  retina.  It  would 
thus  apjjear  that  the  incidence  of  light  on  the  retina  produces 
electrical  changes  compai'able  to  those  resulting  from  the  stimu- 
lation of  an  ordinar}^  nerve ;  the  fact  that  the  changes  frequently 
appear  in  the  form  of  a  "  positive"  instead  of  "negative  varia- 

'  Centrbt.  Med.  Wiss.,  1871,  pp.  423,  438  ;  an  earlier  notice  was  pub- 
lished in  1865. 

•'  Trans.  Rov.  See.  Edin.,  1873. 


G88  SIGHT, 


tion  "  may  in  the  present  state  of  our  knowledge  of  nerve-currents 
be  fairly  considered  as  of  secondary  iniportan(;e. 

Holmgren'  has  shown  that  these  retinal  currents  are  manifested 
with  undiminished  energy  in  eyes  in  which  the  visual  purple  has 
been  completely  bleached^  and  on  the  other  hand  that  the  visual 
purple  may  continue  to  exist  and  to  remain  purple  long  after  the 
retinal  currents  have  disappeared. 

Simple  Sensations. 

Relations  of  the  Sensation  to  the  Stimulus. — If  we  put 
aside  for  the  present  all  questions  of  cohu-,  we  may  say  that 
light,  viewed  as  a  stimulus  affecting  the  retina,  varies  in  in- 
tensity, that  is,  in  the  energy  ol'  the  luminous  vibrations  as 
manifested  by  their  amplitude,  and  in  duration,  that  is,  in 
tlie  length  of  time  a  succession  of  waves  continue  to  fall 
upon  tlie  retina.  The  effect  of  the  light  will  also  depend  on 
the  extent  of  retinal  surface  exposed  to  the  luminous  vibra- 
tions at  the  same  time.  Taking  a  luminous  point,  in  order 
to  eliminate  the  latter  circumstance,  we  may  make  the  fol- 
lowing statements  : 

The  sensation  has  a  duration  much  greater  than  that  of 
the  stimulus,  and  in  this  respect  is  comparable  to  a  muscu- 
lar contrRction  caused  by  such  a  stimulus  as  a  siugle  induc- 
tion-shock. The  sensation  of  a  flash  of  light  for  instance 
lasts  for  a  much  longer  time  than  that  during  which  luminous 
vibrations  are  falling  on  the  retina.  Hence  when  two 
stimuli,  such  as  two  flashes  of  light,  follow  each  other  at  a 
sufficiently  short  interval,  the  two  sensations  are  fused  into 
one  ;  and  a  luminous  point  moving  rapidly  round  in  a  circle 
gives  rise  to  the  seusntion  of  a  continuous  circle  of  light. 
This  again  is  quite  comparable  to  muscular  tetanus.  The 
interval  at  which  fusion  takes  pla(  e,  that  is  the  interval  be- 
tween successive  stimuli  which  must  f.e  exceeded  in  order 
that  successive  distinct  sensations  may  he  produced,  varies 
according  to  the  intensity  of  the  light,  being  shorter  with 
the  stronger  light ;  with  a  faint  light  it  is  about  j\,th  second, 
with  a  strong  light  g'^th  or  ^'^th  second.  This  may  be  shown 
by  rotating  rapidly  before  the  eye  a  disk  arranged  with 
alternate  black  and  white  sectors  of  equal  width.  With  a 
faint  illumination,  the  flickering  indicative  of  the  successive 
sensations  from  the  white  sectors  not  being  completely  fused, 

'  Untersuch.  Phvsiol.  Inst.  Heideb,  Bd.  ii  (1878),  p.  81. 


SIMPLE    SENSATIONS.  680 

cea«!es  wiieii  the  rotation  becomes  so  rapid  that  each  pair  of 
black  and  white  sectors  takes  only  j',^th  second  in  passing 
before  the  eye.  When  a  brigiiter  ilhimination  is  used  the 
rapidity  must  be  increased  l)efore  the  tiickering  disappears. 
That  part  of  the  sensation  which  is  recngp.ized  as  histing 
after  the  cessation  of  the  stimulus  is  frequently  spoken  of 
as  the  ''after-image." 

Tliough  the  sensation  is  longer  with  the  stronger  light  fthat 
from  looking  at  the  sun  lasting  for  some  time),  the  commencement 
of  the  decline  begins  relativeh'  earlier,  hence  the  greater  difficulty 
in  the  complete  fusion  of  successive  sensations  with  the  brighter 
light.  The  interval  at  which  fusion  takes  place  differs  with  dif- 
ferent colors,  being  shortest  with  3'ellow,  intermediate  with  red, 
and  longest  with  blue. 

The  duration  of  a  stimidus  necessary  to  call  forth  a  sen- 
sation is  exceedingly  short;  that  is  to  say,  the  number  of 
vibrations  which  must  fall  on  the  retina  in  order  to  aflect 
consciousness  may  be  exceedingly  small.  Thus  the  shortest 
possible  flash,  such  as  that  of  an  electric  spark,  gives  rise  to 
a  sensation  of  light. 

Objects  in  motion,  when  illuminated  by  a  single  electric  spark, 
appear  motionless,  the  stimulus  of  the  lio^ht  retiected  from  them 
ceasing  before  they  can  make  an  appreciable  change  in  their  posi- 
tion. When  a  movino-  body  is  illuminated  by  several  rapid  flashes 
in  succession,  several  distinct  imaf^es  corresponding  to  the  posi- 
tions of  the  body  durin<«;  the  several  tlashes  are  generated  ;  the 
images  of  the  body  corresponding  to  the  several  flashes  fall  on 
different  parts  of  the  retina. 

The  intensity  of  the  sensation  varies  with  the  luminous 
intensity  of  t!ie  olject;  a  wax  candle  appears  tu-ighter  than 
a  rushlight.  The  ratio,  however,  of  the  sensation  to  the 
stimulus  is  not  a  simple  one.  If  the  luminosity  of  an  object 
be  gradually  increased  from  a  very  feeble  staire  to  a  very 
bright  one,  it  will  be  found  ti>at  the  corresponding  sensa- 
tions, though  they  likewise  gradually  increase,  increase  less 
and  less  slowly  than  the  luminosity;  and  at  last  an  increase 
of  the  luminosity  produces  no  appreciable  increase  of  sen- 
sation ;  a  liiiht,  when  it  reaches  a  certain  brightness,  appears 
so  bright  that  we  cannot  tell  when  it  becomes  any  brighter. 
Hence  it  is  much  easier  to  distiniruish  a  slitrht  difference  of 


G90  SIGHT. 

briglitness  between  two  feeble  liglits  than  tlie  same  difference 
between  two  briojht  lights.  We  can  easily  tell  the  difference 
between  a  rushlight  and  a  wax  candle  ;  but  two  suns,  one 
of  whici»  differed  from  the  other  merely  by  just  the  numiier 
of  luminous  rays  which  a  wax  candle  emits  in  addition  to 
tliose  sent  forth  by  a  rushlight,  would  appear  to  us  to  have 
exactl}'  tiie  same  brightness.  Jn  a  daikened  room  an  object 
placed  before  a  candle  will  throw  what  we  consider  a  deep 
shadow  on  a  sheet  of  paper,  or  any  white  surface.  If,  how- 
ever,  the  sunlight  be  allowed  to  fall  on  the  paper  at  the  same 
time  from  the  opposite  side,  the  shadow  is  no  longer  visible. 
The  difference  between  the  total  light  reflected  from  that 
part  of  the  paper  where  the  shadow  was,  and  which  is  illu- 
minated by  tlie  sun  alone,  and  that  reflected  from  the  rest 
of  the  paper  which  is  illuminated  by  the  candle  as  well  as 
by  the  sun,  remains  the  same  ;  yet  we  can  no  longer  appre- 
ciate that  difference. 

On  the  other  hand,  if  using  two  rushlights,  we  throw  two 
shadows  on  a  white  surface  and  move  one  rushlight  away  until 
the  shadow  caused  by  it  ceases  to  be  visible,  and  having  noted 
the  distance  to  wdiich  it  had  to  be  moved,  repeat  the  same  ex- 
periment with  two  wax  candles,  we  shall  Ihid  that  the  wax  candle 
has  to  be  moved  just  as  far  as  the  rushlight.  In  fact  it  is  found, 
by  careful  observation,  that  within  tolerably  wide  limits,  the 
smallest  dilierence  of  light  which  we  can  appreciate  b}^  visual  sen- 
sations is  a  constant  fraction  (about  y  (bTth)  of  the  total  luminosity 
employed.  The  same  law  holds  good  with  regard  to  the  other 
senses  as  well.  The  smallest  difference  in  length  we  can  detect 
between  two  lines,  one  an  inch  long  and  the  other  a  little  less  than 
an  inch,  is  the  same  fraction  of  an  inch  that  the  smallest  dilfer- 
ence  in  length  we  can  detect  betw^een  a  line  a  foot  long  and  one  a 
little  less  than  a  foot  is  of  a  foot.  Put  in  a  more  general  form, 
then,  the  law,  which  is  often  called  Weber's  law,  is  as  follows  : 
When  a  stimulus  is  continually  increased,  the  smallest  increase 
of  sensation  which  we  can  appreciate  remains  the  same  so  long 
as  the  proportion  which  the  increase  of  the  stimulus  bears  to  the 
whole  stimulus  remains  the  same  ;  that  is  to  say,  the  one  varies 
directly  as  the  other.  Fechner,  regarding  sensation  as  the  sum- 
mation of  a  series  of  increments  of  sensation  corresponding  to 
increments  of  stimulus,  made  use  of  the  i'act  that  when  the 
stimulus  is  continually  diminished  a  point  is  reached  at  which 
no  sensation  whatever  follows  ;  or,  in  other  w^ords,  that  there  is 
a  certain  strength  of  the  stimulus  which  must  be  exceeded  before 
any  sensation  at  all  can  be  produced.  By  the  introduction  of 
this  "  liminal  intensity  "  of  the  stimulus  he  transformed,  with 


SIMPLE    SENSATIONS.  G91 


the  help  of  the  iimthematical  operation  of  integration,  Weber's 
law,  which  is  only  an  expression  of  the  relation  of  increments  of 
stimulus  and  sensation  into  a  formula  spoken  of  as  Fechner's 
formula,  or  Fechner's  law,  which  is  offered  as  a  iiieasurc  of  the 
sensation  in  terms  of  the  stimulus  in  the  general  form  that  "the 
sensation  varies  as  the  logarithm  of  the  stimulus. "'  Independent, 
however,  of  the  important  fact  that  Weber's  law  ceases  to  hold 
good  when  the  stimuhis  is  either  very  small  or  very  great,  i.  e., 
fails  exact!}'  at  the  point  at  which  Fcchner  makes  use  of  it,  there 
are  serious  objections  to  the  validity  of  Fechner's  formula. 2 

Distinction  and  Fusion  of  Sensations. — When  light  falls  on 
a  large  portion  of  the  retina  the  total  sensation  produced  is 
greater  in  amount  than  when  a  small  portion  only  of  the 
retina  is  affected  ;  a  large  piece  of  white  paper  produces  a 
greater  total  etlect  on  our  consciousness  than  a  small  one, 
though,  if  the  surfaces  be  uniformlj'  and  equall}'  illuminated, 
the  intentiity  of  the  sensation  is  in  each  case  the  same  ;  the 
small  piece  of  paper  appears  as  bright  or  as  "  white  "  as  the 
large  one.  If  the  images  of  two  luminous  olijects  fall  on 
the  retina  at  sutlicient  distances  apart,  the  consequent  sen- 
sations are  distinct,  and  the  intensity  of  each  sensation  will 
depend  solely  upon  the  luminosity  of  the  corresponding  ob- 
ject. If,  however,  the  two  objects  are  made  to  approach 
each  other,  a  point  will  be  reached  at  which  the  two  sensa- 
tions are  fused  into  one.  When  this  occurs  the  intensity  of 
the  total  sensation  produced  will  be  greater  than  that  of 
either  of  the  sensations  caused  by  the  single  objects.  A 
number  of  luminous   points  scattered  over  a  wide  surface 

^  Weber's  law  may  be  stated  mathematically  as  A'S'=  K — -,   where 

A*^'  is  the  smallest  appreciable  increment  of  sensation  caused  by  A-^, 
the  corresponding  increment  of  the  stimuhis  x,  and  A"  is  a  constant. 

if  the  increment  be  regarded  as  indefinitely  small,  and  the  equation 
then  be  integrated,  we  get 

S=K]^>gx  -^r  c. 

If  X  be  diminished,  there  will  be  a  certain  value  (liminal  intensity)  of 
X,  at  which  all  sensation  ceases;  if  this  be  a;',  then 

6  =  A'log  x'  -\-  c^ 
or  c  =  —  K  log  .^■ ', 

whence  S=  K  log  x  —  K  log  x\ 

which  is  Fechner's  more  complete  formula. 

^  Gf.  Coutts  Trotter,  Journ.  Physiol.,  i  (1878),  p.  60. 


692  SIGHT. 

would  appear  each  to  have  a  certain  brightness  ;  each  wouhl 
give  rise  to  a  sensation  of  a  certain  intensity.  If  tiiey  were 
all  gathered  into  one  spot,  that  spot  would  api)ear  far  hrighter 
than  any  of  the  previous  points;  the  intensity  of  the  sensa- 
tion would  be  greater.  We  may,  thei-efore,  suppose  the 
retina  to  lie  divided  into  areas  coriespc-nding  to  sensational 
units.  If  the  images  from  two  luminous  objects  fall  on  sepa- 
rate visual  areas,  if  we  may  so  call  them,  two  distinct  sensa- 
tions will  be  i»roduced  ;  if.  on  the  contrary,  they  both  fall 
on  the  same  visual  area,  one  sensation  only  will  be  produced. 
Where  the  sensations  are  separate,  the  intensity  of  the  one 
(with  exceptions  hereafter  to  be  mentioned)  is  not  affected 
by  the  i)resence  of  the  other  ;  but  where  they  become  fused 
the  intensity  of  the  united  sensations  is  greater  than  either 
of,  though  not  equal  to  the  sum  of,  the  single  sensations. 
The  existence  of  these  sensational  units  is  the  basis  of  dis- 
tinct vision.  When  we  speak  of  the  smallest  size  visible  or 
distinguishalile,  we  are  referring  to  the  dimensions  of  the 
retinal  ai'cas  coi-responding  to  these  sensational  units.  Tlie 
retinal  area  must  be  carefully  distinguished  from  the  sensa- 
tional unit,  for  the  sensation  is,  as  we  have  seen,  a  process 
whose  arena  stretches  from  the  retina  to  certain  i)arts  of  tlie 
brain,  and  the  circumscription  of  the  sensational  unit, 
though  it  must  begin  as  a  retinal  area,  must  also  be  con- 
tinued as  a  cerelirMl  area  in  the  i)rain,  tlie  latter  correspond- 
ing to,  and  being  as  it  were  the  projection  of,  the  former. 
AVith  most  people  two  stars  ap|)enr  as  a  single  star  when  the 
distance  between  them  subtends  an  angle  of  less  than  (iO  sec- 
onds, and  Weber  found  that  the  best  eyes  failed  to  distinguish 
two  parallel  white  streaks  when  the  distance  between  the 
two.  measured  from  the  middle  of  each,  subtended  an  angle 
of  less  than  73  seconds.  Hirschmann'  could  distinguish 
objects  50  seconds  distance  from  each  other  An  angle  of 
I'S  seconds  in  an  object  corresponds  in  the  diagrammatic 
eye  (see  p.  fi58  i  to  the  length  of  5.3(5//  in  the  retinal  image, "^ 
and  one  of  50  seconds  to  :j.(;5  //. 

Max  8chultze^  counted  in  the  human  eye  50  cones  along  a  line 
of  200 /i  in  length  drawni  through  the  centre  of  the  yellow^  spot ; 
this  would  give  4  //  for  the  distance  between  the  centres  of  two 

^  Quoted  by  Helmholtz,  Phys.  Optik,  p.  841 . 
^  By  /M  is  meant  onc-thoiisandtli  of  a  niillinieter. 
3  Strieker,  Handbuch,  p.  1023. 


SIMPLE    SENSATIONS.  693 

adjoinmo;  cones  in  the  yellow  spot,  the  average  diameter  of  a 
cone  at  its  widest  part  being  3  //  and  there  being  slight  intervals 
between  neighboring  cones.  Hence  if  we  take  the  centre  of  a 
cone  as  the  centre  of  an  anatomical  retinal  area,  these  anatomi- 
cal areas  correspond  very  fairly  to  the  physiological  visual  areas 
as  determined  above.  That  is  to  say,  if  two  points  of  the  retinal 
image  are  less  than  4  u  apart,  they  may  both  lie  within  the  area 
of  a  single  cone  ;  and  it  is  just  when  they  are  less  than  about  4  a 
apart  that  the}'  cease  to  give  rise  to  two  distinct  sensations.  It 
must  be  remembered,  however,  that  the  fusion  or  distinction  of 
the  sensations  is  ultimately  determined  by  the  brain  and  not  by 
the  retina.  Two  points  of  the  retinal  image  less  than  4  u  apart 
might  lie  both  within  the  area  of  a  single  cone  ;  but  the  reason 
why,  under  such  circumstances,  they  give  rise  to  one  sensation 
only  is  not  because  one  cone-tibre  only  is  stimulated.  Two  points 
of  a  retinal  image  might  lie,  one  on  the  area  of  one  cone  and 
another  on  the  area  ')f  an  adjoining  cone,  and  still  be  less  than  4  ■/ 
apart  ;  in  such  a  case  two  cone-fibres  would  be  stimulated,  and 
yet  onl}'  one  sensation  would  be  produced.  So  also  in  the  less 
sensitive  peripheral  parts  of  the  retina  two  points  of  the  retinal 
image  might  stimulate  two  cones  a  considerable  distance  apart, 
and  yet  give  rise  to  one  sensation  only. 

In  the  case  where  the  two  points  lie  entireh'  within  the  area  of 
a  single  cone,  it  is  exceedingly  probable  that,  even  if  the  adjacent 
cones  or  cone-fibres  in  the  retina  are  not  at  the  same  time  stimu- 
lated, impulses  radiate  from  the  cerebral  ending  of  the  excited 
cone  into  the  neighboring  cerebral  endings  of  the  neighboring 
cones  :  in  other  words,  the  sensation-area  in  the  brain  does  not 
exactly  correspond  to  and  is  not  sharply  defined  like  the  reti- 
nal area,  but  gradually  fades  away  into  neighboring  sensation- 
areas.  We  may  imagine  two  points  of  the  retinal  image  so  far 
apart  that  even  the  extreme  margins  of  their  resj^ective  cere- 
bral sensation- areas  do  not  touch  each  other  in  the  least ;  in 
such  a  case  there  can  be  no  doubt  about  the  two  points  giving 
rise  to  two  sensations.  We  might,  hoAvever,  imagine  a  second 
case  where  two  points  were  just  so  far  apart  that  their  re- 
spective sensation-areas  should  coalesce  at  their  margins,  and 
j'et  that  in  passing  from  the  centre  of  one  sensation-area  to 
the  centre  of  the  other,  we  should  find  on  examination  a  con- 
siderable fiill  of  sensation  at  tlie  junction  of  the  two  areas  ; 
and  in  a  third  case  we  might  imagine  the  two  centres  to  be  so 
close  to  each  other  that  in  passing  from  one  to  the  other  no  ap- 
preciable diminution' of  sensation  could  be  discovered.  In  the 
last  case  there  would  be  but  one  sensation,  in  the  second  there 
might  still  be  two  sensations  if  the  marginal  fall  were  great 
enough,  even  though  the  areas  partially  coalesced.  Thus,  though 
the  mosaic  of  rods  and  cones  is  the  basis  of  distinct  vision,  the 
distinction  or  fusion  of  two  visual  impulses  is  ultimately  deter- 
mined by  the  disposition  and  condition  of  the  cerebral  centres. 


694  SIGHT. 


Hence  the  possibility  of  increasing  by  exercise  the  faculty  of  dis- 
tinguishing two  sensations,  since  by  use  the  cerebral  sensa- 
tion-areas become  more  and  more  diiTerentiated.  This,  however, 
is  even  more  strikingly  shown  in  touch  tiian  in  sight. 


Color  Sensations. 

When  we  allow  sunlight  leflectecl  from  a  cloud  or  sheet 
of  paper  to  fall  into  the  eye,  we  have  a  sensation  which  we 
call  a  sensation  of  white  light.  When  we  look  at  the  same 
light  through  a  prism,  and  allow  ditferent  parts  of  the  spec- 
trum to  fall  in  succession  into  the  e^-e,  we  liave  sensations 
which  we  cnll  respectively  ser.sations  of  red,  yellow,  green, 
and  blue  light.  In  other  words,  rays  of  light  falling  on  tlie 
retina  give  rise  to  ditferent  sensations,  according  to  the 
wave-lengtlis  of  the  rays.  Though  we  speak  of  the  spec- 
trum as  cousisting  of  a  few  colors,  red,  green,  etc.,  there 
are  an  almost  infinite  number  of  intermediate  tints  in  tlie 
spectrum  itself;  and  we  perceive  in  external  nature  a  large 
number  of  colors,  sucli  as  purple,  brown,  gray,  etc.,  which 
do  not  corresi)ond  to  any  of  the  color  sensations  gained  by 
regarding  the  successive  parts  of  tiie  spectrum.  We  find 
however,  on  examination,  tiiat  many  apparently  distinct 
color  sensations  may  be  obtained  by  the  fusion  of  two  or 
more  otlier  color  sensations.  Thus  juirple,  which  is  not 
present  in  the  spectrum,  may  be  at  once  [jroduced  by  fusing 
the  sensations  of  bhie  and  red  in  proper  proportions;  and 
the  various  tints  and  shades  of  nature  may  be  imitated  by 
fusing  a  })articular  color  sensaticn  with  the  sensation  of 
white,  or  b^-  allowing  a  certain  quantity  of  light  of  a  par- 
ticular color  to  fall  sparsely  over  the  area  of  the  retina, 
which  is  at  the  same  time  protected  from  tlie  access  of  any 
other  light,  i.  e.,  as  we  say,  by  mixing  the  color  with  black. 
Thus  the  browns  of  nature  result  from  various  admixtures 
of  yellow,  red,  white,  and  black  ;  and  a  small  quantity  of 
white  light,  scattered  over  a  large  area  of  the  retina,  i.  r., 
white  largely  mixed  with  black,  froms  a  gray.  In  fact,  the 
qualities  of  a  color  depend  (1)  on  the  naiure  of  the  pris- 
matic color  or  colors  falling  on  a  given  area  of  the  retina, 
2.  e.,  on  the  wave-lengths  of  the  constituent  rays;  (2)  on 
the  amount  of  this  colored  light  which  falls  on  the  area  of 
the  retina  in  a  given  time  ;  and  (3)  on  the  amount  of  white 
light  falling  on  the  same  area  at  the  same  time.  When  rays 
corresponding  to  a  prismatic  color  fall  upon  the  retina  un- 


COLOR    SENSATIONS.  6'J5 

accompfuiied  l\y  any  white  liulit,  the  color  is  said  to  he 
"saturated  ;"  and  a  color  is  spoken  of  as  more  or  less  satu- 
rated according  as  it  is  mixed  with  less  or  more  white  light. 
We  are  guided  hy  the  first  of  the  above  conditions  wlien 
we  describe  a  color  as  being  of  such  a  tint  or  hue.  But  we 
liave  no  common  phrases  by  which  we  distinguisli  the  sec- 
ond of  tlie  above  conditions  from  the  third.  The  word 
"  pale,"  it  is  true,  is  most  frequenth'  used  to  express  a  color 
very  sliglitly  saturated  ;  but  the  words  "  rich  "  or  "  deep  " 
are  used  sometimes  as  meaning  highly  saturated,  sometimes 
as  meaning  simpl}'  that  a  large  quantity  of  light  of  the  par- 
ticular hue  is  passing  into  the  eye.  So  also  with  the  phrase 
"  bright ;"  this  we  olten  use  when  a  large  amount  of  colored 
and  wliite  light  falls  at  the  same  time  on  the  same  retinal 
area,  but  we  sometimts  also  use  it  to  express  the  mere  in- 
tensity of  the  sensation. 

The  best  method  of  fusing  color  sensations  is  that  adopted  by 
Maxwell,  of  aliowinw  two  ditlerent  parts  of  the  spectrum  to  lall 
on  the  same  part  of  the  retina  at  the  same  time.  The  use  of 
the  pure  prismatic  colors  eliminates  errors  wdiich  arise  when  pig- 
ments, the  colors  of  which  are  not  pure,  but  mixed,  are  em- 
ployed. And  wiiere  piuments  are  used,  it  is  the  sensations  wdiich 
must  be  mixed  and  not  the  pigments  themselves.  Thus  Avhile 
the  sensations  of  yellow  and  indiuo  when  fused  give  rise  to  a  sen- 
sation of  while,  yellow  and  indigo  pigments  when  mixed  appear 
green  on  account  of  their  reciprocal!}'  absorbing  part  of  each 
other's  color  ;  the  indigo  particles  absorb  the  red  of  the  yellow, 
and  the  yellow  jiarticles  absorb  the  blue  of  the  indigo, "^so  that 
only  green  is  left  for  both  to  retlect.  AVhen  pure  pigments,  ?.  f., 
pigments  corresponding  as  closely  as  possible  to  the  prismatic 
colors,  are  used,  satisfactory  results  may  be  gained,  either  by 
using  the  reflection  of  the  image  of  one  pigment  so  that  it  falls  on 
the  retina  at  the  same  spot  as  the  direct  image  of  the  other,  or 
by  allowing  the  image  of  one  pigment  to  fall  on  the  retina  before 
the  sensation  produced  by  tlie  other  has  ]inssed  away.  The  first 
result  is  easily  reached  by  Ilelmholtz/s  simple  method  of  placing 
two  pieces  of  colored  paper  a  little  distance  apart  on  a  table,  one 
on  each  side  of  a  glass  plate  inclined  at  an  angle.  By  looking 
down  with  one  eye  on'the  glass  plate  the  reflected  image  of  the 
one  paper  may  be  made  to  coincide  with  the  direct  image  of  the 
other,  the  angle  which  the  glass  plate  makes  with  the  table  being- 
ad  justed  to  the  distance  between  the  pieces  of  paper.  In  the 
second  method,  the  "color  top  "  is  used  ;  sectors  of  the  colors 
to  be  investigated  are  placed  on  a  disk  made  to  rotate  very  rap- 
idly, and  the  image  of  one  color  is  thus  brought  to  bear  on  the 
retina  so  soon  after  the  image  of  another,  that  the  two  sensa- 
tions are  fused  into  one. 


69(3  SIGHT. 


When  the  sensalions  corresponding  to  the  several  pris- 
matic colors  are  fused  together  in  varions  combinations,  the 
foUowino;  remarkable  results  are  broui^ht  about: 

1.  When  red  and  yellow  in  certain  proportions  are  mixed 
together  the  result  is  a  sensation  of  orange,  quite  indistin- 
guishable from  the  orange  of  the  spectrum  itself.  Now  the 
latter  is  produced  by  rays  of  certain  wave  length,  whereas 
the  rays  of  red  and  of  yellow  are  respectively  of  quite  a 
ditferent  wave  length.  The  oronge  of  the  spectrum  cannot 
be  made  up  by  any  mixture  of  the  red  and  the  yellow  of 
the  spectrum  in  the  sense  that  the  red  and  yellow  rays  can 
unite  together  to  form  rays  of  the  same  wave-length  as  the. 
orange  rays  ;  the  three  things  are  al)sr)lutely  different.  It 
is  simply  the  mixed  sen>iation  of  the  red  and  yellow  which 
is  so  like  the  sensation  of  orange,  the  mixture  is  entirely 
and  absolutely  a  physiological  one.  And  since  we  must 
suppose  tliat  rays  of  different  wave-length  give  rise  to  dif- 
ferent sensory  iminilses,  and  that  the  sensory  impulses  gen- 
erated by  oi-ange  rays  are  different  from  those  generated  by 
red  and  by  yellow  rays,  we  are  led  to  infer  either  that  the 
sensory  impulses  which  rays  of  a  given  wave-length  origi- 
nate are  themselves  of  a  mixed  character,  or  that  the  mix- 
ture takes  place  at  the  time  when  the  sensory  impulses  are 
becoming  converted  into  sensations.  The  first  of  these 
views  is  the  one  generally  adopted. 

2.  When  certain  colors  are  mixed  together  in  pairs  iu 
certain  definite  proportions,  the  result  is  white.  These  col- 
ors are : 

Red  (near  a),^  and  Blue-green  (near  F), 

Orange  (near  C),  and  Blue  (between  F  and  G), 

Yellow  (near  D),  and  Indigo-blue  (near  G), 

Green-yellow  (near  E),  and  Yiolet  (between  G  and  H), 

and  are  said  to  be  '•  complementary  "  to  each  other.  To 
these  might  be  added  the  peculiar  non-prismatic  color  pur- 
ple, which  with  green  also  gives  white. 

3.  If  we  select  arbitrarily  any  three  distinct  colors,  i.  f? , 
any  three  parts  of  the  spectrum   sufficiently  far  apart,  say 

'  These  letters  refer  to  Frauenhofer's  lines. 


COLOR    SENSATIONS.  697 

red.  green,  and  blue,  we  can.  by  a  pro]ier  adjustment  of  the 
proportions  of  each,  produce  wliite.  Further,  l)y  a  [)i'oper 
addition  of  white,  these  three  colors  can  be  taken  in  such 
l)roportions  as  to  produce  the  sensations  of  all  other  colors. 
That  is  to  say,  given  three  standard  sensation-*,  all  the 
other  sensations  may  be  gained  by  the  proper  mixture  of 
these. 

If  we  suppose  that  the  visual  apparatus  is  so  constructed 
tiiat  we  possess  three  standard  sensations,  and  that  rays  of 
differen.t  wave-length  produce  all  three  of  these  sensations 
to  a  difterent  extent  according  to  their  wave  length,  we  can 
easily  regard  the  whole  of  our  sensations  of  color  as  com- 
pounds of  three  '"'  primary  color  sensations."  We  might 
thus  represent  our  color  sensations  by  such  a  dingram  as 
that  given  in  Fig.  182.  where  one  primary  sensntion  is  seen 
to  be  i»roduced  in  greatest  intensity  by  the  rays  at  the  red 
end  of  the  spectrum,  the  second  by  those  near  the  middle, 
and  the  third  by  those  at  the  violet  end  of  the  spectrum. 
Under  this  view  orange  rays  are  those  which  i)roduce  much 
of  the  first  sensation,  less  of  the  second,  and  hardly  au}^ 
of  the  third  ;  whereas  blue  rays  produce  much  of  the 
third,  less  of  the  second,  and  hardly  any  of  the  first  ;  and 
so  on. 

This  theory  of  three  primary  color  sensations  we  owe  to  Young  ; 
but  since  its  general  accej^tance  has  been  largely  due  to  the  la- 
bors of  Helmholtz,  it  is  frequently  spoken  of  as  the  Young-Helm- 
holtz  theor}^  Young's  view  took  the  form  of  the  hypothesis 
that  there  were  present  in  the  retina  tliree  sets  of  fibres,  each  set 
corresponding  to  a  primar}'  color  sensation,  and  being  sensitive 
in  a  dirterent  degree  to  the  various  rays  of  light.  In  the  retina 
itself  no  such  distinction  of  fibres  can  be  found.  We  are  en- 
tirely in  the  dark  concerning  the  anatomical  basis  not  only  of 
color  sensations  but  also  of  vision  as  a  whole.  We  have  reason 
to  think,  as  we  have  seen  (p.  077)  that  visual  impulses  are  started 
in  that  part  of  the  retina  which  lies  beyond  the  retinal  blood- 
vessels ;  but  in  the  generation  of  those  impulses  we  can  assign 
no  exact  functions  to  rods  or  cones,  to  rod- fibres  or  cone-fibres, 
or  to  the  various  bodies  constituting  the  external  nuclear  layer. 
The  viev/  that  the  cones  rather  than  the  rods  of  the  retina  are 
concerned  in  color  vision  cannot  be  regarded  as  established.  The 
argument  that  cones  are  absent  from  the  retinas  of  nocturnal 
animals,  remains  invalid  until  it  has  been  proved  that  these  ani- 
mals are  color-blind  :  and  the  argument  that  in  the  fovea  cen- 
tralis cones  onl}-  exist,  may  be  .used  equally  well  to  prove  that 
the  rods  are  of  no  use  at  all  in  distinct  vision.  In  the  eyes  of 
Birds,  Reptiles,  and  Amphibia,  colored  globules  are  found  in  the 


G98 


SIGHT. 


cones  at  the  junction  of  the  inner  and  outer  limbs.  In  the  fowl 
these  globules  occur  in  three  colors,  rub3^-red,  orange-yellow,  and 
greenish-3'ellow,  and  Kduie'  has  extracted  three  distinct  pig- 
ments (rhodophane,  xanthopliane  and  chlorophane),  which  how- 
ever are  but  ver}'  feel)ly  sensitive  to  light.  It  has  been  suggested 
that  these  colored  globules  are  connected  with  color  vision,  the 

Fig.  182. 


,/ 

/•' 

'^ 

-^-^___ 

.■<- 

^y^              \ 

„ 

_™-»r- 

_^-^— 

L 

It  0  ^f  C<j\  l^L.  V 

Diagram  of  Three  Primary  Color  Sensations. 

1  is  the  so-called  "  red,"  2  "green,"  and  3  "  violet  "  primary  color  sensations.  iJ, 
O,  F,  etc.,  represent  the  red,  orange,  yellnw,  etc.,  color  of  the  spectrum,  and  the  dia- 
gnini  show.*,  by  the  height  of  the  curve  in  each  case,  to  what  extent  the  several 
primary  color  sensations  are  respectively  excited  by  vibrations  of  different  wave- 
lengths. 

cones  with  red  globules,  for  instance,  allowing  red  light  only  to 
pass  through  the  inner  limb  and  impinge  on  the  outer  limb,  so 
that  these  cones  would  serve  as  organs  for  seeing  red.  But  this 
is  very  doubtful. 

The  Young-Helmholtz  theory  has  not  been  accepted  by  all  in- 
quirers. Its  most  serious  opi^onent  at  the  present  time  is  Iler- 
ing,-  who,  following  Aubert,^  and  indeed  Leonardo  Da  A^inci, 
maintains  that  the  primary  visual  sensations  are  white,  black, 
red,  3^ellow,  green,  and  blue.  He  considers  that  these  several 
sensations  arise  as  the  results  of  changes  in  what  may  be  called 
the  visual  substance  of  the  visual  nervous  apparatus  (see  p.  (383), 
those  changes  which  give  rise  to  black,  green,  and  blue  being  es- 
sentially processes  of  assimilation  or  construction  of  the  visual 
substance,  while  those  which  give  rise  to  white,  red,  and  yellow 
are  processes  of  dissimilation,  or  destruction  of  the  visual  sub- 
stance.     Black  and  white,  green  and  red,  blue  and  yellow,  form 


'  Journal  of  Physiology,  i  (1878),  pp.  109-189. 

*  Zur  Lelire  vom  Lichtsinne.     Wieii.  Sitzungsbericht.,  ixvi  (1872), 
Ixviii,  Ixix,  Ixx. 

^  Physiulogie  der  Xetzhaut,  186-3. 


COLOR    SENSATIONS.  699 

accordino;ly  anta?:onistic  rather  than  complementar}^  pairs,  and 
the  visual  organ  is  conceived  of  as  never  existing  during  Ufe  in  a 
state  of  complete  rest.  A  satisfactor}'  discussion  of  the  relative 
merits  of  this  and  of  the  generally  accepted  view,  would  lead  us 
heyond  tiie  proper  limits  of  this  work,  but  Ilering  uses  his  view 
with  great  ability  to  explain  the  obscure  phenomena  of  "con- 
trasts "  (see  p.  705)  and  ''negative  images  "  (p.  702). 

Admitting,  however,  that  the  hypothesis  of  three  primary 
color  sensations  ex{)lains  many  of  the  phe\iomena  of  color 
vision,  there  still  reniains  the  question,  "  ^Yhat  are  the  three 
primary  color  sensations?"  We  have  spoken  of  any  three 
arbitrarily  selected  color  sensations  producing  by  manipu- 
lation all  the  other  color  sensations  ;  but,  of  what  kind  are 
the  three  sensations  which  may  be  considered  as  the  actual 
primary  sensations  ?  We  cannot  enter  here  into  the  discus- 
sion of  this  question  ;  and  may  simply  state  that  the  most 
generally  accepted  view,  is  that  the  three  primary  sensa- 
tions correspond  to  what  we  call  red,  green,  and  violet ;  and 
in  the  diagram  (Fii^-.  182)  the  up{)er  figure  represents  this 
primary  red  sensation,  the  middle  figure  green,  and  the 
lower  violet. 

Color-blindness. — All  j)ersons  vary  much  in  their  power 
of  discriminating  and  ai)preciating  color,  i.  e.,  in  the  in- 
tensity and  accuracy  of  their  color  sensations  ;  but  some 
people  regard  as  similar,  colors  which  to  most  people  are 
glaringly  distinct,  and  these  persons  are  said  to  he  ''  color- 
blind." Tiie  most  common  form  of  color  blindness  is  that 
of  persons  unable  to  distinguish  green  and  red  from  each 
other.  As  in  the  case  of  Dalton,  they  tell  a  red  gown  lying 
on  a  green  grass  plot,  or  a  red  cherry  among  the  green 
leaves,  by  its  form,  and  not  by  its  color.  They  confound 
not  only  red,  brown,  and  green,  but  also  rose,  purple,  and 
blue.  They  cannot  see  the  red  end  of  the  spectrum,  all  this 
part  appearing  to  them  dark.  Their  vision  is  best  explained 
by  supposing  that  they  lack  altogether  the  primary  sensa- 
tion of  red. 

Hence  the}'  probabh-  see  in  the  spectrum  only  two  colors,  blue 
and  green,  with  various  tints  ;  our  red,  orange,  yellow,  and  green 
appearing  green,  and  all  the  rest  blue,  green-blue  being  to  them 
a  kind  of  gray.  Since  the  sensation  of  green  seems  to  be  abso- 
lutelii  most  intense  in  that  part  of  the  spectrum  which  we  call 
yellow,  though  of  course  relatively  to  the  other  two  primary  sen- 
sations mostf  intense  in  the  green,  our  yellow  probably  corre- 
sponds in  them  to  the  sensation  of  a  bright  deep  green.  ^  All  the 


700  SIGHT. 


colors  they  see  can,  in  fact,  be  produced  by  mixtures  of  yellow 
and  blue. 

Cases  in  which  the  other  primary  sensations  may  be  supposed 
to  be  absent,  i.  e.,  green-blindness  and  violet-lilindness,  are  much 
more  rare,  and  have  not  as  yet  been  examined  with  sufficient 
completeness. 

Influence  of  the  Piynient  of  the  YeVow  Spot. — In  the  macula 
lutea,  which  part  of  the  retina  we  use  chietiy  for  vision,  images 
falling  on  other  parts  of  the  retina  being  said  to  give  rise  to  "  in- 
direct vision,"  the  yellow  pigment  absorbs  some  of  the  greenish- 
blue  rays.  Hence  all  that  which  we  are  in  the  habit  of  calling 
white  is  in  reality  more  or  less  yellow.  We  may  use  this  feature 
of  the  yellow  spot  for  the  purpose  of  making  the  spot,  so  to  speak, 
visible  to  ourselves,  by  an  ex})erimcnt  suggested  by  Maxwell. 
A  solution  of  chrome  alum,  which  only  transmits  red  and 
greenish-blue  rays,  is  held  up  between  the  eye  and  a  Avhite  cloud. 
The  greenish-blue  rays  are  absorbed  by  the  yellow  spot,  and  here 
the  light  gives  rise  to  a  sensation  of  red  ;  whereas  in  the  rest  of 
the  field  of  vision,  the  sensation  is  that  ordinarily  produced  by 
the  purplish  solution.  The  yellow  spot  is  consequently  marked 
out  as  a  rosy  patch.     This  very  soon,  however,  dies  away. 

In  speaking  of  sensation  as  a  function  of  the  stimulus  (p.  688), 
we  referrtd  to  white  light  only  ;  but  the  different  colors  are  une- 
qual in  the  relations  borne  by  the  intensity  of  the  stimulus  to  the 
amount  of  sensation  produced.  Thus  the  more  refrangible  blue 
rays  produce  a  sensation  more  readily  than  the  yellow  or  red 
rays.  Ilcnce  in  dim  lights,  as  those  of  evening  and  moonlight, 
the  blues  preponderate,  and  the  reds  and  yellows  are  less  obvious. 
So,  also,  when  a  landscape  is  viewed  through  a  yellow  glass,  the 
yellow  hue  suggests  to  the  mind  bright  sunlight  and  summer 
weather,  although  the  actual  illumination  which  reaches  the  eye 
is  diminished  by  the  glass.  Conversely  when  the  same  landscape 
is  viewed  through  a  blue  glass  the  idea  of  moonlight  or  winter  is 
suggested. 

The  theory  of  primary  color  sensations  may  be  used  to  explain 
why  any  colored  light,  if  made  sufficiently  intense,  appears  white. 
Thus  a  violet  light  of  moderate  intensity  appears  violet  because 
it  excites  the  primary  sensation  of  violet  much  more  than  those 
of  green  and  red.  If  the  stimulus  be  increased  the  maximum  of 
violet  stimulation  will  be  reached,  while  the  stimulation  of  green 
will  continue  to  be  increased  and  even  that  of  red  to  a  slight  de- 
gree. The  result  will  be  that  the  lisht  api)ears  violet  mixed 
with  green,  tiiat  is  blue.  If  the  stimulus  be  still  further  in- 
creased while  the  green  and  violet  are  l)oth  excited  to  the  maxi- 
mum, the  red  stimulation  may  be  increased  until  the  result  is 
violet,  green,  and  red  in  the  proportions  which  imike  white  light. 
And  so  with  light  of  other  colors. 

After-images. — We  have  already  seen  that  in  vision  the 
sensation  lasts  much  longer  than  the  stimulus.     Under  cer- 


COLOR    SENSATIONS.  701 

tain  circumstances,  such  as  condition  of  the  eye,  intensity 
of  the  stimulus,  etc.,  the  sensation  is  so  prolonged,  that  it  is 
spoken  of  as  an  afler-iniage.  Thus,  if  the  eye  be  directed  to 
llie  sun,  the  image  of  tliat  body  is  present  for  a  long  wliile 
after;  and  if,  on  early  waking,  the  eye  be  directed  to  the 
window  for  an  instant  and  then  closed,  an  image  of  tlie 
window  with  its  bright  panes  and  darker  sashes,  tiie  various 
parts  being  of  the  same  color  as  the  object,  will  remain  for 
an  appreciable  time.  Thesj  images,  which  are  simply  con- 
tinuations of  the  sensation,  are  spoken  of  as  j^o.^^itive  after- 
images. They  are  best  seen  after  a  momentar}'  exposure  of 
the  eye  to  the  stimulus. 

When,  however,  the  e3e  has  been  for  some  time  subject 
to  a  stimulus,  the  sensation  which  follows  the  withdrawal  of 
the  stimulus  is  of  a  dilferent  kind  :  what  is  called  a  neyatice 
afler-iuioge^  or  negative  image^  is  produced.  If,  after  look- 
ing steadfastly  at  a  white  patch  on  a  black  ground,  the  eye 
be  turned  to  a  white  ground,  a  gray  patch  is  seen  for  some 
little  time.  A  black  patch  on  a  white  ground  similarly  gives 
rise  on  a  gray  ground  to  a  negative  image  of  a  white  patch. 
This  ma}'  be  explained  as  the  result  of  exhaustion.  When 
the  white  patch  has  been  looked  at  steadily  for  some  time 
that  part  of  the  retina  on  which  the  image  of  the  patch  fell 
becomes  tired  ;  hence  the  white  light  coming  from  the  white 
ground  subsequently  looked  at,  which  falls  on  this  part  of 
the  retina,  does  not  produce  so  much  sensation  as  in  other 
})arts  of  the  retina;  and  the  image,  consequently,  appears 
gray.  And  so  in  the  other  instance,  the  whole  of  the  retina 
is  tired,  except  at  the  patch  ;  here  the  retina  is  for  awhile 
most  sensitive,  and  hence  the  white  negative  image. 

When  a  red  patch  is  looked  at  the  negative  image  is  a 
green-blue;  that  is.  the  color  of  the  negative  image  is  com- 
plementary to  that  of  the  object.  Thus  also  orange  produces 
a  blue,  green  a  pink,  yellow  an  indigo-blue  negative  image, 
and  so  on.  This,  too,  can  be  explained  as  a  result  of  ex- 
haustion. When  the  colored  patch  is  looked  at  one  of  the 
primary  color  sensaiions  is  much  exhausted,  and  the  other 
two  less  so,  in  varying  proportions,  according  to  the  exact 
nature  of  the  color  <>f  the  i)alch  ,  and  the  less  exhausted 
sensations  become  prominent  in  the  after-image.  Thus  the 
red  patch  exhausts  the  red  sensation,  and  the  negative  image 
is  made  up  chiefly  of  green  and  blue  sensations;  that  is, 
appears  to  be  greenish-blue,  or  bluish-green,  according  to 
the  tint  of  the  red.     Similarly,  when  the  eye,  after  looking 

59 


702  SIGHT. 

at  a  colored  patch,  is  turned  to  a  colored  ground,  the  effects 
may  easily  be  explained  by  reference  to  the  comparative 
exhaustion  of  the  color  sensations  excited  by  the  patch  and 
the  ground  respectively;  if  a  yellow  (i.  e.,  a  green  and  red) 
ground  be  chosen  after  looking  at  a  green  object,  the  nega- 
tive image  will  appear  of  a  reddish-3ellow,  and  so  on. 

What  is  not  so  clear  is  why  negative  images  should  make  their 
appearance  without  any  subsequent  stimulation  of  the  retina. 
When  the  eyes  are  shut,  and  all  access  of  light,  even  through  the 
eyeUds,  carefully  avoided,  the  field  of  vision  is  not  absolutely 
dark;  there  is  still  a  sensation  of  light,  the  so-called  "proper 
light"  of  the  retina.  If  a  white  patch  on  a  black  ground  be 
looked  at  for  some  time,  and  the  eyes  then  shut,  a  negative  (black) 
image  of  the  spot  will  be  seen  on  the  ground  of  the  "proper 
light"  of  the  retina,  having  in  its  immediate  neighborhood  a 
specially  bright  corona.  So,  also,  if  a  window  be  looked  at  and 
the  eyes  then  closed,  ihe  positive  after-image  with  bright  panes 
and  dark  sashes  gives  rise  to  a  negative  after-image  with  bright 
sashes  and  dark  panes  ;  and  similar  effects  appear  with  colors. 
Plateau^  has  attempted  to  explain  the  various  phenomena  of  after- 
images by  supposing  oscillations  to  take  place  in  some  part  of 
the  visual  apparatus,  but  the  matter  is  surrounded  with  diffi- 
culties.' 

Sec.  3.   Visual  Perceptions. 

Hitherto  we  have  studied  sensations  only,  and  have  con- 
sidered an  external  object,  such  as  a  tree,  as  simply  a  source 
of  so  man}^  distinct  sensations,  differing  from  each  other  in 
intensity  and  kind  (color).  In  the  mind  these  sensations 
are  co-ordinated  into  a  perception.  We  are  not  only  con- 
scious of  a  number  of  sensations  of  bright  and  dim  lights, 
of  green,  brown,  black,  etc.,  but  tliese  sensations  are  so 
related  to  each  other,  and  b}'  virtue  of  cerebral  processes  so 
fashioned  into  a  whole  that  we  •'  see  a  tree."  We  sometimes, 
in  illustration  of  such  an  effect,  speak  of  an' image  or  pic- 
ture in  the  mind  corresponding  to  the  physical  image  on  the 
retina. 

When  we  look  upon  the  external  world  a  variety  of  images 
are  formed  at  the  same  time  on  the  retina,  and  give  rise  to 
a  number  of  contemporaneous  visual  sensations.  The  sum 
of  these  sensations  constitute  "the  field  of  vision,"  which 


'  Theorie  Gen.  des  Appearances  Visuelles,  Bruxelles,  1834. 
'■*  Cf.  Hering,  op.  cit. 


VISUAL    PERCEPTIONS.  703 

vnries,  of  course,  with  every  movement  of  the  eye.  Tliis 
Held  of  vision,  being  in  reality  an  aggregate  of  sensations, 
is  of  course  a  .^iiibjective  matter  ;  but  we  are  in  the  habit  of 
using  the  same  phrase  to  denote  the  sum  of  external  ob- 
jects which  give  rise  to  the  aggregate  of  visual  sensations  ; 
in  common  language  tlie  field  of  vision  is  "all  that  we  can 
see  "  in  any  |)Osition  of  the  eye,  and  we  have  a  field  of  vision 
for  each  eye  separately  and  for  the  two  eyes  combined. 

Using  for  the  present  the  words  in  their  subjective  sense 
we  may  remark,  that  we  are  able  to  assign  to  each  constit- 
uent sensation  its  place  among  the  aggregate  of  sensations 
constituting  the  field  of  vision  ;  we  can,  as  we  say,  localize 
the  sensation.  We  can  sa\'  whether  it  belongs  to  (what  we 
regard  as)  the  right  hand  or  left-hand,  the  upper  or  the  lower 
part,  of  the  field  of  vision.  We  are  able  to  distinguish  the 
relative  positions  of  any  two  distinct  sensations;  and  the 
relative  positions,  together  with  the  relative  intensities  and 
qualities  (color)  of  the  sensations  arising  from  any  object 
determine  our  perception  of  the  object.  It  need  hardly  l)e 
remarked  that  this  localization  is  purely  subjective.  We 
simply  determine  the  position  of  the  sensation  in  the  field 
of  vision  '^which  is  itself  a  wholly  subjective  matter) ;  we  do 
not  determine  the  position  of  the  object.  The  connection 
between  the  positioti  of  the  oliject  in  the  external  world  and 
the  position  of  the  sensation  in  the  field  of  vision  cannot  be 
determined  by  visual  observation  alone.  All  the  information 
which  can  be  gained  b}'  the  eye  is  limited  to  the  field  of 
vision,  and  provided  that  the  relative  position  of  the  sensa- 
tions in  the  field  of  vision  remained  the  same,  the  actual 
position  of  external  ol\iects  might,  as  far  as  vision  is  con- 
cerned, be  changed  without  our  being  aware  of  it. 

As  a  matter  of  fact  the  field  of  vision  in  one  important  particu- 
lar does  not  correspond  to  the  field  of  external  objects.  The 
image  on  the  retina  is  inverted  ;  the  rays  of  light  proceeding 
from  an  object  which  by  touch  we  know"  to  be  on  what  w^e  call 
our  right  hand,  fall  on  the  left-hand  side  of  the  retina.  If,  there- 
fore, the  field  of  vision  corresponded  to  the  retinal  image,  the  ob- 
ject would  be  seen  on  the  left  hand.  We,  however,  see  it  on  the 
right  hand,  because  w-e  invariably  associate  right-hand  tactile 
localization  with  left-hand  visual  localization  ;  that  is  to  say,  our 
field  of  vision,  when  interpreted  by  touch,  is  a  re-inversion  of  the 
retinal  image. 

The  dimensions  of  the  field  of  vision  of  a  single  eye  are 
about   145°   for  the   horizontal    and    IQC^   for  the   vertical 


704  SIGHT. 

meridian,  the  former  being  distinctly  greater  tlian  tlie  latter. 
The  horizontal  dimension  of  the  field  of  vision  for  tlie  two 
eyes  is  about  180^.  By  movements  of  the  eyes,  liovvever, 
apart  from  those  of  the  head,  the  extent  may  be  increased 
to  2^0^  in  the  horizontal  and  200^  in  the  vertical  direction. 
The  satisfactory  perception  of  external  objects  requires 
distinct  vision  ;  and  of  this,  as  we  have  alieady  said,  the 
formation  of  a  distinct  image  on  the  retina  is  an  essential 
condition.  We  can  receive  visual  sensations  of  all  kinds 
witli  the  most  imperfect  dioptric  apparatus,  but  our  percep- 
tion of  an  object  is  precise  in  proportion  to  the  clearness  of 
the  image  on  tlie  retina. 

Region  of  Distinct  Vision. — If  we  take  two  points,  such  as 
two  black  dots,  only  just  so  far  apart  that  they  can  be  seen 
distinctly  as  two  wlien  placed  near  the  axis  of  vision,  and 
then,  keeping  the  axis  fixed,  move  the  two  points  out  into 
the  circumferential  parts  of  the  field  of  vision,  it  will  be 
found  that  the  two  soon  appear  as  one.  The  two  sensations 
become  fused,  as  they  would  do  if  brought  nearer  to  each 
other  in  the  centre  of  the  field.  The  farther  away  from  the 
centre  of  the  field,  the  farther  apart  must  two  points  be  in 
order  that  the}'  may  be  &een  as  two.  In  other  words,  vision 
is  much  more  distinct  in  the  centre  of  the  field  than  towards 
the  circumference.  Practically  the  region  of  distinct  vision 
may  be  said  to  be  limited  to  the  macula  lutea,  or  eA^en  to 
the  fovea  centralis;  by  continual  movements  of  tlie  eye  we 
are  constantly  bringing  any  object  which  we  wish  to  see  in 
such  a  position  that  its  image  falls  on  this  region  of  the 
retina. 


The  diminution  of  distinctness  does  not  take  place  equally'  from 
the  centre  to  the  circumference  along  all  meridians.  The  outline 
described  by  a  line  uniting  the  points  where  two  spots  cease  to 
be  seen  as  two  when  moved  along  difterent  radii  from  the  centre, 
is  a  very  irregular  figure. 

The  sensations  of  color  are  much  more  distinct  in  the  centre  of 
the  retina  than  towards  the  circumference.  If  the  visual  axis  be 
fixed  ami  a  piece  of  colored  paper  be  moved  towards  the  outside 
of  the  field  of  vision,  the  color  undergoes  changes  and  is  eventu- 
ally lost,,  red  disappearing  first,  then  green,  and  blue  last.  A 
purple  color  becomes  blue,  and  a  rose  color  a  bluish-white.  In 
fact,  there  .seems  to  be  a  certain  amount  of  redd^lindncss  in  the 
peripheral  parts  of  all  retinas. 


MODIFIED    PERCEPTIONS.  705 


Modified  Perceptions. 

Since  our  perception  of  external  objects  is  based  on  the 
distinctness  of  the  sensations  which  go  to  form  the  percep- 
tion, it  might  be  expected  that  when  an  image  of  an  object 
is  formed  on  the  retina  the  sensory  impulses  would  corre- 
spond to  the  retinal  image,  the  sensations  coirespond  to  the 
sensory  impulses  and  the  percei)tion  corresponding  to  the 
sensations,  and  that,  therefore,  the  mental  condition  result- 
ing from  our  looking  at  an\'  object  or  view  would  correspond 
exactly  to  the  retinal  image.  We  find,  however,  that  this  is 
not  the  case.  Tlie  sensations,  and  probably  even  the  simple 
sensory  impulses  produced  by  an  image  react  upon  each 
other,  and  these  reactions  modify  our  perceptions,  inde- 
pendently of  the  physical  conditions  of  the  retinal  image. 
There  arise  certain  discrepancies  between  the  retinal  image 
and  the  perception,  some  having  their  source  in  the  retina, 
some  in  the  brain,  and  others  being  of  such  a  nature  that  it 
is  difficult  to  sa}'  where  the  irrelevancy  is  introduced. 

Irradiation. — A  white  patcli  on  a  dark  ground  appears 
larger,  and  a  dark  patch  on  a  white  ground  smaller  than  it 
really  is.  This  is  especially  so  when  the  ol)ject  is  somewhat 
out  of  focus,  and  may.  in  this  case,  be  partly  explained  by 
the  diffusion  circles  which,  in  each  case,  encroach  from  the 
white  upon  the  dark.  But  over  and  beyond  this,  any  sensa- 
tion, coming  from  a  given  retinal  area,  occupies  a  larger 
sliare  of  the  field  of  vision,  when  the  rest  of  the  retina  and 
central  visual  apparatus  are  at  rest,  than  when  they  are 
simultaneously  excited.  It  is  as  if  the  neighboring,  either 
retinal  or  cerebral,  structures  were  sympatheticall}'  thrown 
into  action  at  the  same  time. 

Contrast. — If  a  white  strip  be  placed  between  two  black 
strips,  the  edges  of  the  white  strip,  near  to  the  black,  will 
api)ear  whiter  than  its  median  portion;  and  if  a  white  cross 
be  placed  on  a  black  background,  the  centre  of  the  cross 
will  api)ear  sometimes  so  din),  compared  with  the  parts  close 
to  the  black,  as  to  seem  shaded.  This  occurs  even  when  the 
object  is  well  in  focus  ;  the  increased  sensation  of  light  which 
causes  the  ap[)arent  greater  whiteness  of  the  borders  of  the 
cross  is  the  result  of  the  "contrast"  with  the  black  placed 
immediately  close  to  it.  Still  more  curious  results  are  seen 
with  colored  objects.      If  a  small  piece  of  gray  paper  be 


706  SIGHT. 

placed  on  a  sheet  of  green  i)aper,  and  both  covered  with  a 
sheet  of  thin  tissue-paper,  the  gray  paper  will  appear  of  a 
pink  color,  the  complementary  of  the  green.  This  effect  of 
contrast  is  far  less  striking,  or  even  wholly  absent,  when  the 
small  piece  of  paper  is  white  instead  of  gray,  and  generally 
disappears  when  the  thin  covering  of  tissue-paper  is  re- 
moved. It  also  vanishes  if  a  bold  broad  black  line  be  drawn 
round  the  small  piece  of  paper,  so  as  to  isolate  it  from  the 
ground  color.  If  a  book  or  pencil  be  placed  vertically  on 
a  sheet  of  white  paper,  and  illuminated  on  one  side  by  the 
sun,  and  on  the  other  by  a  candle,  two  shadows  will  be  pro- 
duced, one  from  the  sun,  which  will  be  illuminated  by  the 
yellowish  light  of  the  candle,  and  the  other  from  the  candle, 
which  will  in  turn  be  illuminated  by  the  white  light  of  the 
sun.  The  former  naturally  appears  yellow  ;  the  latter,  how- 
ever, appears  not  white  but  blue  ;  it  assumes,  by  contrast,  a 
color  complementar}^  to  that  of  the  candlelight  which  sur- 
rounds it.  If  the  candle  be  removed,  or  its  light  shut  off 
by  a  screen,  the  blue  tint  disappears,  but  returns  when  the 
candle  is  again  allowed  to  produce  its  shadow.  If,  before 
the  candle  is  brought  back,  vision  l>e  directed  through  a 
narrow  blackened  tube  at  some  part  falling  entirely  within 
the  area  of  what  will  be  the  candle's  shadow,  the  area,  which 
in  the  absence  of  the  candle  appears  white,  will  continue  to 
appear  white  when  the  candle  is  made  to  cast  its  shadow, 
and  it  is  not  until  the  direction  of  the  tube  is  changed  so  as 
to  cover  part  of  the  ground  outside  of  the  shadow,  as  well 
as  part  of  the  shadow,  that  the  latter  assumes  its  blue  tint.^ 

Filling  up  the  Blind  Spot. — Though,  as  we  have  seen,  that 
part  of  the  retina  which  corresponds  to  the  entrance  of  the 
optic  nerve  is  quite  insensible  to  light,  we  are  conscious  of 
no  l)lank  in  the  field  of  vision.  When  in  looking  at  a  page 
of  print  we  fix  the  visual  axis  so  that  some  of  tiie  print  must 
fall  on  the  blind  spot,  no  gap  is  perceived.  We  could  not 
expect  to  see  a  black  patch,  because  what  we  call  black 
is  the  absence  of  the  sensation  of  light  from  structures 
which  are  sensitive  to  ligiit;  we  must  have  visual  organs  to 
see  black.  But  there  are  no  visual  organs  in  the  blind  spot, 
and  consequently  we  are  in  no  ivay  at  all  affected  by  the 
rays  of  light  which  fall  on  it.  There  is  in  our  subjective 
fiehl  of  vision  no  gap  corresponding  to  the  gap  in  the  retinal 


Cf.  HerinsT,  loc.  cit. 


MODIFIED    PERCEPTIONS.  707 


image.  We  refer  the  sensations  comino-  from  two  points  of 
the  retina  lying  on  opposite  margins  of  tlie  blind  spots  to 
two  points  lying  close  together,  since  vve  have  no  indication 
of  tlie  space  which  separates  them.  Concerning  the  effects 
which  are  prodnced  when  an  object  in  the  field  of  view  passes 
into  the  region  of  the  blind  spot  there  has  been  mnch  dis- 
cussion. In  ordinary  vision,  of  course,  the  existence  of  the 
blind  spot  is  of  little  moment  since  it  is  outside  the  region 
used  for  distinct  vision,  and  besides  the  image  of  an  object 
does  not  fall  on  blind  spots  of  both  eyes  at  the  same  time. 

Ocular  Spectra. — So  far  from  our  perceptions  exactly  cor- 
responding to  the  arrangements  of  the  luminous  rays  which 
fall  on  the  retina,  we  may  have  visual  sensations  and  per- 
ceptions in  the  entire  absence  of  light.  Any  stimulation  of 
the  retina  or  of  the  optic  nerve  sufficiently  intense  will  give 
rise  to  a  A'isual  sensation.  Gradual  pressure  on  the  eyeball 
causes  a  serisati(  n  of  rings  of  colored  light,  the  so-called 
phosphenes ;  a  sudden  blow  on  the  eye  causes  a  sensation 
of  flashes  of  light,  and  the  seeming  identity  of  the  visual  sen- 
sations so  brought  about  with  visual  sensations  produced  by 
light  is  well  illustrated  b}'  the  statement  once  gravely  made 
in  a  German  court  of  law,  by  a  witness  who  asserted  that 
on  a  pitch  dark  night  he  recognized  an  assailant  by  help  of 
the  flash  of  liglit  caused  l)y  the  assailant's  hand  coming  in 
contact  with  his  eye.  Electrical  stimulation  of  the  eye  or 
optic  nerve  will  also  give  rise  to  visual  sensations. 

The  sensations  which  may  arise  without  any  light  falling 
on  the  retina  need  not  necessarily  be  undefined  ;  on  the  con- 
trar\',  they  may  be  most  clearly  defined.  Complex  and  co- 
herent visual  images  or  perceptions  may  arise  in  the  brain 
without  any  corresponding  objective  luminous  cause.  These 
so-called  ocular  spectra  ov  phantoms,  which  are  the  result 
of  an  intrinsic  stimulation  of  some  (probably  cerei)ral)  part 
of  the  visual  ap[)aratus,  have  a  distinctness  which  gives 
them  an  apparent  objective  reality  quite  as  striking  as  that 
of  ordinary  visual  ^Terceptions.^  They  may  occasionally  be 
seen  with  the  eyes  open  (and  therefore  while  ordinary  visual 
perceptions  are  being  generated)  as  well  as  when  the  e^^es 


^  I  am  acquauited  with  a  case  in  which  ocular  spectra  of  a  pleasing 
and  gorgeous  character,  such  as  visions  of  flowers  and  hmdscapes,  can  be 
brought  on  at  once  by  compressing  the  eyeballs  with  the  orbicularis 
muscle. 


708  SIGHT. 

are  closed.  They  sometimes  become  so  frequent  and  obtru- 
sive as  to  be  distressing,  and  form  an  important  element  in 
some  kinds  of  delirium,  such  as  delirium  tremens. 

Appreciation  of  Apparent  Size. — By  tlie  eye  alone  we  can 
only  estimate  tlie  appaj-ent  size  of  an  object,  we  can  only 
tell  what  space  it  takes  in  the  field  of  vision,  we  can  only 
[jcrceive  the  dimensions  of  the  retinal  image,  and  therefore 
liave  a  rigiit  only  to  speak  of  the  angle  which  the  diameter 
of  the  object  subtends.  The  real  size  of  an  object  must  be 
determined  by  other  means.  But  our  perception  of  even 
the  apparent  size  of  an  oi>ject  is  so  modified  by  concurrent 
circumstances  that  in  many  cases  it  cannot  be  relied  on. 
The  apparent  size  of  the  moon  must  be  the  same  to  every 
eye,  and  yet  wiiile  some  i)ersons  will  be  found  ready  to  com- 
pare the  moon  in  mid-heavens  with  a  threepenny  piece, 
others  will  liken  it  to  a  cart-wheel  ;  that  is  to  say,  the  angle 
subtended  by  the  moon  seems  to  tlie  one  to  be  about  equal 
to  that  subtended  l>v  a  threepenny  piece  held  at  the  dis- 
tance from  the  eye  at  which  it  is  most  commonly  looked  at, 
and  to  the  other  al)Out  equal  to  that  subtended  by  a  cart- 
wheel similarly  viewed  at  the  distance  at  which  it  is  most 
commonly  looked  at.  If  a  line  such  as  A  C,  Fig.  183,  be 
divided  into  two  e(iual  parts  A  B^  B  C\  and  A  B  be  divided 

Fig.  1S3. 
e     6     •     •     •     •  • 


A 


B 


by  distinct  marks  into  several  parts,  as  is  shown  in  the  figure, 
while  B  C  l»e  left  entire,  the  distance  A  B  will  always  appear 
greater  than  C  B.  So  also,  if  two  equal  squares  be  marked, 
one  with  horizontal  and  the  other  with  vertical  alternate 
dark  and  light  bands,  the  fc^ruier  will  appear  higher,  and  the 
latter  broader,  than  it  really  is.  Hence  short  persons  affect 
dresses  horizontally  striped  in  order  to  increase  their  ap- 
parent height,  and  very  stout  persons  avoid  longitudinal 
stripes.  Two  perfectly  parallel  lines  or  bands,  each  of  which 
is  crossed  by  slanting  parallel  short  lines,  will  appear  not 
parallel,  but  diverging  or  converging  according  to  the  direc- 
tion of  the  cross-lines. 

Again,  when  a  short  person  is  placed  side  by  side  with  a 
tall  person,  the  former  appears  shorter  and  the  latter  taller 


BINOCULAR    VISION.  709 

than  each  really  is.  The  moon  on  the  horizon  appears 
larger  than  when  at  the  zenith,  partly  because  it  can  then 
be  most  easily  compared  with  terrestrial  objects,  and  partly 
perhaps  because,  from  a  conception  we  have  of  the  heavens 
being  flattened,  we  judoe  the  moon  to  be  farther  off  at  tlie 
horizon  tlian  at  the  zeiiith  ;  and  being  fartlier  off,  and  yet 
subtending  the  same  angle,  must  needs  be  judged  larger. 
The  absence  of  comparison  may,  however,  have  an  opposite 
effect,  as  when  a  person  looks  larger  in  a  fog  ;  being  seen  in- 
distinctly, he  is  judued  to  lie  farther  off  than  he  really  is,  and 
so  api)ears  to  be  proportionately  larger,  just  as  conversely 
distant  mountains  appear  small,  when  in  a  clear  atmosphere 
they  are  seen  distinctly  and  so  judged  to  be  near.  Indeed, 
our  daily  life  is  full  of  instances  in  which  our  direct  percep- 
tion is  modified  by  circumstances.  Among  those  circum- 
stances previous  experience  is  one  of  the  most  potent,  and 
thus  simple  perceptions  becotne  mingled  with  what  are  in 
reality  judgments,  though  frequently  made  unconsciously. 
But  this  intrusion  of  past  experience  into  present  percep- 
tions and  sensations  is  most  obvious  in  binocular  vision,  to 
which  we  now  turn. 

Sec.  4.  Binocular  Vision. 

Corresponding  or  Identical  Points, 

Though  we  have  two  eyes,  and  must  therefore  receive 
from  every  object  two  sets  of  sensations,  our  perception  of 
any  ol)ject  is  under  ordinary  circumstances  a  single  one  ;  we 
see  one  object,  not  two.  By  putting  either  eye  into  an  un- 
usual position,  as  by  squinting,  we  can  render  the  perception 
double;  we  see  two  objects  where  only  one  exists.  From 
which  it  is  evident  that  singleness  of  perception  depends  on 
the  image  of  the  object  falling  on  certain  parts  of  each 
retina  at  the  same  time,  these  parts  being  so  related  to  each 
other  that  the  sensations  from  each  are  blended  into  one 
perception  ;  and  it  is  also  evident  that  the  movements  of  the 
eyeballs  are  adapted  to  bring  the  image  of  the  object  to  fall 
on  these  '•  corresponding  "  or  "  identical"  parts,  as  they  are 
called,  of  each  retina. 

When  we  look  at  an  object  with  one  eye  the  visual  axis 
of  that  eye  is  directed  to  the  object,  and  when  we  use  two 
eyes  the  visual  axes  of  the  two  eyes  converge  at  the  object, 
the  eyeballs  moving  ace  )rdingly.    The  corresponding  points 

60 


710 


SIGHT. 


of  tlie  two  retinas  are  those  on  which  the  two  images  of  the 
object  fall  when  the  visual  axes  converge  at  the  object. 
Thus  in  Fig.  184,  if  Cc,  Cc^  be  the  two  visual  axes,  c,  c^ 
being  the  centres  of  the  fovefe  centrales  of  the  two  eyes, 
then,  the  object  AGE  l)eing  seen  single,  the  point  a  on  the 
one  retina  will  '•  correspond  "  to  or  be  ''  identical  "  with  the 
point  a,  on  the  other,  and  the  point  h  in  the  one  to  the  point 
&,  in  the  other.  Hence  a  point  lying  anywhere  on  tlie  right 
side  of  one  retina,  has  its  corresponding  point  on  the  right 
side  of  the  other  retina,  and  the  points  on  the  left  of  one 
correspond  with  those  on  the  left  of  the  other.  Thus,  while 
the  upper  half  of  the  retina  of  the  left  eye  corresponds  to  the 

Fig. 184. 


Diagram  illustrating  Corresponding  Points.  L,  tlie  left ;  i?,  the  right  eye;  A'» 
the  optical  tentre ;  Oi,  61,  Cx  are  points  in  the  right  eye  corrresponding  to  the 
points  a,  b,  c,  in  the  left  eye.  The  two  figures  below  are  projections  of  L  the  left  and 
M  the  right  retina.  It  will  be  seen  that  a  on  the  malar  side  of  L  corresponds  to  at, 
on  the  nasal  side  of  li. 


upper  half  of  the  retina  of  the  right  e^ye,  and  the  lower  to 
the  lower,  the  naaal  side  of  the  left  eye  corresponds  with 
the  malar  side  of  the  right,  and  the  malar  of  the  left  with 
the  naaal  side  of  the  right. 

Since  tlie  blending  of  the  two  sensations  into  one  only 
occurs  wlien  the  two  images  of  an  object  fall  on  these  cor- 
responding points  of  the  two  retinas,  it  is  obvious  that  in 
single  vision  with  two  eyes  the  ordinary  movements  of  the 


BINOCULAR    VISION.  711 

eyeballs  must  be  such  as  to  briiio;  the  visual  axes  to  converge 
at  the  ol)ject  so  that  the  two  images  ma}'  fall  on  correspond- 
ini^  points.  When  the  visual  axes  do  not  so  converge,  and 
when  therefore  the  images  do  not  fall  on  corresponding 
points,  the  two  sensations  are  not  blended  into  one  percep- 
tion, and  vision  becomes  double. 

3Iovements  of  the  EyehalU. 

The  eye  is  virtually  a  ball  placed  in  a  socket,  the  orbit 
and  the  bull)  forming  a  ball-and-socket  joint.  In  its  socket 
joint  the  optic  ball  is  capable  of  a  variety  of  movements, 
but  it  cannot  by  any  voluntary  effort  be  moved  out  of  its 
socket. 

It  is  stated  that  by  a  very  forcible  opening  of  the  eyelids  the 
eyeball  may  be  slightly  protruded  ;  but  this  trifling  locomotion 
may  be  neglected.  By  disease,  however,  the  position  of  the  eye- 
batt  in  the  socket  may  be  materially  changed. 

Each  eyeball  is  capable  of  rotating  round  an  immobile 
centre  of  rotation,  which  has  been  found  to  be  placed  a  lit- 
tle (1.77  mm.)  beliind  the  centre  of  the  eye;  but  the  move- 
ments of  the  eye  round  the  centre  are  limited  in  a  peculiar 
way.  The  shoulder-joint  is  a  similar  ball-and-socket  joint ; 
and  we  know  that  we  can  not  only  move  tlie  arm  up  and  down 
round  a  horizontal  axis  passing  through  the  centre  of  rota- 
tion of  the  head  of  the  humerus,  and  from  side  to  side  round 
a  vertical  axis,  but  we  can  also  rotate  it  round  its  own  lon- 
gitudinal axis.  When,  however,  we  come  to  examine  closely 
the  movements  of  the  eyeball  we  find,  as  was  shown  by  Bon- 
ders, that  though  we  can  move  it  up  and  down  round  a  hor- 
izontal axis,  as  when  with  fixed  liead  we  direct  our  vision 
to  the  heavens  or  to  the  ground,  and  from  side  to  side,  as 
when  we  look  to  left  or  right,  and  though  by  combining  these 
two  movements  we  can  give  the  eyeball  a  variety  of  incli- 
nations, we  cannot,  by  a  voluntary  efi'ort.  rotate  the  eyel>all 
round  its  longitudinal  visual  axis.  The  arrangement  of  the 
muscles  of  the  eyeball  would  permit  of  such  a  movement, 
but  we  cannot  by  any  direct  efibrt  of  will  bring  it  about  by 
itself;  we  can  only  effect  it  indirectly  when  we  attempt  to 
move  the  eyeballs  in  certain  special  ways. 

If,  when  vision  is  directed  to  an}^  object,  the  head  be 
moved  from  side  to  side,  the  eyes  do  not  move  with  it ;  they 


712  SIGHT. 


appear  to  remain  stationary,  very  much  as  the  needle  of  a 
ship's  compass  remains  stationary  when  the  head  of  the  ship 
is  turned.  The  change  in  the  position  of  the  visual  axis  to 
which  the  movement  of  the  head  would  naturally  give  rise 
is  met  by  compensating  movements  of  the  eyeballs  ;  were 
it  not  so,  steadiness  of  vision  would  be  impossible. 

There  is  one  position  of  the  eyes  which  has  been  called  the 
2wimari/  position.  It  corresponds  to  that  which  may  be  attained 
by  looking  at  the  distant  horizon  wuth  the  head  vertical  and  the 
body  upright ;  but  its  exact  determination  requires  special  pre- 
cautions. The  visual  axes  are  then  parallel  to  each  other  and  to 
the  median  plane  of  the  head.  All  other  positions  of  the  eyes 
are  called  secondary  positions.  In  a  secondary  position  the  visual 
line  takes  anew  direction,  and  a  plane  drawn  through  the  centre 
of  rotation  at  right  angles  to  the  primary  directionof  the  visual 
line  acquires  importance  ;  for  it  was  suggested  by  Listino;,  and 
proved  by  Bonders  and  Helmholtz,  that  the  change  from  the  pri- 
mary to  any  secondary  position  is  brought  about  by  a  rotation 
of  the  eye  round  an  axis  lying  in  this  plane.  This  law  of  the 
movements  of  the  eye  is  knowm  as  Listing's  law.  The  chief  axes  in 
this  plane  are  the  transverse  axis  of  the  eye,  rotation  round  which 
causes  the  eye  to  move  up  and  down,  and  the  vertical  axis,  rota- 
tion round  wdiich  causes  the  eye  to  move  from  side  to  side  ;  rota- 
tion round  other  axes  in  the  plane  causes  oblique  movements. 
When,  one  eye  being  closed,  we  look  with  the  other  in  the  pri- 
mary position  at  a  vertical  colored  stripe  on  a  gray  wall  until  a 
negative  image  of  the  stripe  is  produced,  and  then  move  the  eye 
away  from  the  stripe,  the  negative  image  remains  vertical,  how- 
ever much  the  eye  is  moved  either  horizontally  from  side  to  side, 
or  vertically  up  and  downi ;  in  these  movements,  wdiich  are  rota- 
tions round  the  vertical  and  transverse  axes  respectively,  the  re- 
lations of  the  retina  to  the  visual  line  are  unchanged  ;  the  me- 
ridian in  which  the  negative  image  lies,  and  wdiich  was  vertical  in 
the  primary  position,  "remains  vertical  in  the  new^  positions.  A 
horizontal  negative  image  similarly  remains  horizontal.  If  the 
eye  be  moved  from  the  primary  position  in  an  oblique  direction, 
the  negative  image,  whether  horizontal  or  vertical,  becomes  in- 
clined ;  but  Hehnholtz'  showed  that  an  oblique  linear  negative 
image  also  maintains  its  inclination  wdien  the  eye  is  moved  from 
the  primary  position,  in  the  direction  of  the  line  of  (or  at  right 
angles  to  the  line  of)  the  negative  image  ;  that  here  too  the  me- 
ridian passing  through  the  visual  line  and  the  negative  image 
remains  unchanged  ;  and  that  therefore  the  movement  in  this 
case  also  must  be  brought  abotit  b}'  rotation  roimd  an  axis  at 
right  angles  to  the  plane  passing  through  the  meridian  of  the 

^  Proc.  Koy.  Soc,  xiii  (1864),  p.  186. 


BINOCULAR    VISION.  713 


negative  image  {i.  e..  the  visual  line  in  its  new  direction)  and 
the  visual  line  in  the  primary  position.  In  other  words,  just  as 
a  vertical  or  horizontal  movement  of  the  eye  is  a  rotation  round 
a  horizontal  or  vertical  axis  in  the  plane  of  rotation  spoken  of 
above,  so  an  oblique  movement  is  a  rotation  round  an  oblique 
axis  in  the  same  plane,  and  not  in  an}'  wa}'  a  rotation  round  the 
visual  axis  itself.  AVhen  the  horizontal  or  vertical  negative  im- 
age in  the  above  experiment  becomes  inclined  in  an  oblique  move- 
ment of  the  eye,  its  motion  is  similar  to  that  of  the  spokes  of  a 
wheel ;  but  this  change  of  position  of  the  meridians  of  the  retina 
must  not  be  confounded  with  the  actual  rotation  of  the  eyeball 
on  its  visual  axis. 

All  movements  then  starting  from  the  primary  position, 
whether  rectangular  or  oblique,  are  executed  without  rotation  of 
the  eyeball  ;  but  this  is  not  the  case  in  moving  from  one  secon- 
dary position  to  another.  Moreover  Listing's  law  holds  good 
only  so  long  as  the  visual  axes  remain  parallel.  When  the  vis- 
uafaxes  are  made  to  converge,  some  amount  of  rotation  occurs, 
and  that  even  when  their  horizontal  direction,  proper  to  them  in 
the  primary  position,  is  maintained.  The  rotation  is,  with  the 
exception  of  a  particular  position,  still  more  marked  when,  as  is 
usually  the  case  during  the  convergence,  the  eyes  are  directed 
downwards. 

It  was  once  thought  that  the  maintenance  of  the  position  of 
the  eyeballs  when  the  head  was  turned  to  the  shoulders,  while 
vision  was  directed  to  an  object  in  front,  was  ellected  by  means 
of  a  rotation  of  the  eyeballs.  This  Donders  proved  to  be  an  er- 
ror, though  some  slight  amount  of  rotation  does  take  place.  In 
various  other  movements  of  the  eye  too  rotation  occurs  to  a  va- 
riable extent. 

Musdes  of  the  Eyeball. — The  eyeball  is  moved  by  six 
muscles,  the  j^ecti  inferior^  Hiiperior,  internuti^  and  externui^^ 
and  the  obliqui  iiift'rior  and  i^uperior.  It  is  found  by  cal- 
culation from  the  attachments  and  directions  of  the  mus- 
cles, and  confirmed  by  actual  observation,  that  the  six 
muscles  ma}'  be  considered  as  three  pairs,  each  pair  rotating 
l:lie  eye  round  a  i)articular  axis.  The  relative  attachments 
and  the  axes  of  rotation  are  diagram matieally  shown  in  Fig. 
185.  Thus  the  rectus  superior  and  tiie  rectus  inferior  rotate 
the  eye  round  a  horizontal  axis,  which  is  directed  from  the 
upper  end  of  the  nose  to  the  temple  ;  the  obliquus  superior 
and  obliquus  inferior  round  a  horizontal  axis  directed  from 
the  centre  of  the  eyeball  to  the  occiput;  and  the  rectus  in- 
ternus  and  rectus  externus  round  a  vertical  axis  (which, 
being  at  right  angles  to  the  plane  of  the  i)aper,  cannot  be 
shown  in  the  diagram),  passing  through  the  centre  of  rota- 
tion of  the  eyeball  parallel  to  the  medium  plane  of  the  head 


u 


SIGHT. 


when  the  head  is  vertical.  Thus  the  latter  pair  acting  alone 
would  turn  the  eye  from  side  to  side,  the  otlier  straight  pair 
acting  alone  would  move  the  eye  up  and  round,  while  the 
oblique  muscles  acting  alone  would  give  the  eye  an  oblique 
movement.  The  rectus  externus  acting  alone  would  turn 
the  eye  to  the  malar  side,  the  internus  to  the  nasal  side,  the 
rectus  superior  upwards,  the  rectus  inferior  downwards,  the 
oblique  superior  downwards  and  outwards,  and  the  inferior 


Fig.  185. 


ohZ^upr 


/r.vnf. 


Diagram  of  the  Attachments  of  the  Muscles  of  the  Eye,  and  of  their  Axes  of  Ko- 
tatiou,  the  latter  being  represented  by  dotted  lines.  The  axis  of  rotation  of  the 
rectus  externus  and  internus,  being  perpendicular  to  the  plane  of  the  paper,  cannot 
be  shown,— After  Fick. 


upwards  and  outwards.  The  recti  superior  and  inferior  in 
moving  the  e^'e  up  and  down  also  turu  it  somewhat  inward, 
and  at  the  same  time  give  it  a  slight  amount  of  rotation  ; 
but  this  is  corrected  if  the  oblique  muscles  act  at  the  same 
time;  and  it  is  found  that  tlie  rectus  superior  acting  with 
the  obliquus  inferior  moves  the  eye  upwards,  and  the  rectus 
inferior  with  the  obliquus  superior  downwards  in  a  vertical 
direction.  In  oblique  movements  also,  the  obliqui  are  al- 
ways associated  with  the  recti.  Hence  the  various  move- 
ments of  the  eyeball  may  be  arranged  as  follows: 


BINOCULAR    VISION. 


715 


S 


f  Elevation. 

Depression. 

j  Adduction  to 

nasal  side. 
I  Adduction  to 
[    malar  side. 

f  Elevation  with 
{       adduction. 

Depression  with 
j        adduction. 
"j  Elevation  with 

abduction. 
I  Depression  with 
[       abduction. 


Rectus  superior  and  obliquus  in- 
ferior. 

Rectus  inferior  and  obliquus  su- 
perior. 

Rectus  internus. 

Rectus  extern  us. 

Rectus  superior  and  internus  with 

obliquus  inferior. 
Rectus  inferior  and  internus  with 

obliquus  superior. 
Rectus  superior  and  externus  with 

obliquus  inferior. 
Rectus  inferior  and  externus  with 

obliquus  superior. 


Co-ordination  of  Visual  Movements. — Thus  even  in  the 
movements  of  a  single  eye,  a  considerable  amount  of  co- 
ordination takes  place.  When  the  eye  is  moved  in  any 
otiier  than  the  vertical  and  horizontal  meridians,  impulses 
must  descend  to  at  least  three  muscles,  and  in  such  relative 
enerofy  to  each  of  the  three  as  to  produce  the  required  in- 
clination of  the  visual  axis.  But  the  co-ordination  observed 
in  binocular  vision  is  more  striking  still.  If  the  movements 
of  any  person's  eyes  be  watched  it  will  be  seen  that  the  two 
eyes  move  alike.  If  the  right  eye  moves  to  the  right,  so 
does  also  the  left ;  and  if  the  object  looked  at  be  a  distant 
one.  exactly  to  the  same  extent;  if  the  right  eye  looks  up, 
the  left  eye  looks  up  also,  and  so  in  every  other  direction. 
Very  few  persons  are  able  by  a  direct  effort  of  the  will  to 
move  one  eye  independentl}-  of  the  other;  though  some, 
and  among  them  one  distinguished  both  as  a  physiologist 
and  an  oculist,  have  acquired  this  power.  In  fact,  the  move- 
ments of  the  two  eyes  are  so  arranged  that  in  the  various 
movements  the  images  of  any  object  should  fall  on  the  cor- 
responding points  of  the  two  retiuj^,  and  that  thus  single 
vision  should  result.  We  cannot  by  any  direct  effort  of  our 
will  place  our  eyes  in  such  a  position  that  the  rays  of  light 
proceeding  from  any  object  shall  fall  on  parts  of  the  retina 
which  do  not  correspond,  and  thus  give  rise  to  tv/o  distinct 
visual  images.  We  can  bring  the  visual  axes  of  the  two 
eyes  from  a  condition  of  parallelism  to  one  of  great  con- 
vergence, but  we  cannot,  without  special  assistance,  bring 
them  from  a  condition  of  parallelism  to  one  of  divergence. 


716  SIGHT. 


The  stereoscope  will  enable  us  to  create  a  divergence.  If  in  a 
stereoscopic  picture  the  distance  between  the  pictures  be  in- 
creased so  gradually  that  the  impression  of  a  single  object  be  not 
lost,  the  visual  axes  may  be  brought  to  diverge.  Helmholtz, 
while  looking  at  a  distant  object  with  a  prism  before  one  eye, 
with  the  angle  of  the  prism  directed  towards  the  nose  and  the 
vision  of  the  object  kept  carefully  single,  found  after  turning  the 
angle  very  slowly  up  or  down,  and  keeping  the  image  of  the  ob- 
ject single  all  the  time,  that  on  removing  the  prism  a  double 
image  was  for  a  moment  seen  ;  showing  that  the  eye  before  which 
the  i3rlsm  was  placed  had  moved  in  disaccordance  with  the  other. 
The  double  image,  however,  in  a  few  seconds  after  the  removal 
of  the  prism  became  single,  on  account  of  the  eyes  coming  into 
accordance. 

It  is  only  when  loss  of  co-ordination  occurs,  as  in  various 
diseases,  and  in  alcoholic  or  other  poisoning,  that  the  move- 
ments of  the  two  eyes  cease  to  agree  with  each  other.  It 
is  evident,  then,  that  when  we  look  at  an  object  to  the  rigiit, 
since  we  thereby  abduct  the  right  eye  and  adduct  the  left, 
we  throw  into  action  the  rectus  externus  of  the  right  eye 
and  the  rectus  internus  of  the  left;  and  similarly  when  we 
look  to  the  left  we  use  the  rectus  externus  of  tiie  left  and  the 
rectus  internus  of  the  right  eye.  When  we  look  at  a  near 
object,  and  therefore  converge  the  visual  axes,  we  use  the 
recti  interni  of  both  eyes;  and  when  we  look  at  a  distarjt 
object,  and  bring  the  axes  from  convergence  towards  paral- 
lelism, we  use  the  recti  externi  of  both  eyes.  In  the  various 
movements  of  tiie  eye  thei-e  is,  therefore,  so  to  speak,  the 
most  delicate  picking  and  choosing  of  the  muscular  instru- 
ments. Bearing  this  in  mind,  it  cannot  be  wondered  at 
that  the  various  movements  of  the  eye  are  dependent  for 
their  causation  on  visual  sensations.  In  older  to  move  our 
eyes,  we  must  either  look  at  or  for  an  object;  when  we  wish 
to  converge  our  axes,  we  look  at  some  near  object,  real  or 
imaginary,  and  the  convergence  of  the  axes  is  usually  accom- 
panied by  all  the  conditions  of  near  vision,  such  as  increased 
accommodation  and  contraction  of  the  pupil.  And  so  with 
other  movements. 

The  close  association  of  the  movements  of  the  eye  may  be  illus- 
trated by  the  following  case.  Suppose  the  eyes,  to  start  with, 
directed  for  the  far  distance,  and  that  it  is  desired  to  direct  atten- 
tion to  a  nearer  point  lying  in  the  visual  line  of  the  right  eye. 
In  this  case  no  movement  of  the  right  eye  is  required  ;  all  that  is 
necessary  is  for  the  left  eye  to  be  turned  to  the  right,  that  is  for 
the  rectus  internus  of  the  left  eye  to  be  thrown  into  action.  But 
in  ordinary  movements  the  contraction  of  this  muscle  is  always 


BINOCULAR    VISION.  717 


associated  with  either  the  rectus  externus  of  the  right  eye  (as 
when  both  e^-es  are  turned  to  the  right),  or  the  rectus  internus  of 
that  eye,  as  in  convergence;  the  muscle  is  quite  unaccustomed 
to  act  alone.  This  would  lead  us  to  suppose  that  in  the  case  in 
question  the  contraction  of  the  rectus  internus  of  the  left  eye  is 
accompanied  by  a  contraction  of  both  recti  externus  and  internus 
of  the  right  eye,  keeping  that  eye  in  lateral  equilibrium.  And 
when  we  come  to  examine  our  own  consciousness,  we  feel  a 
sense  of  eflbrt  in  the  right  as  well  as  in  the  left  eye,  and  the 
slitrht  amount  of  rotation  which  accompanies  convergence  (see 
p.  713)  may  be  discovered  also  in  the  right  as  well  as  in  the  left 
eye. 

Such  a  complex  co-ordination  requires  for  its  carrying  out 
a  distinct  nervous  machinery;  and  we  have  reasons  for 
thinking  that  such  a  machinery  exists  in  certain  parts  of 
tiie  corpora  quadiigemina  or  in  the  underlying  structures. 
(See  p.  671.)  In  the  nates,  Adamuk  finds  a  common  centre 
for  both  eyes,  stimulation  of  tlie  right  side  producing  move 
ments  of  both  eyes  to  the  left,  of  the  left  side  movements 
to  the  rigiit;  while  stimulation  in  the  middle  line  behind 
causes  a  downward  movement  of  both  eyes,  witli  conver- 
gence of  the  axes,  and  in  the  front  an  upward  movement 
with  return  to  parallelism,  both  accompanied  b}^  tiie  natur- 
ally associated  movements  of  the  pupil.  Stimulation  of 
various  parts  of  the  nates  causes  various  movements,  de- 
pending on^the  position  of  the  spot  stimulated.  After  an 
incision  in  the  middle  line,  stimulation  of  the  nervous 
centre  on  one  side  produces  movements  in  the  eye  of  the 
same  side  only. 

The  Horopter. 

AVlien  we  look  at  any  object  we  direct  to  it  the  visual 
axes,  so  that  wiien  the  object  is  small,  the  "  corresponding  " 
parts  of  the  two  retinte.  on  which  the  two  images  of  the  oli- 
ject  fall,  lie  in  their  respective  foveae  centrales.  But  while 
we  are  looking  at  the  ])articular  object  tlie  images  of  other 
objects  surrounding.it  fall  on  the  retina  suri'ounding  the  fo- 
vea, and  thus  go  to  form  what  is  called  indirect  vision.  And 
it  is  obviously  of  advantage  tliat  these  images  also  should 
fall  on  •'corresponding"  parts  in  the  two  eyes.  Now  for 
any  given  position  of  the  eyes  there  exists  in  the  tield  of 
vision  a  certain  line  of  surface  of  such  a  kind  that  the 
images  of  the  points  in  it  all  fall  on  corresponding  points  of 
tlie  retina.     A  line  or  surface  having  this  property  is  called 


718 


SIGHT. 


a  horopter.  The  horopter  is  in  fnct  the  aggregate  of  all 
those  points  in  space  which  are  projected  on  to  correspond- 
ing points  of  the  retina;  hence  its  determination  in  any 
particular  case  is  simply  a  matter  of  geometrical  calculation. 
In  some  instances  it  becomes  a  very  complicated  figure. 
The  case  whose  features  are  most  easily  grasped,  is  a  circle 
drawn  in  the  plane  of  tiie  two  visual  axes  througli  the  point 
of  the  convergence  of  the  axes  and  the  optic  centres  of  the 
two  e3'es.     It  is  obvious  from  geometrical  relations  that  in 


Diagram  lllustraling  a  Simple  Horopter. 

When  the  visual  axes  converge  at  C,  the  images  a  a  of  any  point  A  on  the  circle 
drawn  through  Cand  the  optical  centres  k  k,  will  fall  on  corresponding  points. 

Fig.  18fi  the  images  of  any  point  in  the  circle  will  fall  on  cor- 
responding points  of  the  two  retinae.  When  we  stand  up- 
right and  look  at  tlie  distant  horizon  the  horopter  is 
(approximately,  for  normal  long-sighted  persons)  a  plane 
drawn  through  our  feet,  that  is  to  say,  is  the  ground  on 
which  we  stand.     The  advantai^e  of  this  is  obvious. 


In  determining  the  position  of  corresponding  points  it  must  be 
remembered,  as  Ilelmholtz'  has  shown,  that  while  the  horizontal 
meridians  of  the  two  fields  really  correspond,  it  is  the  apparent 
and  not  the  real  vertical  meridians  which  are  combined  into  one 
image  in  binocular  vision,  and  it  is  therefore  by  these  that  the 
corresponding  points  must  be  determined.    If  two  areas  be  marked 

1  Proc.  Eoy.  vSoc,  xiii  (1864),  p.  196. 


VISUAL    JUDGMENTS.  719 


with  lines  nearly  but  not  quite  vertical,  those  on  the  right  side 
inclining  to  the  left,  and  those  on  the  left  to  the  right,  the  former 
when  judged  by  the  right  e^'e  will  appear  vertical,  tiiough  their 
slant  willbe  apparent  to  tlie  left  eye.  and  the  latter  will  appear 
vertical  to  the  left  eye.  but  not  to  the  right.  When  combined  in 
a  stereoscope  picture,  the  lines,  in  spite  of  their  not  being  par- 
allel, will  a])pear  completely  to  coincide,  showing  that  it  is  the 
apparent  position  of  the  vertical  lines  which  must  be  taken  into 
consideration  in  determining  corresponding  points. 


Sec.  5.   Visual  Judgments. 

Binoctilar  vision  is  of  use  to  us,  inasmuch  as  the  one  eye 
is  able  to  fill  up  the  gaps  and  imperfections  of  the  other. 
For  example,  over  and  above  the  monocular  tilling  up  of  the 
blind  spot,  of  which  we  spoke  in  page  706,  since  the  two 
blind  spots  of  the  two  eyes,  being  each  on  the  nasal  side, 
are  not  "  corresponding  "  parts,  the  one  eye  supplies  that 
part  of  the  field  of  vision  which  is  lacking  in  the  other. 
And  other  imperfections  are  similarly  made  good.  But  the 
great  use  of  binocular  vision  is  to  afibrd  us  means  of  form- 
ing visual  judgments  concerning  the  form,  size,  and  distance 
of  objects. 

Judgment  of  Distance  and  Size.— Tlie  perceptions  which 
we  gain  simply  and  solely  by  our  field  of  vision  concern  two 
dimensions  only.  We  can  become  aware  of  the  apparent 
size  of  any  part  of  the  field  corresponding  to  any  particular 
object,  and  of  its  topographical  relations  to  the  rest  of  the 
field,  but  no  more.  Had  we  nothing  more  to  depend  on,  our 
sight  would  be  almost  valueless  as  far  as  an \- exact  informa- 
tion of  the  external  world  was  concerned.  By  association 
of  the  visual  sens:\tions  with  sensations  of  touch,  and  with 
sensations  derived  from  the  movements  of  the  eyeballs  re- 
c][uired  to  make  any  such  part  of  the  field  as  corresponds  to 
a  particular  object  distinct,  we  are  led  to  form  judgments, 
i.f.^  to  draw  conclusions  concerning  the  external  world  by 
means  of  an  interpretation  of  our  visual  perceptions.  Look- 
ing before  us.  we  say  we  see  a  certain  object  of  a  certain 
color  nearly  in  front  of  us,  or  much  on  our  right  hand,  or 
much  on  our  left ;  that  is  to  say,  we  judge  such  an  object  to 
be  in  such  a  position  because  from  the  constitution  of  our 
brain,  strengthened  by  all  our  experience,  we  associate  such 
a  part  of  our  field  of  vision  with  such  an  object.     The  sub- 


720  SIGHT. 

jective  visual  complex  sensation  or  perception  is   to  ns  a 
syml)ol  of  the  external  object. 

Even  with  one  eye  we  can,  to  a  certain  extent,  form  a  jiulg- 
ment,  not  only  as  to  the  position  of  th.e  oliject  in  a  i)lane  at 
right  angles  to  our  visnal  axis,  but  also  as  to  its  distance 
from  us  along  the  visual  axis.  If  the  object  is  near  to  us 
we  have  to  accon^.modate  for  near  vision  ;  if  far  from  us,  to 
relax  our  accommodation  mechanism  so  that  the  eye  be- 
comes adjusted  for  distance.  The  muscular  sense  (see 
Chap.  lY,  sec.  4)  of  this  etiort  enables  us  to  form  a  judg- 
ment whether  the  object  is  far  or  near.  Seeing  the  narrow 
range  of  our  accommodation,  and  the  slight  muscular  effort 
which  it  entails,  all  monocular  judgments  of  distance  must 
be  subject  to  much  error.  Every  one  who  has  tried  to  thread 
a  needle  without  using  both  eyes  knows  how  great  these 
errors  may  be.  When,  on  the  other  hand,  we  use  two  eyes, 
we  have  still  the  variations  in  accommodation,  and  in  addi- 
tion have  all  the  assistance  whicli  arises  from  the  muscular 
effort  of  so  directing  tlie  two  eyes  on  the  object  that  single 
vision  shall  result.  When  the  object  is  near,  we  converge 
our  visual  axes;  when  distant,  we  bring  them  back  towards 
parallelism.  This  necessary  contraction  of  the  ocular  muscles 
affords  a  muscular  sense,  by  the  help  of  which  we  form  a 
judgment  as  to  the  distance  of  the  object.  Hence,  when  by 
any  means  the  convergence  which  is  necessary  to  bring  the 
object  into  single  vision  is  lessened,  the  object  seems  to 
become  more  distant;  when  increased,  to  move  towards  us, 
as  may  be  seen  in  the  stereoscope. 

The  judgment  of  size  is  closely  connected  with  that  of 
distance.  Our  perceptions,  gained  exclusively  from  tiie 
field  of  vision,  go  no  farther  than  the  apparent  size  of  the 
image,  i.  e.,  of  the  angle  subtended  by  the  object.  The  real 
size  of  the  object  can  only  be  gathered  from  the  apparent 
size  of  the  image  when  the  distance  of  the  object  from  the 
eye  is  known.  Thus  perceiving  directly  the  apparent  size 
of  the  image,  we  judge  the  distance  of  the  object  giving  the 
image,  and  upon  that  come  to  a  conclusion  as  to  its  size. 
And  conversely,  when  we  see  an  ol»ject,  of  whose  real  size 
we  are  otherwise  aware,  or  are  led  to  think  we  are  aware, 
our  judgment  of  its  distance  is  influenced  by  its  apparent 
size.  Thus  when  in  our  field  of  vision  there  appears  the 
image  of  a  man,  knowing  othervvise  the  ordinary  size  of 
man,  we  infer,  if  the  image  be  very  small,  that  the  man  is 
far  off.    The  reason  of  the  image  being  small  may  be  because 


VISUAL    JUDGMENTS. 


721 


the  man  is  far  off,  in  which  case  onr  judgment  is  correct;  it 
may  be.  however,  because  the  image  has  been  lessened  by 
artificial  dioptric  means,  as  when  the  man  is  looked  at 
througli  an  inverted  telescope,  in  which  case  our  judgment 
becomes  a  delusion.  So  also  an  image  on  a  screen  when 
gradually  enlarged  seems  to  come  forward,  when  gradually 
diminished  seems  to  recede.  In  these  cases  the  influence  on 
our  judgment  of  the  muscular  sense  of  binocular  adjust- 
ment, or  monocular  accommodation,  is  thwarted  by  the 
more  direct  influence  of  the  association  between  size  and 
distance. 

Judg-ment  of  Solidity. — When  we  look  at  a  small  circle  all 
parts  of  the  circle  are  at  the  same  distance  from  us,  all 
parts  are  equally  distinct  at  the  same  time,  whetlier  we  look 
at  it  with  one  eye  or  with  two  eyes.  Wlien,  on  tiie  other 
hand,  we  look  at  a  s|)here,  tiie  various  parts  of  which  are  at 
different  distances  from  us,  a  sense  of  the  accommodation, 


Fig.  1S7 


\ 

/ 

\  / 

\ 

\ 

^                  \ 

B 

1 

/ 

\ 

/ 

\ 

/ 

\ 

but  much  more  a  sense  of  the  binocular  adjustment,  of  the 
convergence  or  the  opposite  of  the  two  eyes,  required  to 
make  the  various  parts  successively  distinct,  makes  us  aware 
that  the  various  parts  of  the  sphere  are  unequally  distant; 
and  from  that  we  form  a  judgment  of  its  solidity.  As  with 
distance  of  objects,  so  with  solidity,  which  is  at  bottom  a 
matter  of  distance  of  the  parts  of  an  ol»ject,  we  can  form  a 
judgment  with  one  eye  alone  ;~  but  our  ideas  become  much 
more  exact  and  trtistworthy  when  two  eyes  are  used.  And 
we  are  much  assisted  by  the  ettects  produced  by  the  reflec- 
tion of  light  from  the  various  surfaces  of  a  solid  object  ;  so 
much  so,  that  raised  surfaces  may  be  made  to  appear  de- 
pressed, or  mce  verna^  and  flat  surfaces  either  raised  or 
depressed,  by  appropriate  arrangements  of  shadings  and 
shadow. 

Binocular  vision,  moreover,  affords  us  a  means  of  judging 


722  SIGHT. 


of  the  solidity  of  objects,  inasmuch  as  tlie  inia^^e  of  any 
solid  object  vvliich  falls  on  to  the  right  eye  cannot  be  exactly 
like  that  which  falls  on  the  left,  tlioiigli  both  are  combined 
in  the  single  perception  of  the  two  eyes.  Thns,  vvlien  we 
look  at  a  truncated  pyrnmid  placed  in  the  middle  line  before 
ns,  tlie  image  which  falls  on  the  right  eye  is  of  the  kind 
represented  in  F'ig.  187  R,  while  that  whicli  falls  on  the  left 
eye  has  the  form  of  Fig.  187  L  ;  yet  the  perception  gained 
from  the  two  images  together  corresponds  to  the  form  of 
which  Fig,  187  13  is  the  projection.  Whenever  we  thus 
combine  in  one  perception  two  dissimilar  images,  one  of  the 
one,  and  the  other  of  the  other  eye,  we  judge  that  the  object 
giving  rise  to  the  images  is  solid. 

This  is  the  simple  principle  of  the  stereoscope,  in  which 
two  slightly  dissimilar  pictures,  such  as  would  correspond 
to  the  vision  of  each  eye  separately,  are,  by  means  of  re- 
flecting mirrors,  as  in  Wheatstone's  original  instrument,  or 
by  prisms,  as  in  the  form  introduced  by  Brewster,  made  to 
cast  images  on  corresponding  parts  of  the  two  retinas  so  as 
to  produce  a  single  perception.  Though  each  picture  is  a 
surface  of  two  dimensions  only,  the  resulting  perception  is 
the  same  as  if  a  single  object,  or  group  of  ol»jects,  of  three 
dimensions  had  been  looked  at. 

It  might  be  supposed  that  the  judgment  of  solidity  which 
arises  wiien  two  dissimilar  images  are  thus  combined  in  one 
perception,  was  due  to  the  fact  that  all  parts  of  the  two  im- 
ages cannot  fall  on  corresponding  parts  of  the  two  retinas 
at  the  same  time,  and  that  therefore  the  combination  of  tlie 
two  needs  some  movement  of  the  eyes.  Thus,  if  we  super- 
impose 11  on  li  (Fig.  187),  it  is  evi(lent  that  when  the  bases 
coincide  the  truncated  apices  will  not,  and  cice  vema  ;  hence, 
when  the  bases  fall  on  corresponding  parts,  the  apices  will 
not  be  combined  into  one  image,  and  vice  versa;  in  order 
that  both  may  be  combined,  there  must  be  a  slight  rapid 
movement  of  the  e3'es  from  the  one  to  the  other.  That, 
however,  no  such  movement  is  necessary  /or  each  particu- 
lar case  is  shown  by  the  fact  that  solid  objects  appear  as 
such  when  illuminated  by  an  electric  spark,  the  duration  of 
which  is  too  short  to  permit  of  any  movements  of  the  eyes. 
If  the  flash  occurred  at  the  moment  that  the  eyes  were  bi- 
nocularly  adjusted  for  the  bases  of  the  pyramids,  the  two 
apices  not  falling  on  exactly  corresponding  parts  would  give 
rise  to  two  perceptions,  and  the  whole  object  ought  to  ap- 
pear confused.     That  it  does  not,  but,  on  the  contrary,  ap- 


PROTECTIVE    MECHANISMS    OF    THE    EYE.         723 

pears  a  single  solid,  must  be  the  result  of  cerebral  opera- 
tions, resulting  in  what  we  have  called  a  judgment. 

Struggle  of  the  Two  Fields  of  Vision. — If  the  images  of 
two  surfaces,  one  black  and  the  other  white,  are  made  to 
fall  on  corresponding  parts  of  the  eye,  so  as  to  be  united 
into  a  single  perception,  the  result  is  not  always  a  mixture 
of  the  two  impressions,  that  is  a  gray,  but,  in  many  cases, 
a  sensation  similar  to  that  produced  when  a  polished  sur- 
face, such  as  plumbago,  is  looked  at;  the  surface  appears 
brilliant.  The  reason  proliably  is  because  when  we  look  at 
a  polished  surface  the  amount  of  reflected  light  which  falls 
upon  the  retina  is  generally  dit!erent  in  the  two  eyes ;  and 
hence  we  associate  an  unequal  stimulation  of  the  two  reti- 
nas with  the  idea  of  a  polished  surface.  So  also  when  the 
impressions  of  two  colors  are  united  in  binocular  vision,  the 
result  is  in  most  cases  not  a  mixture  of  the  two  colors,  as 
when  the  same  two  impressions  are  brought  to  bear  together 
at  the  same  time  on  a  single  retina,  but  a  struggle  between 
the  two  colors,  now  one,  and  now  the  other,  becoming  prom- 
inent, intermediate  tints  however  being  frequently  passed 
through.  This  may  arise  from  the  difficulty  of  accommo- 
dating at  the  same  time  for  the  two  different  colors  (see  p. 
675) ;  if  two  eyes,  one  of  which  is  looking  at  red,  and  the 
other  at  blue,  be  both  accommodated  for  red  rays,  the  red 
sensation  will  overpower  the  blue,  and  vice  ven^a.  It  may 
be  however  that  the  tendency  to  riiythmic  action,  so  mani- 
fest in  other  simpler  manifestations  of  protoplasmic  activity, 
makes  its  appearance  also  in  the  higher  cerebral  labors  of 
binocular  vision. 


Sec.  6.   The  Protective  Mechanisms  of  the  Eye. 

Tiie  eyeball  is  protected  b}- the  eyelids,  which  are  capable 
of  movements  called  respectively  opening  and  shutting  the 
eye.  The  eye  is  shut  by  the  contraction  of  the  orbicularis 
muscle,  carried  out  either  as  a  reflex  or  voluntary  act,  by 
means  of  the  facial  nerve.  The  eye  is  opened  chiefly  by  the 
raising  of  the  ni)per  eyelid,  tlirough  the  contraction  of  the 
levator  pali)ebrrti  cairied  out  by  means  of  the  third  nerve. 
The  upper  eyelid  is  also  raised  and  the  lower  depressed,  the 
eye  being  tiius  opened,  by  means  of  plain  muscular  fibres 
existing  in  the  two   eyelids  and  governed   by  the   cervical 


724  SIGHT. 

sympathetic.  The  shutting  of  the  eye  as  in  winking  is  in 
general  effected  move  rapidly  than  tlie  opening. 

The  eye  is  kept  continually  moist  partly  by  the  secretion 
of  the  glands  in  tiie  conjunctiva,  and  of  the  Meibomian 
glands,  but  chiefly  by  the  secretion  of  the  lachrymal  gland. 
Under  ordinary  circumstances  the  fluid  thus  formed  is  car- 
ried away  by  the  lachrymal  canals  into  the  nasal  sac  and 
thus  into  the  cavity  of  the  nose.  When  the  secretion  be- 
comes too  abundant  to  escape  in  this  way  it  overflows  on 
to  the  cheeks  in  the  form  of  tears. 

If  a  quantity  of  tears  be  collected,  they  are  found  to  form 
a  clear  faintly  alkaline  fluid,  in  many  respects  like  saliva, 
containing  about  one  per  cent,  of  solids,  of  which  a  small 
part  is  proteid  in  nature.  Among  the  salts  present  sodium 
chloride  is  conspicuous. 

The  nervous  mechanism  of  the  secretion  of  tears,  in  many 
respects,  resembles  that  of  the  secretion  of  saliva.  A  flow 
is  usually  brought  al)Out  either  in  a  reflex  manner  by  stimuli 
applied  to  the  conjunctiva,  the  nasal  mucous  membrane, 
tongue,  optic  nerve,  etc.,  or  more  directly  by  emotions. 
Tenons  congestion  of  the  head  is  also  said  to  cause  a  flow. 
The  efferent  nerves  belong  either  to  the  cerebro-spinal  sys- 
tem (the  lachrymal  and  orbital  branches  of  the  fifth  nerve), 
or  arise  from  the  cervical  sympathetic,  the  afferent  nerves 
varying  according  to  the  exciting  cause. 

Herzenstein^  and  Wolferz^  showed  that  stimulation  of  the  pe- 
ripheral end  of  the  divided  lachrymal  branch  of  the  fifth  nerve 
produced  a  copious  flow  of  tears.  After  division  of  this  branch 
stimulation  of  the  nasal  mucous  membrane  produced  no  in- 
creased flow  :  the  reflex  act  could  not  bu  carried  out.  Stimula- 
tion of  the  orbital  (subcutaneous  malar)  branch  also  produced 
an  increased  flow,  but  not  to  so  marked  an  extent,  or  so  con- 
stantly as  did  stimulation  of  the  lachx*ymal  branch.  According 
to  Wolferz^  and  lieich,^  stimulation  of  the  upper  end  of  the 
divided  cervical  sympathetic  also  produces  an  increased  flow, 
even  after  division  of  the  lachrymal  nerve  ;  Herzenstein's  results 
on  this  point  were  uncertain  or  negative.  Reich  also  maintains 
that  stimulation  of  the  peripheral  portion  of  the  divided  root  of 
the  fifth  nerve  does  not  excite  the  gland,  but  that,  after  such  a 
division,  the  flow  of  tears  may  be  excited  in  a  reflex  manner  as 

'  Du  Bois-Eeymond's  Archiv,  1807,  p.  651. 

'^  Dissertatio.     Henle  and  Meissner's  Bericlit,  1871,  p.  245. 

3  Op.  eit. 

*  Archiv  f.  Ophthalmol.,  xix  (1873),  p.  38. 


ANATOMY    OF    THE    EAR.  725 


usual.  This  would  show  that  the  secretory  fibres  in  the  lach- 
rymal branch  do  not  belong  properly  to  the  fifth  nerve.  Reich 
believes  that  thev  come,  however,  not  from  the  facial,  as  might 
by  analogy  with  'the  submaxillary  gland  be  supposed,  but  ffom 
the  sympathetic. 

The  act  of  winking  undoubtedly  favors  the  passage  of 
tears  through  the  lachrymal  canals  into  the  nasal  sac,  and 
hence  when  the  orbicularis  is  paralyzed  tears  do  not  pass  so 
readily  as  usual  into  the  nose  ;  but  the  exact  mechanism  by 
which  this  is  etfected  has  been  much  disputed.  According 
to  some  authors,  the  contraction  of  the  orbicularis  presses 
the  fluid  onwards  out  of  the  canals,  which,  upon  the  relaxa- 
tion of  the  orbicularis,  dilate  and  receive  a  fresh  quantity. 
Demtschenko^  states  that  a  special  arrangement  of  muscular 
fibres  keeps  the  canals  open  even  during  the  closing  of  the 
lids,  so  that  the  pressure  of  the  contraction  of  the  orbicu- 
laris is  able  to  have  full  ettect  in  drivinsf  the  tears  throuo^h 
the  canals. 


CHAPTER   III. 
HEARING,  SMELL,  AND  TASTE. 

Sec.  I.     Hearing. 

[^Phi/sioldgicol  Anatomy  of  the  Ear. 

The  ear,  or  organ  of  hearing,  is  composed  of  three  parts, 
called  the  external^  middle^  and  mternal  ear. 

The  external  ear  consists  of  an  outer  projecting  portion, 
called  the  2:>inna,  and  the  auditory  canal,  or  meatus  audito- 

'  Hofmann  and  Schwalbe's  Bericht,  1873,  p.  530. 
61 


726 


HEARING,  SMELL,  AND  TASTE. 


riiis  e.xferni.^.  ''Fig.  188.)  The  pinna  is  a  somewliat  oblong 
funnel-shaped  organ,  the  smaller  [)ortion  of  the  funnel  being 
attached  to  the  skull  by  ligamentous  tissue  ;  the  larger  por- 
tion serving  to  eollect  and  convey  the  sonorous  undulations 
to  the  meatus.  It  is  composed  of  cartilage  covered  by  in- 
tegument. Its  surface  is  irregularly  curved  and  depressed. 
The  outer  pi'ojecting  rim  is  the  heJix ;  anterior  to  the  helix 
is  a  second  elevation,  called  the  anlihelix,  which  describes 
a  curve  partially  around  a   deep  depression  which  leads  to 


Fig.  188. 


Vertical  Section  of  the  Meatus  Auditorius  aud  Tympanum  (Scarpa). 

a,  cartilaginous  part  of  the  meatus;  b,  osseous  portion  ;  c,  raembrana  tympani;  d, 
cavity  of  the  tympanum  ;  e.  Eustachian  tube. 

the  meatus,  called  the  concha.  Between  the  helix  and  anti- 
helix  is  the  /a -s'.'^' a  of  the  helix.  The  antihelix  bifurcates  at 
its  superior  portion,  and  incloses  the  /b.s.sa  of  the  antihelix. 
Projecting  posteriorly  from  the  anterior  portion  of  the  con- 
cha is  a  papillary  prominence  called  the  tragus  ;  posterior 
to  this,  separated  by  a  fissure,  is  the  antitragus^  which  is  a 
continuation  of  the  helix.  On  the  inferior  portion  of  the 
pinna  is  a  soft  pendulous  portion,  termed  the  lobule.  The 
meatus  leads  from  the  concha  to  the  middle  ear,  from  which 


ANATOMY    OF    THE    EAR.  727 

it  is  separated  by  the  tymj)aiiic  memhrane.  Its  direction  is 
forwards,  inwards,  and  slightly  upwards  ;  its  lower  surface 
being  longer  than  the  upper  on  account  of  the  obliquity  of 
the  position  of  the  tympanic  membrane.  The  canal  consists 
of  an  external  membrano  cartilaginous  portion,  which  is 
continuous  with  the  pinna,  and  an  internal  oi^seoua  portion 
formed  by  the  mnsloid  bone.  In  the  external  portion  of 
the  canal  are  found  numerous  hairs  and  sebaceous  glands  ; 
in  the  internal  portion  are  found  the  ceruminous  glandi^^ 
which  secrete  a  peculiar  substance  commonly  known  as  the 
earwax. 

The  middle  ear  or  tympanum  is  an  irregular  flattened  cav- 
ity, situated  in  the  petrous  portion  of  the  temporal  bone, 
and  lined  with  a  mucous  membrane.  It  is  separated  from 
the  meatus  by  a  membranous  diaphragm,  which  is  the  tym- 
panic memhrane:  and  from  the  internal  ear  by  an  osseo- 
membranous  partition,  which  forms  a  common  wall  for  both. 
Through  tiie  Eustachian  tube  it  communicates  with  the 
pharynx.  On  its  posterior  wall  are  seen  orifices  of  the  mas- 
toid cells.  The  tympanic  menil)raue  is  a  semitransparent, 
oval  membrane,  concave  on  its  external,  and  convex  on  its 
internal  surface,  where  it  has  attached  the  long  process  of 
the  nmlleus,  one  of  the  ossicles.  It  is  placed  in  an  oblique 
position,  sloping  downwards,  forwards,  and  inwards  at  an 
angle  of  about  45°.  Its  ciiciimference  is  attached  to  a 
groove  in  the  temporal  bone.  In  the  foetus  this  portion  of 
the  bone  exists  as  a  separate  piece,  called  the  tympanic 
hone  (Fig.  189),  but  it  afterwards  becomes  ossified  to  the 
temporal.  The  tympanic  membrane  consists  of  three  layers  : 
the  external,  middle,  and  internal.  The  external  is  a  con- 
tinuation of  the  integument  covering  the  meatus  ;  the  in- 
ternal is  a  continuation  of  the  mucous  membrane  lining  the 
tympanum  ;  the  middle  layer,  which  is  the  most  important, 
is  tense,  strong,  and  fibrous,  made  up  of  circular  and  radi- 
ating fibres,  with  a  small  amount  of  elastic  tissue  inter- 
mixed. 

In  the  internal  wall  of  the  tympanum  are  two  small  open- 
ings, the  fenestra  ovalis  and  fenestra  rotunda^  which  com- 
municate with  the  labyrinth.  The  fenestra  rotunda  is  closed 
by  a  membrane.  Extending  between  the  tympanic  mem- 
brane and  the  fenestra  ovalis  are  the  ossicles,  consisting  of 
three  small  bones,  which  form  a  system  of  levers.  These 
ossicles  are  termed,  from  their  resemblance  to  particular  ob- 
jects, the  malleus,  incus,  and  stapes.  (Fig.   190.)    The  mal- 


728 


HEARING,    SMELL,    AND    TAST 


leus  consists  of  a  head,  neck,  long  and  short  process,  and 
handle.  The  head  articulates  with  the  roof  of  the  tympa- 
num, and  in  a  depression  of  the  incus;  the  handle  is  di- 
rected downwards,  and  attached  by  its  whole  length  to  the 
tympanic  membrane  ;  the  long  process  {procei^ms  gracilis) 
is  directed  forwards,  an  1  has  attached  the  insertion  of  the 


Fig.  189.— Inner  View  of  the  Membrana  Tympani  in  the  Foetus,  with  the  Malleus 
attached. 

a,  membrane  or  drum  of  the  tympanum  ;  b,  malleus;  c,  baud  of  circular  iibres  at 
the  circumference;  d,  inferior,  and  e,  superior  tympanic  artery  ;  /,  tympanic  bone. 

Fig.  190.— Plan  of  the  Ossicles  in  Position  in  the  TyTnpanum  with  their  Muscles. 

a,  cavity  of  the  tympanum;  b.  membrana  tympani;  c,  Eustachian  tube;  d,  mal- 
leus; e,  incus;  /,  stapes;  gr,  laxator  tympani  muscle;  //,  tensor  tympani;  t,  sta- 
pedius. 

laxator  tympani  muscle  ;  the  sliort  process,  which  is  at  the 
base  of  the  long  process,  has  attached  the  insertion  of  the 
tensor^  tympani  muscle.  The  incus  consists  of  a  i»ody,  a  long 
and  short  process.  The  body  of  the  incus  has  a  depression, 
in  which  articulates  the  head  of  the  malleus  ;  the  short  pro- 
cess is  attaclied  to  the  posterior  wall  of  the  tympanum  ;  tlie 
long  process  (lenticular  process)  is  placed  almost  vertically, 
and  at  its  end  is  a  rounded  process  (the  os  07^biculare)  which 


ANATOxMY    OF    THE    EAR. 


729 


articulates  with  the  head  of  the  stapes.  Tlie  stapes  con- 
sists of  a  head,  neck,  two  crura  and  a  base.  The  head 
articulates  with  the  long  process  of  the  incus ;  the  neck 
serves  as  a  point  of  insertion  of  the  stapedius  muscle  ;  the 
crura  diverue  from  the  neck,  and  unite  with  the  oval  base 
at  its  greatest  diameter.  The  base  is  fixed  in  the  fenestra 
ovalis  by  attacliments  formed  by  the  lining  membranes  of 
both  the  tympanum  and  internal  ear.  These  ossicles  are 
connected  with  each  other,  and  to  the  walls  of  tlie  tympa- 
num by  ligaments,  and  at  their  articulations  they  are  fur- 
nislied  with  cartilages  and  synovial  membranes.  Tliey  are 
enveloped  l)y  prolongations  of  the  mucous  membrane  lin- 
ing the  tympanum. 

The  internal  ear  ov  labyrinth  is  the  most  essential  portion 
of  the  auditory  apparatus.     It  consists  of  three  portions  : 


Fig.  191. 


Fig.  192. 


Natural  siz 


Interior  of  the  Osseous  Labyrinth.  V,  vestibule;  av,  aqueduct  of  the  vestibule  ; 
0,  fovea  hemielliptica  ;  r,  fove^a  hemispherica  ;  S,  semicircular  canals  ;  s,  superior;  p, 
posterior;  ?',  horizontal  ;  a,  a,  a,  the  ampullar  extremity  of  each;  C,  cochlea;  ac, 
aqueduct  of  the  cochlea  ;  sv,  o.sseous  zone  of  the  lamina  spiralis,  above  which  is  the 
scala  vestibuli,  communicating  with  the  vestibule;  «<,  scala  tympaui  below  the  spiral 
lamina.— After  S(EMMe;krixg. 

the  vestibule^  semicircular  canals^  and  cochlea;  and  is  situ- 
ated within  the  petrous  portion  of  the  temporal  bone.   Witl 


tl 


ted  within  the  petrous  portion  ot  the  temporal  bone.    Within 
;ie  osseous  labyrinth  is  a  membranous  labyrinth  to  which 


730 


HEARING,    SMELL,    AND    TASTE. 


the  auditory  nerve  is  distributed.  The  vestibule  is  an  irregu- 
lar chamber,  which  serves  as  a  common  means  of  communi- 
cation between  the  tympanum  and  the  semicircular  canals 
and  cochlea.  On  its  external  wall  is  the  fenestra  ovalis,  closed 
by  tlie  base  of  the  stapes.  On  its  internal  wall  is  a  depres- 
sion called  the  fovea  hemi^phe?'ica^  which  is  perforated  by 
minute  openings  for  the  passage  of  auditory  nerve-fila- 
ments. Above  and  posterior  to  this  depression  is  another, 
the  /bivft  hemielli plica.  Posterior  to  the  fovea  hemi- 
spherica  is  the  orifice  of  the  aqueductus  vestibuli.  In  the 
posterior  wall  are  five  openings  leading  to  the  semicircu- 
lar canals.  Anteriorly-,  it  communicates  with  the  cochlea 
by  the  aperfurae  acalae  venfibuli  cochlese-.  The  semicircular 
canals  are  three  in  number:  the  superior^  posterior  or 
inferior.,  and  liorizontal.  They  form  the  greater  portion  of 
a  circle,  and  communicate  with  the  vestibule  by  five  open- 
ings, one  of  which  is  common  to  the  superior  and  horizontal 
canals.  The  superior  canal  is  situated  vertically,  and  at  right 
angles  with  the  posterior  surface  of  the  petrous  bone;  the 

Fig    19.]. 


Representation  of  the  Semiciicuhir  Cauals  Enlarged  (from  a  model  in  University 
College  Museum),  a,  .superior  vertical ;  b,  postiMior  or  inferior  vertical ;  and  c,  hori- 
zontal canal ;  d,  common  opening  of  the  two  vertical  canals  ;  e,  part  of  the  vestibular 
cavity  ;  /,  opening  of  the  aqueduct  of  the  vestibule. 

posterior  canal  is  also  vertical,  and  parallel  with  the  poste- 
rior surface  of  the  petrous  bone  ;  the  inferior  canal  is  placed 
horizontally  and  at  right  angles  to  the  others.     At  the  com- 


ANATOMY    OF    THE    EAR. 


•31 


meiicement  of  each  of  these  canals  is  a  dilated  portion  called 
the  ampulla. 

The  cochlea  occupies  the  anterior  portion  of  the  lab^-rinth. 
Its  base,  which  corresponds  to  tlie  ivternal  auditory  meatufi^ 
is  perforated  by  many  minute  orifices  for  the  passage  of 
filaments  of  tiie  cochlear  branch  of  the  auditory  nerve. 
The  cochlea  consists  of  a  central  axis,  ov  modiolus,  which  has 
a  spiral  canal  wound  around  it.  This  canal  makes  two  and  a 
half  complete  turns,  and  terminates  in  the  apex  of  tlie 
cochlea  in  an  expansion  termed  the  nnfundihulum.  (Fig. 
194.)     The  modiolus  is  somewhat  cone-shaped,  and  forms 

Fig    194. 


Section  through  the  Cochlea (Breschet).  a,  axis  with  its  canals;  h,  infiindilnilum 
or  enlargnd  upper  end  of  the  axis;  c, septum  of  the  cochlea;  cf, membrane  of  Corti ; 
e,  membrane  of  Reissner;  /,  Hiatus  or  helicotrema;  st,  scala  tympani ;  sv,  scala 
vestibuli. 

the  internal  wall  of  the  canal,  being  perforated  in  its  centre 
and  sides  by  apertures  for  tlie  passage  of  the  filaments  of  the 
auditory  nerve.  The  canal  is  divided  into  two  passages  or 
scalae  by  a  septum  called  the  lamina  apiralia^  which  is  partly 
osseous  and  partly  membranous.  Tlie  osseous  portion  pro- 
jects from  the  modiolus,  midway  across  the  canal;  it  consists 
of  two  laminae  between  which  the  nerve-filaments  run.  The 
membranous  portion  extends  from  the  external  margin  of 
the  osseous  lamina  to  the  external  wall  of  the  canal.  It 
consists  of  two  layers ;  the  superior  is  the  membrane  of  Corti 
or  membrana  tectoria  ;  the  inferior,  the  membrana  basilaris, 
which  is  attached  externally  to  the  j?lanum  i<.emilunare. 
These  membranes  are  placed  })arallel  with  each  other,  and 


732 


HEARING,  SMELL,  AND  TASTE. 


contain  between  them  the  organ  of  Corti.,  which  rests  on 
the  hasilary  merahrane.    (Fig.  195.) 

The  ticala  vesfihiilv  communicates  below  with  the  vesti- 
bule by  the  apertarse  acalae  vestihuJi  cochlea  ;  the  lower  pas- 
sage, or  ^cala  tympani^  communicates  with  the  tympanum 
b}'  the  fenestra  rotunda.  Tiiese  scahie  communicate  at  the 
apex  of  the  cochlea  by  an  opening  termed  the  hiatua  or 
helicotrema,  which  exists  in  consequence  of  a  deficiency  of 
the  last  half  turn  of  the  lamina  spiralis. 

*  Fig.  195. 


A  I  iagrara  of  a  Section  of  the  Tub;e  of  the  Cuci.lea  Eiilarj^ed  (modified  from 
Henle).  SV,  seala  vestibuli ;  ST,  scala  tympani;  CC,  canal  of  tlie  cochlea;  1,  mem- 
brane of  Reissner;  2,  cochlear  branch  of  the  auditory  nerve;  3,  lamina  spiralis 
o^sea  ;  4,  phmiim  semilnnare  ;  a,  lamina  denticnlata  ;  6,  sulcus  spiralis;  c,  tympanic 
lip  of  the  sulcus  spiralis ;  d,  inner  rods  of  Corti ;  e,  outer  rods  of  Corti ;  /,  lamina 
reticularis;  t,  inner  hair-cells;  m6,  membrana  basilaris;  7hc,  membrane  of  Corti;  p, 
outer  hair-cells;  sm,  central  space  between  the  rods. 

The  osseous  portion  of  the  lamina  spiralis  has  on  its  su- 
perior external  portion  a  denticulated  cartilaginous  sub- 
stance called  the  lamina  denHculata.  From  the  superior 
surface  of  tlie  spiral  lamina,  and  internal  to  the  lamina 
denticnlata,  is  a  delicate  membrane  extending  upwards  and 
outwards  at  an  angle  of  al)out  45°  to  the  external  wall  of 
the  scala.     This  is  called  the  membrane  of  Reissner.     It  di- 

1  The  upper  scala  is  divided  into  two  parts  by  a  membranous  partition, 
the  upper  of  which  is  called  the  scala  vestibuli;  the  other,  ductus 
cochlearis.  (Fig.  195). 


ANATOMY    OF    THE    EAR. 


733 


vides  the  scala  into  two  passages,  the  lower  of  w^liich  is  the 
ductui^  coehleariii.  This  duct  ends  in  the  apex  of  the  cochlea 
in  a  coeca,  and  communicates  at  the  base  with  the  saccule  b}^ 
the  ductuii  reuniena ;  it  contains  the  essential  portion  of  the 
auditory  apparatus  of  the  cochlea,  and  is  a  part  of  the  mem- 
branous labyrinth. 

The  organ  of  Corti  rests  upon  the  basilary  membrane. 
It  consists  of  tiie  inner  and  outer  hair-cells,  and  two  rows 
of  elonoated  cells,  placed  parallel  with  each  other,  having 
an  inclining  position  so  that  their  free  extremities  rest 
against  each  other  and  thus  form  the  arch  of  Corti^  which 
covers  the  central  space.  (Fig.  195.)    These  rows  are  called 

Fig    196 


Petrous  Bone  partly  removed  to  show  the  Membranous  Labyrintli  iu  place 
(Breschet). 
a,  small  sac ;  fc,  its  otolith ;  c,  ductus  reuniens ;  d,  large  sac  or  utricle ;  e,  its  otolith ; 
/,  arapullary  enlargement  on  a  semicircular  tube  ;  g,  semicircular  tube. 

the  inner  and  outer  jo(\^.  or  pillars  of  Corti.  From  the  supe- 
rior extremity  of  botli  the  inner  and  outer  rods,  finger-like 
processes  project  externally.  At  their  bases  corresponding 
to  the  central  space  are  single  rows  of  nucleated  cells.  On 
the  internal  side  of  the  inner  rods  is  a  single  row.  and  on  the 
external  side  of  the  outer  rods  are  tiiree  rows  of  elongated 
ciliated  cells.  Extending  across  the  top  of  the  organ  of 
Corti,  from  the  inner  liair-cells  to  the  external  wall  of  the 

62 


734 


HEARING,    SMELL,    AND    TASTE. 


cnnal,  is  a  very  delicate  structure  called  the  reticular  mem- 
brane. The  auditory  nerve-filaments  prohahly  terminate  in 
the  ciliated  cells,  being  intimately  connected  with  the  cilia. 

The  osseous  labyrinth  is  lined  by  a  fihro-serous  membrane 
which  secretes  a  watery  fluid,  called  the  peril i/mph.  The  peri- 
lymph fills  the  scalte  of  the  cochlea,  and  surrounds  the  duc- 
tus cochlearis  and  the  membranous  portions  of  the  labyrinth, 
which  are  situated  in  the  vestil)ule  and  semicircular  canals. 

The  membranous  labyrinth  is  a  closed  sac  consisting  of 
the  semicircular  canals,  a  vestibular  portion,  and  the  ductus 

Fig.  197. 


Distribution  of  Nerves  to  the  Membranous  Labyrinth  (Beeschet), 


ff,  nerve  to  the  saccule;  h,  nerve  entering  the  ainpullary  enlargement  on  a  semi- 
circular tube;  c,  branch  of  nerve  entering  the  large  sac  or  utricle. 

cochlearis  of  the  cochlea.  The  semicircular  canals  are  of 
the  same  form  as  the  ossecnis  canals,  and  are  contained 
within  them.  The  vestibular  portion  consists  of  an  expanded 
body,  the  utricle^  and  a  smaller  l)ody,  the  saccule.  The 
utricle  is  bituated  at  the  fovea  liemiellii)tica ;  the  semicircu- 
lar canals  open  on  its  internal  surface.  The  saccide  lies  at 
the  fovea  hemispherica ;  it  is  connected  with  the  ductus 
cochlearis  by  tiie  ductus  reuiriens.  Jn  the  walls  of  the 
saccule  and  utricle  are  two  calcareous  bodies  called  the 
otoliths.  The  walls  of  the  am})ulla.  accordirg  to  i5owman,also 
contain  some  grains  of  a  similar  substance.  The  walls  of 
the  membranous  labyrintii  consist  of  a  fibrous  tissue,  lined 


ANATOMY    OF    THE    EAR. 


735 


by  pavement  micleated  epitbeliura  cells,  having  a  structnre- 
less  basement-menilirane.  These  epithelial  cells  are  much 
moditied  at  the  place  of  entrance  of  the  fibres  of  the  audi- 
tor}' nerve.  The  vestibular  branches  of  the  auditory  nerve 
are  distributed  to  the  ampulh^,  utricle,  and  saccule.  (Fi^. 
197.)    In  the  utricle  and  saccule  the  fibres  terminate  in  oval 

Fig.  lys. 


Diasram  of  the  Mode  of  Termination  of  the  Auditory  Nerve  in  the  Anipullse  and 
Sacculi.  1,  the  wall  of  the  amjiiilla;  2,  structureless  basement-membrane  ;  3,  doubly- 
contoured  nerve-fibres;  4,  axis-cylinder  traversing  the  basement-membrane;  5, 
plexiform  union  of  fine  nerve^fibres  with  interspersed  nuclei;  6,  fusiform  cells,  with 
nucleus  and  dark  fibre  in  their  interior;  7,  supporting  cells;  8,  auditory  hairs. 


plates,  called  the  maculas  acuatic-pe^  which  are  more  or  less 
colored  by  the  deposition  of  yellow  pigment.  In  the  am- 
pullcXB  the  fibres  terminate  in  elevations,  called  the  cri><t8e 
acusticae.  After  the  nerve-filament  pierces  the  membra- 
nous wall  at  these  points,  the  axis-cylinder  alone  penetrates 


736  HEARING,    SMELL,    AND    TASTE. 

the  basement-membrane  ;  it  then  forms  a  plexus  of  delicate 
nerve-fibres  with  nuclei,  and  finally  terminates  in  fusiform 
epithelial  cells  which  have  terminal  cilia,  called  the  auditory 
hairs.  (Fig.  19S.)  These  ciliated  cells  are  supported  by  co- 
lumnar epithelium. 

The  membranous  labyrinth  is  lined  by  polygonal  nucleated 
epithelium,  which  secretes  the  endolymph  which  fills  the  sac] 

As  in  the  eye,  so  in  the  ear,  we  have  to  deal  first  witii  a 
nerve  of  special  sense,  the  stimulation  of  which  gives  rise 
to  a  special  sensation  ;  secondly  with  terminal  organs  through 
which  the  physical  changes  proper  to  the  special  sense  are 
enabled  to  acton  the  nerve;  and  thirdly  with  subsidiary 
apparatus,  by  which  the  usefulness  of  the  sense  is  increased. 
The  central  connections  of  the  auditory  nerve  are  such  that 
whenever  the  auditory  libres  are  stimulated,  wdiether  by 
means  of  the  terminal  organs  in  the  usual  way  or  by  the 
direct  application  of  stimuli,  electrical,  mechanical,  etc.,  the 
result  is  always  a  sensation  of  sound.  Just  as  stimulation 
of  the  optic  fibres  produces  no  other  sensation  than  that  of 
light,  so  stimulation  of  the  auditory  fibres  produces  no  other 
sensation  than  that  of  sound. ^  The  terminal  organs  of  the 
auditor}'  nerve  are  of  two  kinds:  the  complicated  organ  of 
Corti  in  the  cochlea,  and  the  epithelial  arrangements  of  the 
macuhe  and  cristas  acustic?e  in  other  parts  of  the  labyrinth. 
Waves  of  sound  falling  on  the  auditory  nerve  itself,  produce 
no  effect  whatever  ;  it  is  only  when  bj'  the  medium  of  the 
endolymph  they  are  brought  to  bear  on  the  delicate  and 
peculiar  epithelium  cells  which  constitute  the  peripheral 
terminations  of  the  nerve,  that  sensations  of  sound  arise. 
Such  delicate  structures  are  for  the  sake  of  protection  nat- 
urally withdrawn  from  the  surface  of  the  body  where  they 
would  be  subject  to  injury.  Hence  the  necessity  of  an 
acoustic  apparatus,  forming  the  middle  and  external  ear,  by 
which  the  waves  of  sound  are  most  advantageously  con- 
ve3'ed  to  the  terminal  organs. 

,The  Acoustic  Apparatus. 

Waves  of  sound  can  and  do  reach  the  endolytnph  of  the 
labyrinth   by  direct  conduction   through   the   skull.     Since 

^  It  will  be  seen  later  on  that  there  are  reasons  for  thinking  that  im- 
pulses passing  along  the  auditory  nerve  may  give  rise  to  other  effects  than 
auditory  sensations. 


THE    TYMPANUM.  737 

however  sonorous  vibrations  are  transmitted  witli  great  dif- 
ficulty from  the  air  to  solids  and  liquids,  and  most  sounds 
come  to  us  through  tlie  air,  some  special  apparatus  is  re- 
quired to  transfer  the  aerial  vibrations  to  the  liquids  of  the 
internal  ear.  This  apparatus  is  supplied  by  the  tympanum 
and  its  appendages. 

The  Concha. — The  use  of  this,  as  far  as  hearing  is  con- 
cerned, is  to  collect  the  waves  of  sound  coming  in  various 
directions,  and  to  direct  them  on  to  the  nieml>rana  tympani. 
In  ourselves  of  moderate  service  only,  in  many  animals  it 
is  of  great  importance. 

The  Membrana  Tympani.— It  is  a  ch;ir;icteristic  i^roperty 
of  stretched  mt-mlnanes  tiiat  they  are  readily  thrown  into 
vibration  by  aerial  waves  of  sound.  The  membrana  tym- 
pani, from  its  peculiar  conformation,  being  funnel-shaped 
with  a  depressed  centre  suirounded  by  sides  gently  convex 
outwards,  is  peculinrly  susceptil)le  to  sonorous  vibrations, 
and  is  most  readily  thrown  into  corresponding  movements 
when  waves  of  sound  reach  it  by  the  meatus.  It  has  moreover 
this  useful  feature,  that  unlike  other  stretched  membranes, 
it  has  no  marked  note  of  its  own.  It  is  not  thrown  into 
vibrations  by  waves  of  a  particular  length  more  readily  than 
by  others.  It  answers  ecpially  well  within  a  considerable 
range,  to  vibrations  of  very  different  wave-lengths.  Had 
it  a  fundamental  tone  of  its  own,  we  should  lie  distracted 
by  the  prominence  of  this  noie  in  most  of  the  sounds  we 
hear. 

The  Auditory  Ossicles. — Tlie  malleus,  the  handle  of  which 
descending  forwards  and  inwards,  is  attached  to  the  mem- 
biana  tympani.  and  the  incus,  whose  long  process  is  con- 
nected by  means  of  its  os  orbiculare  or  lenticular  pi'ocess 
and  the  stapes  to  the  fenestra  ovalis,  form  together  a  body 
which  rotates  round  an  axis,  passing  through  the  short  pro- 
cess of  the  incus,  the  bodies  of  the  incus  and  malleus,  and 
the  ])r()cessus  gracilis  of  the  malleus.  When  the  malleus  is 
carried  inwards,  the  incus  moves  inwards  too,  and  when  the 
malleus  returns  to  its  position,  the  incus  returns  with  it,  the 
peculiar  saddle  shai)ed  joint  with  its  catch  teeth  permitting 
this  movement  readily,  but  preventing  the  stapes  being 
pulled  back  when  the  membrana  tympani  with  the  malleus 
is,  for  any  reason,  pushed  outwards  more  than  usual;  the 


7o8  HEARING,    SMELL,    AND    TASTE. 

joint  then  gapes,  so  as  to  permit  the  malleus  to  be  moved 
alone.  Various  ligaments,  the  superior  or  suspensory,  an- 
terior, and  external,  also  serve  to  keep  tiie  malleus  in  place. 
The  whole  series  of  ossicles  maybe  regarded  as  a  lever,  the 
fulcrum  of  which  is  situated  at  the  ligamental  attachment 
of  the  short  processus  of  the  incus  to  the  posterior  wall  of 
the  tympanum.  The  long  malleal  arm  of  this  lever  is  about 
9^  mm.,  the  short,  stapedial,  G^  mm.  in  length  ;  hence  the 
movements  of  the  stapes  are  less  than  those  of  the  t3'mpa- 
nura  ;  but  the  loss  in  amplitude  is  made  up  b}'  a  gain  of 
force,  which  is  in  itself  an  obvious  advantage. 

Tiius  every  movement  of  the  tympanic  membrane  is  trans- 
mitted through  this  chain  of  ossicles  to  the  membrane  of 
the  fenestra  ovalis,  and  so  to  the  {)erilympli  of  the  laby- 
rinth; the  vibrations  of  the  tympanic  membrane  are  con- 
veyed with  increased  intensity,  though  with  diminished 
amplitude,  to  the  latter.  That  the  bones  thus  move  en 
ina.H^e  has  been  proved  by  recording  their  movements  in 
the  usual  graphic  method.  A  very  light  style  attached  to 
the  incus  or  stapes  is  made  to  write  on  a  travelling  surface  ; 
when  the  meml)rana  tympani  is  thrown  into  vibrations  by 
a  sound,  the  curves  described  by  the  style  indicate  that  the 
chain  of  bones  moves  with  every  vibration  of  the  tym- 
panum. On  the  other  hand,  the  comparatively  loose  at- 
tachments of  the  several  bones  is  an  obstacle  to  the  molec- 
ular transmission  of  sonorous  vibrations  through  them. 
Mcn-eover  sonorous  vibrations  can  only  be  transmitted  to  or 
pass  ulong  such  bodies  as  either  are  very  long  compared  to 
the  length  of  the  sound-waves,  or,  as  in  the  case  of  mem- 
branes and  strings,  have  one  dimension  very  much  smaller 
than  the  others.  Now  the  bones  in  question  are  not  espe- 
cially thin  in  anyone  dimension,  but  are  in  all  their  dimen- 
sions exceedingly  small  compared  with  the  length  of  the 
vibrations  of  even  the  shrillest  sounds  we  are  capable  of 
hearing;  hence  they  must  be  useless  for  the  molecular 
propagation  of  vibrations. 

The  tensor  tympani  muscle,  even  in  a  quiescent  state,  is 
of  use  in  preventing  the  membrana  tympani  being  pushed 
out  far.  When  it  contracts  it  renders  the  membrana  tym- 
pani more  tense  and  hence  has  been  supposed  to  act  either 
as  a  damper  lessening  the  amount  of  vibration  of  the  mem- 
brane in  the  case  of  too  powerful  sounds,  or  as  a  sort  of 
accommodation  mechanism  atiuuin":  the  membrane  to  the 


THE    EUSTACHIAN    TUBE.  739 

sounds  which  fall  upon  it.  Its  activity  in  this  direction  is 
regulated  by  a  reflex  action.  In  some  persons  the  muscle 
seems  to  be  {tartly  under  the  dominion  of  the  will,  since  a 
peculiar  crackling  noise  which  these  persons  can  produce 
at  pleasure  appears  to  be  caused  b}'  a  contraction  of  the 
tensor  tympani. 

Hensen^  has  directly  observed  the  action  of  the  tensor  tympani 
in  the  dog  and  cat,  and  finds  that  while  the  muscle  is  readily 
thrown  into  contraction  at  the  commencement  of  everv  sound  or 
noise,  it  returns  to  rest  and  becomes  relaxed  again  during  the 
continuance  of  a  prolonged  note.  He  suggests  that  by  throwing 
the  muscle  into  activit}'  the  sound  of  a  consonant  may  make  the 
membraua  tympani  tense  and  thus  render  it  better  adapted  to 
carry  on  the  vibrations  of  the  vowel  sound  following  the  conso- 
nant. 

The  stapedius  muscle  is  supposed  to  regulate  the  move- 
ments of  the  stapes,  and  es})ecially  to  prevent  its  base  being- 
driven  too  far  into  the  fenestra  ovalis  during  large  or  sud- 
den movements  of  the  menU)rana  tympani. 

A  contraction  of  the  stapedius  by  itself  would  have  the  effect 
of  pulling  the  hinder  end  of  the  base  of  the  stapes  out  of,  and  of 
pushing  the  front  end  into,  the  fenestra  ovalis  ;  and  this  might 
give  rise  to  a  wave  in  the  perilymph.  For  speculations  on  this 
and  on  the  reason  why  the  stapedius  is  governed  by  the  facial 
and  the  tensor  tympani  b}'  the  fifth  nerve,  see  Budge. - 

The  so-cailed  laxator  tympani  is  considered'  to  be  not  a  muscle 
at  all,  but  a  pan  of  the  ligamentous  supports  of  the  malleus. 

The  Eustachian  Tube. — This  serves  to  maintain  an  equi- 
librium of  pressure  l)et\veen  the  external  air  and  that  within 
the  tympanum,  and  to  serve  as  an  exit  for  the  secretions  of 
tiiat  cavity.  Were  the  tympanum  permanently  closed  the 
vibi-ations  of  the  membraua  tympani  would  be  injuriously 
atfected  by  variations  of  pressure  occurring  either  inside  or 
outside. 

The  Eustachian  tube  is  undoubtedly  open  during  swalloAving, 
but  it  is  still  disputed  whether  it  remains  permanently  open,  or 
is  opened  only  at  intervals. 

'  Ardi.  f.  Anat.  n.  Phvs.,  1878  (Phvs.  Abth.),  p.  312. 

2  Pfluger's  Archiv  (1874),  ix,  4()().  " 

3  Helnihohz,  Pfliii^er's  Archiv,  i  (1808),  1  ;  Henle,  Anatoniie,  ii,  740. 


740  HEARING,    SxMELL,    AND    TASTE. 


Auditory  Sensations. 

Each  vibration  communicated  by  the  stapes  to  the  peri- 
lymph travels  as  a  wave  over  the  vestil)iile,  the  semicircular 
canals,  and  otlier  parts  of  the  labyrinth,  and  is  there  trans- 
mitted to  the  endolymph  ;  it  passes  on  from  the  vestibule 
into  the  scala  vestibuli  of  the  cochlea,  and  descending  the 
scala  tympani  ends  as  an  impulse  against  the  membrane  of 
the  fenestra  rotunda.  In  the  maculae  and  crista  the  vibra- 
tions of  the  endolymph  are  supposed  to  throw  into  cori-e- 
sponding  vibiations  the  so-called  auditory  hairs.  In  the 
cochlea  the  vibrations  of  the  perilymph  are  supposed  to 
throw  into  vibrations  the  basilar  membrane  with  the  super- 
imposed organ  of  Corti,  consisting  of  the  rods  of  Corti  with 
the  inner  and  outer  hair-cells.  The  vibrations  thus  trans- 
mitted to  these  structures  give  rise  to  nervous  impulses  in 
the  terminations  of  the  auditory  nerves,  and  these  impulses 
reaching  certain  parts  of  the  brain  produce  what  we  call 
auditory  sensations.  We  are  accustomed  to  divide  our 
auditory  sensations  into  those  caused  by  noises  and  those 
caused  by  musical  sounds.  It  is  the  characteristic  of  the 
latter  that  the  vibrations  which  constitute  them  are  period- 
ical; they  occur  and  recur  at  regulnr  intervals.  When  no 
periodicity  is  present  in  the  vibrations,  when  the  repetition 
of  the  several  vibrations  is  irregular,  or  the  period  so  com- 
plex as  not  to  be  readily  a))preciated,  the  sensation  pro- 
duced is  that  of  a  noise.  There  is,  however,  no  abi'upt  line 
between  the  two.  Between  a  pure  and  a  simple  musical 
sound,  produced  by  a  series  of  vibrations,  each  of  which 
has  exactly  the  same  wave-length,  and  a  harsh  noise  in 
which  no  consecutive  vibrations  may  be  alike,  there  are 
numerous  intermediate  stages. 

In  both  noises  and  musical  sounds  we  recognize  a  char- 
acter which  we  call  loudness.  This  is  determined  by  the 
amplitude  of  the  vibrations  ;  the  greater  the  disturbance  of 
the  air  (or  other  medium)  the  louder  the  sound.  In  a  musical 
sound  we  recognize  also  a  character  which  we  call  [)itch. 
This  is  determined  by  the  wave-length  of  the  vibrations  ;  the 
shorter  the  wave-length,  the  laiger  the  number  of  consecutive 
A'ibrations  which  fall  upon  the  ear  in  a  second,  the  higher  the 
pitch.  We  are  able  to  speak  of  a  whole  series  of  tones  or 
musical  sounds  of  different  pitch,  from  the  lowest  to  the 
highest  audible  tone.  And  even  in  many  noises  we  can,  to 
a  certain  extent,  recognize  a  pitch,  indicating  that  among 


AUDITORY    SENSATIONS.  741 

the  multifarious  vibrations  tliere  is  a  period icit}'  witli  fixed 
intervals. 

Last]}',  we  distiuouish  musical  souuds  by  their  quality; 
the  same  note  souuded  on  a  jiiano  and  on  a  violin  [)roduce 
very  ditferent  sensations,  even  wlien  a  series  of  vibrations 
Ijaving  in  eacli  case  the  same  period  of  repetition  is  set 
ooino;.  Tliis  arises  from  the  fact  that  the  musical  sounds 
generated  bv  most  musical  instriimenls  are  not  simple  but 
compound  vibrations.  Wlien  the  note  C  in  the  trel)le  for 
instance  is  struck  on  the  piano,  it  is  perfectly  true  that  a 
series  of  vibrations  with  a  period  characteristic  of  the  pure 
tone  of  the  treble  C  are  started,  but  it  is  also  true  that  those 
vibrations  are  accompanied  by  other  vibrations  with  periods 
characteristic  of  the  C  in  the  octave  above,  of  the  G  above 
that,  of  the  C  in  the  next  octave,  and  of  tlie  E  above  that. 
And  it  is  the  effect  of  all  these  vibrations  together  on  the 
ear  which  causes  the  sensation  which  we  associate  with  the 
sound  of  the  treble  C  on  the  piano.  Almost  all  musical 
sounds  are  tlius  composed  of  what  is  called  a  *'  fundamental 
tone,"  accompanied  by  a  number  of  ''overtones."  And  the 
overtones,  varying  in  number  and  relative  prominence  in 
ditferent  instruments,  give  rise  to  a  difference  in  the  sensa- 
tion caused  i>y  the  whole  tone.  So  that,  while  the  funda- 
mental tone  deteumines  the  pitch  of  the  sound,  the  quality 
of  the  sound  is  determined  by  the  number  and  relative 
prominence  of  the  overtones.  In  a  similar  wa}'  we  distin- 
guish the  quality  of  noises,  such  as  a  banging,  crackling,  or 
rustling  noise,  by  the  predominance  of  vilirations  having  a 
less  orderly  character,  and  recurring  less  regularly  than 
those  of  a  musical  sound. 

Since  w^e  have  a  very  considerable  appreciation,  capable 
by  exercise  of  astonisliing  enlargement,  of  the  loudness, 
])itch,  and  quality  of  a  wide  range  of  noises  and  musical 
sounds,  it  is  clear  that,  within  the  limits  of  hearing,  each 
vibration  or  series  of  vibrations  must  produce  its  erfect  on 
the  auditory  nerves,  according  to  the  measure  of  its  inten- 
sity and  period.  Out  of  those  effects,  out  of  the  sensory 
impulses  to  whicli  the  several  vibrations  thus  give  rise,  are 
generated  our  sensations  of  the  noise  or  of  the  sound. 

The  vibrations  of  a  musical  sound  (and  since  noises  are 
so  imperfectly  understood,  we  may,  with  benefit,  chiefly  con- 
tine  ourselves  to  musical  sounds),  as  the}^  pass  through  the 
air  (or  other  medium)  are  not  discrete;  the  vibrations  cor- 
responding to  the  fundamental  tone  and  overtones  do  not 


742  HEARING,    SMELL,    AND    TASTE. 

travel  as  so  many  separate  waves  ;  they  all  tooether  form 
one  complex  disturbance  of  the  medium  ;  and  it  is  as  one 
coiiipoaite  wave  that  the  sound  falls  on  the  memlirana  tvm- 
pani,  and,  passing  through  the  auditoiy  apparatus,  breaks 
on  the  terminations  of  the  auditory  nerve.  And,  when  two 
or  more  musical  sounds  are  heard  at  the  same  time,  the  same 
fusion  of  the  waves  occur.  Since  we  can  distinguish  several 
tones  reaching  our  ear  at  the  same  time,  it  is  clear  that  we 
must  possess  in  our  minds  or  in  our  ears  some  means  of 
analyzing  these  composite  waves  of  sound  which  fall  on  our 
acoustic  organs,  and  of  sorting  out  their  constituent  vibra- 
tions. 

There  is  at  hand  a  simj)le  and  easy  physical  method  of 
analyzing  composite  sounds.  If  a  person  standing  before 
an  open  piano  sings  out  any  note,  it  will  be  observed  that  a 
number  of  the  strings  of  the  piano  will  l)e  throvvn  into  vibra- 
tion, and  on  examination  it  will  lie  found  that  those  strings 
which  are  thus  set  going  correspond  in  pitch  to  the  funda- 
mental tone  and  to  the  several  overtones  of  the  note  sung. 
The  note  sung  readies  the  strings  as  a  complex  wave,  but 
these  strings  are  able  to  analyze  the  wave  into  its  constit- 
uent vibraticms,  each  string  taking  up  those  vibrations,  and 
those  vibi-ations  only  which  belong  to  the  tone  given  forth 
by  itself  when  struck.  If  we  suppose  that  each  terminal 
fil)ril  of  the  auditory  nerve  is  connected  with  an  organ  so 
far  like  a  piano-string  that  it  will  readily  vibrate  in  response 
to  a  series  of  vibrating  im[)ulses  of  a  given  period  and  to 
none  other,  and  that  we  possess  a  numl)er  of  such  terminal 
organs  sufficient  for  the  analysis  of  all  the  sounds  which  we 
can  analyze,  and  that  each  terminal  organ  so  affected  by 
particular  vibrations  gives  rise  to  a  sensory  impulse,  and 
thus  to  a  sensation  of  a  distinct  chai'acter, — if  wc  suppose 
these  organs  to  exist,  our  appreciation  of  sounds  is  in  a 
large  measure  explained.  In  tlie  organ  of  Corti  we  find 
structures  the  arrangement  of  wiiich  irresistibly  suggests  to 
us  that  these  are  the  organs  we  are  seeking.  We  have  only 
to  suppose  that  of  the  long  series  of  rods  of  Corti,  varying 
regularly  as  these  do  from  the  bottom  to  the  top  of  the 
spiral,  in  length  and  in  the  span  of  their  arcli,  each  pair  will 
vibrate  in  response  to  a  particular  tone,  and  the  whole  mat- 
ter seems  explained.  But.  the  more  the  sui)ject  is  inquired 
into,  the  more  complex  and  difficult  it  appears;  and  we  are 
obliged  to  conclude  that  the  part  played  by  the  rods  of  Corti 


AUDITORY    SENSATIONS.  743 


is  onlv  a  subordinate  part  of  the  function  of  the  whole  organ 
of  Corti. 

In  the  first  place,  it  is  difficult  to  see  how  the  rods  of  Corti, 
even  if  they  are  thrown  into  vibration,  can  orioiuaie  sensor}-  im- 
pulses, for  the  fibrils  of  the  auditory  nerve  terminate  in  the  inner 
and  outer  hair-cells  ;  and  it  is  in  these  cells,  and  not  along  the 
course  of  the  fibrils,  as  they  pass  under  and  between  the  rods  of 
Corti,  that  the  sensory  impulses  must  beuin.  In  the  second 
place,  the  variation  in  length  of  the  fibres  along  the  series  is  in- 
sufficient for  the  w^ork  assigned  to  them.  Moreover,  they  appear 
not  to  be  elastic.  Lastly,  they  are  wdiolh'  absent  in  birds,  who 
very  clearh'can  appreciate  musical  sounds.  This  last  fact  proves 
indubitably  that  the  rods  in  question  are  not  absolutely  essential 
for  the  recognition  of  tones.  In  the  face  of  these  difficulties  it 
has  been  suggested  that  the  basilar  membrane,  which  is  present 
in  birds,  and  which,  being  tense  radially,  but  loose  longitudinally, 
i.  e.,  along  the  spiral  of  the  cochlea,  may,  as  physical  investiga- 
tions show,  be  considered  as  consisting  of  a  number  of  parallel 
radial  strings,  each  capable  of  independent  vibrations,  is  the 
sought- for  organ  of  analysis.  According  to  this  view\  a  partic- 
ular vibration  reaching  the  scala  tympani  of  the  cochlea  throws 
into  sympathetic  vibrations  a  small  portion  of  the  basilar  mem- 
brane, the  vibrations  of  which  in  turn  so  atTect  the  structures 
overlying  it  that  sensory  impulses  are  generated.  These  sensory 
impulses  reaching  the  brain  give  rise  to  a  corresponding  sensation 
of  a  particular  tone.  According  to  Hensen  the  radial  dimensions 
of  the  basilar  membrane  in  man  diminish  downwards  from  .40.") 
mm.  at  the  hamulus  to  .0-H2-")  mm.  near  the  bottom  of  the  spiral, 
giving  a  much  greater  range  than  the  rods  of  Corti,  the  difierence 
in  length  of  which  is  simply  that  between  .048  and  .085  mm.  for 
the  inner,  and  between  .019  and  .085  for  the  outer,  fibres. 

The  remarkable  reticular  membrane  which  has  such  peculiar 
relations  with  the  hair-cells,  and  through  them  with  the  basilar 
membrane,  must,  one  might  imagine,  have  some  special  func- 
tion ;  but  it  is  impossible  to  assign  to  it  any  satisfactory  duty. 
The  structural  arrangements  seem,  if  anythinir.  to  indicate  that 
when  a  segment  of  the  basilar  membrane  is  thrown  into  vibra- 
tions, the  overlying  hair-cells,  reticular  membrane,  and  rods  of 
Corti  vibrate  en  masse  together  with  it.  But  this  renders  the 
whole  matter  still  more  difficult.  Indeed  the  whole  subject  is  in 
the  highest  degree  obscure,  and  the  most  we  can  say  is  that  the 
organ  of  Corti  as  a  wdiole  seems  to  be  in  some  way  connected 
with  the  appreciation  of  tones,  but  that  at  present  it  is  very 
hazardous  to  attempt  to  explain  how  it  acts,  or  to  assign  par- 
ticular functions  to  particular  parts.  The  distinction  betw^een 
the  inner  and  outer  hair-cells  seems  to  be  ver}-  parallel  to  that 
between  the  rods  and  the  cones  of  the  retina ;  but  even  this 
analogy  may  be  a  flillacious  one. 

Hensen,  has  observed  that  among  the  audi  tor  v  hairs  of  the 


744  HEARING,    SMELL,    AND    TASTE. 


Crustacea,  some  will  vibrate  to  particular  notes  ;  but  the  auditory 
hairs  of  the  mammal  are  far  too  much  of  the  same  length  to  per- 
mit the  supposition  that  they  can  act  as  organs  of  analysis. 

If  the  organ  of  Corti  is  the  means  by  which  we  appreciate 
tones,  it  is  evident  that  by  it  also  we  must  be  able  to  estimate 
loudness,  for  the  quality  of  a  musical  sound  is  dependent  on  the 
relative  intensity,  as  well  as  on  the  nature,  of  the  overtones. 
And  since  noise  is  at  best  but  confused  music,  the  cochlea  must 
be  a  means  of  appreciating  noises  as  well  as  sounds.  But  this 
would  leave  nothing  whatever  for  the  rest  of  the  labyrinth  to  do 
as  far  as  the  appreciation  of  sound  is  concerned.  We  have  no 
reason  to  think  that  any  impulse  which  could  affect  the  hair-cells 
of  the  macuhe  and  crista?  could  not  afiect  the  hair-cells  of  the 
organ  of  Corti.  That  this  part  of  the  ear  is  however  concerned 
in  hearing  is  shown  by  its  being  the  only  auditory  organ  in  the 
ichthyopsida,  unless  we  suppose  that  in  the  higher  vertebrates 
its  function  has  been  wholly  transferred  to  the  cochlea.  That  the 
semicircular  canals  have  duties  apart  from  hearing  we  shall  show 
later  on. 

Concerning  the  function  of  the  other  parts  of  the  internal  ear 
we  know  very  little.  The  otoliths  have  been  supposed  to  inten- 
sify the  vibrations  of  the  endolymph  ;  but  since  apparently  they 
are  lodged  in  a  quantity  of  mucus  it  is  probable  that  they  really 
act  as  dampers.  A  similar  damping  action  has  been  suggested 
for  the  membrane  of  Corti  [memhrana  tectoria)  overhanging  the 
fibres  and  hair-cells ;  and  some  writers  have  supposed  that  mus- 
cular fibres  present  in  the  planum  semilunare  may  by  tightening 
the  basilar  membrane  serve  as  a  sort  of  accommodation  mech- 
anism. 

It  must,  however,  1)8  borne  in  mind  that  even  making  the 
fullest  allowance  for  the  assistance  afforded  us  by  the  organ 
of  Corti,  the  nppreciation  of  any  sound  is  ultimately  a 
mental  act  The  analysis  of  the  vibrations  by  the  fibres  of 
Corti  or  the  basilar  membrane  is  simply  preliminary  to  a 
synthesis  of  the  sensory  impulses  so  generated  into  a  com- 
plex sensation.  We  do  not  receive  a  distinct  series  of  spe- 
cific auditory  impulses  resulting  in  a  specific  sensation  for 
every  possible  variation  in  tlie  wave-length  of  sonorous  vi- 
brations any  more  than  we  receive  a  distinct  series  of 
specific  visual  impulses  for  every  possible  wave-length  of 
luminous  vibrations.  In  each  case  we  have  probably  a 
numl)er  of  primary  sensations,  from  the  various  mingling 
of  which,  in  different  proportions,  our  varied  complex  sen- 
sations arise  ;  the  difference  between  the  eye  and  the  ear 
being  that  whereas  in  the  former  the  number  of  primary 
sensations  appears  to  be  limited  to  three,  viz.,  red,  green, 
and  violet ;  in  the  latter,  thanks  to  the  organ  of  Corti,  the 


AUDITORY    SENSATIONS.  745 

number  is  very  large  ;  what  the  exact  number  is  we  cannot 
at  present  tell.  Our  appreciation  of  a  sound  is  at  bottom 
an  appreciation  of  the  combined  effect  produced  by  the 
relative  intensities  to  which  the  primary  auditory  sensations 
are,  with  the  help  of  the  organ  of  Corti,  excited  i\y  the 
sound. 

Whatever  be  the  explanation  of  the  manner  in  which  our 
distinct  auditor}^  sensations  arise,  the  range  and  precision 
of  our  appreciation  of  musical  sounds  is  very  great.  Vi- 
brations with  a  recurrence  below  30  a  second  are  unable  to 
produce  a  sensation  of  sound ;  if  the  waves  are  powerful 
enough  we  may  feel  them,  but  we  do  not  hear  them  if  the 
vibrations  are  simple,  and  sueli  as  would  give  rise  to  a  pure 
tone;  if  the  fundamental  tone  is  accompanied  by  overtones 
we  ma}'  hear  these,  and  are  thus  apt  to  say  we  liear  the 
former  when  in  reality  we  only  hear  tlie  latter.  The  note 
of  the  16-feet  organ  pipe,  83  vibrations  a  second,  gives  us 
the  sensation  of  a  droning  sound.  A  tone  of  40  vibrations 
is  however  quite  distinct.  In  the  other  direction  it  is  pos- 
sible to  hear  a  note  caused  by  38,000  vil)rations  a  second, 
though  the  limit  for  most  persons  is  far  lower,  about  16,000.^ 
Some  persons  hear  grave  sounds  more  easily  than  high  ones, 
and  vice  versa.  This  may  lie  so  pronounced  as  to  justify 
the  subjects  being  spoken  of  as  deaf  to  grave  or  high  tones 
respectively. 

The  power  of  distinguishing  one  note  from  another  varies, 
as  is  well  known,  in  different  individuals,  according  as  they 
have  or  have  not  a  '*  musical  ear."  A  well-trained  ear  can 
distinguish  the  difference  of  a  single  or  even  of  a  half  vibra- 
tion a  second,  and  that  through  a  long  range  of  notes,  the 
sensation  not  obeying  Weber's  law.^  Tlie  range  of  an  ordi- 
nary appreciation  of  tones  lies  between -40  and  4000  vibra- 
tions a  second,  ^.  6?.,  between  the  lowest  bass  C  ( C,  33  vibra- 
tions) and  the  highest  treble  C  (C^  4224  vibrations)  of  the 
piano  ;  tones  above  and  below  these,  even  when  audible, 
being  distinguished  from  each  other  with  great  difficulty. 

When  two  consecutive  sounds  follow  each  other  at  a  suf- 
ficiently short  interval  the  sensations  are  fused  into  one. 

^  Helmholtz,  TOnempfindnngen,  p.  30.  Cf.  Preyer  (Grenzen  der  Ton- 
walirnehmung.  Physiolog.  Abliandliingen,  i,  1,  1876),  who  places  the 
grave  limit  as  varying  from  15  to  24,  and  the  acute  limit  from  16,000  to 
40,U00  vibrations  per  second. 

'  Cf.  Preyer,  op.  cit.  and  Acustische  Untersuch.,  ibid.,  ii,  4  (1879). 


746  HEARING,    SMELL,    AND    TASTE. 

In  this  respect  auditoiT  sensations  are  of  shorter  duration 
than  ocular  sensations.  Wlien  ocular  sensations  are  repeated 
ten  times  in  a  second  thej  become  fused  (p.  689),  whereas 
the  ticks  of  a  pendulum  heatinu  100  in  a  second  are  readily 
audible  as  distinct  sounds.  When  two  tuning-forks  not 
quite  in  tune  are  struck  together  the  interference  of  the 
vibrations  gives  rise  to  an  alternating  rise  and  fall  of  the 
sound,  known  as  **  i>eats."  Wiien  the  beats  follow  each 
other  as  rapidly  as  132  in  a  second  they  cease  to  be  recog- 
nized, that  is  to  sa}',  the  sensations  which  they  cause  become 
fused.  Just  before  they  disappear  they  give  a  peculiar  dis- 
agreeable roughness  to  the  sound.  The  pleasure  given  by 
musical  sounds  dei)ends  largely  on  the  absence  of  this  in- 
complete fusion  of  sensations. 

Corresponding  to  entoptic  phenomena  there  are  various 
entotic  piienomena,  sensations  or  modifications  of  sensations 
originating  in  the  tympanum  or  in  the  labyrinth  ;  moreover 
sensations  of  sound  may  rise  in  the  auditory  nerve  or  in  the 
brain  itself,  without  any  vibration  whatever  falling  on  the 
labyrinth. 

A  nditory  Judgments. 

In  seeking  for  the  cause  of  our  visual  sensations  we  inva- 
riably refer  to  the  external  w(Mld.  The  sensation  caused  by 
a  direct  stimulation  of  the  optic  nerve  or  retina  by  a  blow 
or  a  galvanic  current,  we  identify  with  that  caused  by  a  flash 
of  light.  A  sensation  arising  from  any  stimulation  of  the 
left  side  of  our  retina  we  regard  as  caused  by  some  object 
on  the  right-hand  side  of  our  external  visible  world.  In  a 
similar  way,  but  to  a  less  extent,  we  project  our  auditory 
sensations  into  tiie  world  outside  us,  and  when  the  auditory 
nerve  is  affected  we  seek  the  cause  in  vibrations  starting  at 
a  greater  or  less  distance  from  us.  We  do  not  think  of  the 
sound  as  originating  in  the  ear  itself. 

This  mental  projection  of  the  sound  is  much  more  com- 
plete when  the  ear  is  stimulated  by  vibrations  reaching  it 
through  the  raembrana  tympani  than  when  the  vibrations 
are  conducted  l\y  the  solids  of  the  head  directly  to  the 
perilymph  of  the  labyrinth.  When  the  meatus  externus  is 
filled  with  fluid  and  tiie  vibrations  of  the  raembrana  tympani 
are  in  consequence  interfered  with,  the  apparent  outward- 
ness of  sounds  is  to  a  very  large  extent  lost ;  sounds,  how- 
ever caused,  seem  under  these  circumstances  to  arise  in  the 


SMELL.  747 

ear.  Hence  it  would  seem  tliat  our  judgment  of  the  objec- 
tiveness  of  sounds  is  largely  dependent  on  coincident  sen- 
sations derived  in  some  way  or  other  from  the  tympanum. 

When  sounds  impinge  on  the  solids  of  the  head,  as  when  a 
watch  is  held  between  the  teeth,  the  membrana  tympani  is  still 
functional.  Vibrations  are  conveyed  from  the  temporal  bone  to 
it  and  hence  pass  in  the  usual  way,  in  addition  to  those  trans- 
mitted directly  from  the  bone  to  the  perilymph. 

Onr  judgment  of  the  distance  of  sounds  is  very  limited. 
A  sound  whose  characters  we  know  appears  to  us  near  when 
it  is  loud,  and  far  off  when  it  is  faint.  A  blindfold  person 
will  be  unable  to  distinguish  between  the  difference  of  inten- 
sity produced  by  a  tuning-fork  being  held  before  him,  fii'st 
with  the  liroad  edge  of  tlie  fork  toward  him  and  then  with 
the  narrow  edge,  and  the  ditference  caused  by  the  removal 
of  the  tuning-fork  to  a  distance.  We  can  on  the  whole  bet- 
ter appreciate  the  distance  of  noises  than  of  musical  sounds. 

Our  judgment  of  the  direction  of  sounds  is  also  very  lim- 
ited. Our  chief  aid  in  this  is  the  position  in  which  we  have 
to  place  the  head  in  order  tliat  we  may  hear  the  sound  to 
the  l)est  advantage.  If  a  tuning-fork  be  held  in  the  median 
vertical  plane  over  the  head,  though  it  is  easy  to  recognize 
it  as  being  in  the  median  plane,  it  becomes  very  ditHcult 
when  the  eyes  are  shut  to  say  what  is  its  position  in  that 
plane,  i.  e.,  whether  it  is  more  towards  the  front  or  back  of 
the  head.  In  this  respect,  too,  our  appreciation  is  more 
accurate  in  the  case  of  noises  than  of  musical  sounds,  with 
the  exception  of  those  given  out  by  the  human  voice,  the 
direction  of  which  can  be  judged  better  than  even  that  of  a 
noise. 

Sp:c.  2.  Smell. 

lPhi/f<ioIogical  Anatomij  of  the  Nasal  Foasse. 

The  nasal  fossse  ai*e  two  irregular  cavities  which  commu- 
nicate anteriorly  with  the  air,  through  the  anterior  nares, 
and  posteriorly  with  the  pharynx  through  the  posterior  nares. 
The  fossje  are  partially  divided  into  upper,  middle,  and 
lower  aii"-j)assages  or  chambers  by  the  superior,  middle,  and 
inferior  tiirl'inated  bones.  The^'are  lined  by  the  Schneide- 
rian  or  pituitary  mucous  membrane,  which  is  continuous 
anieriorl}'  with  the  integument  and  posteriorly  with  the  mu- 


748 


HEARING,  SMELL,  AND  TASTE. 


cons  membrane  of  the  phaiynx ;  and  with  the  membrane 
lining  the  dncts  and  sinuses  connected  with  the  fossae.  At 
the  position  of  the  distribution  of  the  olfactory  nerve-fila- 
ments it  is  much  thicker,  more  vascular,  pigmented,  and 
lined  by  columnar  nucleated  epithelium  cells;  the  remain- 
ing portion  of  the  membrane  covering  the  fossae,  excepting 
near  the  anterior  nares,  is  lined  by  columnar  ciliateil  ei)i- 
thelium.  This  membrane  contains  racemose  mucous  glands, 
which  secrete  mucus  for  the  purpose  of  keeping  the  mem- 
brane constantly  moist,  which  is  a  condition  essential  to 
perfect  olfaction. 


Fig. 199. 


Fig  199. — Vertical  section  of  riglit  nasal  fossa, 
showing  outer  side  of  fossa.  1,  olfactory  tract;  2, 
olfactory  nerves;  3,  middle  turbinated  bone;  4, 
lower  turbinated  bone;  .5,  branches  from  the  fifth 
nerve.  Branches  of  the  fifth  are  also  shown  in  the 
anterior  portion. — After  Arnold. 


Fig.  200.— Cells  of  the  Olfactory  Mucous  Membrane,    a,  b,  c,  after  Schultze  ,  d,  e., 
f,  after  Lockhart  Clarke. 

The  olfactory  tract  is  a  prolongation  of  the  cerebrum, 
which  terminates  anteriorly  in  a  bull)ulous  expansion,  the 
olfactory  ganglion.  It  consists  principally  of  gray  matter. 
This  ganglion  rests  upon  the  cribriform  plate  of  the  eth- 
moid bone,  and  in  this  position  sends  about  twenty  filaments, 
which  consist  of  gray  matter  alone,  through  the  cribriform 
plate  to  be  distributed  to  the  pituitary  mem-brane  of  the 
upper  third  of  the  sei)tum  nasi,  the  upper  portion  of  tiie 
roof  of  the  nose,  the  superior,  and  a  portion  of  the  middle 


SMELL.  749 

turbinated  bones.  (Fig.  109.)  The  whole  surface  correspond- 
ing to  the  distribution  of  tlie  olfactory  nerves  is  colored 
brownish  by  the  pigment  in  the  epithelial  cells  of  the  mucous 
glauds  and  membrane.  This  pigmented  region  is  called  the 
regio  offactoria,  and  is  the  essential  portion  of  the  nasal 
fossai  concerned  in  olfaction. 

According  to  Schultze  the  epithelium  of  the  i^egio  olfac- 
toria  is  of  two  kinds:  the  first  (Fig.  200,  a)  consists  of  yel- 
low nucleated  protoplasmic  cells,  which  have  a  cylindrical 
body  terminating  at  its  free  extremity  as  a  squared  trun- 
cated surface  ;  the  other  extremity  of  the  body  js  stretched 
out  as  a  filamentous  prolongation,  which  expands  into  a 
triangular  plate  as  it  approaches  the  submucous  tissue. 
From  the  base  of  this  plate  a  number  of  filaments  are  given 
off,  which  are  prolonged  into  the  submucous  tissue.  The 
second  variety  of  epithelium  cells  (( )  is  found  at  the  borders 
of  tiie  7'egio  olfacloria,  The^'  are  similar  to  those  just  de- 
scribed, excepting  that  their  free  surface  is  covered  with 
cilia.  Between  the  epithelium  cells  the  olfactory  nerves 
terminate.  These  terminal  filaments  [b  f)  are  long  delicate 
structures,  which  have  a  number  of  fusiform  expansions 
along  their  course;  in  the  largest  expansion  is  found  an 
oval  nucleus.  The  terminal  filamtiils  are  called  the  olfac- 
tory cells.  As  yet  no  connection  between  the  subepithelial 
and  interepithelial  nerve  filaments  has  been  demonstrated. 
The  epithelial  cells  (d  and  e)  in  the  above  figure  are  shown 
connected  with  the  subepithelial  tissue.  The  fifth  nerve 
supplies  the  fossic  with  sensory  filaments.] 

Odorous  particles  present  in  the  inspired  air  passing 
through  the  lower  nasal  chambers  diffuse  into  the  upper 
nasal  chambers,  and  falling  on  the  olfactory  e[)ithelium  pro- 
duce sensory  impulses,  wliich.  ascending  to  tlie  brain,  give 
rise  to  sensations  of  smell.  We  may  presume  that  the  sen- 
sory impulses  are  origin-ited  by  the  contact  of  the  odorous 
particles  with  the  peculiar  rod-shaped  olfactory  cells  de- 
scribed by  Max  Sckullze  ;  but  we  are  as  much  in  the  dark 
about  this  matter  as  about  the  develo[)raent  of  visual  sen- 
sory impulses  in  the  rods  and  cones,  or  of  auditory  sensory 
impulses  in  the  organ  of  Corti. 

The  subsidiary  apparatus  of  smell  is  exceedingly  meagre. 
B}'  the  forced  nasal  inspiration,  called  snirfi ng,  we  draw  air 
so  forcibly  through  the  nostrils  that  currents  pass  up  into 
the  up[)er  as  well  as  the  lower  nasal  chambers  ;  and  thus  a 

63 


750  HEARING,    SMELL,    AND    TASTE. 

more  complete  contact  of  the  odorous  particles  with  the 
olfactory  membrane  than  that  supplied  by  mere  ditlusion  is 
provided  for. 

We  have  ever}^  reason  to  think  that  any  stimulus  applied 
to  the  olfactory  nerve  will  produce  the  sensation  of  smell ; 
but  the  proof  of  this  is  not  so  clear  as  in  the  case  of  the 
optic  and  auditory  nerves.  We  are,  however,  suliject  to 
sensations  of  smell  not  caused  by  oljective  odors.  The  ol- 
factor}^  membrane  is  the  only  part  of  the  body  in  which 
odors  as  such  can  give  rise  to  any  sensations  ;  and  the  sen- 
sations to  which  they  give  rise  are  always  those  of  smell, 
The  mucous  membrane  of  the  nose  is,  however,  also  an  instru- 
ment for  the  development  of  afferent  impulses  other  than 
the  specific  olfactory  ones.  Chemical  stimulation  of  the 
olfactor}'  membrane  by  pungent  sul)stances,  such  as  am- 
monia, gives  rise  to  a  sensation  distinct  from  that  of  smell, 
a  sensation  wiiich  affords  us  no  informatii  n  concerning  tiie 
chemical  nature  of  the  stimulus,  and  which  is  indistinguish- 
able from  the  sensations  produced  l\y  cliemical  stimulation 
of  other  parts  of  the  nasal  membrane  as  well  as  of  other 
surfaces  equally  sensitive  to  chemical  action.  It  is  probable 
that  these  two  kinds  of  sensations  tlius  arising  in  the  ol- 
factory membrane  are  conveyed  l»y  different  nerves,  the 
former  by  the  olfactory,  the  latler  l)y  the  fifth  nerve. 

For  the  development  of  smell  it  appears  necessary  that 
the  odorous  particles  should  be  conveyol  to  the  nasal  mem- 
brane in  a  gaseous  medium,  or  at  least  that  the  surface  of 
the  membrane  should  not  be  exposed  at  the  same  time  to 
tlie  action  of  fluids.  Thus  when  the  nostril  is  filled  with 
rose-water,  the  odor  of  roses  is  not  perceived  ;  and  simply 
filling  the  nostrils  with  distilled  water  suspends  for  a  time 
all  smell,  the  sense  returning  gradually  after  the  water  has 
been  removed;  the  water  apparently  acts  injuriously  on  the 
delicate  olfactory  cells. 

Each  substance  that  we  smell  causes  a  specific  sensation, 
and  we  are  not  only  able  to  recognize  a  multitude  of  dis- 
tinct odors,  but  also  to  distinguish  individual  odors  in  a 
mixed  smell. 

As  in  the  previous  senses,  we  i)roject  our  sensation  into 
the  external  world  ;  the  smell  appears  to  be  not  in  our  nose, 
but  somewhere  outside  us.  We  can  judge  of  the  position 
of  the  odor,  however,  even  less  definitely  than  we  can  of 
that  of  a  sound. 

The  sensation  takes  some  time  to  develop  after  the  contact 


TASTE.  751 

of  the  stimnlns  with  tlie  olfactory  membrane,  and  may  last 
very  long.  When  the  stimulus  is  repeated  the  sensation 
very  soon  dies  out;  the  sensory  terminal  organs  speedily 
become  exhausted.  Mental  associations  cluster  more  strongly 
round  sensations  of  smell  than  round  any  other  impressions 
we  receive  from  without.  And  reflex  efl'ects  are  very  fre- 
quent, many  people  fainting  in  consequence  of  the  contact 
of  a  few  odorous  particles  witli  their  olfactory'  cells. 

Apparently  the  larger  the  surface  the  more  intense  the 
sensation  ;  animals  with  acute  scent  having  a  proportionately 
large  area  of  olfactory  men-jbrane.  The  (piantity  of  material 
required  to  produce  an  olfactory  sensation  may  be,  as  in  the 
case  of  musk,  almost  immeasurably  small. 

When  two  ditferent  odors  are  presented  to  the  two  nostrils, 
an  oscillation  of  sensation  similar  to  that  spoken  of  in  bi- 
nocular vision  (p.  722)  takes  place. 

The  assertion  that  the  olfactory  nerve  is  the  nerve  of  smell  has 
been  disputed.  Cases  have  been  recorded^  of  persons  who  ap- 
peared to  have  possessed  the  sense  of  smell,  and  yet  in  whom  the 
olfactory  lobes  were  found  after  death  to  be  absent.  Magendie 
asserted  that  animals  could  still  smell  after  the  removal  of  the 
olfactory  lobes  ;  but  the  stimulus  which  he  applied  was  ammonia, 
in  no  way  a  test  of  smell.  Bifli,  operating  on  blind  puppies, 
came  to  the  conclusion  that  true  smell  disappeared  after  destruc- 
tion of  the  olfactory  lobes,  and  Prevost-  also  found  that  in  dogs 
smell  disappeared  after  section  of  the  olfactor}-  nerves.  On  the 
other  hand,  it  is  stated  that  section  or  injury  of  the  fifth  nerve 
causes  a  loss  of  smell  though  the  olfactory  nerve  remains  intact; 
but  in  these  cases  it  has  not  been  shown  that  the  olfactory  mem- 
brane remains  intact,  and  it  is  quite  possible  that,  as  in  case  of 
the  eye,  changes  may  take  place  in  the  nasal  membrane  as  the 
result  of  the  injury  to  the  fifth  nerve,  sutficient  to  prevent  its  per- 
formin<2j  its  usual  functions. 


Sec.  3.  Taste. 

\_PhymologicaJ  AnaAomij  of  the  Gudatory  Mucous  Membrane. 

Tlie  peripheral  organs  concerned  in  the  sense  of  taste  are 
localized  in  the  mucous  membrane  covering  the  dorsum  of 
the  tongue,  the  fauces,  soft  palate,  and  uvula,  and  possibly 

^  Bernard  CI.,  Svst.  Nerve.,  ii,  p.  228. 
•"^Archives  de  Sci.  Phys.  et  Nat.,  1871,  p.  209. 


752 


HEARING,    SMELL,    AND    TASTE. 


a  portion  of  tlie  upper  part  of  the  pharynx.  This  membrane 
is  analogous  in  strncLure  to  other  membranes  of  its  type, 
except  on  the  dorsum  of  the  tongue,  where  its  structure  is 
similar  to  that  of  the  integument.  At  this  position  it  con- 
sists of  a  coj^ium^  with  a  papillary  and  a  superficial  epithelial 
layer. 

The  structure  of  the  corium  is  .similar  to  that  of  the 
skin,  but  is  thinner  and  less  compact.  It  serves  as  a  point 
of  insertion  of  the  muscular  fibres  of  the  tongue. 
*  The  papillse  are  thickly  distributed  over  the  whole  dorsal 
surface,  but  more  particularly  marked  in  the  anterior  two- 
thirds.  They  project  as  minute  prominences,  which  give 
the  tongue  a  roughened,  cliaracteristic  appearance.  The 
papillye  are  of  two  kinds,  the  simple  and  compound.  The 
simple  papilli«  are  similar  to  those  found  in  tlie  skin  ;  they 
are  found  scattered  over  the  whole  dorsal  surface,  between 
the  compound  papillue.  They  are  most  numerous  in  the 
posterior  portion  of  the  organ.  The  compound  papillie  are 
of  three  varieties  :  the  papilUe  maximj^  or  circumvallat.e,  the 
papilUe  medi»  or  fungi  formes,  and  the  papilte  minimai  or 
tiliformes. 

The jMpillae  circumeallatae (Fig. 201 ),  which  ai-e  the  largest, 
are  about  eight  or  ten  in  number  and  form  a  V-shaped  row 

Fig.  201. 


Vertical  Section  of  the  Circumvallate  Papillse  (from  Kolliker).  J  o. — A,  the  pa- 
pillse; B,  the  surrounding  wall;  a,  the  epithelial  covering;  b,  thf  nerves  of  the 
papilla  and  wall  spreading  towards  the  surface  ;  c,  the  secondary  papillse. 


at  the  junction  of  the  middle  and  posterior  two-thirds  of 
the  tongue.  -They  consist  of  a  central  broad  papilla,  sur- 
rounded by  an  annular  ring  or  wall  of  al>out  the  same  ele- 
vation, and  ssparated  from  the  centre  ])apilla  by  a  circular 
fissure.  The  central  papilla,  as  well  as  the  surrounding 
wall,  is  covered  by  simple  papilUe.  Each  of  them  receives 
one  or  more  capillary  loops  and  nerve  filaments. 


TASTE. 


753 


The  papillae,  fangiformes  (Fig.  202)  are  found  principally 
on  the  tip  and  sides  of  the  tongue,  although  scattered 
sparsely  over  the  whole  of  the  anterior  two-tiiirds.  These 
are  so  named  from  their  fungiform  shape,  being  expanded 
at  their  free  extremit}^  and  projecting  on  a  sh.ort  thick 
pedicle.  They  are  covered  by  simple  papilhe,  and  contain 
plexuses  of  vessels  and  nerves. 

Fig.  202. 


■Ml 


Surface  and  Section  of  the  Fungiform  Papilke  (from  Kolliker,  and  after  Todd  and 
Bowman). — A,  the  surface  of  a  fuu^ifurm  papilla,  partially-  deuuded  of  its  epi- 
thelium, 3_5  .  a,  epithelium  ;  B,  section  of  a  fuugiform  papilla  with  the  bloodvessels 
injected  ;  a,  artery,  v,  vein  ;  c,  capillary  loops  of  simple  papillae  in  the  neighboring 
structure  of  the  tongue. 

The  jjajjiUde  filiformes  (Fig.  203)  are  by  far  the  most 
numerous,  and  are  found  thickly  distributed  over  the  entire 
surface  of  the  anterior  two-thirds  of  the  tongue.  They  are 
minute,  conical  in  shape,  and  generally  arranged  in  bi- 
penniform  rows,  which  are  more  or  less  parallel  with  the 
two  rows  of  papilhe  circumvallatie.  Their  free  surface  is 
covered  with  simple  papilht.  The  ei)ithelium  covering  them 
is  greatly  modified,  and  appears  in  the  form  of  hairlike  pro- 
cesses. (Fig.  203.)  These  processes  are  batlied  in  mucus, 
are  movaide,  and  have  a  general  iiudination  pointing  back- 
wards. The  existence  of  these  hairlike  i)roct'Sses  on  the 
filiform  papillae  suggests  that  this  variety  of  papilhe  is 
intimately  connected  with  the  tactile  sensii)ility  of  the 
tongue,  and  not  with  gustation.  In  carnivora  and  herbiv- 
ora  these  j)rocesse'S  are  of  a  horiiN  structure,  and  perform 
an  active  function  in  the  attrition  and  prehension  of  food. 
In  man  their  special  function  appears  through  their  intimate 
connection  with  the  tactile  sense,  to  guide  the  tongue  in  its 
variable  and  complicated  movements. 


^54 


HEARING,    SMELL,    AND    TASTE. 


The  ultimate  terminations  of  the  gustatory  nerves  are  yet 
enveloped   in    obscurity.       According    to    Engelmann,   the 


Fir;.   203. 


h    A 

A.  Vertical  section  near  the  middle  of  the  dorsal  surface  of  the  tongue  :  a  a,  fungi- 
form papilUe;  h,  filiform  papillae,  with  their  hairlike  processes;  c,  similar  ones  de- 
prived of  their  epithelium,  magnified  2  diameters. 

B.  Filiform  compound  papillae  :  a,  artery  ;  v,  vein  ;  c,  capillary  loops  of  the  secon- 
dary papillae  ;  h,  line  of  basement-membrane  ;  rf,  secondary  papillae,  deprived  of  e  e, 
the  e|)ithelium  ;  /,  hairlike  processes  of  epithelium  capping  the  simple  papillae,  mag- 
nified 25  diameters;  gr,  separated  nucleated  particles  of  epithelium,  magnified  300 
diameters. 

1,  2,  hairs  found  on  the  surface  of  the  tongue;  3,  4,  5,  ends  of  hairlike  epithelial 
processes,  showing  varieties  in  the  imbricated  arrangement  of  the  particles,  but  in 
all  a  coalescence  of  tlie  particles  towards  the  point.  5,  incloses  a  soft  hair,  magnified 
160  diameters.— After  Todd  and  Bowman. 

glossopharyngeal  nerves  terminate  in  flask-shaped  organs, 
which  are  termed  the  gustatory  hulha  or  taste  buds.     (Fig. 


TASTE. 


755 


204.)  These  bulbs  are  found  principally  in  the  papillary 
surface  of  the  wall  of  the  circumvallate  papilhii.  Tliey  are 
also  found  in  the  funoiform  papillae,  but  are  less  numerous. 
Tiiey  consist  of  a  flask-shaped  fundus,  which  rests  upon  the 
subepithelial  tissue,  and  a  mouth  which  opens  upon  the 
surface  of  the  mucous  menilirane.  The  mouth  is  known  as 
the  gustatory  pore.  The  fundus  of  the  flask  is  composed  of 
two'varieties  of  cells  :  the  ouler  or  invesfing  cells  are  fusi- 
form, nucleated,  and  oranular,  placed  parallel  and  arranged 
concentrically  in  a  direction  from  the  base  to  the  neck; 
they  thus  form  a  wall  which  incloses  elongated  nucleated 
cells  with  filamentous  processes,  which  extend  through  the 
gustatory  pore  and  project  as  very  finely  pointed  or  trun- 
cated  extremities.     These  inner  cells   are  called  the  guda- 


FlG.  204. 


Gustatory  Bulbs  from  the  Lateral  Gustatory  Organ  of  the  Eabbit.     Mag.  4o0  diain. 

torij  cells,  and  are  supposed  to  be  the  essential  terminal 
elements  concerned  in  gustation.  Their  relation  to  thegus- 
tatoiy  nerves  has  not  as  yet  been  clearly  demonstrated,  but 
they  aie  evidently  connected  with  the  ganglionic  plexuses 
of  nerve-fil»res  at  the  papillary  bases.  The  gustatoiy  nerves 
are  also  S!ip[)08ed  to  terminate  in  the  epithelium  of  the  pa- 
pillae.] 

The  word  taste  is  frequently  used  when  the  word  smell 
ought  to  be  emi)loyed.  \Ve  speak  of  '"tasting"  odoriferous 
substances,  sucli  as  an  onion,  wines,  etc..  when  in  reality  we 
onh'  smell  them  as  we  hold  them  in  our  mouth.  ;  this  is 
proved  by  the  fact  that  the  so-called  taste  of  these  things 
is  lost  wMien  the  nose  is  held,  or  the  nasal  memltranc  ren- 
dered inert  b}-  a  catarrh. 


756         HEARING,  SMELL,  AND  TASTE. 

The  terminal  organs  of  the  sense  of  taste  thus  more 
strictly  defined,  are  the  endings  of  the  glosso-pharyngeal  and 
lingnal  nerves  in  the  mucous  membrane  of  the  tongue  and 
palate,  those  nerves  serving  as  the  special  nerves  of  taste. 
The  subsidiary  apparatus  is  confined  to  the  tongue  and  lii)s, 
which  by  their  movements  assist  in  bringing  the  sapid  sub- 
stances into  contact  with  the  mucous  membrane  of  the 
mouth. 

The  so-called  gustatory  buds  cannot  be  regarded  as  specific 
organs  of  taste,  since  tbey  occur  in  places  (e.  (/.,  epiglottis)  wholly 
devoid  of  taste. 

Though  we  can  hardly  be  said  to  project  our  sensation  of 
taste  into  the  external  world,  we  assign  to  it  no  subjective 
localization.  When  we  place  quinine  in  our  mouth,  the  re- 
sulting sensation  of  taste  gives  us  no  information  as  to  where 
the  quinine  is,  though  we  may  learn  that  by  concomitant 
general  sensations  arising  in  tlie  buccal  mucous  membrane. 

We  recognize  a  multitude  of  distinct  tastes,  Nvhich  may  be 
broadly  classified  into  acid,  saline,  bitter,  and  sweet  tastes. 
Sapid  substances  have  the  power  of  producing  these  sensa- 
tions by  virtue  of  their  chemical  nature.  But  other  stimuli 
will  also  give  rise  to  sensations  of  taste.  When  the  tongue 
is  tapped,  a  taste  is  felt;  and  when  a  constant  current  is 
passed  through  the  mouth,  an  alkaline,  or,  according  to 
Vintschgau,'  a  bitter  metallic  taste  is  developed  when  the 
anode,  and  an  acid  taste  when  the  kathode  is  placed  on  the 
tongue.  It  is  prol>able  that  in  these  cases  the  terminal  or- 
gans are  indirectly  affected  by  the  current.  When  hot  or 
pungent  substances  are  introduced  into  the  mouth,  sensa- 
tions of  general  feeling  are  excited,  which  obscure  any 
strictly  gustatory  sensations  which  may  be  present  at  the 
same  time. 

Though  analogy  would  lead  us  to  suppose  that  a  stimulus 
applied  to  any  part  of  the  course  of  the  real  gustatory  fibres 
of  either  the  glosso-pharyngeal  or  lingual  nerves,  would 
give  rise  to  a  sensation  of  taste  and  nothing  else,  the  proof 
is  not  forthcoming;  since  both  these  nerves  are  mixed 
nerves  containing  other  aflTerent  fibres  as  well  as  those  of 
taste. 

When  the  constant  current  is  used  as  a  means  of  exciting 

^  Pfluger's  Archiv,  xx  (1879j,  p.  81. 


TASTE.  757 

taste,  gustatory  sensations  are  fonnd  to  he  developed  in  tlie 
back,  edges,  and  tip  of  the  tongne.  the  soft  palate,  the  an- 
terior pillar  of  the  fauces,  and  a  small  tract  of  the  posterior 
part  of  the  hard  palate.  They  are  absent  from  the  anterior 
and  middle  dorsum,  and  under  surface  of  the  tongue,  the 
front  portion  of  the  hard  palate,  the  posterior  pillars  of  the 
fauces,  the  gums,  and  the  lips  Sapid  substances  ore  un- 
suitable as  a  test  for  this  purpose,  on  account  of  their  rapid 
diti'usion.  Bitter  substances  produce  most  effect  when 
placed  on  the  back  of,  and  sweet  substances  when  placed  on 
the  tip  of  the  tongue  ;  but  the  tasting  power  of  the  tip  of 
the  tongue  varies  very  much  in  different  individuals,  and  in 
mauy  seems  almost  entirely  absent.'  It  is  said  that  acids 
arc  best  appreciated  by  the  edge  of  the  tongue. 

It  is  essential  for  the  development  of  taste,  that  the  sub- 
stance to  be  tasted  should  be  dissolved  :  and  the  effect  is  in- 
creased by  friction.  The  larger  the  surface  the  more  intense 
the  sensation.  The  sensation  takes  some  time  to  develop, 
and  endures  for  a  long  time,  though  this  may  be  in  fact  due 
to  the  stimulus  remaining  in  contact  with  the  terminal  or- 
gans. A  temperature  of  about  40°  is  the  one  most  favorable 
for  the  production  of  the  sensation.  At  temperatures  much 
above  or  below  this,  taste  is  much  impaired.  The  nerves  of 
taste  are,  as  we  have  said,  the  glosso-pharyngeal  and  the 
lingual  or  gustatory.  The  former  supplies  the  back  of  the 
tongue,  and  section  of  it  destroys  taste  in  that  region.  The 
latter  is  distributed  to  the  front  of  the  tongue,  and  section 
of  it  similarly  deprives  the  tip  of  the  tongue  of  taste.  There 
is  no  reason  for  doubting  that  the  gustatory  fibres  in  the 
glosso-pharyngeal  are  proper  fibres  of  that  nerve  ;  but  it  has 
been  urged  by  many  that  the  gustatory  fibres  of  the  lingual 
are  derived  from  the  chorda  tympani.  and  that  those  fibres 
of  the  lingual  which  come  from  the  fifth  are  employed  ex- 
clusively in  the  sensations  of  touch  and  feeling. 

The  arguments  in  favor  of  this  latter  view  are  as  follows : 
Cases  have  been  observed  in  which  the  fifth  nerve  has  been  de- 
stroyed in  the  cranium,  and  yet  taste  in  the  front  of  the  tongue  has 
not  been  lost.  Cases  have  been  observed  where  the  chorda  tj'm- 
pani  has  been  diseased,  or  injured  in  the  tympanum,  and  where 
taste  has  been  impaired.  It  is  asserted  that  when  the  lingual  is 
divided  above  the  junction  of  the  chorda,  taste  in  front  of  the 
tongue  is  not  lost,  'while  it  disappears  alter  section  of  the  united 

'  Cf.  Vintschgau,  Pfliiger's  Archiv,  xix  (1879),  p.  236. 
64 


758  FEELING    AND    TOUCH. 


lin,2;ual  and  chorda.  It  is  also  stated  that  the  glosso-pharyngeal 
having  been  divided,  and  taste  in  consequence  confined  to  the 
front  part  of  the  tongue,  subsequent  section  of  tlie  chorda  within 
the  tympanum  has  removed  taste  altogether.  On  the  other  hand, 
cases  have  been  observed  where  the  fifth  was  alone  diseased  and 
yet  taste  was  lost  (in  front  of  the  tongue);  and  it  is  moreover 
urged  that  while  stimulation  of  the  central  end  of  a  divided 
chorda  gives  rise  to  no  sensation  of  taste,  stimulation  of  an  un- 
divided chorda  might  give  rise  to  such  sensations  by  simply  pro- 
moting a  flow  of  saliva,  and  that  division  of  the  chorda  might 
affect  taste  by  interfering  with  the  normal  flow  of  saliva.  And 
even  if  the  chorda  contain  gustatory  fibres  these  might  have  their 
ultimate  origin  in  the  fifth,  coming  from  that  nerve  to  the  facial 
by  the  spheno-palatine  ganglion  and  superficial  petrosal  nerve. 


CHAPTER   IV. 

EEELmG  AKD  TOUCH. 

Sec.  1.  General  Sensibility  and  Tactile  Perceptions. 

We  have  taken  the  foregoing  senses  first  in  the  order  of 
discussion  on  account  of  their  being  eminently  specific. 
The  eye  gives  us  onl}^  visual  sensations,  the  ear  only  audi- 
tory sensations.  The  sensations  are  produced  in  each  case 
by  specific  stimuli;  tlieeye  is  only  affected  l)y  light  and  the  ear 
by  sound.  Moreover,  the  information  they  afford  us  is 
confined  to  the  external  world  ;  they  tell  us  nothing  about 
ourselves.  The  various  visual  sensations  vvhicli  arise  in  our 
retina  are  referred  by  us  not  to  the  retina  itself,  but  to  some 
real  or  imaginar3'  ol)ject  in  the  world  without  (including  as 
part  of  the  external  world  such  portions  of  our  own  bodies 
as  are  visil)le  to  ourselves).     Sucii,  also,  witli  diminishing 


GENERAL    SENSIBILITY.  759 

precision,  is  the  information  gained  by  liearing,  taste,  and 
smeli. 

All  the  other  afferent  nerves  of  the  body,  centripetal  im- 
pulses along  which  are  able  to  affect  our  consciousness,  are 
the  means  of  conveying  to  us  information  concerning  our- 
selves. The  sensations,  arising  in  them  from  the  action  of 
various  stimuli,  are  referred  by  us  to  appropriate  parts  of 
our  own  body.  ^Vhen  any  bod}'  comes  in  contact  with  our 
finger,  we  know  that  it  is  our  linger  which  has  been  touched ; 
from  the  resultant  sensation  we  not  only  learn  the  existence 
cf  certain  qualities  in  the  object  touched,  but  we  also  are 
led  to  connect  the  cognizance  of  those  qualities  with  a  par- 
ticular part  of  our  own  body. 

Like  the  more  specific  senses  previously  studied,  the  sen- 
sations of  which  we  are  now  speaking,  and  which  may  be 
referred  to  under  the  name  of  touch,  using  that  word  for 
the  present  in  a  wide  meaning,  require  for  tlieir  production 
terminal  organs  (see  p.  504)  ;  and  the  chief  but  not  exclu- 
sive organ  of  touch  is  to  be  found  in  the  epidermi.s  of  the 
skin  jind  certain  underl3'ing  nervous  structures.  For  the 
development  of  specific  tactile  sensations  these  terminal 
organs  are  as  essential  as  are  the  terminal  organs  of  the  eye 
for  sight  or  of  the  ear  for  hearing.  Contact  of  the  skin 
with  a  hard  or  with  a  hot  body  gives  rise  to  a  distinct 
sensation,  whereb}-  we  recognize  that  we  have  touched  a 
bard  or  a  hot  body.  But  the  api)lication  of  either  body  or 
of  any  other  stimulus  to  a  nerve-trunk  gives  rise  to  a  sensa- 
tion of  gejieral  feeling  only,  corresponding  to  the  simple 
sensation  of  light  which  is  produced  by  direct  stimulation 
of  the  optic  nerve.  We  have  no  more  tactile  jjerception  of 
a  body  wliicli  is  in  contact  with  a  nerve-trunk  than  we  could 
have  visual-  perception  of  any  luminous  object,  the  rays 
proceeding  from  which  were  strong  enough  to  excite  sen- 
sor}-  impulses  when  directed  on  to  tlie  optic  nerve  instead 
of  on  to  the  retina,  supposing  such  a  thing  to  be  possible. 
It  is  further  characteristic  of  these  ordinary  nerves  of  gen- 
eral feeling,  that  the  sensations  caused  by  an}'-  stimulation 
of  them  beyond  a  certain  degree  develop  that  state  of  con- 
sciousness which  we  are  in  the  habit  of  speaking  of  as 
"  pain."  Putting  aside  the  general  feeling  which  many 
parts  of  the  eye  possess,  a  very  strong  luminous  stimula- 
tion of  the  retina  is  required  to  produce  a  sensation  of  pain, 
if  indeed  it  can  be   at  all  brought  about ;  whereas  a  very 


760  FEELING    AND    TOUCH. 

moderate  stimulation  of  the  skin,  and  almost  every  stimula- 
tion of  an  ordinary  nerve-trunk,  is  said  by  us  to  be  painful. 

Though  ihe  skin  is  the  cliief  organ  of  touch,  the  mucous 
membrane  lining  the  various  passages  of  tlie  body  also 
serves  as  an  instrument  for  the  same  sense,  but  only  for  a 
short  distance  from  tiie  respective  orifices.  We  can  recog- 
nize hard  or  hot  bodies  with  our  lips  or  mouth,  but  a  hot 
liquid  when  it  has  reached  the  oesophagus  or  stomach,  sim- 
ply gives  rise  to  a  sensation  of  pain.  We  cannot  distin- 
guish tlie  sensation  caused  by  it  from  the  sensation  caused 
b\'  a  drauglit  of  a  too  acid  fluid. 

Tlie  stimuli  which,  when  applied  to  the  skin,  give  rise  to 
tactile  perceptions  are  of  two  kinds  only:  (1)  mechanical, 
that  is,  the  contact  of  bodies  with  varying  degrees  of  pres- 
sure;  and  (2)  thermal,  i.  e,,  the  raising  or  lowering  of  the 
temperature  of  the  skin  by  the  approach  or  contact  of  hot 
or  cold  bodies.  We  can  judge  of  the  weight  and  of  the 
temperature  of  a  body  because  we  can,  through  touch,  per- 
ceive how  much  it  presses  when  allowed  to  rest  on  our  skin 
or  how  hot  it  is.  But  we  can  through  touch  derive  no  other 
perceptions  and  form  no  other  judgments.  An  electric 
shock  sent  through  the  skin  will  give  rise  to  a  sensation, 
but  the  sensation  is  an  indefinite  one,  because  the  electric 
current  acts  not  on  the  terminal  organs  of  touch,  but  on  the 
fine  nerve-branches  of  the  skin.  We  cannot  distinguish  the 
sensation  so  caused  from  a  mechanical  prick  of  similar  in- 
tensity, we  cannot  perceive  that  the  sensation  is  caused  by 
an  flectric  current.  Similarly  certain  chemical  substances, 
such  as  a  strong  acid,  will  give  rise  to  a  sensation,  but  we 
cannot  perceive  the  acid,  we  can  form  no  judgment  of  its 
nature  such  as  we  could  if  we  tasted  it;  and  if  the  acid 
does  not  permeate  the  skin  so  as  to  act  directly  and  chemi- 
cally on  the  nerve-fibres,  we  cannot  distinguish  the  acid 
from  any  other  liquid  giving  rise  to  the  same  simple  contact 
impressions.  The  terminal  organs  of  the  skin  are  such  as 
are  onl}'  affected  by  pressure  or  by  temperature.  Con- 
versely pressure  or  a  variation  in  temperature  brought  to 
bear  on  a  nerve-trunk,  instead  of  on  the  terminal  organs, 
produces  no  specific  tactile  sensations  of  pressure  or  tem- 
perature, but  merely  general  sensations  of  feeling  rapidly 
rising  into  pain. 


TACTILE    SENSATIONS.  761 

Sec.  2.  Tactile  Sensations. 
Sen^atioiis  of  Pressure. 

As  with  visual,  so  with  tactile  and  indeed  with  nil  other 
sensations,  the  intensity  of  the  sensation  maintains  that 
general  rehition  to  the  intensity  of  the  stimulus  which  we 
spoke  of  at  p.  690  as  being  formulated  under  Wei)er's  law. 
We  can  distinguish  the  difference  of  pressure  between  one 
and  two  grams  as  readily  as  we  can  that  between  ten  and 
twenty  or  one  hundred  and  two  hundred. 

Wlien  two  sensations  follow  each  other  in  the  same  si)ot 
at  a  surticiently  short  interval  they  are  fused  into  one  ;  thus, 
if  the  linger  be  brouglit  to  bear  lightly  on  a  lotating  card 
having  a  series  of  holes  in  it,  the  holes  cease  to  be  felt  as 
such  when  they  follow  each  other  at  a  rapidity  of  about 
1.500  in  a  second.  The  vibrations  of  a  cord  cease  to  be  ap- 
preciable by  touch  when  they  reach  the  same  rapidity. 
When  sensations  are  generated  at  points  of  the  skin  too 
close  together  they  become  fused  into  or»e  ;  but  to  this  point 
we  shall  return  presently. 

The  sensation  caused  by  pressure  is  at  its  maximum  soon 
after  its  beginning,  and  thenceforward  diminishes.  The 
more  suddenly  the  pressure  is  increased,  the  greater  the 
sensation;  and  if  the  increase  be  sutticiently  gradual,  even 
very  great  pressure  may  be  applied  without  giving  rise  to 
an}'  sensation.  A  sensation  in  any  spot  is  increased  by 
contrast  with  surrounding  areas  not  sulject  to  pressure. 
Thus  if  the  finger  be  dipi)ed  into  mercury  the  pressure  will 
be  felt  most  at  the  surface  of  the  fluid  :  and  if  the  finger  be 
drawn  up  and  down,  the  sensation  caused  will  be  that  of  a 
ring  moving  along  the  finger. 

All  parts  of  the  skin  are  not  equally  sensitive  to  pressure  ; 
small  ditferences  of  simple  pressure  are  more  readily  appre- 
ciated when  brought  to  bear  on  tiie  palmar  surface  of  the 
finger,  or  on  the  forehead,  than  on  the  arm  or  on  the  sole  of 
the  foot.  Jn  mak-ing  these  detei-minations  all  muscular 
movement  should  be  avoided  in  order  to  eliminate  the  mus- 
cular sense,  of  which  we  shall  speak  presently  ;  and  the  area 
stimulated  should  be  as  small  and  the  surfaces  in  contact  as 
uniform  as  possible.  In  a  similar  manner  small  consecutive 
variations  of  pressure,  as  in  counting  a  pulse,  are  more 
readily  appreciated  by  certain  parts  of  the  skin  than  by 
others ;  and   the   minimum   of  pressure   which   can  be  felt 


762  FEELING     AND    TOUCH. 

fliffeis  in  different  parts.  In  all  cases  variations  of  pressure 
are  more  easily  distinguished  when  they  are  successive  than 
when  they  are  simultaneous. 

Sensations  of  Temperature. 

When  the  temperature  of  the  skin  is  raised  or  lowered  in 
any  spot  we  receive  sensations  of  heat  and  cold  respec- 
tively, and  by  these  sensations  of  the  temperature  of  our 
own  skin  we  form  judgments  of  the  temperature  of  bodies 
in  contact  with  it.  Bodies  of  exactly  the  same  temperature 
as  the  region  of  the  skin  to  which  they  are  applied  produce 
no  such  thermal  sensations,  though  we  can,  from  the  very 
absence  of  sensations,  form  a  judgment  as  to  their  temper- 
ature;  and  good  conductors  of  heat  appear  respectively 
hotter  and  colder  than  bad  conductors  raised  to  the  same 
temperature. 

We  may  consider  the  skin  as  having  at  any  given  time  and  in 
any  given  spot  a  normal  temperature  at  which  the  sensation  of 
temperaeure  is  at  zero  ;  for  under  ordinary  circumstances  we  are  not 
directly  conscious  of  the  temperature  of  our  skin  ;  it  is  only  when 
the  normal  temperature  at  the  spot  is  raised  or  lowered  that  we 
have  a  sensation  of  heat  or  cold  respectively.  This  normal  tem- 
perature may  be  at  the  same  time  difterent  in  different  parts  of  the 
body  ;  thus  at  a  time  when  neither  the  forehead  nor  the  hand  are 
giving  rise  to  any  sensation  of  temperature,  we  may,  by  putting 
the  hand  to  the  forehead,  frequently  feel  the  former  hot  or  cold 
because  the  normal  temperatures  of  the  tw^o  ]iai-ts  differ.  The 
normal  temperature  in  any  spot  may  also  vary  froiii  time  to  time. 
Thus  when  the  hand  is  placed  in  a  warm  medium  for  some  time, 
the  sensation  of  warmth  ceases  ;  a  new  normal  temperature  is 
established  with  the  zero  of  sensation  at  a  higher  level,  a  depres- 
sion or  elevation  of  this  new  temperature  giving  rise  however  as 
before  to  sensations  of  heat  and  cold  respectively.  That  it  is  the 
changed  condition,  and  not  the  change  itself,  of  which  we  are 
conscious  is  shown  by  the  fact  that  \vhen  a  portion  of  skin  is 
cooled,  by  brief  contact  with  a  cold  metal  for  instance,  we  are 
still  conscious  of  the  spot  being  cold  after  the  cooling  agent  has 
been  removed,  that  is  at  a  time  when  the  cooled  spot  is  in  reality 
being  heated  by  the  surrounding  warmer  tissues.^ 

The  change  in  the  temperature  of  the  skin  necessary  to 
produce  a  sensation  must  have  a  certain  rapidity  ;  and  the 
more   gradual  the   change   the  less   intense  the  sensation. 

1  Hering,  Wien.  Sitzungsbericht,  Ixxv  (1877). 


TACTILE    SENSATIONS.  763 

Tlie  repeated  dipping  of  the  hand  into  hot  water  produces 
a  greater  sensation  than  when  the  hand  is  allowed  to  remain 
all  tlie  time  in  the  water,  though  in  the  latter  case  the  tem- 
perature of  the  skin  is  most  affected.  Tlie  same  effect  of 
contrast  is  seen  in  these  sensations  as  in  those  of  pressure. 
We  can  with  some  accuracy  distinguish  variations  of  tem- 
perature, especially  those  lying  near  the  normal  temperature 
of  the  skin.  These  sensations,  in  fact,  follow  Weber's  law, 
though  apparently  sensations  of  slight  cold  are  more  vivid 
than  those  of  slight  heat,  the  range  of  most  accurate  sensa- 
tion seeming  to  lie  between  27^  and  33°.  The  regions  of 
the  skin  most  sensitive  to  variations  in  temperature  are  not 
identical  with  those  most  sensitive  to  variations  in  pressure. 
Thus  the  cheeks,  eyelids,  temples,  and  lips  are  more  sensi- 
tive than  the  hands.  The  least  sensitive  p;ir{s  are  the  legs, 
and  front  and  back  of  the  trunk. 

The  simplest  view  which  can  be  taken  with  regard  to  the  dis- 
tinction between  ])rcssure  and  temperature  sensations  is  to  sup- 
pose that  two  distinct  kinds  of  terminal  organs  exist  in  the  skin, 
one  of  which  is  affected  only  by  pressure,  and  the  other  only  by 
variations  in  temperature  ;  and  tliat  the  two  kinds  of  peripheral 
organs  are  connected  with  diffurent  parts  of  the  central  sensory 
organs  by  separate  nerve-fibres.  Certain  pathological  cases  have 
been  quoted^  as  showing  not  only  that  this  is  the  case,  but  that 
the  two  sets  of  fibres  pursue  ditlerent  courses  in  the  spinal  cord. 
Thus,  in  certain  diseases  or  injuries  to  the  brain  or  si)in:il  cord, 
h3'pertesthesia  as  regards  temperature  has  been  observed  unac- 
companied by  an  augmentation  of  sensitiveness  to  pressure  ;  and 
conversely  instances  have  been  seen  where  the  patient  could  tell 
when  he  was  touched,  but  could  not  distinguish  between  hot  and 
cold.  Against  this  view  it  might  be  urged  that  these  pathological 
cases  have  not  received  the  critical  examination  which  they  de- 
mand ;  and  that  there  are  facts  which  show  a  close  dependence 
between  the  sensations  of  pressure  and  temperature.  When  each 
stimulus  is  brought  to  bear  on  a  very  limited  area,  the  two  sen- 
sations are  frequently  confounded,  and  Weber  has  pointed  out 
that  cold  bodies  feel  heavier  than  hot  bodies  of  the  same  weight. 
Xo  case  has  yet  been  recorded  where  a  hot  body,  a  cold  bod}',  and 
a  body  of  the  tempetature  of  the  skin,  all  felt  exactly  alike,  when 
each  was  api)lied  with  the  same  pressure  ;  and  the  cases  Avhere  a 
hot  sponge  or  spoon  was  felt  (because  it  was  hot),  and  yet  the 
sensation  v/as  confounded  with  one  of  pressure,  indicate  that  the 
same  terminal  organs  are  affected  by  both  stimuli. 

^  Brown-Seqnard,  Jonrn.  d.  Phvs.,  1863,  vol.  viii ;  Archives  de  Phys., 
18G8,  vol.  i. 


764  FEELING    AND    TOUCH. 

With  regard  to  the  nature  of  the  terminal  organ?  in  the 
skin,  it  may  he  stated  that  the  coiyuscula  tactus  were  re- 
garded by  their  discoverers  as  specific  organs  of  touch.  The 
end-bull>s  of  Krause  luive  also  been  regarded  in  tiie  same 
light.  But  the  evidence  we  possess  concerning  this  matter 
is  at  present  inconclusive. 


Sec.  3.  Tactile  Perceptions  and  Judgments. 

Wiien  a  bod}-  presses  on  any  spot  of  our  skin,  or  when 
tlie  temperature  of  the  skin  at  tliat  spot  is  raised,  we  are  not 
only  conscious  of  pressure  or  of  heat,  but  perceive  tliat  a 
particular  part  of  our  body  has  been  touched  or  heated.  We 
refer  the  sensations  to  their  place  of  origin,  and  we  thus  by 
touch  perceive  the  relations  to  ourselves  of  the  body  which 
gives  rise  to  the  tactile  sensations,  in  the  same  way  as  in 
our  visual  perception  of  external  objects  we  refer  to  external 
nature  the  sensations  originating  in  certain  parts  of  the 
retina.  When  we  are  touched  on  the  finger  and  on  the  back 
we  refer  the  sensations  to  the  finger  and  to  the  back  re- 
spectively, and  when  we  are  touched  at  two  i)laces  on  the 
same  finger  at  the  same  time  we  refer  the  sensations  to  two 
points  of  the  finger.  In  this  way  we  can  localize  our  sensa- 
tions, and  are  thus  assisted  in  perceiving  the  space  relations 
of  objects  with  which  we  come  in  contact. 

Tliis  power  of  localizing  pressure-sensations  varies  in  dif- 
ferent i)arts  of  the  body.  The  following  tal)le  from  Weber 
gives  the  distance  at  which  two  points  of  a  pair  of  compasses 
must  be  held  apart,  so  that  when  the  two  points  are  in  con- 
tact with  the  skin  the  two  consecpient  sensations  can  be 
localized  with  sutlicient  accuracy  to  be  referred  to  two  points 
of  the  body,  and  not  confounded  together  as  one: 


Tip  of  tongue,         .... 

1.1mm. 

Palm  of  last  phalanx  of  finger, 

2.2     " 

Palm  of  second     ''             ''     . 

.'       4^4     " 

Tip  of  nose, 

.       6.5     " 

White  part  of  hps, 

.       8.8     " 

Back  of  second  phalanx  of  finger, 

.     11.1     " 

Skin  over  malar  bone,     . 

.     15.4     " 

Back  of  hand,          .... 

.     29.8     " 

Forearm, 

.     39.6     " 

Sternum, 

.     44.0     ^' 

Back, 

.     66.0     " 

TACTILE    PERCEPTIONS    AND    JUDGMENTS.         765 

And  a  very  similar  distribution  has  been  observed  in  ref- 
erence to  tiie  localization  of  sensations  of  temperature.  As 
a  general  rule  it  may  be  said  that  the  more  mobile  parts  are 
those  hy  which  we  can  thus  discriminate  sensations  most 
readily.  The  lighter  tiie  pressure  used  to  give  rise  to  the 
sensations,  the  more  easily  are  two  sensations  distinguisiied; 
thus  two  points  which,  when  touching  lightly,  appear  as 
two,  may,  when  firmly  pressed,  give  rise  to  one  sensation 
ou\y.  The  distinction  between  the  sensations  is  obscured 
by  neighboring  sensations  arising  at  the  same  time.  Thus 
two  points  brought  to  bear  within  a  ring  of  heav}-^  metal 
pressing  on  the  skin  are  readily  confused  into  one.  And  it 
need  hardly  be  said  tluit  these  tactile  perceptions,  like  all 
other  perceptions,  are  immensel}-  increased  by  being  exer- 
cised. 

Our  ''field  of  touch,"  if  we  may  be  allowed  the  expression,  is 
composed  of  tactile  areas  or  units,  in  the  same  way  that  our  Held 
of  vision  is  composed  of  visual  areas  or  miits.  The  tactile  sensa- 
tion is,  like  the  visual  sensation,  a  symbol  to  us  of  some  external 
event,  and  we  refer  the  sensation  to  its  appropriate  place  in  the 
field  of  touch.  All  that  has  been  said  (p.  093)  concerning  the 
subjective  nature  of  the  limits  of  visual  areas  applies  eqiially  well, 
inuUitis  mi(t(nuli.<.  to  tactile  areas.  AVhen  two  points  of  the  com- 
passes are  felt  as  two  distinct  sensations  it  is  not  necessary  that 
two  and  only  two  nerve-fibres  should  be  stimulated  ;  all  that  is 
necessar}^  is  that  the  two  cerebral  sensation-areas  should  not  be 
too  completely  fused  together.  The  imj)rovement  by  exercise  of 
the  sense  of  touch  must  be  explained  not  by  an  increased  devel- 
opment of  the  terminal  organs,  not  by  a  growth  of  new  nerve- 
fibres  in  the  skin,  but  by  a  more  exact  limitation  of  the  sensa- 
tional areas  in  the  brain,  by  the  development  of  a  resistance 
which  limits  the  radiation  taking  place  from  the  centres  of  the 
several  areas. 

]>y  a  multitude  of  simultaneous  and  consecutive  tactile 
sensations  thus  converted  into  perceptions  we  are  able  to 
make  ourselves  acquainted  with  the  form  of  external  objects. 
We  can  tell  b}-  variations  of  pressure  whether  a  surface  is 
rough  or  smooth,  plane  or  cuj-ved,  what  variations  of  sui-- 
face  a  body  presents,  and  how  far  it  is  heavy  or  light  ;  and 
from  the  information  thus  gained  we  build  up  judgments  as 
to  the  form  and  nature  of  ol'jects.  judgments  however  which 
are  most  intimately  bound  up  with  visual  judgments,  the 
knowledge  derived  b}-  one  sense  cori'ecting  ajid  completing 
that  obtained  by  the  other.  As  in  other  senses  so  in  this, 
our  sensations  may  mislead  us  and  cause  us  to  form  erro- 


766  FEELING    AND    TOUCH. 

neons  judgments.  This  is  well  illustrated  by  the  so-called  ex- 
periment of  Aristotle.  It  is  impossible  in  an  ordinary  po- 
sition of  the  fingers  to  bring  the  radial  side  of  the  middle 
finger  and  the  ulnar  side  of  the  ring  finger  to  bear  at  the 
same  time  on  a  small  object  such  as  a  marble.  Hence  when 
with  the  eyes  shut  w'e  cross  one  finger  over  the  other,  and 
place  a  marble  between  them  so  that  it  touches  the  radial 
side  of  the  one  and  the  ulnar  side  of  the  other,  we  recognize 
that  the  object  is  such  as  could  not  under  ordinary  condi- 
tions be  touched  at  the  same  time  by  tiiese  two  portions  of 
our  skin,  and  therefore  judge  that  we  are  touching  not  one 
but  two  marbles. 

Distinct  tactile  sensations  are,  as  we  have  seen,  produced 
only  when  a  stimulus  is  applied  to  a  terminal  organ.  Wlien 
sensations  or  afl'ections  of  general  sensilulit}'  other  than  tlie 
distinct  tactile  sensations  are  developed  in  the  termination 
of  a  nerve,  we  are  able,  though  witii  less  exactitude,  to  re- 
fer the  sensation  to  a  particular  part  of  the  body.  Thus 
when  we  are  i)ricked  or  burnt,  we  can  feel  where  the  prick 
or  burn  is.  When  a  sensory  nerve-trunk  is  stimulated,  the 
sensation  is  always  referred  to  the  peripheral  terminations 
of  the  nerve.  A  blow  on  the  ulnar  nerve  at  the  elbow  is 
felt  as  a  tingling  in  the  little  and  ring  fingers  corresponding 
to  the  distribution  of  the  nerve.  Sensations  started  in  the 
stump  of  an  amputated  limb  are  referred  to  tlie  absent 
member. 

Stimulation  of  a  nerve-trunk  gives  rise  to  general  sensa- 
tions only  ;  no  distinct  tactile  perceptions  can  tluis  be  pro- 
duced. When  cold  is  applied  to  the  elbow  it  is  felt  as  cold 
in  the  skin  of  the  elbow ;  but  a  cooling  of  the  ulnar  nerve 
at  this  spot  simply  gives  rise  to  pain  which  is  referred  to 
the  unlar  side  of  the  liand  and  iirm. 


Sec.  4.  The  Muscular  Sense. 

When  we  co!ne  into  contact  with  external  bodies  we  are 
conscious  not  only  of  the  pressure  exerted  by  the  object  on 
our  skin,  but  also  of  the  pressure  which  we  exert  on  tlie 
object.  If  we  place  the  hand  and  arm  flat  on  a  table,  we 
can  estimate  the  pressure  exerted  by  bodies  resting  on  the 
palm  of  the  hand,  and  so  come  to  a  conclusion  as  to  their 
weights  ;  in  this  case  we  are  conscious  only  of  the  pressure 
exerted  by  the  body  on  our  skin.     If  however  we  hold  the 


MUSCULAR    SENSE.  7o7 

body  in  ibe  hand,  we  not  only  feel  the  pressure  of  tbe  body, 
but  we  are  also  aware  of  the  muscular  exertion  required  to 
support  and  lift  the  body.  We  are  conscious  of  a  muscular 
sense  ;  and  we  find  by  experience  that  when  we  trust  to  this 
muscular  sense  as  well  as  to  the  sensation  of  pressure,  we 
can  form  much  more  accurate  judgments  concerning  the 
weight  of  bodies  than  when  we  rely  on  pressure  alone. 
When  we  want  to  tell  how  heavy  a  body  is,  we  are  not  in 
the  habit  of  allowing  it  simpl}-  to  press  on  the  hand  laid 
flat  on  the  table  ;  we  hold  it  in  our  hand  and  lift  it  up  and 
down.  We  appeal  to  our  muscular  sense  to  inform  us  of 
the  amount  of  exertion  necessary  to  move  it.  and  b}^  help 
of  tliat,  judge  of  its  weigiit.  And  in  all  the  movements  of 
our  body  we  are  conscious,  even  to  an  astonishingly  accu- 
rate degree,  as  is  well  seen  in  the  discussions  concerning 
vision,  of  the  amount  of  the  contraction  to  whicli  we  are 
putting  our  muscles.  In  some  way  or  other  we  are  made 
aware  of  what  particular  muscles  or  groups  of  muscles  are 
being  thrown,  into  action,  and  to  what  extent  that  action  is 
being  carried.  We  are  also  conscious  of  the  varying  con- 
dition of  our  muscles,  even  when  they  are  at  rest;  tlie  tired 
and  especially  the  paralyzed  limb  is  said  to  ''  feel  "  heavy. 
In  tliis  way  tiie  state  of  our  muscles  largely  determines  our 
general  feeling  of  health  and  vigor,  of  weariness,  ill  health, 
and  feebleness. 

It  has  been  suggested  that  since  muscle  possesses  little  or  no 
general  sensibility,  coniparativeW  little  pain  being  felt  for  instance 
when  muscles  are  cut,  our  muscular  sense  is  cliietly  derived  from 
the  traction  of  the  contracting  muscle  on  its  attachments  ;  and 
undoubtedl}^  in  cramp,  when  it  can  be  localized,  the  pain  is 
chiefly  felt  at  the  joints  :  and,  as  w^e  know,  Pacinian  bodies  are 
abundant  around  the  joints.  The  investigations  of  Sachs,  how- 
ever,' seem  to  sliow  that  atierent  nerves,  having  a  different  dis- 
position from  the  ordinary  motor  nerves  which  terminate  in  end- 
plates,  are  present  in  muscle  ;  and  analogy  would  lead  ns  to  sup- 
pose that  these  afferent  fibres,  though  possessing  a  low  general 
sensibiHty,  might  be  easily  excited  "by  a  muscurar  contraction  ; 
but  further  investigations  are  necessary  before  these  can  be  ac- 
cepted as  the  trtie  nerves  of  the  muscular  sense ."^ 

In  favor  of  the  view  that  the  mtiscular  sense  is  peripheral  and 
not  central  in  origin,  may  be  urged  the  fact  that  the  sense  is  felt 
when  the  muscles  are  thrown  into  contraction  by  direct  galvanic 

^  Eeichert  and  Du  Bois-Revmond's  Archiv,  1874,  p.  175. 
^  Cf.  Tschiriew,  Archives  de  Physiol.,  vi  (1879),  p.  89. 


'68  FEELING     AND    TOUCH. 


stimulation  instead  of  by  the  agency  of  the  will.  Many  authors, 
even  while  admitting  the  existence  of  a  muscular  sense  of  periph- 
eral origin,  contend  that  we  also  possess  and  are  very  largely 
guided  in  our  movements  by  what  might  be  called  ''neural'' 
sense  of  central  origin.  That  is  to  say,  the  changes  in  the  cen- 
tral nervous  system  involved  in  initiating  and  carrying  out  a 
movement  of  the  body  so  affect  our  consciousness  that  we  have 
a  sense  of  the  eftbrt  itself. 

It  has  been  observed  that  when  the  posterior  roots  are  divided, 
movements  become  less  orderly,  as  if  they  lacked  the  guidance  of 
a  muscular  sense  ;  and  although  the  impairment  of  the  movements 
may  be  due  in  part  to  the  coincident  loss  of  tactile  sensations,  it 
is  probable  that  it  is  increased  by  the  loss  of  muscular  sense. 
There  is  a  malad}^  or  rather  a  condition  attending  various  dis- 
eased states  of  the  central  nervous  system  called  locomotor  ataxy, 
the  characteristic  feature  of  which  is  that,  though  there  is  no 
loss  of  direct  power  over  the  muscles,  the  various  bodily  move- 
ments are  effected  imperfectly  and  Avith  difficulty,  from  want  of 
proper  co-ordination.  In  such  diseases  the  pathological  mischief 
is  frequently  found  in  the  posterior  columns  of  the  spinal  cord 
and  the  posterior  roots  of  the  spinal  nerves,  that  is  in  distinctly 
afferent  structures  ;  and  the  phenomena  seem  in  certain  cases  at 
least  due  to  inefficient  co-ordination  caused  by  the  loss  of  both 
the  muscular  sense  and  of  ordinary  tactile  sensation.  The  pa- 
tients walk  with  difficulty,  because  they  have  imperfect  sensa- 
tions both  of  the  condition  of  their  muscles  and  of  the  contact  of 
their  feet  with  the  ground.  In  many  of  their  movements  they 
have  to  depend  largely  on  visual  sensations ;  hence  when  their 
eyes  are  shut,  they  become  singularly  helpless.  In  other  cases 
again  ataxy  may  be  present  without  any  impairment  of  touch  ; 
but  a  discussion  of  the  varied  phenomena  of  this  class  of  maladies 
cannot  be  entered  into  here. 

Among  the  names  of  those  who  have  contributed  largely  to 
our  knowledge  of  the  physiology  of  the  various  senses,  the  fol- 
lowing (the  more  purely  physical  inquirers  being  passed  over) 
call  for  special  mention.  In  vision,  the  labors  of  Young'  on  ac- 
commodation and  color  sensations,  of  Purkinje^  on  subjective 
phenomena,  of  Donders^  and  Helmholtz'  on  the  various  dioptric 
features  of  the  eye  and  the  movements  of  the  eyeballs,  and  of 
Wheatstone  on  binocular  vision,  were  of  first  importance  ;  and  to 
these,  on  the  psychological  side,  may  be  added  the  speculations 
of  Berkeley.^  It  need  hardly  be  said  that  in  his  Phi/Biological 
Optics  Helmholtz  has  treated  the  whole  subject  in  such  a  com- 
plete and  masterly  way  as  to  make  it  almost  entirely  his  own. 

1  Phil.  Trans.,  1801, 

2  Beobacht,  u.  Yersuch.  zur  Physiol,  d.  Sinne,  1825,  and  other  papere. 
^  Xnmerous  papers  from  1846  onwards. 

*  Numerous  papers,  and  Handbucii  der  Phvsiol,  Optik,  1867. 
^  Theory  of  Vision,  1709. 


ANATOMY    OF    THE    SPINAL    CORD.  769 


In  both  sight  and  hearing,  and  indeed  in  the  senses  in  general, 
we  owe  mucli  to  Johannes  Muller.^  The  physiology  of  touch, 
and  the  relations  obtaining  in  the  senses  in  general  between  the 
stimulus  and  the  sensation,  was  largely  advanced  by  the  labors  of 
Weber.-  Lastly,  the  researches  of  Helmholtz'on  musical  sounds 
mark  an  epoch "^in  the  history  of  the  physiology  of  hearing. 


CHAPTER    V. 
THE  SPIXAL  COED. 

IThe  Physiological  Anatomy  of  the  Spinal  Cord. 

The  spinal  cord  extends  from  the  foramen  magnum  to 
the  second  lumbar  vertebra.  Above,  it  is  continuous  with  the 
medulla  oblongata;  below,  it  terminates  in  an  extremity  of 
gray  matter,  the  filiun  terminale,  wliich  lies  in  the  midst  of 
a  nnmber  of  nervous  cords  tliat  form  the  caiida  equina. 

The  spinal  cord  is  a  long,  somewhat  flattened,  eylindri- 
form  bod}'.  It  consists  of  a  central  portion  of  gray  matter, 
wliich  is  covered  by  longitudinal  strands  of  white  fibrous 
matter.  It  is  a  bilateral,  symmetrical  organ,  tlie  halves  of 
which  are  separated  anteriorly  and  posteriorly  by  the  ante- 
rior and  posterior  median  fissures,  and  joined  in  the  middle 
longitudinal  line  by  a  band  of  nervous  matter  which  is 
termed  the  commissure.  (Fig.  205.)  The  anterior  median 
fissure  is  wider  an'd  shallower  than  the  posterior  median 
fissure.  Each  iialf  of  the  cord  is  marked  by  two  longitu- 
dinal furrows,  from  which  emerge  the  anterior  and  posterior 
roots  of  the  spinal  nerves.     These  furrows  are   termed  the 


1  Phys.  d.  Gesichtssinns,  1826,  and  Handb.  der  Physiol.,  1835. 
^  De  Aiire,  etc.,  1820.     Wagner's  Handworterbuch,  Art.  Tastsinn. 
^  Tonempfindnngen,  1870. 


770 


THE    SPINAL    CORD. 


anterolateral  and  postero-lateral  grooves.  Tliey  divide  each 
half  into  three  portions  :  the  anterior^  lateral^  and  posterior 
columns  The  anterior  column  is  situated  between  the  an- 
terior median  fissure  and  the  antero-lateral  groove  ;  the 
middle  column,  between  the  antero-  and  postero-latei'al 
grooves;  the  posterior  column  between  the  posterolateral 


h        h    b        b 

Transverse  Section  of  Spinal  Cord,  through  the  middle  of  llie  Lumbar  Enlargement, 
showing  on  the  right  side  the  course  of  the  Nerve-roots,  and  on  the  left  the  posi- 
tion of  the  priucipal  tracts  of  Vesicular  Matter,  a,  a,  anterior  colnrans  ;  p,  p,  poste- 
rior columns;  L,  L,  lateral  columns;  a,  anterior  median  fissure;  p,  posterior  median 
fissure;  b,  b,  b,  b,  anterior  roots  of  spinal  nerves;  c,  c,  posterior  roots;  d,  d,  tracts  of 
vesicular  matter  in  anterior  col  umn  ;  e,  tracts  of  vehicular  matter  in  posterior  column  ; 
/,  central  canal,  surrounded  by  the  gray  commissure;  g,  substantia  gelatinosa  of  Ro- 
lando. 


groove  and  the  posterior  median  fissure.  The  anterior  and 
lateral  columns  are  sometimes  spoken  of  as  the  antero-lateral 
column.  The  fibres  of  the  columns  are  continuations  of  the 
fibres  of  the  spinal  nerves,  or  of  fibres  which  arise  in  the  gan- 
glionic cells  of  the  cord ;  and  have  for  the  most  part  a  longi- 
tudinal direction  ;  other  fibres  have  a  transverse  or  oblique 
direction  in  their  course  to  other  columns  or  to  nerve  cells. 


ANATOMY    OF    THE    SPINAL    CORD.  771 

The  gra}-  substance  of  the  cord  (Fig.  205)  is  in  the  form  of 
two  cresceutic  portions,  which  are  connected  together  b}^ 
the  gray  commissure,  and  presents  an  appearance  similar  to 
that  of  the  letter  H.  Each  cresoentic  portion  consists  of 
two  extremities,  which  are  termed  the  cornua.  The  anterior 
cornu  is  thicker,  larger,  and  contains  a  much  greater  propor- 
tion of  nerve-cells.  It  consists  principally'  of  very  fine  nerve- 
fibres,  and  three  distinct  columns  of  larger  multipolar  cells. 
These  columns  are  best  seen  in  the  cervical  and  lumbar  re- 
gions, and  are  frequently  spoken  of  as  the  motor  cells  ;  and 
some  of  them  as  trophic  cells. 

The  posterior  cornu  is  smaller  and  narrower  than  the 
anterior;  the  cells,  also,  are  of  much  smaller  size.  Near 
the  posterior  extremit}'  of  the  cornu  is  an  expanded  gelati- 
nous portion,  which  is  termed  the  subdanfia  gelafinosa  of 
Eolando  (Fig.  205).  At  the  anterior  internal  portion,  near 
the  central  canal,  is  a  column  of  small  nerve-cells,  which  is 
called  the  posterior  vesicular  or  Clarke's  column.  Tliis  col- 
umn is  most  distinct  in  the  dorsal  region.  The  cells  of  the 
posterior  cornua  are  sometimes  spoken  of  as  the  sensory  cells. 

The  commissure  (Fig.  206)  consists  of  a  band  of  gray  and 
white  fibrous  matter,  which  serves  to  connect  the  two  sides 
of  the  cord.  The  anterior  portion  or  white  commissure  is 
composed  of  a  band  of  decussating  white  fibres,  which  for 
the  most  part  extends  between  the  anterior  cornua  and  col- 
umns of  the  two  sides  The  gray  commissure  consists  of  an 
anterior  and  posterior  transverse  band  of  fibres,  between 
which  is  a  very  fine  nerve-fibre  plexus,  which  are  for  the 
most  part  derived  from  the  cell  processes.  In  the  centre  of 
the  commissure  is  the  central  canal.  The  wall  of  the  canal 
is  formed  b}'  a  connective  tissue  and  is  lined  by  columnar 
epithelium.  It  extends  from  the  fourth  ventricle  of  the 
brain  to  the  filum  terminale. 

The  cord  is  thicker  in  the  cervical  and  the  lumbar  and  lower 
dorsal  regions,  at  points  corresponding  to  the  origin  of  the 
brachial,  and  the  lumbar  and  sacral  plexuses.  This  enlarge- 
ment is  due,  for  the  most  part,  to  the  increased  proportion 
of  gray  matter.  The  quantity  of  white  matter  progressively 
increases  from  below  upwar(ls.     (See  pp.  788  and  789.) 

The  arrangement  of  the  fibres  of  the  spinal  nerves  after  they 
have  entered  the  substance  of  the  cord  is  of  great  physio- 
logical interest.  Upon  examining  sections  of  the  cord  these 
fibres  appear  to  have  a  general  horizontal,  oblique,  or  lon- 
gitudinal direction.    The  fibres  of  the  posterior  roots  have  at 


72 


THE    SPINAL    CORD. 


first  either  an  oblique  or  horizontal  direction.  The}'  then  as- 
sume different  courses  :  some  of  tliem  are  lost  sight  of  in 
the  gray  matter  of  the  posterior  cornua;  others  pass  ob- 
liquely downwards  or  upwards,  through  the  posterior  gray 
substance, and  are  finally  traced  to  the  anterior  cornua  or  col- 
umns, where  they  assume  a  longitudinal  direction,  either  run- 
ning up  or  down  ;  others,  upon  entering  the  posterior  gray 
matter  have  a  longitudinal  direction,  running  into  the  seg- 
ments (p.  787)  above  or  below  the  })oint ;  others,  seen  upon 


b  b 

Median  portion  of  a  Transverse  Section  of  the  Spinal  Cord  of  a  Child  six  months  old, 
from  the  lower  jiart  of  the  Cervical  Region,  treated  with  the  double  Chloride  of  Potas- 
sium and  Gold.  Magnified  50  diameters,  a,  a,  anterior  columns ;  b,  b,  posterior  col- 
umns ;  c,  central  canal;  d,  line  indicating  the  epithelium  of  the  central  canal;  e, 
connective  tissue  surrounding  the  central  canal;  /,  nerve-fibre  plexus  around  the 
central  canal ;  </,  posterior  transverse  fibres  of  the  gray  commissure  ;  h,  anterior 
transverse  fibres  of  the  gray  commissure;  t,  decussation  of  fibres  in  the  anterior 
white  commissure. 

transverse  sections  (Fig.  205)  run  towards  the  anterior 
cornu,  or  across  the  commissure  to  the  lateral  or  posterior 
columns  of  the  opposite  side.  The  fibres  of  the  anterior 
roots  (Fig.  205)  run  posteriorly,  nearly  horizontally,  until 
they  reach  the  anteiior  cornu.  Some  of  the  fibres  then  ap- 
pear to  be  continuous  with  the  processes  of  the  multipolar 


REFLEX    ACTIONS.  773 

cells  ;  others  run  to  the  lateral  or  to  the   anterior  columns  ; 


others  run  to  the  posterior  gray  matter  ;  and  others  through 
the  anterior  white  commissure,  and  are  traced  to  the  cells 
of  the  anterior  cornu,  or  to  the  anterior  or  lateral  columns. 
The  nervous  elements  of  the  spinal  cord  are  bound  to- 
gether b\'  a  modified  connective  tissue,  called  the  neuroglia^ 
which  serves  also  as  a  nidus  for  the  ramifications  of  the  l»lood- 
vessels.] 

Sec.  1.  As  a  Centre  of  Reflex  Action. 

We  have  already  discussed  (Book  1,  Chapter  III)  the 
general  features  of  reflex  action,  so  that  we  can  now  confine 
ourselves  to  special  points  of  particular  interest.  Since  the 
frog  and  the  mammal  differ  very  markedly  from  each  other 
in  respect  of  their  reflex  spinal  phenomena,  it  will  be  con- 
venient to  consider  them  separately'. 

In  the  Frog. 

The  salient  feature  of  the  ordinary  reflex  actions  of  the 
frog  is  their  purposeful  character,  though  every  variety  of 
movement  may  be  witnessed,  from  a  simple  spasm  to  a  most 
complex  muscular  manoeuvre.  The  nature  of  any  move- 
ment called  forth  is  determined: 

1.  By  the  nature  of  the  afferent  impulses.  Simple  ner- 
vous impulses  generated  by  the  direct  stimulation  of  afferent 
nerve-fibres  evoke  as  reflex  movements  merely  irregular 
spasms  in  a  few  muscles  ;  whereas  the  more  complicated 
differentiated  sensory  impulses  generated  by  the  application 
of  the  stimulus  to  the  skin,  give  rise  to  large  and  purposeful 
movements.  It  is  much  more  easy  to  produce  a  reflex  action 
by  a  slight  pressure  on  the  skin  than  by  even  strong  induc- 
tion-shocks applied  directly  to  a  nerve-trunk.  If,  in  a  brain- 
less frog,  the  area  of  skin  supplied  by  one  of  the  dorsal 
cutaneous  nerves  be  separated  by  section  from  the  rest  of 
the  skin  of  the  back,  the  nerve  being  left  attached  to  the 
piece  of  skin  and  carefully  protected  from  injury,  it  will 
be  found  that  slight  stimuli  applied  to  the  surface  of  the 
piece  of  skin  easily  evoke  reflex  actions,  whereas  the  trunk 
of  the  nerve  may  be  stimulated  with  even  strong  currents 
without  producing  anything  more  than  irregular  movements. 

In  ordinary  mechanical  and  chemical  stimulation  of  the 
skin  it  is  a  series  of  impulses  and  not  a  single  impulse  which 

65 


774  THE    SPINAL    CORD. 

passes  upwards  along  the  sensory  nerve,  the  changes  in 
which  may  be  compared  to  the  ciianges  in  a  motor  nerve 
during  tetanus.  In  every  reflex  action,  in  fact,  the  central 
mechanism  may  be  looked  upon  as  being  thrown  into  activ- 
ity through  a  summation  of  the  afferent  impulses  reaching 
it*.^ 

When  a  muscle  is  thrown  into  contraction  in  a  reflex  ac- 
tion, the  note  which  it  gives  forth  does  not  vary  with  the 
stimulus,  but  is  constant,  being  the  same  as  that  given  forth 
by  a  muscle  thrown  into  contraction  by  the  will.  From 
which  w^e  infer  that  in  a  reflex  action  tlie  aflferent  impulses 
do  not  simply  pass  through  the  centre  in  the  same  way  that 
they  pass  along  afferent  nerves,  but  are  profoundly  modified. 
And  this  explains  why  a  reflex  action  takes  always  a  con- 
siderable time,  and  frequently  a  very  long  time,  for  its  de- 
velopment. When  the  toes  of  a  brainless  frog  are  dipped 
in  dilute  sulphuric  acid,  several  seconds  may  elapse  before 
the  feet  are  withdrawn.  Making  every  allowance  for  tiie 
time  needed  for  the  acid  to  devek^p  sensory  impulses  in  the 
peripheral  endings  of  the  afferent  nerve,  a  very  large  frac- 
tion of  the  period  must  be  taken  up  by  the  molecular  actions 
going  on  in  the  nerve-cells.  In  other  words,  the  interval 
between  the  advent  at  the  central  organ  of  afferent,  and  the 
exit  from  it  of  efferent  impulses,  is  a  busy  time  for  the 
nerve-cells  of  that  organ  ;  during  it  many  processes,  of 
which  at  present  we  know  little  or  nothing,  are  being  car- 
ried on. 

2.  By  the  intensity  of  the  stimulus.  We  have  already 
pointed  out  (p.  164)  that  while  tiie  effects  of  a  weak  stim- 
ulus applied  to  an  afferent  nerve  are  limited  to  a  few,  those 
of  a  strong  stimuhis  may  spread  to  many  efferent  nerves. 
Granting  that  any  particular  afferent  nerve  is  more  partic- 
ularly associated  with  certain  efferent  nerves  than  with  any 
others,  so  that  the  reflex  impulses  generated  by  impulses 
entering  the  cord  by  the  former,  pass  with  tlie  least  resist- 
ance down  the  latter,  we  must  evidently  admit  further  that 
other  efferent  nerves  are  also,  though  less  directly,  con- 
nected with  the  same  afferent  nerve,  the  passage  into  the 
second  efferent  nerve  meeting  with  an  increased  but  not  in- 
superable resistance.  When  a  frog  is  poisoned  with  strych- 
nia, a  slight  touch  on  any  part  of  the  skin  may  cause  con- 

'  Cf.  Stirling,  Ludwig's  Arbeiten,  1874. 


REFLEX    ACTIONS.  775 

vulsions  of  the  whole  body ;  that  is  to  say,  the  afferent  im- 
pulses passing  along  any  single  afferent  nerve  may  give  rise 
to  the  discharge  of  efferent  impulses  along  any  or  all  of  the 
efferent  nerves.  This  proves  that  a  physiological  if  not  an 
anatomical  continuity  obtains  between  all  the  nerve-cells  of 
the  spinal  cord  which  are  concerned  in  reflex  action,  that 
the  nerve-cells  with  their  processes  form  a  functionally  con- 
tinuous protoplasmic  network.  This  network  however  is 
marked  out  into  tracts  presenting  greater  or  less  resistance 
to  the  progress  of  the  impulses  into  which  afferent  impulses, 
coming  from  this  or  that  afferent  nerve,  are  transformed  on 
their  advent  at  the  network;  and  accordingly^  the  path  of 
any  series  of  impulses  in  the  network  will  be  determined 
largely  by  the  energy  of  the  afferent  impulses.  And  the 
action  of  strychnia  is  most  easily  explained  by  supposing 
that  it  reduces  and  equalizes  the  normal  resistance  of  this 
network,  so  that  even  weak  impulses  travel  over  all  its  tracts 
with  great  ease. 

3.  By  the  locality  where  the  stimulus  is  apj)lied.  Pinch- 
ing the  folds  of  skin  surrounding  the  anus  of  the  frog  pro- 
duces different  effects  from  those  witnessed  when  the  flank 
or  toe  is  pinched  ;  and,  speaking  generally,  the  stimulation 
of  a  particular  spot  calls  forth  particular  movements.  From 
this  we  may  infer  that  the  protoplasmic  network  spoken  of 
above  is,  so  to  speak,  mapped  out  into  nervous  mechanisms 
by  the  establishment  of  lines  of  greater  or  less  resistance, 
so  that  the  disturbances  in  it  generated  by  certain  afferent 
impulses  are  directed  into  certain  efferent  channels.  But 
the  arrangement  of  these  mechanisms  is  not  a  fixed  and 
rigid  one.  We  cannot  predict  exactly  the  nature  of  the 
movement  which  will  result  from  the  stimulation  of  any 
particular  spot.  Moreover,  under  a  change  of  circum- 
stances a  movement  quite  different  from  the  normal  one 
may  make  its  appearance.  Thus  when  a  drop  of  acid  is 
placed  on  the  right  fiank  of  a  frog,  the  right  foot  is  almost 
invariably  used  to  rub  off  the  acid  ;  in  this  there  appears 
nothing  more  than  a  mere  "  mechanical  "  reflex  action.  If 
however  the  right  leg  be  cut  off,  or  the  right  foot  be  other- 
wise hindered  from  rubbing  off  the  acid,  the  left  foot  is, 
under  the  exceptional  circumstances,  used  for  the  purpose. 
This  at  first  sight  looks  like  an  intelligent  choice.  A  choice 
it  evidently  is  ;  and  were  there  many  instances  of  similar 
choice,  and  weie  there   any  evidence  of  a  variable  automa- 


776  THE    SPINAL    CORD. 

tism,  like  that  of  a  conscious  volition,  being  manifested  by 
the  spinal  cord  of  the  frog,  we  should  be  justified  in  sup- 
posing that  the  choice  was  determined  by  an  intelligence. 
It  is,  however,  on  the  other  hand,  quite  possible  to  suppose 
that  the  lines  of  resistance  in  the  spinal  protoplasm  are  so 
arranged  as  to  admit  of  an  alternative  action  ;  and  seeing 
how  few  and  sim[)le  are  the  ap[)arent  instances  of  choice 
witnessed  in  a  brainless  frog,  and  how  absolutely  devoid  of 
spontaneity  or  ii-regular  automatism  is  the  spinal  cord  of 
the  frog,  this  seems  the  more  probalde  view/ 

Moreover  to  this  often  quoted  behavior  of  the  frog  may  be 
opposed  the  behavior  of  the  snake.  This  animal  when  decapi- 
tated executes  movements  the  purpose  of  wdiich  is  obviously  to 
twine  the  body  round  any  object  with  which  it  comes  in  contact ; 
thus  it  very  speedily  twists  itself  round  an  arm  or  a  stick  pre- 
sented to  it.  It  will  however  with  equal  and  fatal  readiness 
twine  itself  round  a  red  hot  bar  of  iron  or  lump  of  live  coal.- 

It  may  be  remarked  that  tw^o  entirely  different  questions  are 
started  by  this  exhibition  of  choice  on  the  part  of  the  frog  ;  the 
one  is  whether  the  spinal  cord  of  the  frog  possesses  intelligence, 
the  other  is  whether  it  possesses  consciousness;  and  care  must 
be  taken  to  keep  the  two  questions  apart.  Intelligence  in  the 
ordinary  meaning  of  that  word  undoubtedly  presupposes  con- 
sciousness ;  but  we  are  not  at  liberty  to  say  that  consciousness 
may  not  exist  without  intelligence.  It  is  quite  possible  to  con- 
ceive of  the  simplest  and  most  "  mechanical  "  reflex  action  being 
accompanied  by  consciousness  ;  the  coexistence  of  the  conscious- 
ness being  merely  an  adjunct  to,  and  in  no  appreciable  way  mod- 
ifying the  mechanical  elaboration  of,  the  act.  On  the  other  hand, 
though  it  is  possible  to  conceive  of  such  a  concomitant  and  ap- 
parently useless  consciousness,  and  though  if  we  admit  an  evo- 
lution of  consciousness  W'C  must  suppose  such  forms  of  conscious- 
ness to  exist,  yet  inasmuch  as  our  reason  for  believing  in  the 
possession  by  any  being  of  a  consciousness  like  our  ow^n  is  based 
on  the  similarity  of  the  behavior  of  that  being  with  our  own  be- 
havior, we  are  precluded  from  distinctly  predicating  consciousness 
except  in  the  cases  wdiere  an  intelligenee  similar  to  our  own  is 
manifested.  But  the  discussion  of  this  subject  w^ould  lead  us 
too  far  away  from  tlie  object  of  the  present  book. 

Jt  may  be  added  that  the  movements  evoked  by  even  a 
segment  of  the  cord  may  be  purposeful  in  character;  hence 


^  Pfliiger,  Die  sensorisclie  Function  des  Eiickenmarks,  1853.  San- 
ders-Ezn,  Ludwig's  Arbeiten,  1867.  Gergens,  PHiiger's  Archiv,  xiii 
(1876),  p.  61. 

^  Osawa  and  Tiegel,  Pfliiger's  Archiv,  xvi  (1877),  p.  90. 


REFLEX    ACTIONS.  777 

we  must  conclude  that  every  segment  of  the  protoplasmic 
network  is  mapped  out  into  meclianisms. 

4.  By  the  condition  of  the  cord.  The  action  of  strychnia, 
just  alluded  to,  is  an  instance  of  an  apparent  augmentation 
of  reflex  action  best  explained  by  supposing  that  the  re- 
sistances in  the  cord  are  lessened.  There  are,  probably,  how- 
ever, cases  in  which  the  explosive  energy  of  the  nerve-cells 
is  positively  increased  above  the  normal.  Conversely,  by 
various  influences  of  a  depressing  character,  as  by  various 
ana?slheti('S,  reflex  action  may  be  lessened  or  prevented  ; 
and  this  again  may  arise  either  from  an  increase  of  resis- 
tance, or  fiom  a  diminished  action  of  the  nerve-cells  them- 
selves. In  the  mammal  the  condition  of  apncBa  is  antagonistic, 
not  only  to  the  convulsions  proceeding  fi'om  the  convulsive 
centre  in  the  medulla,  but  also  to  reflex  actions  arising  in 
any  part  of  the  cord,  such  as  those  produced  by  strychnia. 

Inhibition  of  Keflex  Action. — When  the  brain  of  a  frog 
is  reinoved  reflex  actions  are  developed  to  a  much  greater 
degree  than  in  the  entire  animal.  We  ourselves  are  con- 
scious of  being  able  by  an  effort  of  the  will  to  stop  reflex 
movements,  such  for  instance  as  are  induced  by  tickling. 
There  must,  therefore,  be  in  the  brain  some  mechanism  or 
other  for  preventing  the  normal  development  of  the  spinal 
reflex  actions.  And  we  learn  by  expeiiment  tliat  stimula- 
tion of  certain  parts  of  the  I'rain  has  a  remarkable  effect  on 
reflex  action.  In  a  i'rog,  from  which  the  cerebral  hemispheres 
only  have  been  removed,  the  optic  thalami,  optic  lobes, 
medulla  oblongata,  and  spinal  cord  being  left  intact,  a  cer- 
tain average  time  will  (see  p.  774)  be  found  to  elapse  be- 
tween the  dipping  of  the  toe  into  very  dilute  sulphuric  acid, 
and  the  resulting  withdrawal  of  the  foot.  li\  however,  the 
optic  lobes  or  optic  thalami  be  stimulated,  as  by  putting  a 
crystal  of  sodium  chloride  on  them,  it  will  be  found,  on  re- 
peating tiie  experiment,  while  these  structures  are  still  under 
the  influence  of  the  stimulation,  that  the  time  intervening 
between  the  action  of  the  acid  on  the  toe  and  the  with- 
drawal of  the  foot  is  very  much  prolonged.  That  is  to  say, 
the  stimulation  of  the  optic  lobes  has  caused  impulses  to 
descend  to  the  cord,  which  have  tliere  so  interfered  with  the 
action  of  the  nerve-cells  engaged  in  reflex  action  as  greatly 
to  retard  the  generation  of  reflex  impulses  ;  in  other  words, 


778  THE    SPINAL    CORD. 


the  stimulation  of  the  optic  lobes  has  inhibited  the  reflex 
action  of  the  cord/ 


It  is  worthy  of  notice  that  the  inhibitory  action  of  the  optic 
lobes  spoken  of  above  bears  exclusively  on  the  length  of  the 
period  of  incubation.  We  have  no  evidence  that  it  diminishes 
the  minimum  intensity  of  stimulation  required  to  produce  a  re- 
flex action.  On  the  other  hand,  the  augmenting  eflect  of  strychnia 
may  manifest  itself  without  any  change  in  the  latent  period  or 
period  of  incubation,  if  we  may  use  the  phrase.  When  a  frog  is 
poisoned  with  small  doses  of  strychnia  the  reflex  movements 
caused  by  a  very  slight  stimulus  may  be  very  great,  but  the 
period  of  incubation  may  be  the  same  as  that  of  a  frog  in  a  nor- 
mal condition  ;  when  the  dose  is  increased,  the  period  instead  of 
being  diminished  is  increased,  the  increase  being  very  consider- 
able when  minimum  stimuli  are  employed,  Ijut  much  less  marked 
with  strong  stimuli.  ^ 

If  quinine  ■  be  injected  under  the  skin  of  the  back  of  a  frog 
the  period  of  incubation  of  reflex  action  will  be  much  pro- 
longed. If,  after  the  retardation  has  become  clearly  developed, 
the  brain  be  removed,  the  period  of  incubation  rai)idly  returns  to 
the  normal.  And  if  the  quinine  is  similarly  injected  beneath  the 
skin  of  a  frog,  from  which  the  brain  has  previously  been  removed, 
no  such  retardation  makes  its  appearance.  From  this  we  may 
infer  that  the  injection  of  the  quinine  inhibits  the  reflex  actions 
of  the  spinal  cord  by  stimulating  an  inhibitory  mechanism  in  the 
brain.  The  difference  is,  however,  said  not  to  be  manifested  when 
mechanical  instead  of  chemical  or  thermal  stimuli  are  used  ;  and, 
indeed,  the  experiment  is  one  requiring  further  investigation. 

LangendorP  concludes  that  in  frogs  the  inhibitory  action  of 
one  side  of  the  brain  is  exerted  on  the  reflex  actions  of  the  op- 
posite side  of  the  body,  the  inhibitory  impulses  crossing  in  the 
medulla  oblongata. 

Such  an  inhibitory  effect  is,  however,  not  confined  to  the 
optic  lobes.  Stimuli,  if  sutRciently  strong,  ap[)lied  to  any 
afferent  nerve,  will  inhibit,  i.e.,  will  retard,  or  even  wholly 
prevent,  reflex  action.  If  the  toes  of  one  leg  are  dipped 
into  dilute  sulphuric  acid  at  a  time  when  the  sciatic  of  the 

^  Setschenow,  Ueber  die  Hemmungsmechanismen  fiir  die  Eeflex- 
thiitigkeit  des  Eiickenmarks,  1863.  Setschenow  and  Paschutin,  Neue 
Versuche,  1865.  Herzen,  Exp.  sur  les  Centres  moderateurs  de  Taction 
reflexe,  1864. 

2  Wundt,  Mechanik  der  Nerven,  ii  (1876),  p.  70. 

=»  Chaperon,  Pfluger's  Archiv,  ii  (1869),  p.  293. 

*  Du  Bois-Reyraond's  Archiv,  1877,  p.  95. 


REFLEX    ACTIONS.  779 

Other  leg  is  being  powerfully  stimulated  with  an  interrupted 
current,  the  period  of  incubation  will  be  found  to  be  much 
prolonged,  and  in  some  cases  the  reflex  withdrawal  of  the 
foot  will  not  take  place  at  all.  And  this  holds  good,  not 
onl3'  in  the  complete  absence  of  the  optic  lobes  and  medulla 
oblongata,  but  also  when  only  a  porti^jn  of  the  spinal  cord, 
sufficient  to  carr}'  out  the  reflex  action  in  the  usual  way,  is 
left.  There  can  be  no  question  here  of  any  s|)ecific  iniiibi- 
tory  centres,  such  as  have  been  supposed  to  exist  in  the 
oj^tic  lol)es.  We  have  already  seen  that  the  action  of  such 
nervous  centres,  automatic  or  reflex,  as  the  respiratory  and 
vaso-motor  centres,  may  be  either  inhibited  or  augmented 
by  art'erent  impulses.  The  micturition  centre  in  the  mam- 
mal may  be  easil}'  inhibited  l)y  impulses  passing  downward 
to  the  lumbar  cord  from  the  brain,  or  upwards  along  the 
sciatic  nerves.  Goltz  observed  that  in  the  case  of  the  dog 
(see  p.  539),  micturition  set  up  as  a  reflex  act  by  simple 
pressure  on  tiie  abdomen,  or  by  sponging  the  anus,  was  at 
once  stopped  by  sharply  pinching  the  skin  of  the  leg.  And 
it  is  a  matter  of  common  experience  that  micturition  may 
])e  suddenly  checked  by  an  emotion  or  other  cerebral  event. 
The  erection-centre  in  the  lumbar  cord  is  also  susceptible 
of  being  inhibited  by  impulses  reachirjg  it  from  various 
sources.  And,  though  the  reflex  mechanism  of  croaking 
belongs  to  the  optic  lobes,  and  not  to  the  spinal  cord,  this 
may  be  quoted  in  reference  to  the  inhibition  of  reflex  action, 
since  the  croaking  which,  as  we  shall  shortly  see,  in  a  frog 
deprived  of  its  cerebral  hemispheres,  invariably  follows  the 
stroking  of  the  flanks  in  a  particular  way,  fails  to  appear  if 
a  sensory  nerve,  such  as  tiie  sciatic,  be  powerfully  stimu- 
lated at  the  same  time. 

These  various  facts  clearly  show  that  the  spinal  cord,  and 
indeed  the  whole  cerebral  nervous  system,  may  be  regarded 
as  an  intricate  mechanism  in  which  the  direct  effects  of 
stimulation  or  automatic  activity  are  modified  and  governed 
by  the  checks  of  inhil)itor3^  influences;  but  we  have  as  3'et 
much  to  learn  befoi"^.  vve  can  speak  with  certainty  as  to  the 
exact  manner  in  which  inhil)ition  is  brought  about.  Seeing 
that  in  the  ordinary  actions  of  life  the  si)inal  cord  is  to  a 
large  extent  a  mere  instrument  of  tiie  cerebral  hemispheres, 
we  may  readily  expect  that  regulative  inhibitory  impulses 
passing  from  tfie  latter  to  the  former  would  be  of  frequent 
occurrence:  and  the  experiments  quoted  al)ove  show  that 
the  optic  lobes  when  stimulated  are  especially  prone  to  give 


780  THE    SPINAL    CORD. 

rise  to  such  inhibitory  impulses  ;  but  facts  do  not  at  present 
justify  us  in  speaking  of  the  optic  lobes  as  being  the  organ 
for  tlie  inhibition  of  reflex  action,  or  in  regarding  their  ab- 
sence as  the  cause  of  the  exaltation  of  reflex  activity  vvliich 
is  so  obvious  in  tiie  brainless  frog. 

The  inhibitory  action  of  the  cerebral  bemispheres  is  illustrated 
by  the  ''  croaking  frog  "  alluded  to  above.  An  entire  frog  when 
stroked  on  the  flanks  in  a  particular  way  may  or  may  not 
"  croak  ;"  a  frog  from  whicb  the  cerebral  hemispheres  alone 
have  been  removed,  all  other  parts,  including  the  optic  lobes, 
having  been  left  intact,  will  invariably  croak  when  stroked  in 
the  same  way.  But  Langendorf  ■  linds  that  the  same  regular  re- 
sponse to  stimulation,  i.  c,  the  same  absence  of  inhibition,  is  wit- 
nessed in  a  frog  which  has  been  merely  blinded,  for  instance  by 
section  of  botli  optic  nerves,  the  cerebral  hemispheres  being  left 
intact.  From  this  it  might  be  inferred  that  the  inhibitory  activity 
of  the  cerebral  hemispheres  was  so  to  « peak  furnished  by  the  sense 
of  sight.''  Langle}^^  on  the  other  hand,  finds  that  ordinary  reflex 
action  produced  by  the  stimulation  of  one  sciatic  is  diminished 
by  section  of  the  other  sciatic,  and  he  regards  the  result  as  indi- 
cating not  that  the  mere  section  acts  as  a  stimulus  exciting  an 
inhibitory  mechanism  or  producing  an  inhibitory  result,  but 
that  in  a  normal  state  of  things  afferent  impulses  passing  up  the 
sciatic  nerve  maintain  the  activity  of  the  spinal  cord,  keep  it,  so 
to  speak,  awake,  and  hence  when  these  are  interrupted  by  the 
section  of  the  nerve,  the  spinal  cord  is  more  diflicult  to  move  by 
impulses  reaching  it  from  other  nerves. 

We  may  put  the  whole  matter  in  a  somewhat  general  way  as 
follows  :  In  treating  of  the  senses,  we  have  seen  that  two  sensory 
impulses  may,  according  to  circumstances,  unite  in  producing  a 
sensation  greater  than  that  caused  by  either  alone,  or  they  may 
lessen  each  other's  influence,  or  they  may  have  no  ettect  on  each 
other  at  all,  each  sensory  impulse  producing  its  effects  quite  in- 
dependent of  the  other.  We  have,  moreover,  seen  that  the  va- 
rious automatic  centres,  whether  sporadic  or  belonging  to  the 
central  nervous  system,  may  in  reference  to  any  given  afferent 
impulse  be  affected  in  the  way  of  inhibition  or  of  augmentation, 
or  may  not  be  affected  at  all.  Indeed  we  may  say  probably  of 
any  mass  of  active  living  protoplasm,  whether  automatic  or 
reflex,  whether  concerned  in  consciousness  or  not,  that  it  is  so 
related  to  other  parts  of  the  body  that  its  activity  may  be  dimin- 
ished or  exalted  or  unaffected  by  events  occurring  in  those  parts. 


^  Archiv  f.  Anat.  u.  Phys.,  1877  (Pliys   Abth.),  p.  435. 

^  Cf.  v.  Boetticher,  "  Ueber  Reflexliemmung,"  Prever's  Abhandl.,  ii, 
3  (1878) ;  and  his  critic,  Spode,  Archiv  f.  Anat.  u.  Phys.,  1879  (Phys. 
Abth.),  p.  113. 

'  Proc,  Cambridge  Philos.  Soc,  1879. 


REFLEX    ACTIONS.  781 


Whether  inhibition  or  exaltation  or  indifference  is  in  any  given 
case  predominant  will  depend  on  circumstances  and  arrange- 
ments, the  nature  of  which  we  at  present  iniderstand  in  a  very 
imperfect  manner.  And  the  difficulties  are  increased  rather  than 
diminished  by  presupposing  the  existence  of  an  unlimited  number 
of  inhibitory  and  augmenting  fibres. 


In  the  Mammal. 

In  the  frog  the  shock  \Yhich  follows  upon  division  of  the 
spinal  cord,  and  which  for  awhile  inhibits  retlex  activity, 
soon  passes  away;  within  a  very  short  time  after  tlie  me- 
dulla oblongata,  ior  instance,  has  been  divided,  the  most 
complicated  reflex  movements  can  be  canied  on  by  the 
spinal  cord  when  the  appropriate  stimuli  are  applied.  With 
the  mammal  the  case  is  very  different.  For  days  even  alter 
division  of  the  spinal  cord  the  parts  of  the  body  supplied 
b3'  nerves  springing  from  the  cord  below  tliesec-tion  exhibit 
very  feeble  reactions  only.  In  tiie  dog,  for  instance,  after 
division  of  the  spinal  cord  in  the  lower  dorsal  region,  the 
hind  limbs  hang  flaccid  and  motionless,  and  j)inching  tiie 
hind  foot  evokes  as  a  response  either  slight  irregular  move- 
ments or  none  at  all.  Indeed  were  our  observations  limited 
to  this  period  we  might  infer  that  the  reflex  actions  of 
the  spinal  cord  in  tlie  mammal  were  but  feeble  and  insig- 
nificant. If,  however,  the  animal  lie  kept  alive  for  a  longer 
period,  for  weeks  or  better  still  f(-r  months,  though  no  union 
or  regeneration  of  the  spinal  cord  takes  place  reflex  move- 
ments of  a  powerful,  varied,  and  complex  eiiaracter  mani- 
fest themselves  in  the  hind  liml  s  and  liinder  parts  of  the 
body  ;  a  very  feeble  stimulus  aj)i)lied  to  the  skin  of  these 
regions  promptly  gives  rise  to  extensive  and  yet  co-ordinate 
movements  Comi)ared  with  the  reflex  actions  of  the  frog, 
the  movements  carried  out  l)y  the  lower  portion  of  the  spinal 
cord  of  the  mammal  wliile  they  are  more  energetic  may  per- 
haps be  regnrded  assess  definite  and  complete  and  less  i)ur- 
poseful  :  tiiough  even  this  is  not  admitted  by  Goltz'  and  his 
pupils,  to  whou:  we  are  largely  indebted  for  information  on 
this  subject.  A  striking  feature  in  the  phenomena  atten- 
dant on  this  isolation  of  the  lumbar  cf'rd  in  the  mammal  is 
the  occurrence  of  apparently  spontaneous  movements  in  tlie 
parts  which  it  governs.     When  the  animal  has  thoroughly 

1  Pfluger's  Archiv,  viii  (1874),  p.  460 ;  ix  (1874),  p.  358. 
66 


782  THE    SPINAL    CORD. 

recovered  from  the  operation  tlie  hind  liml»s  rarel}^  remain 
at  rest  for  any  long  period  ;  tiiey  move  restlessl}^  in  various 
ways;  and  wiien  tlie  animal  is  suspended  by  tlie  upper  part 
of  the  body,  tlie  penrlent  hind  limbs  are  continually  being 
drawn  up  and  let  down  again  with  a  monotonous  rhythmic 
regularity  highly  but  perhaps  falsely  suggestive  of  auto- 
matic rhythmic  discharges  from  the  central  mechanisms  of 
the  cord.  This  greater  proneness  to  activity  is,  however, 
just  what  might  be  expected,  when  we  take  into  considera- 
tion the  more  rapid  metabolic  changes  and  the  consequent 
greater  molecular  mobilit}'  of  the  whole  nervous  system  of 
the  mammal.  Another  fact  worthy  of  attention  is  tiiat  the 
reflex  phenomena  in  mammals  (dogs)  vary  very  much  both 
in  different  individuals  and  in  the  same  individual  under 
different  circumstances.  Race,  age,  and  previous  training 
seem  to  have  a  marked  effect  in  determining  the  extent 
and  cliaracter  of  tlie  reflex  actions  which  the  lumbar  cord  is 
capable  of  carrying  out ;  and  these  seem  also  to  be  largely 
influenced  by  passing  circumstances,  such  as  whether  food 
has  been  recently  taken  or  not.  It  is  evident  that  the  reflex 
as  well  as  other  phenomena  of  the  mammalian  spinal  cord 
present  a  large  field  for  inquiry,  being  much  more  varied 
and  extensive  tiian  previous  experience  had  led  us  to  sup- 
pose. 

Vicarious  reflex  movements  may  also  be  witnessed  in 
mammals,  though  not  perhaps  to  sucli  a  striking  extent  as 
in  frogs.  In  dogs,  in  whicli  partial  removal  of  the  cerebral 
hemispheres  has  apparently  heightened  the  reflex  excita- 
bility of  the  spinal  cord,  the  remarkal)le  scratcliing  move- 
ments of  the  hind  leg  which  are  called  forth  by  stimulating 
particular  spots  on  the  side  of  the  body,  are  executed  liy 
the  leg  of  the  opposite  side,  when  the  leg  of  the  same  side 
is,  even  without  any  great  force  l)eing  applied,  prevented 
from  carrying  them  out.^  Here  too  tlie  absence  of  a  truly 
pur[)oseful  character  of  the  movements  is  very  marked,  and 
the  plienoinena  afford  a  strong  support  to  the  "mechanical" 
explanation  of  the  more  complicated  behavior  of  the  frog. 

According  to  Owsjannikow,-  if  in  the  rabbit  the  spinal  cord 
be  divided  at  the  cahimus  scriptonus,  a  moderate  stimulus  ap- 
plied to  the  hind  foot  causes  movements  in  one  or  other  or  both 

^  Gergens,  Pfliiger's  Arehiv,  xiv  (1877),  p.  340. 
2  Ludwig's  Arbeiten,  1874,  p.  308. 


REFLEX    ACTIONS.  783 


hind  legs,  but  none  in  the  fore  legs,  and  a  stimulation  of  the  fore 
foot  causes  movements  in  the  ifore  but  not  in  the  hind  legs  ; 
whereas  if  a  zone  of  nervous  tissue  only  6  to  5  mm.  in  height  be 
left  above  the  calamus  scriptorius,  stimulation  of  either  foot  may 
produce  a  movement  in  any  part  of  the  body.  This  would  seem 
to  shov,^  that  the  mechanisms  co-ordinating  the  movements  of  the 
fore  limbs  with  those  of  the  hind  limbs,  which  in  tiie  frog  are 
scattered  over  the  whole  spinal  cord,  are  in  the  mammal  (rabbit) 
gathered  into  the  medulla  oblongata.  The  region  referred  to 
above  lies,  it  may  be  remarked,  near  to  the  "  convulsive  centre  " 
(see  p.  490).  AVoroschilotf'  has  oljserved  that  in  the  rabbit  direct 
stimulation  with  an  interrupted  current  of  the  cervical  cord, 
down  as  far  as  the  origin  of  the  sixth  cervical  nerve,  causes  co- 
ordinated rhythmic  springing  movements  of  the  body,  whereas 
when  the  same  stimulus  is  applied  to  lower  regions  of  the  cord, 
a  rigid  tetanus  results  ;  this  too  indicates  the  existence  in  the 
cervical  cord  of  peculiar  co-ordinating  mechanisms. 

Muscular  movements,  as  parts  of  a  reflex  aclion,  may 
occur  on  stimulation  of  not  only  the  ordinary  spinal  and 
cranial  sensor}'  nerves,  but  also  of  the  nei'ves  of  special 
sense.  A  sound  or  a  flasli  of  light  readil}'  i)roduees  a  start, 
a  bright  light  causes  many  persons  to  sneeze,  and  reflex 
movements  ma}^  even  result  from  a  taste  or  smell. 


The  Time  i^equired  for  Bejiex  Actions. 

When  we  stimulate  one  of  our  eyelids  with  a  sharp  electrical 
shock,  both  eyehds  blink.  Hence,  if  the  length  of  time  inter- 
vening between  the  stimulation  of  the  right  eyelid  and  the  move- 
ment of  the  left  eyelid  be  carefully  measured,  this  will  give  the 
time  required  for  the  development  of  a  retlex  action.  Exner^ 
found  this  to  be  from  .0(5(52  to  .0578  sec,  being  less  for  the 
stronger  stimulus.  Deducting  from  these  figures  the  time  re- 
quired for  the  passage  of  afferent  and  efferent  impulses  along  the 
fifth  and  facial  nerves  to  and  from  the  medulla,  and  for  the  latent 
period  of  the  muscular  contraction  of  the  orbicularis,  there  would 
remain  .0555  to  .0471.  sec.  for  the  time  consumed  in  the  cen- 
tral operations  of  the  reflex  act.  The  calculations,  however, 
necessar}'  for  this  reduction,  it  need  not  be  said,  are  open  to 
sources  of  error.  Exner  found  that  when  he  used  a  visual  stimu- 
lus, viz.,  a  flash. of  light,  the  time  was  not  only  exceedingly  pro- 
longed, .2168  sec,  but  very  variable. 


^  Lndwig's  Arbeiten,  1874,  p.  99. 

2  Pti tiger's  Archiv,  viii  (1874j,  p.  526. 


784  THE    SPINAL    CORD. 


The  time  required  for  any  reflex  act  varies,  according  to  Ros- 
entlial/  very  considerably  witli  the  strength  of  tlie  stimukis  em- 
plo^^ed,  being  less  for  the  stronger  stimuli ;  it  is  greater  in  trans- 
verse than  in  longitudinal  conduction,  and  is  much  increased  by 
exhaustion  of  the  cord.  It  has  been  stated  that  the  central  pro- 
cesses of  a  reflex  action  are  propagated  in  the  frog  at  the  rate  of 
about  8  meters  a  second  ;  but  this  value  cannot  be  depended  on. 
The  time  thus  occupied  by  purely  reflex  actions  must  not  be  con- 
founded with  the  interval  required  for  mental  operations  ;  of  the 
latter  we  shall  speak  presently. 


Sec.  2.   Asa  Centre  or  Group  of  Centres  of  Automatic 
Action. 

Irregular  automatism,  i.  p.,  a  spontaneity  comparable  to 
our  own  volition,  is  wholly  absent  from  tiie  spinal  cord.  A 
brainless  frog  placed  in  a  condition  of  complete  equilibrium 
in  which  no  stimulus  is  brought  to  bear  on  it,  remains  per- 
fectly motionless  till  it  dies. 

Of  the  various  regular  automatic  centres,  both  the  nu- 
merous ones  in  the  medulla  oblongata,  such  as  the  vaso- 
motor, respiratory,  etc.,  and  the  more  sparse  ones  in  other 
regions  of  the  cord,  such  as  those  connected  with  micturi- 
tion (p.  539;,  defecation  (p.  887).  erection,  parturition,  and 
so  on.  we  have  treated  or  sliall  have  to  treat  so  fully  in  ref- 
erence to  their  respective  mechanisms,  and  discussed  how 
far  they  are  purely  automatic,  or  in  reality  merely  reflex  in 
nature,  that  n(jthing  more  need  be  said  here. 

The  connection  between  the  spinal  cord  and  the  automatic 
movements  of  the  lymph-hearts  of  the  frog  has  also  (p.  IGl)  been 
briefly  referred  to.  Yolkmann-  was  the  first  to  observe  that 
the  dtstruction  of  even  a  small  portion  of  special  regions  of  the 
spinal  cord  puts  an  end  to  the  pulsations  of  these  organs,  the 
region  or  centre  for  the  anterior  pair  of  hearts  being  opposite 
the  third  vertebra,  and  that  for  the  posterior  pair  being  opposite 
the  seventh,  or  according  to  Priestley^  sixth,  vertebra.  Eckhard* 
however  observed  that  the  pulsations,  though  ceasing  upon  the 

^  Monatsbericht,  d,  Berlin.  Acad.,  1873,  p.  104.  See  also  Sitziings- 
bericht  d.  phys.  nied.  Ges.  Erlangen,  1875,  and  Wundt,  Mechanik  der 
Nerven,  etc.,  Al)th.  ii  (187()). 

■'  MuUer's  Archiv,  1844,  p   419. 

^  Journal  of  Phys.  i  (1878),  ])p.  1  and  19. 

"  Zt.  f.  rat.  Med.*  viii,  p.  24.  and  Exp.  Phvs.  Xerv.  Svstem,  18GG,  p. 
259. 


LYMPH-HEARTS.  785 


destruction  of  the  regions  of  the  spinal  cord  above  mentioned, 
after  awhile  returned  ;  still  the  pulsations  thus  independent  of 
the  spinal  cord  differed  in  character  from,  being  more  partial  and 
irregular  than,  those  vyitnessed  when  the  spinal  cord  was  intact. 
Goltz'  saw  the  pulsations  return  in  about  three  weeks  after  they 
had  been  stopped  by  section  of  the  tenth  (coccygeal)  spinal  nerve, 
though  no  regeneration  of  the  nervous  tract  had  taken  place ; 
and  lie  states  "that  with  care  the  hearts  may  then  be  wholly  re- 
moved fi-om  the  body  without  arresting  their  pulsations.  Wal- 
deyer.-  though  he  described  ganglionic  cells  in  the  neighborhood 
of'the  hearts,  found  the  return  of  pulsations  after  division  of  the 
coccygeal  nerve  or  destruction  of  the  spinal  cord  too  inconstant 
to  prove  their  independence  of  the  spinal  cord,  and  Heidenhain' 
arrived  at  a  similar  conclusion. 

According  to  some  authors  stimulation  of  the  coccj'geal  nerves 
with  the  interrupted  current  brings  about  a  tetanic  systole  of  the 
posterior  lymph-hearts,  but  stimulation  with  a  strong  constant 
current  causes  a  standstill  in  diastole.  +  Priestley^  however  finds 
that  the  interrupted  current  applied  to  the  spinal  centre  produces 
a  slowing  of  the  lymph-hearts  passing  on  to  complete  arrest  as 
the  strength  of  the  current  is  increased.  If  the  current  be  made 
still  stronger,  the  inhibition  gives  way  to  tetanic  contraction. 
The  effects  of  the  constant  current  var}'  according  to  circum- 
stances. Goltz^  found  that  the  lymph-hearts  might  like  the 
blood-heart  be  inhibited,  and  brought  to  a  diastolic  standstill  in 
a  rertex  manner,  by  striking  sharply  the  exposed  intestines,  and 
that  they  might  also  be  similarl}^  inhibited  b}"  pinching  the  auri- 
cles of  the  blood-heart ;  the  centre  of  this  reflex  inliibition  ap- 
peared to  be  in  the  medulla  and  the  afferent  impulses  to  pass 
along  the  vagus.  Suslowa'  traced  these  afferent  inhibitory  im- 
pulses from  the  intestine  through  the  rami  communicantes.  He 
found  that  after  destruction  of  all  the  posterior  sensory  spinal 
roots,  the  h'mph-hearts  remained  in  a  (diastolic)  standstill, 
which  however  gave  place  to  a  return  of  pulsatile  activity  as 
soon  as  the  rami  communicantes  were  also  divided,  the  experi- 
ment in  his  opinion  indicating  that  the  inhibitory  impulses  pass- 
ing along  the  latter  channel  from  the  intestine  are  of  a  tonic 
character.  Suslowa  also  found  tliat  stimulation  of  a  transverse 
section  of  the  optic  thalami  or  optic  lobes  produced  a  diastolic 
standstill  of  the  lymph-hearts,  whereas  stimulation  of  a  trans- 
verse section  of  thQ  spinal  cord  itself  increased  their  activity  ; 

'  Cbl.  f.  Med.  Wiss.,  1863,  p.  497. 
2  Stud.  Bresl.  Inst.,  iii,  p.  71. 

^  Disquisiliones  de  nervis  organisque  centralibiis  cordis  cordiumve, 
etc.,  1864. 

*  Eekhard,  loc.  cit.     Wakleyer,  loc.  cit. 

^   Op.  cit. 

^   Cbl.  f.  Med.  Wiss.,  1863,  pp.  17  and  497  ;  1864,  p.  690 

'  Cbl.  f.Med.  Wiss.,  1867,  p.  833.  Zt.  f.  rat.  Med.,  31  (1868),  p.  224. 


'S6  THE    SPINAL    CORD. 


that  the  inhibitory  centres  of  Setschenow  in  fact  govern  also  the 
lymph-hearts. 

It  has  l^een  maintained  that  tlie  spinal  cord  exercises  over 
the  skeletal  muscles  a  tonic  action  coniparahle  to  that  of 
the  vaso-motor  centres  over  the  smooth  muscles  of  the  ar- 
teries. There  is,  however,  no  adequate  sup|)(>rt  to  this  view. 
When  a  muscle  is  cut  across  in  the  living  hody,  the  section 
gapes,  because  all  the  muscles  of  tlie  body  are  sliglitly 
stretciied  beyond  tiieir  normal  length.  When  one  side  of 
the  face  is  paralyzed  the  mouth  is  drawn  to  tlie  opposite 
side,  not  because  tlie  paralyzed  muscles  have  lost  their  tone, 
but  because  there  are  on  the  paralyzed  side  no  contractions 
to  antagonize  the  effect  of  the  continually  repeated  contrac- 
tions of  the  sound  side.  And  tiie  view  is  distinctly  dis- 
proved by  the  fact  tiiat,  according  to  most  observers,  when 
in  the  living  body  the  nerve  going  to  a  muscle  is  cut  no  per- 
manent lengtliening  of  the  muscle  is  caused.  After  the 
sciatic  i)lexus  of  one  leg  of  a  brainless  frog  has  been  cut, 
that  leg  hangs  down  more  helplessly  than  the  other  when 
the  animal  is  suspended.  This  might  at  first  sight  be 
considered  as  the  result  of  loss  of  tone  ;  but  the  same  flac- 
cidity  is  observed  in  a  leg  in  which  tlie  posterior  roots  only 
of  tlie  sciatic  plexus  have  been  divided.  The  difference 
between  the  leg  of  the  one  side  and  that  of  the  other  in 
these  cases  is  tliat  the  sound  leg  is  rather  more  flexed  than 
the  other;  and  evidentl}'  this  slight  flexion,  since  it  disap- 
pears on  section  of  the  posterior  roots,  is  the  result  of  a 
reflex  and  not  of  an  automatic  action. 

Tschiriew^  afiirms  that  with  a  certain  degree  of  tension,  sec- 
tion of  the  nerve  in  the  living  body  is  followed  by  a  lengthening 
of  the  muscle,  and  he  contends  for  the  existence  of  a  muscular 
tone  not  of  automatic  but  of  reflex  nature,  originating  in  afler- 
ent  impulses  started  in  the  nerves  of  the  tendon  of  the  muscle 
whenever  the  tendon  is  subjected  to  a  certain  degree  of  tension. 
He  believes  that  the  nerve-fibres,  which  he  has  traced  to  the  ten- 
dons and  aponeuroses  of  muscles,  and  which  he  regards  as  iden- 
tical with  the  fibres  described  by  {Sachs  (see  p.  767),  are  the  only 
afferent  fibres  belonging  to  muscle  and  are  simple  afterent  nerves, 
not  specific  nerves  of  muscular  sense.  He  explains'  the  so-called 
tendon-reflex  or  knee  phenomena,  i.  e.,  the  contractions  in  the 

1  Archiv  f.  Anat.  u.  Phvs.,  1879  (Phvs.  Abth.),  p.  78. 

2  Archiv  f.  Psych.,  viii"(1878),  Hft.  3. 


CONDUCTION    OF    IMPULSES.  787 


muscles  of  the  thigh  caused  by  sharply  striking  the  patellar  ten- 
don, as  reflex  movemenLs  started  by  atierent  impulses  passing 
along  the  same  nerves. 

Sec.  3.  As  a  Conductor  of  Afferent  and  Efferent 
Impulses. 

When  we  move  our  foot,  or  feel  something  touching  our 
foot,  efferent  or  afferent  imi)iilses  must  evidently  pass  along 
the  whole  length  of  the  sjunal  cord  on  their  way  from  and 
to  tiie  brain.  We  might  suppose  that  in  such  cases  sensory 
impulses  are  conveyed  straight  along  a  libre  from  the  pe- 
ripherv  to  the  sen^orium.  and  volitional  impulses  straight 
along  a  fibre  from  the  ''organ  of  the  will  "  to  the  muscular 
fibre.  Or  we  might  suppose  that  the  conduction  is  not  sim- 
ple, but  carried  out  by  a  more  or  less  complicated  system  of 
relays.  Both  anatomical  and  physiological  considerations 
show  that  the  latter  view  is  the  coriect  one. 

The  i)henomeiia  of  reflex  action  have  shown  us  that  the 
cord  contains  a  number  of  more  or  less  complicated  mech- 
anisms capable  of  producing,  as  reflex  results,  co-ordinated 
movements  altogether  similar  to  those  which  are  called  forth 
by  the  vvill.  Now  it  must  be  an  economy  to  the  body,  that 
the  will  should  make  use  of  these  mechanisms  already 
present,  by  acting  directly  on  their  centres,  ratlier  than  that 
it  should  have  recourse  to  a  special  apparatus  of  its  own  of 
a  similar  kind.  And  from  an  anatomical  point  of  view,  it 
is  clear  that  the  white  matter  of  the  upper  cervical  cord 
does  not  contain  a  sutficient  number  of  fil)res,  even  of  at- 
tenuated dimensions,  to  connect  the  bi-ain.  by  aflferent  or 
efferent  ties,  with  every  sensory  or  motor  nerve-ending  of 
the  trunk  and  limbs. 

Regarded  in  a  genetic  aspect,  the  spinal  cord  is  a  series  of  ce- 
mented segments,  having  mutual  relations  one  with  the  other, 
and  all  being  governed  by  the  dominant  cerebral  segments.  And 
we  might  fairly  expect  to  find  that  in  each  segment  of  the  cord 
part  of  the  structures  are  purely  segmental,  and  serve  as  a  ner- 
vous centre  for  the  atierent  and  efierent  nerves  corresponding  to 
a  portion  of  the  body,  while  part  are  commissural  structures 
connecting  the  segment  with  other  segments,  and  the  remainder 
are  structures  connecting  the  governed  segment  with  the  govern- 
ing cerebral  organs.  Some  such  arrangement  as  this  is  indicated  by 
the  directions  taken  by  the  fibres  of  the  roots  of  the  spinal  nerve  ; 
and  the  view  is  supported  by  the  results  gained  by  comparing 
sections  of  the  spinal  cord  taken  at  different  points  of  its  length. 


788 


THE    SPINAL    CORD. 


If  a  curve  be  constructed  representing  the  sectional  area  of  the 
nerve-roots  entering  the  spinal  cord,  at  tlieir  respective  points, 
along  its  whole  length  from  the  first  cervical  to  the  last  sacral 
nerve,  some  such  form  as  that  shown  in  Fig.  207  would  be  ob- 
tained.    If  instead  of  the  sectional  area  of  each  pair  of  roots  the 


Fig.  207. 


'     ^?   l^f  i:i    II    I    V    IV  ill    I)    i  %1\  Yi  X  IX  vlil  VII  VI   V  IV   111   (\    i  Vii  vil  VI  ^  W  !il   fl    j 

Diagram  showing  the  relative  Sectional  Areas  of  the  Spinal  Xerves,  as  they  join 
the  Spinal  Cord.    (To  be  read  from  left  to  light.) 

In  this  and  the  succeeding  figures  taken  from  Woroschiloff 's  paper  in  Ludwig's 
Arbeiten,  1S7-1,  -Mid  constructed  from  Stilling's  data  of  the  human  spinal  cord,  the 
cervical,  dorsal,  lumbar,  and  sacral  nerves  are  used  as  abscissse  ;  3  mm.  to  the  in- 
terval between  each  two  nerve-roots.  The  ordinates  are  in  millimeters,  each  mm. 
corresponding  to  a  square  unit  of  surface  of  nerve-root  section,  of  gray  substance, 
or  of  white  substance. 

Fig.  208. 


4   V  IV  ill  11  i  V  IV  III  ij  I  )dixi  X  ut Vlil VII  vi  v  iv  lii  li  i  viiivii  vi  v  iv  iii  ii  i 

Diagram  showing  the  United  Sectional  Areas  of  the  Spinal  Nerves,  proceeding 
from  below  upwards.  The  ordinates  in  this  figure  are  smaller  than  in  the 
preceding. 


Fig 


IS 

10 
B 


^l    V  IV  m  ii   1   y  lY  m  ii   i  xii  xi  x  ixvitiviivi  V  iv  iij  ii  i  vuiviiv]  v  iv  in  a 

Diagram  showing  the  Variations  in  the  Sectional  Area  of  the  Gray  Matter  of  the 


Spinal  Cord,  along  its  length. 


CONDUCTION    OF    IMPULSES. 


789 


Fig.  210. 


'  v  IV  11/  i\    I    V  IV  111   II   i  >ai  XI  X  IX  viii^i  VI  V  /v  in  ii    i  vi!iviivi  v  iv  ni  n   i 
Diagram  showing  the  Variations  in  the  Sectional  Area  of  the  Lateral  Columns  of 
the  Spinal  Cord,  along  its  length. 


Fig.  211. 


15 

fO 

r—^^~\ 

s 

^^^ 

-^— 

^                 y       ^- 

o 

V  IV  111    II 

1    V   IV  ill    11 

)^i  XI  y  ixviii  vii  VI  V  IV  111  11  1  viii  vii  VI  v  iv  ill  l 

1 

Diagram  showing  the  Variations  in  the  Sectional  Area  of  the  Anterior  Coluraus 
of  the  S[>inal  Cord,  along  its  length. 


Fig.  212. 


V  IV  111  II  i   V  IV  III  11   I  }ai  XI  X  IX  m  vn  vi  v  im  m  ii   i  viii  vii  vi  v  iv  in  ii  \ 

Diagram  showing  the  Variations  in  the  Sectional  Area  of  the  Posterior  Columns 
of  the  Spinal  Cord,  along  its  length. 

continued  summation  of  the  roots  were  used  to  construct  the 
curve,  the  form  would  be  that  of  Fi^j.  208.  If  the  variations  of 
the  sectional  area  of  tlie  gray  matter  at  different  points  of  its 
length  were  thrown  into  a  curve,  the  form  would  be  that  of  Fig. 
209,  If  the  variations  of  the  sectional  area  of  the  lateral  col- 
umns were  taken,  the  curve  would  take  the  form  of  Fig.  210. 
The  anterior  columns  similarly  treated  would  give  Fig.  211,  and 
the  posterior  Fig.  212.  A  comparison  of  these  several  figures 
suggests  the  view  that  the  gray  matter  of  the  cord  is  pre-emi- 
nently segmental,  falling  and  rising  as  it  does  with  the  amount 
of  nerve-fibre  passing  into  each  part  of  the  cord,  and  that  the 
lateral  columns,  increasing  as  they  do  from  below  upward,  much 
more  steadily  than  either'the  gra}'  matter  or  the  anterior  and 


790  THE    SPINAL    CORD. 


posterior  columns,  are  the  chief  means  hy  which  the  brain  is 
brouiijht  into  connection  vvith  the  several  segments  of  the  cord, 
and  thus  with  the  nerves  of  the  body  at  large. 

Our  information  concerning  tiie  conduction  of  Impulfses 
along  the  spinal  cord  is  derived  partly  from  expeiiment  and 
])artly  from  i)atliological  observation.  Both  these  metlmds 
liave  their  advantages  and  disadvantages.  Jn  experiments 
there  is  danger  of  confounding  the  immediate  and  temporary 
effects  of  the  operation,  such  as  those  produced  by  shock, 
with  the  more  real  and  lasting  effects.  It  is  difficult  too  in 
sucii  cases  to  determine  the  existence  of  sensations,  and  to 
distinguish  between  reflex  and  purely  voluntary  movements. 
In  pathological  cases  we  have  the  advantage  of  being  able 
cleaiiy  to  define  sensation  and  volition,  but  this  is  frequently 
more  than  counterbalanced  by  the  diffuse  nature  of  the 
injury  or  disease,  and  the  want  of  exact  anatomical  verifi- 
cation. When  these  facts  are  borne  in  mind,  it  will  easily 
be  understood  that  in  no  part  of  physiology  are  the  state- 
ments of  investigators  more  conflicting  and  unsatisfactory. 

According  to  the  views  put  forward  by  Brown-Siquard 
and  others,  transverse  division  of  the  lateral  half  of  the 
cord  is  followed  on  the  same  side,  below  the  injury,  by  loss 
of  voluntary  movement,  accom})anied,  not  by  loss  of  sei  sa- 
tion,  but  by  hypenpsthesia,  and  on  the  opposite  side  by  loss 
of  sensation  without  any  affection  of  voluntary  movement; 
whereas  a  longitudinal  median  incision  tlirough  the  cord 
causes  on  both  sides  loss  of  sensation  in  an  area  corre- 
sponding to  the  length  of  the  incision,  without  any  impair- 
ment of  voluntar}'  movement.  That  is  to  say,  sensory  im- 
l)ulses  entering  into  the  cord  at  its  posterior  root  immediately 
cross  to  the  other  side  of  the  cord  and  so  ascend  to  the 
brain,  whereas  effeient  impulses  of  volition,  though  they 
cross  in  the  region  of  the  medulla  oblongata  or  higher  up 
(and  hence  in  cases  of  paralysis  from  cerebral  mischief,  the 
light  side  loses  the  power  of  voluntary  movement  when  the 
lelt  he!tiis[diere  is  affected,  and  uice  versa)^  keep  to  the  same 
side  of  the  cord  along  its  whole  length.  (Fig.  213.)  The 
l)aths  may  be  somewhat  more  closely  defined  by  stating  that 
the  sensory  impulses  pass  from  the  posterior  roots  along  a 
certain  length  of  the  posterior  columns,  and  then  cross  over 
to  the  gray  matter  of  the  opposite  side,  in  which  they  ascend 
to  the  brain,  while  volitional  impulses,  having  crossed  in  the 
pons  Varolii  and  medulla  oblongata  before  their  entrance 


CONDUCTION    OF    IMPULSES. 


791 


into  the  cord,  descend  in  the  antero-lateral  columns,  keeping 
to  the  same  side  throughout,  and  leave  the  cord  by  the  an- 
terior roots.  Accordinu:  to  Vulpian'  and  others,  the  vo- 
litional impulses  are  c-onfined  in  the  cervical  region  to  the 
lateral  columns,  thouoh  in  the  dorsal  and  lumbar  regions 
they  travel  in  tlie  anterior  columns  as  well,  and  the  decus- 
sation is  not  confined  to  or  completed  in  the  region  of  the 
medulla,  but  is  continued  some  way  down  ;  and  similarly 
the  decussation  of  the  sensory  irai)ulses  is  not  sudden  but 

[Fig.  213. 


Diagrram  showing  tlie  course  of  the  Motor  and  Sensiry  Fibres  in  the  Spinal  Cord 
and  Medulla  Oblongata,  ^r,  ganglion  on  the  posterior  root ;  ^r,  posterior  root;  ar, 
anterior  root ;  I,  left  side  ;  r,  right  side  ;  mo,  medulla  oblongata  ;  1,  2,  3,  indicate  the 
alteration  in  the  po.-<ition  of  the  motor  conductor  fibres;  1,  a  fibre  coming,  from  the 
centres  above  the  pons  Varolii;  2.  puint  of  crossing  and  decussating,  in  the  pons 
Varolii  or  medulla  oblongata  ;  3,  showing  fibre  going  down  the  opposite  side  of  the 
cord.  The  sensory  fibres  ol  the  posterior  root  (/>?•)  dt-cussate  soon  after  entrance  into 
the  substance  of  the  cord,  and  coniinue  up  to  the  cerebral  centres  on  the  opposite 
side  to  which  they  entered.] 

gradual,  so  that  section  of  a  lateral  half  of  the  cord  affects 
sensation  on  both  sides,  though  most  on  the  opposite  side. 
Schiff,  and  others  with  him,  make  a  distinction  between 
the  conduction  of* distinct  tactile  sensations  and  that  of 
general  sensibility,  as  well  as  between  the  conduction  of 
A'olitional  impulses  and  that  of  impulses  merely  forming 
part  of  a  reflex  action.  They  hold  that  purely  volitional 
impulses  pass  exclusively  along  the  antero-lateral  columns, 
and  purcl\-  tactile  sensations  along  the  posterior  columns  of 


^  Syst.  Xerv.,  ley.  xvii. 


792  THE    SPINAL    CORD. 


the  same  side,  and  that  tlie  gray  matter  is  capable  of  trans- 
mitting in  all  directions  sncli  afferent  impnlses  as  only  give 
rise  to  affections  of  general  sensil)ility,  and  such  efferent 
impulses  as  are  parts  of  reflex  actions.  Hence,  according 
to  them,  when  at  any  part  of  the  cord  the  continuity  of  the 
wliite  matter  is  wholly  l»roken,  so  tliat  the  parts  above  the 
injury  are  connected  with  those  below  by  gray  matter  only, 
tactile  sensations  and  voluntary  movements  are  entirely  ab- 
sent in  the  parts  below  the  injury,  though  violent  stimula- 
tion of  those  parts  will  give  rise  to  pain,  and  reflex  actions 
in  them  may  be  induced  by  stimuli  applied  to  parts  above 
the  injury.  Conversely,  when  at  any  point  the  gray  matter 
is  destroyed  ])ut  the  white  left  intact,  voluntary  movements 
and  tactile  sensations  remain  in  the  parts  below  tiie  injury, 
though  even  violent  stimuli  applied  to  those  parts  give  rise 
to  no  pain,  and  reflex  actions  cannot  be  induced  in  them  by 
stimuli  applied  to  the  parts  above  the  seat  of  injury. 

Schiff'  states  that  when  in  any  part  of  the  cord  the  posterior 
columns  only  are  left,  all  the  rest  of  the  white  and  the  gray  mat- 
ter being  removed,  tactile  sensations  remain  though  no  pain  is 
felt ;  there  is  analgesia  but  not  aua?sthesia ;  a  rabbit  thus  oper- 
ated on  is  readily  awakened  for  a  moment  from  sleep  (artificially 
induced  by  bleeding)  when  the  hind  limbs,  or  jiarts  below  the 
seat  of  injury,  are  even  lightly  touched,  but  exhibits  no  sign  of 
pain  when  the  nerves  are  laid  bare  and  pinched,  or  when  needles 
are  driven  through  the  skin.  This  experiment,  however,  on 
which  Schiff  rests  his  theory  of  analgesia,  does  not  prove  the 
existence  of  tactile  sensati(nis  ;  it  simply  shows  that  a  peculiar 
condition  may  be  brouoht  about  in  which  a  sensory  impulse  pro- 
duces a  maximum  initial  result  and  then  ceases  to  have  any  ef- 
fect. The  animal  moved  at  every  fresh  stimulus,  whether  slight 
or  strong,  whether  applied  to  the  skin  or  to  a  bare  nerve,  but 
after  the  first  explosion  the  central  organs  concerned  in  the  mat- 
ter, whatever  they  were,  appeared  to  be  exhausted.  The  condi- 
tion is  certainly  a  remarkable  one,  and  may  bear  many  interpre- 
tations. 

To  make  these  views  logically  complete,  we  must  suppose 
that  after  section  of  a  lateral  half  of  the  cord,  tactile  sen- 
sations and  voluntary  movements  would  be  entirely  lost  on 
the  same  side  below  tlie  seat  of  injury,  but  that  pain  would 
still  be  felt,  and  tiie  parts  would  still  be  capable  of  being 
thrown  into  movements  by  reflex  action. 

1  Lehrb.,  p.  251. 


CONDUCTION    OF    IxMPULSES.  793 


Such  are  the  two  chief  opinions  held  on  this  subject,  and  it 
must  be  confessed  that  neitlier  is  satisfactory.  Much  confusion 
has  probably  arisen  from  difterent  kinds  of  animals  being  used, 
and  difterent  parts  of  the  cord  operated  on,  and  from  the  want 
of  a  searching  microscopic  examination  of  the  results  of  the  va- 
rious operations.  These  objections  cannot  be  urged  against  the 
inquiries  of  Miescher  and  Woroscliiloft',' in  so  far  as  their  ex- 
periments were  all  C(mducted  on  rabbits,  and  on  the  same  dorsal 
part  of  the  cord.  Miescher  found  tliat  the  afferent  impulses 
which,  starting  from  the  sciatic  nerve  and  travelling  up  to  the 
medullary  vaso-motor  centre,  caused  a  rise  in  blood-pressure  by 
acting  on  that  centre,  passed  almost  exclusively  by  the  lateral 
columns.  When  one  lateral  column  was  divided,  stmiulation  of 
either  sciatic  produced  much  less  than  the  normal  eft'ect ;  when 
both  columns  were  divided,  no  effect  at  all  was  produced.  When 
only  the  lateral  columns  were  left,  the  other  parts  being  de- 
stroyed, the  vaso-motor  influences  of  the  sciatic  stimulation  ap- 
peared to  be  quite  normal.  From  which  it  would  appear  that 
afferent  impulses,  such  as  affect  the  vaso-motor  centre,  pass  from 
one  sciatic  up  both  lateral  columns  ;  and  Miescher  came  to  the 
conclusion  that  they  passed  more  on  the  opposite  than  on  the 
same  side.  He  also  thought  that  impulses  coming  from  more 
distant  parts  travelled  more  to  the  outside  of  the  columns  than 
those  from  nearer  parts.  It  need  hardly  be  urged  that  one  set 
of  experiments  of  this  kind,  the  result  of  which  can  be  deffnitely 
stated  in  millimeters  of  mercur}^  as  measurements  of  the  rise  of 
blood-pressure,  are  worth  a  score  of  others,  in  which  trust  has 
to  be  placed  in  variable  and  illusory  signs  of  sensation.  On  the 
other  hand,  it  is  obvious  that  the  path  of  the  afferent  impulses 
which  affect  the  vaso-motor  centre  might  be  quite  different  from 
that  of  the  afferent  impulses  giving  rise  to  sensations.  Woro- 
schiloff^  however  has  repeated  Miescher's  experiments,  using  the 
ordinary  signs  of  sensation  instead  of  blood-pressure,  and  has 
come  to  the  conclusion  that  both  the  afferent  impulses,  which, 
starting  in  the  hind  limbs,  give  rise,  either  by  developing  into 
sensations  or  by  originating  reflex  actions,  to  movements  in  the 
head  and  fore  limbs,  and  the  efferent  impulses,  which,  starting 
in  the  brain  or  upper  part  of  the  spinal  cord,  either  by  volition 
or  as  the  result  of  stimulation,  produce  movements  in  the  hind 
limbs,  pass  also  exclusively  through  the  lateral  columns.  The 
course  of  the  afferent  impulses  differs  however  from  that  of  the 
efferent  impulses,  in  so  far  that  the  former  cross  over  largely 
from  one  side  of  the  cord  to  the  other,  while  tiie  latter,  though 
they  also  cross,  do  so  to  a  small  extent  onl\'.  The  results  of  both 
these  inquiries  then  lead  to  the  conclusion,  that  in  the  dorsal 
spinal  cord  of  the  rabbit  the  lateral  columns  form  the  chief  bridge 


'  Ludwi^'s  Arbeiten,  1870,  p.  172. 
'  Ibid.,  1874,  p.  99. 


794  THE    SPINAL    CORD. 


between  the  fore  and  bind  part  of  tbe  body  for  the  conduction  of 
impulses  of  all  kinds. 

We  must  of  coursa  be  cautious  in  inferring  tbat  what  has  been 
found  to  be  true  of  the  dorsal  cord  is  also  true  of  other  parts  of 
the  cord  ;  still  the  experimental  results  just  described,  when  com- 
pared with  the  anatomical  facts  mentioned  at  pp.  787-90,  with 
which  they  wonderfully  agree,  enable  us  perhaps,  to  a  certain  ex- 
tent, to  interpret  the  observations  of  others  in  some  such  way  as 
follows.  In  the  first  place,  if  there  be  any  truth  in  our  interpre- 
tation of  the  phenomena  of  strychnia  poisoning,  the  gray  matter 
must  be  physiologically  continuous,  and  a  stimulus  of  sufficient 
strength  may  cause  impulses  to  travel  in  every  direction  along  its 
whole  length.  In  the  second  place,  this  protoplasmic  network 
is  marked  out  by  barriers  of  resistance  into  nervous  mechanisms 
for  the  carryin2;out  of  co-ordinated  muscular  movements  and  for 
the  association  of  afferent  impulses  with  these  movements.  If 
we  suppose,  as  we  have  already  urged,  that  volition  makes  use 
of  these  already  existing  mechanisms  instead  of  requiring  sepa- 
rate co-ordinating  mechanisms  in  many  respects  exactly  like  them, 
we  should  expect  to  tind  that  a  volitional  impulse,  tending  to- 
wards any  movement,  in  descending  from  the  brain,  passes  into 
the  gray  matter  of  the  cord,  at  the  spot  where  the  appropriate 
mechanism  exists,  before  it  emerges  in  the  anterior  root;  and 
conversely,  that  an  afferent  impulse  passes  first  into  the  mech- 
anism with  which  it  is  naturally  associated  for  the  production  of 
the  frequently  occurring  reflex  a(;tion,  before  it  travels  up  to  the 
brain  b}'  some  tract  more  direct  than  the  gra}'  matter.  And  we 
should  look  also  for  similar  arrangements  connecting  any  group 
of  nerves,  not  only  with  the  brain,  but  with  distant  parts  of  the 
cord.  In  harmou}-  with  these  functional  requirements  we  should 
be  prepared  to  And  that  the  entrance  of  any  large  group  of  nerves 
into  the  spinal  cord  was  associated  with  a  large  development  of 
gray  matter  for  the  local  co-ordinating  mechanisms,  and  with  a 
corresponding  increase  of  certain  parts  of  the  white  matter, 
whose  function  was  to  bring  these  mechanisms  into  connection 
with  both  the  afferent  and  efferent  nerves  ;  on  the  other  hand  we 
should  expect  to  tind  that  the  longitudinal  connecting  tracts  of 
white  matter  would  steadily  increase  from  below  upwards,  inas- 
much as  a  larger  and  larger  number  of  mechanisms  had  to  be 
connected  with  the  brain," though  the  increase  would  not  be  so 
rapid  or  uniform  as  that  of  the  united  sectional  areas  of  the 
nerves,  since  some  part  of  these  connecting  tracts  would  serve  to 
connect  distant  parts  of  the  spinal  cord  itself.  In  other  words, 
we  should  anticipate  some  such  an  anatomical  variation  of  the 
cord,  as  we  actually  do  tind  to  be  the  case  :  the  gray  matter  va- 
rying directly  in  proportion  to  the  nerves  entering  into  it  (Figs. 
207,  209),  and  the  anterior  and  posterior  columns  following  the 
gray  matter  very  closely  (Figs.  211,  212),  while  the  lateral  col- 
umns (Fig.  210)!!^  though  not  exactly  parallel  to  the  united  sec- 


CONDUCTION  OF  IMPULSES.  795 


tional  areas  of  the  nerves  (Fig.  208),  steadily  increase  from  be- 
low upwards. 

For  the  present  we  may  be  content  with  some  such  general  ex- 
position as  the  above,  but  we  already  possess  the  beo-innings  of 
a  more  exact  analysis.  The  AVallerian  method  has  been  applied 
to  the  spinal  cord  with  some  striking  results.  Tiirck'  long  ago 
showed  that  in  cases  of  disease  of  the  brain  certain  definite  tracts 
of  degenerated  nerves  may  be  traced  downwards  along  the  spinal 
cord  in  the  anterior  and  lateral  columns,  while  in  cases  of  local- 
ized spinal  disease  similar  tracts  appear  above  the  seat  ot  disease 
in  the  posterior  and  lateral  columns.  Similar  results  have  been 
obtained  by  subsequent  inquirers  ;  and  Schietferdecker,^  studying 
with  care  the  condition  of  the  cord  consequent  upon  its  complete 
division  at  any  point  (chiefiy  at  the  junction  of  tlie  lumbar  and 
dorsal  regions),  finds  tracts  of  degenerated  fibres  which  run  above 
the  seat  of  injury  chiefiy  in  the  posterior,  but  also  to  a  less  ex- 
tent in  the  hinder  circumferential  parts  of  the  lateral  columns, 
and  heloii:  the  seat  of  injury  in  the  anterior  columns,  and  as  scat- 
tered bundles  in  the  lateral  columns.  The  former,  having  their 
''trophic  centres"  below,  may  be  regarded  as  fibres  carrying 
impulses  upward,  the  latter  as  carrying  impulses  downwards  ; 
both  are  most  abundant  in  the  immediate  neighborhood  of  the 
cicatrix  where  the  cord  was  divided;  and,  though  they  may  be 
traced  a  long  way  in  their  respective  directions,  diminish  more 
or  less  gradually.  These  facts  may  fairly  be  taken  as  showing 
that  a  region  of  the  spinal  cord  is  connected  by  afferent  fibres 
with  regions  higher  up,  and  by  efferent  fibres  with  regions  lower 
down,  the  fibres  running  in  the  tracts  described  above  ;  but  it 
would  be  hazardous  to  venture  a  more  exact  opinion  as  to  the 
exact  function  of  the  respective  tracts  until  our  knowledge  of 
similar  degenerations  has  been  greatl}-  enlarged.  Schiefferdecker 
is  himself  struck  by  the  fact  that  the  great  mass  of  the  lateral 
columns  is  unaffected  by  the  section  ;  this  he  explains  by  the 
hypothesis  that  the  larger  number  of  the  fibres  of  these  columns, 
being  connected  at  both  ends  with  homologous  nerve-cells,  con- 
duct equallj'in  bach  directions,  and  hold  both  their  terminal  cells 
as  ''trophic  centres,"  so  that  when  they  are  cut  off  from  the  one 
set  they  can  still  depend  on  the  other.  Flechsig'  has  ('btained 
some  noteworthy  results  by  the  embryological  method.  Observ- 
ing that  the  fibres  of  difierent  tracts  acquire  their  medullary 
sheaths  at  different  times,  he  has  been  enabled  to  difierentiate  the 
longitudinal  fibres  of  the  spinal  cord  into  separate  tracts,  some  of 
which  appear  to  pass  on  into  or  down  from  the  crura  cerebri, 
some  to  end  or  begin  in  the  medulla  oblongata,  and  others  to  end 
and  begin  in  the.  spinal  cord  itself.     His  results  in  many  points 

•  Wien.  Sitzungsbericht.,  Bd.  vi   (1851). 
2  Virchow's  Archiv,  Bd.  67  (1876),  p.  542. 
^  ^  Die  Leitungsbahne  im  Gehirn  und  Riickenmark  des  Menschen,  Leip- 
zig, 1876. 


796  THE    SPINAL    CORD. 


coincide  with  those  of  Tiirck  and  Schiefferdecker,  and  in  some 
respects  are  inconsistent  with  the  general  view  given  ahove  ;  but 
further  inquiries  are  necessary  before  these  various  anatomical 
data  and  the  results  of  ph}  siological  experiment  and  observation 
can  be  united  in  a  consistent  exposition. 

In  an  ordinary  state  of  things,  with  the  cord  quite  intact,  we 
should  expect  to  find  that  both  voluntary  and  sensory  impulses 
spread  into  the  gray  matter  as  little  as  Avas  consistent  with  their 
due  propagation,  and  that  they  passed  chietly  along  their  own 
side ;  but  we  can  also  readily  itnagine  that  when  the  ordmary 
tracts  were  interfered  with,  as  after  section  of  the  white  matter, 
powerful  impulses  (nnd  these  would  naturally  be  sensory  ones, 
since  the  generation  of  sensory,  but  not  of  voUtional  impulses,  is 
in  the  hands  of  the  experimenter,  and.  moreover,  is  of  almost 
unlimited  range)  might  spread  in  many  directions  over  the  gray 
matter.  Such  errant  impulses  would  of  necessity,  when  they 
reached  the  conscious  centre,  appear  not  as  tactile,  but  simply  as 
the  ditiused  sensations  which  we  call  pain.  Hence  it  would  be 
said  that  the  gray  matter  conveyed  the  sensory  impulses,  not  of 
touch,  but  of  pain. 

Moreover,  we  must  bear  in  mind  that  the  barriers  of  resistance 
in  the  protoplasm  of  the  gray  matter  are  not  wholly,  even  if 
largely,  structural.  We  have  seen  that  the  whole  cord  may  be 
mhibited  in  reference  to  reflex  action.  This  total  inhibition  is 
probably  made  up  of  individual  inhibitions  ;  and,  in  studying  the 
effects  of  section  or  injury  of  the  spinal  cord  we  must  bear  in 
mind  that  the  change  caused  by  the  operation  most  probably 
affects  the  transmission  of  impulses,  not  only  negatively  by  break- 
ing down  accustomed  tracts,  but  also  positivel}-  by  altering  the 
action  of  inhibitory  impulses.  We  have,  in  all  probability,  an 
instance  of  this  in  the  remarkable  hyperfesthesia  which  is  a  con- 
stant effect  of  a  lateral  section  of  the  cord.  Since  it  appears  im- 
mediately after  the  operation,  it  cannot  be  due  to  any  inflamma- 
tory process.  Nor  can  it  be  explained  as  simpl}^  the  result  of  the 
increased  supply'  of  blood  to  the  peripheral  terminations  of  the 
sensor}'  nerves,  caused  by  the  section  involving  vaso-motor  tracts ; 
since  the  simple  section  of  a  vaso-motor  tract,  as  when  the  cer- 
vical sympathetic  is  divided,  does  not  give  rise  to  hyperpesthesia. 
Nor  can  we  explain  it  as  due  to  a  one-sided  hypereemia  of  the 
spinal  cord  itself,  for  we  have  no  evidence  that  such  a  state  of 
things  is  brought  about.  Since  it  lasts  for  a  very  considerable 
time,  it  cannot  be  due  to  any  passing  exciting  effect  of  the  opera- 
tion. In  the  frog,  after  hemisection  of  the  cord  below  the  brachial 
plexus,  this  h3'perpesthesia  is  manifested  by  increased  reflex 
movements  occurring  in  the  lower  limbs  as  well  as  in  the  upper 
when  the  lower  limbs  are  stimulated  ;  and  when  the  hemisection 
is  converted  into  a  complete  section  a  hypersesthesia  still  remains 
in  both  lower  limbs,  but  it  is  then  spoken  of  simply  as  increased 
reflex  action,  due  to  the  isolation  of  the  lower  cord  from  an  in- 
hibitory centre  placed  higher  up.     In  the  rabbit,  according  to 


CONDUCTION    OF    IMPULSES.  797 


Woroschiloff,  h}' pereesthesia,  after  hemisection  of  the  dorsal  cord, 
manifests  itself,  not  so  much  in  increased  reflex  actions  in  the 
lower  limbs  as  in  increased  movements  of  the  upper  part  of  the 
body  when  a  stimulus  is  applied  to  the  lower  limbs.  This  may 
be  interpreted  as  indicating  that  in  the  rabbit  the  hemisection 
removes  inhibitory  influences  which  previously  were  checking  not 
so  much  the  so  to  speak  direct  reflex  conversion  of  aflerent  into 
efferent  impulses,  as  the  propagation  of  the  afferent  impulses  to 
higher  parts  of  the  spinal  cord,  and  so  upwards  to  the  brain. 
We  have  already  insisted  on  the  probable  complexit}^  of  the  cen- 
tral processes  involved  in  a  reflex  action  of  even  the  simplest 
kind.  And  of  the  long  chain  of  molecular  events  intervening  in 
the  central  (reflex)  mechanism  between  the  advent  of  the  simple 
afferent  impulse  and  the  issue  of  the  simple  efterent  impulses,  we 
may,  witliout  too  great  a  presumption,  su[)pose  that  those  on 
what  we  may  call  the  afferent  side  of  the  chain  might  be  aftected 
by  extrinsic  (inhibitory  or  other)  influences  more  than  those  on 
the  efferent  side,  or  than  those  more  central,  and  vice  versa. 
Hence,  adopting  the  view  ah'eady  urged,  that  the  spinal  mechan- 
isms which  serve  for  reflex  actions  are  also  the  instruments  of 
the  higher  cerebral  operations,  the  aflerent  side  of  the  mechanism 
being  more  especially  connected  with  sensation,  and  the  efterent 
with  volition,  we  see  the  possibihty  of  the  removal  of  certain 
inhibitory  influences  manifesting  itself  especially  as  an  apparent 
increase  of  sansibility.  And  this  naturally  would  occur  more 
readily  in  the  rabbit,  where  the  reflex  actions  of  the  cord  are  so 
largely  subordinated  to  the  operations  of  the  brain,  than  in  the 
frog,  where  they  still  retain  so  much  of  their  ])rimitive  indepen- 
dence. When  the  section  passes  through  the  whole  cord  instead 
of  half,  the  absence  of  inhibition  can  of  course  only  be  shown  by 
increased  reflex  action  in  both  cases.  When  these  obscure  in- 
hibitory mechanisms  have  been  more  completely  worked  out, 
many  of  the  at  present  discordant  results  of  operations  and  in- 
juries will  probabl}'  be  explained  away. 

Much  discussion  has  arisen  on  the  question  whether  the 
spinal  cord  itself  is  irrital)le,  tiiat  is  whether  it  can  he  ex- 
cited by  stimuli  applied  directly  to  it.  Undoubtedh',  the 
cord,  as  a  whole,  is  irritable;  if  two  electrodes  be  plunged 
into  it,  and  a  current  sent  through  it,  muscular  movements, 
arterial  constriction*,  and  other  results  follow.  But  in  such 
a  case  the  current  may  fall  into  nerve-roots,  which  are  as 
irritable,  at  least,  as  the  nerve-trunks.  But  even  if  the 
nerve-roots  l)e  eliminated,  the  white  matter  at  least  is  irrita- 
ble ;  for  Fick  and  Engelken^  found  that  movements  resulted 

1  Dii  Bois-Revraond's  Archiv,  1867,  p.  198.  Pfliiger's  Archiv,  ii 
(1869),  p.  414. 

67 


798  THE    BRAIN. 

when  the  anterior  columns  were  isolated  for  some  way  clown 
and  stimulated  with  an  electric  current.  With  regard  to  tlie 
gray  matter  Van  Deen  and  Schilf  maintain  that  though  it 
will  convey  both  motor  and  sensory  impulses,  it  cannot 
originate  them.  They  speak  of  it  accordingly  as  kitie>^odic 
and  sesfheHodic,  as  simply  attording  paths  for  motor  and 
sensory  impulses.  But  tiieir  arguments  cannot  be  regarded 
as  conclusive,  and  Miescher^  found  that  when  after  division 
of  the  spinal  cord  lie  removed  the  posterior  columns  for  a 
certain  distance,  so  as  to  get  rid  of  all  afferent  nerve-fibres, 
the  exposed  gray  matter,  as  tested  by  the  effects  on  blood- 
pressure,  still  remained  sensitive,  especially  to  mechanical 
stimulation. 


CHAPTEJ^    VT. 
THE  BRAIK. 

\_The  Phi/siological  Anatomy  of  the  Brain. 

The  brain  is  that  poi-tion  of  the  cerebro  si)inal  axis  which 
is  situated  within  the  cranium.  It  consists  of  a  number  of 
ganglionic  collections  of  nervous  matter,  which  are  intimatel}' 
connected  with  each  other  by  intercommunicating  fibres, 
and  with  the  general  system  by  the  sensory  and  motor 
nerves.  The  mass  of  the  brain  substance  is  formed  by  the 
cerebrum,  cerebellum,  pons  Tarolii,  and  medulla  oblongata. 

M'lie  medulla  oblongata  (Figs  214,  215,  and  21(5)  is  con- 
tinuous below  with  the  si)inal  cord,  and  above  witli  the  pons 
Varolii.  It  is  situated  obliquely,  pointing  downwards  and 
backwards,  and  rests  upon  the  basilar  groove  of  the  occipital 

^  Op.  cit. 


ANATOMY    OF    THE    BRAIN. 


799 


bone.  It  is  rlivicled  anteriorly  and  posteriorly  into  two  por- 
tions bv  tl'.e  anterior  and  posterior  median  fissures,  which  are 
continuations  of  the  snme  fissures  in  the  spinal  cord.  The 
halves  are  symmetrical  and  marked  hy  orooves,  dividing 
eacli  of  them  into  four  smaller  portions,  wliicli   from   before 


Fig. 214. 


Fig. 215 


\^ 


Fig.  214.— View  of  the  Anterior  Surface  of  the  Pons  Varolii  and  Medulla  Oblon- 
gata, a  a,  anterior  pyramids  ;  6,  tlieir  decussation  ;  c  c,  olivary  bodies  ;  d  d,  restiform 
bodies;  e,  arciform  fibres;/,  fibres  described  by  Solly  as  passing  from  the  anterior 
column  of  the  cord  to  the  cerebellum  ;  g,  anterior  column  of  the  spinal  cord;  h, 
lateral  column  ;  p,  pons  Varolii ;  t,  its  upper  fibres;  5,5,  roots  of  the  fifth  pair  of 
nerves. 

Fig.  215.— View  of  the  Posterior  Surface  of  the  Pons  Varolii,  Corpora  Quadri- 
gtmina,  and  Medulla  Oblongata.  The  peduncles  of  the  cerebellum  are  cut  short  at 
the  side,  a  a,  the  upper  pair  of  corpora  quadrigeniiua  ;  b  b,  the  lower  ;  //,  superior 
peduncles  of  the  cerebellum  ;  c,  eminence  connected  with  the  nucleus  of  the  hypo- 
glossal nerve ;  e,  that  of  the  glosso-pharyngeal  nerve  ;  i,  that  of  the  vagus  nerve  ;  dd, 
restiform  bodies  ;  pp,  posterior  pyramids;  vv.  groove  in  the  middle  of  the  fourth 
ventricle,  ending  below  in  the  calamus  scriptorlus;  7  7,  roots  of  the  auditory  nerves. 


backwards  are :  the  anterior  pyramids,  lateral  tracts,  resti- 
form bodies,  and  poHerior  pyramids. 

The  anterior  pyramids  are  continuous  with  the  anterior  col- 
umns of  the  cord,  and  are  composed  principally  of  fibres  of  the 
anterior  columns,  and  partly  of  fii)i-es  of  the  lateral  tracts  and 
posterior  columns  of  both  sides.    The  fibres  from  the  opposite 


800 


THE    BRAIN. 


side  are  received  tliroiigh  four  or   five  decussating  bands 
which  cross  in  the  median  line.     (Fig.  214.)     These  bands 

Fig.  216. 


Shows  the  Under  Surface  or  Base  of  the  Encephalon  freed  from  its  Merahraues.  A, 
anterior;  B,  middle;  and  c,  posterior  lobe  of  cerebrum,  a,  the  fore  part  of  the  great 
pngitudinal  fissure;  b,  notch  between  hemispheres  of  the  cerebellum;  c,  optic 
commissure  ;  d,  left  peduncle  of  cerebrum  ;  e,  posterior  perforated  space  ;  e  to  r,  inter- 
peduncular space  ;//',  convolution  of  Sylvian  fissure;  h,  termination  of  gyrus  uncin- 
atus  behind  the  Sylvian  fissure;  i,  infundibulum  ;  I,  right  middle  crus  or  peduncli 
of  cerebellum  ;  m  m,  hemispheres  of  cerebellum;  n,  corpora  albicantia;  o,  pons 
Varolii,  continuous  at  each  side  with  middl-;  crura  of  cerebellum  ;  p,  anterior  per- 
forated space  ;  q,  horizontal  fissure  of  cerebellum  ;  r,  tuber  ciaereum  ;  ss",  Sylvian 
fissure;  t,  left  peduncle  or  cms  of  cerebrum;  mm,  optic  tracts;  v,  medulla  oblon- 
gata ;  X,  marginal  convolution  of  the  longitudinal  fissure.  1  to  9  indicate  the  several 
pairs  of  cerebral  nerves,  numbered  according  to  the  usual  notation,  viz. :  1,  olfactory 
nerve;  2,  optic;  3,  motor  nerve  of  eye;  4,  pathetic;  5,  trifacial;  6,  abducent  nerve 
of  eye  ;  7,  auditory,  and  7',  facial ;  8,  glosso-pliaryngeal ;  8',  vagus,  and  8",  spinal  ac- 
cessory nerve. 


are  formed   by  fibres  from  the  lateral  tracts,  of  fibres  from 
the  anterior  columns,  and  of  fibres  from  the  posterior  col- 


ANATOMY    OF    THE    BRAIN.  801 

urans.  The  lateral  tracts  are  continuous  with  tlie  lateral 
columns  cf  the  cord  ;  each  lias  resting  upon  it  a  small  oval 
mass  of  nervous  matter  called  the  olivary  body.  This  hody 
consists  of  white  matter  externall}',  and  contains  a  gray 
nucleus,  the  corpus  dentatum.  Running  from  the  anterior 
columns  and  curving  around  the  lower  end  of  the  olivary 
hod}'  is  a  narrow  hand  of  fibres  called  the  fibrf^  arciformes. 
The  restiforin  bodies  are  the  largest  of  the  four  portions, 
and  are  continuous  with  the  posterior  columns  of  the  cord; 
they  diverge  as  they  ascend  and  form  the  inferior  peduncles 
of  the  cerebellum.  (Fig.  218.)  The  posterior  pyramids  are 
small  narrow  cords  (fasciculi  graciks),  wliich  are  situated  one 
on  each  side  of  the  posterior  median  fissure,  and  separated 
from  the  restiform  bodies  by  slight  grooves.  These  bodies 
also  diverge  with  the  restiform  bodies,  and  become  blended 
with  them. 

The  fibres  of  the  anterior  pyramids  are  distributed  to 
the  cerebrum  and  cerebellum.  Of  the  cerebral  fibres,  some 
pass  directly  through  the  pons  Varolii ;  others  join  fibres  from 
the  olivary  l^ody  to  form  the  olivary  fasciculus.  The  cere- 
bellar fibres  pass  beneath  the  olivary  body  and  are  distrib- 
uted to  the  cerebellum.  The  fibres  of  the  lateral  tracts  run 
in  three  directions.  The  internal  form  the  greater  portion  of 
the  decussating  bands  and  a  part  of  the  anterior  pyramids. 
The  middle  ascend  in  the  floor  of  the  fourth  ventricle  and 
join  with  fiiir».s  of  the  restiform  bodies  and  posterior  P3'ra- 
mids  to  form  {he  fasciculi  teretes.  which  are  located  one  on 
each  side  of  the  median  fissure.  The  external  fil)res  join 
with  the  fii)res  of  the  restiform  bodies,  and  pass  to  the  cere- 
bellum. The  restiform  bodies  receive  fibres  from  l)oth  the 
anterior  and  lateral  columns,  and  after  entering  the  pons 
divide  int(j  two  portions:  the  inner  joins  the  fibi-es  of  the 
posterior  pyramids  and  are  traced  in  the  fasciculi  teretes  ; 
the  outer  fibres  are  distributed  to  the  cerebellum  and  form 
its  inferior  peduncle.  Tiie  fibres  of  the  posterior  pyramids 
are  continued  up  to  the  cerebrum  tiirough  the  fasciculi  te- 
retes or  to  the  cerebellum.  The  outer  fibi-es  of  the  restiform 
bodies  and  posterior  pyramids  diverge  as  they  ascend  in 
the  medulla  (Fig.  215),  and  form  the  postero-lateral  bound- 
aries of  a  lozenge  shaped  si)ace,  which  is  called  the  fourth 
ventricle.  The  ventricle  (Fig.  21<S)  is  bounded  antero-lat- 
erally  by  two  bands  of  matter  extending  from  the  cerebel- 
lum to  the  cerebrum,  called  the  pi'ocessus  e  cerehello  ad 
testes.     The  floor  is  formed  by  the  posterior  surface  of  the 


802  THE    BRAIN, 


pons  Varolii  and  medulla  oblongata;  the  roof  is  formed  l>y 
a  band  of  gray  matter,  the  valve  of  Vi6iii<HenH^  which  stretches 
across  between  the  processus  e  cerebello  ad  testes,  and  V)y 
the  under  surface  of  the  cerebellum.  In  the  portion  of  the 
floor  of  the  fourth  ventricle  corresponding  to  the  point  of 
divergence  of  the  posterior  pyramids  and  restiform  bodies 
is  a  part  which,  from  its  resemblance  to  the  point  of  a  pen, 
is  called  the  calamus  acriptoriui^  (J^'ig-  218). 

In  the  lower  part  of  the  medulla  the  gray  substance  is 
arranged  as  it  is  in  the  spinal  cord.  Approaching  upwards 
it  is  increased  in  quantity  and  becomes  mixed  with  white 
fibres.  The  gray  commissure  is  exposed  in  the  floor  of  the 
fourth  ventricle;  the  posterior  cornua  l)ecome  expanded 
and  form  the  tv.berculo  cinero  of  Rolando,  which  appear  at 
the  surface  of  the  medulla  oblongata  between  the  lateral 
tracts  and  restiform  bodies.  Beneath  the  floor  of  the  ven- 
tricle are  a  number  of  special  dep(  sits  of  gray  matter,  with 
which  are  connected  the  roots  of  origin  of  all  the  cranial 
nerves,  with  the  exception  of  tiie  optic  and  olfactory.  On 
each  side  of  tiie  median  fissure  is  a  longitudinal  eminence, 
tha  fasciculus  tereles.  On  the  lower  part  of  the  floor  are  a 
number  of  transverse  lines,  the  lineae  transversse  ;  these  are 
fibres  of  the  auditory  nerves,  which  emerge  from  the  median 
fissure  (Fig.  218). 

The  pons  Varolii  or  mesocephalon  (  Figs.  214,  2 IB)  is  com- 
posed of  gray  and  white  matter,  and  serves  as  a  medium  of 
communication  between  the  medulla  oblongata  and  the  cer- 
ebrum and  cerebellum  ;  also,  connecting  the  two  hemispheres 
of  the  cerebellum  by  transverse  commissural  bands.  Its 
posterior  surface  forms  tiie  upper  part  of  the  floor  of  the 
fourth  ventricle  ;  the  anterior  surface  rests  upon  the  basilar 
groove  of  the  occipital  hone.  Recent  writers  speak  of  the 
pons  Varolii  as  being  constituted  only  of  the  transverse 
fibres  connecting  the  hemispheres  of  the  cerel)ellum,  and  of 
what  is  commonly  known  as  the  pons  Varolii,  as  the  tuber  an- 
nulare. 

The  crura  cerebri  (Fig.  21R)  ai'e  two  bands  of  white 
fibrous  matter,  which  extend  from  the  pons  Varolii  to  the  un- 
der surface  of  each  cerebral  hemisphere,  where  they  run  to 
the  corpora  striata  and  optic  thalami,  or  directly  to  the 
cerebral  cortex.  In  the  interior  of  each  band  is  a  gra}'' 
body,  called  the  locus  niger^  which  separates  the  fibies 
of  each  cms  into  two  layers;  tiie  superficial  or  anterior 
layer  is  called  the  crusta,  and  is  composed  of  fibres  coming 


ANATOMY    OF    THE    BRAIN. 


803 


from  the  nnterior  columns,  nnd  anterior  portion  of  the  lateral 
columns,  and  of  fibres   from   tlie  posterior   columns  which 


Fig.  21^ 


Dissection  of  Brain,  from  above,  exposing  the  Third,  Fourth,  and  Fifth  Ventri- 
cles, with  the  surrounding  parts. 
3^.  a,  anterior  part,  or  genu  of  corpus  callosum  ;  6,  corpus  striatum  ;  b',  the  corpus 
striatum  of  left  side,  dissected  so  as  to  expose  its  gray  substance ;  c,  points  by  a  line 
to  the  tsenia  semicircularis  ;  d,  optic  thalamus  ;  e,  anterior  pillars  of  fornix  divided  ; 
below  they  are  seen  descending  in  front  of  the  third  ventricle,  and  between  them 
is  seen  part  of  the  anterior  commissure  ;  in  front  of  the  letter  e  is  seen  the  slitlike 
fifth  ventricle,  between  the  .two  laminai  of  the  septum  lucidum  ;  /,  soft  or  middle 
commissure;  g  is  placed  in  the  posterior  part  of  the  third  ventricle;  immediately 
behind  the  latter  are  the  posterior  commissure  (just  visible)  and  the  pineal  gland, 
the  two  crura  of  which  extend  forwards  along  the  inner  and  upper  margins  of  the 
optic  thalami  ;  h  and  j,  the  corpora  quadrigemina  ;  A-,  superior  crus  of  cerebellum; 
close  to  k  is  the  valve  of  Vieussens,  which  has  been  divided  so  as  to  expose  the  fourth 
ventricle;  /,  hippocampus  major  and  corpus  fimbriatum,  or  tienia  hippocampi;  m, 
hippocampus  minor;  n,  emineutia  collateralis;  o,  fourth  ventricle;  p,  posterior  sur- 
face of  medulla  oblongata  ;  r,  section  of  cerebellum ;  .?.  upper  part  of  left  hemisphere 
of  cerebelhim  exposed  by  the  removal  of  part  of  the  posterior  cerebral  lobe. — After 
HiRSCHFELD  and  Leveille. 


804  THE    BRAIN. 

decussated  at  the  anterior  pyramids  ;  the  deep  or  posterior 
layer  is  called  the  tegmentum^  and  is  composed  of  fibres 
from  the  lateral  tracts,  posterior  columns  and  olivary  fiis- 
cicnli,  and  from  the  cerebellum.  The  fibres  of  the  crura  in 
their  course  to  the  cortex  of  the  cerebrum  run  through 
or  beside  four  large  giiiglia,  the  corp(M-a  striata  and  optic 
thalami  (Fig.  217).  These  are  called  the  '•  basal  ganglia." 
They  are  imbedded  in  the  cerebral  substance,  and  are  com- 
posed of  both  white  and  gray  matter.  The  corpora  striata 
lie  anterior  and  external  to  the  optic  thalami  ;  their  external 
surface  is  gray,  and  the}'  present  in  a  transverse  section  a 
striated  appearance,  being  composed  of  alternating  layers  of 
gray  and  white  substance.  Each  ganglia  is  cotnposed  essen- 
tially of  two  nuclei ;  the  largist  is  the  lenticular  or  extra- 
ventricular  nucleus;  the  smaller  is  the  caudate  or  intraven- 
tricular nucleus  (Fig.  220).  Running  upwards  between  the 
lenticular  nucleus  and  the  optic  thalamus  behind,  and  the 
lenticular  nucleus  and  caudate  nucleus  in  front,  is  a  band  of 
white  matter  which  is  called  the  internal  cap>^ide.  External 
to  the  lenticular  nucleus  is  a  second  band  called  the  external 
capsale.  The  optic  thalami  are  two  oblong  bodies  situated 
posterior  and  internal  to  the  corpora  striata;  each  resting 
upon  and  embracing  the  corresponding  crus  cerebri.  Exter- 
nally they  are  composed  of  white  matter,  and  internally  of 
both  W'hite  and  gray  matter. 

The  anterior  fibres  or  crusta  of  the  crus  cerebri  run  to 
the  corpus  striatum  of  its  ovvn  side;  the  posterior  fibres  or 
tegmentum  run  to  the  optic  thalamus.  Of  these  fibres  some 
probably  terminate  in  the  ganglia,  while  others  are  con- 
tinued on  to  different  parts  of  the  cerebral  cortex,  either 
through  the  basal  ganglia  or  the  capsules  above  referred  to. 

The  corpora  gaadrigernina  or  optic  lobes  (Figs.  215, 
217)  are  situated  below  the  i)osterior  border  of  the  corpus 
callosum  and  above  the  aqueduct  of  Sylvius.  These  bodies 
are  four  in  number,  and  are  placed  in  pairs  ;  the  anterior 
pair,  wdiich  is  the  largest,  is  called  the  nates;  the  posterior 
pair  is  called  the  testes.  They  both  consist  of  gray  and 
white  matter,  and  are  connected  on  each  side  with  the  optic 
thalami  and  optic  tracts  b\^  bands  of  nervous  matter  called 
brachia.  Those  connecting  the  nates  with  the  thalamus  are 
called  the  anterior  brachia  ;  those  c(mnecting  the  testes,  the 
posterior  brachia.  The  corpora  (piadrigemina  receive  fibres 
from  the  cerebellum  through  the  processus  ad  testes,  from 
the  olivary  fasciculi  and  the  optic  tracts  and  third  nerves. 


ANATOMY    OF    THE    BRAIN. 


805 


The  corpora  geinculoia  are  two  small  bodies  situated  on 
each  side,  external  to  the  corpora  quadrigemina,  and  be- 
neath and  posterior  tothe  optic  thalamus.  They  are  called 
from  their  situations  the  internal  and  external.  Tlie  inter- 
nal and  testes,  and  the  external  and  nates,  are  jointly  con- 
nected with  the  optic  tracts. 

The  cerebellum  (Fig.  218)  or  lesser  brain  rests  in  the  in- 
ferior occipital  toss*.    It  consists  of  two  lateral  hemispheres, 

Fig.  218. 


View  of  CerebellurD   in   Section   and  of  Fourth  Ventricle,  with  the   neighboring 
parts  (from  Sappeyi. 

1,  median  groove  of  fourth  ventricle,  ending  below  in  the  calamus  scripforiii.'!,vri\h 
the  longitudinal  eminence.-  formed  by  the  fasciculi  leretes,  one  on  each  side;  2,  the 
same  groove,  at  the  place  where  the  white  streaks  of  the  auditory  nerve  emerge 
from  it  to  cross  the  floor  of  the  ventricle;  3,  interior  peduncle  of  the  cerebellum, 
formed  by  the  rcstiform  body;  4,  posterior  pyramid;  above  this  is  the  calamus 
scriptorius ;  5,  superior  peduncle  of  cerebellum,  or  processus  e  cerebello  ad  testes; 
6  6,  fillet  to  the  side  of  the  crura  cerebri  ;  7, 7,  lateral  grooves  of  the  crura  cerebri ; 
8,  corpora  quadrigemina. — After  Hieschfeld  and  Leveille. 


which  are  joined  together  by  a  central  lobe,  the  vermiform 
processes.  The  hemispheres  are  also  connected  with  each 
other  by  the  transverse  commissural  band  of  the  pons  Var- 
olii. This  band  is  called  the  middle  peduncle.  The  cere- 
bellum is  connected  to  the  cerebrum  by  the  pj^ocess us  e  cere- 
bello ad  lesfeti^  which  are  called  the  i<up)erior  peduncles  (Fig. 

68 


806  THE    BRAIN. 

218),  and  below  with  the  medulla  oblongata  b}'  the  inferior 
pedunch's.  The  cerebellum  is  composed  of  both  white  and 
gray  matter,  and  if  a  vertical  section  be  made  through  the 
middle  of  one  of  the  hemispheres  in  an  antero-posterior  di- 
rection, the  interior  will  be  seen  to  consist  of  white  matter, 
in  which  is  imbedded  a  gray  mass  called  the  corpus  denta- 
turn.  The  surface  of  the  white  central  matter  is  covered  by 
a  number  of  projecting  laminoe,  each  of  which  has  secon- 
dary or  tertiary  laminne  projecting  from  it.  The  laminae  con- 
sist of  a  central  white  matter  which  is  covered  with  gi'ay 
matter,  and  on  account  of  the  peculiar  foliated  appearance 
which  they  present  in  a  transverse  section  have  been  called 
arbor  vitse. 

The  cerebrum  constitutes  the  great  mass  of  the  brain  sub- 
stance. It  is  partially  divided  into  two  iiemispheres  by  the 
longitudinal  fissure,  which  divides  it  completely  anteriorly 
and  posteriorly,  but  only  partially  so  in  the  median  line, 
where  the  fissure  is  interrupted  by  a  broad  transverse  com- 
missural band  called  the  corpus  callosum. 

The  surface  of  the  hemispheres  is  marked  by  rounded 
ridges  or  convolutions^  which  are  separated  from  each  other 
b3^  iissures  called  sulci.  The  convolutions  are  very  compli- 
cated and  tortuous  in  their  course,  but  they  possess  suffi- 
cient individuality  in  their  arrangement  to  enable  tliem  to 
be  differentiated  and  named.  Each  hemisphere  is  divided 
into  five  lobes:  W\q  frontal^ parietal,  sphtno-leniporal^occip- 
ital  and  central  lobe,  or  island  of  Reil.  The  fissure  of  Syl- 
vius in  running  from  the  under  surface  of  the  brain  passes 
upwards  and  backwards  and  divides  into  two  branches,  the 
superior  and  longitudinal.  Anterior  to  the  fissure  is  situ- 
ated the  frontal  lobe  ;  the  parietal  lobe  is  separated  from 
the  frontal  lobe  by  the  fissure  of  Rolando,  and  from  the 
spheno-temporal^  which  is  below  it,  by  the  longitudinal 
branch  of  the  fissure  of  Sylvius ;  behind  both  of  these  is 
the  occipital  lobe.  The  central  lobe,  or  island  of  Reil,  lies 
within  the  fissure  of  Sylvius.  Each  of  these  lobes  consists 
of  a  number  of  recognized  convolutions.  The  first  convo- 
lution is  called  the  superior  or  first  frontal  (Fig.  219,  3), 
and  lies  along  the  margin  of  the  great  longitudinal  fissure  ; 
the  inferior  or  third  frontal  convolution  (I )  is  situated  just 
above  the  fissure  of  Sylvius,  and  curves  around  the  superior 
branch  of  the  fissure;  the  middle  or  second  frontal  (2)  is 
situated  between  these  two,  from  which  it  is  separated  by 
the  superior  and  inferior  frontal  fissures.     The  anterior  cen- 


ANATOMY    OF    THE    BRAIN. 


807 


tral  (4)  is  separated  from  the  posterior  central  (5)  b}'  the 
fissure  of  Rolando  ;  it  communicates  with  the  first  and  third 
frontal  convolutions.  The  posterior  central  (5)  is  continu- 
ous above  with  the  upper  parietal  (B)  convolution.  The 
supra-marijinal  convolution  (A)  lies  below  the  upper  parie- 
tal and  back  of  the  posterior  central.  It  curves  around  tlie 
extremity  of  the  longitudinal  branch  of  the  fissure  of  Syl- 
vius, and  then  running  downwards  and  forwards  forms  the 
superior  or  first  spheno-temporal  i^7).    This  convolution  then 

Fig.  219. 


Brain  of  Man. 

1,  the  inferior  or  third  frontal  convolution  ;  2,  middle  or  second  frontal ;  3,  supe- 
rior or  first  frontal;  4,  anterior  central;  5,  posterior  central;  A,  supra-marginal; 
B,  a,  superior  parietal ;  ^,  b,  angular  convolution;  7,  superior  or  first  spheno-tem- 
poral; 8,  middle  or  second  spheno-temporal;  9,  inferior  or  third  spheno-temporal ; 
10,  11,  12,  occipital  convolutions;  R,  fissure  of  Rolando  ;  S,  fissure  of  Sylvius. 


curves  backwards  and  forms  the  middle  or  second  spheno- 
temporal  (_8),  then  continuing  upwards  forms  an  angular 
curvature,  and  is  called  the  angular  or  posterior  parietal 
convolution  {,3,  b).  Below  the  middle  spheno-temporal  is 
the  inferior  or  third  spheno-temporal  ( 9 ) ;  this  forms  the 
lower  border  of  the  spheno-temporal  lobe.  The  occipital 
convolutions  (10,  11,  12)  are  not  well  exhibited  in  a  lateral 
view.  A  very  important  convolution,  the  gyrus  fornicatus^ 
curves  around  the  upper  part  of  the  corpus  callosum.  This 
convolution  commences  in  front  of  the  anterior  perforated 


808  THE    BRAIN. 

space,  curves  around  over  the  corpus  callosum,  and  then 
winding  around  downwards  and  forwards  eml)racing  tlie 
crus,  i)asses  forwards  as  tlie  gyrus  uncuiatui^^  and  at  its  an- 
terior aspect  becomes  sharply  curved  to  form  the  subiculum 
cornu  Ammoiiia. 

The  cerebrum  is  composed  of  both  white  and  gray  matter. 
Tlie  latter  is  found  for  the  most  part  as  constituting  the 
cortex  of  the  organ,  wliere  it  covers  the  convolutions  and 
dips  down  in  the  sulci.  It  is  about  two  or  three  mm.  in 
thickness,  and  consists  of  a  number  of  superposed  lamina  of 
nerve-cells  and  very  fine  nerve-fil>res,  which  are  imbedded 
in  a  matrix  called  the  neuy^oglia.  These  cells  are  of  rounded 
and  irregular  forms,  and  in  the  middle  layers  are  of  a  pyram- 
idal shape,  with  their  bases  generally  looking  towards  the 
centre  of  the  organ.  The  nerve-fibres  are  extremely  fine,  and 
according  to  KoUiker  measure  from  about  one  to  two  mmm. 
in  diameter.  The  prolongations  of  the  cells  are  probably 
continuous  with  the  axis-cylinders  of  the  medullated  nerve- 
fil»res,  which  run  to  the  central  |)arts  of  the  brain  ;  or  with  pro- 
longations of  other  cells,  thus  forming  intercommunications. 

In  the  interior  of  the  cerebrum  are  several  parts  which 
are  here  worthy  of  mention.  The  third  ventricle  is  an  open 
space  filled  witli  fluid,  which  is  bounded  laterally  by  the  optic 
thalami;  above  by  the  velum  interpositum,  which  is  a  re- 
flection inwards  and  forwards  of  the  pia  mater  through  a 
transverse  fissure  below  the  posterior  border  of  tiie  corpus 
callosum.  The  floor  is  formed  b}^  nervous  matter  which 
closes  the  interpeduncular  space ;  posteriorly  it  is  bounded  by 
the  posterior  commissure.  Below  the  commissure  is  an  open- 
ing, which  is  the  canal  leading  to  the  fourth  ventricle,  called 
the  aqueduct  of  Sylvius.  Extending  across  the  ventricle  are 
three  commissures:  the  anterior,  middle,  and  posterior. 
The  anterior  passes  through  the  corpora  striata  to  each 
of  the  hemispheres.  The  middle  (gray  commissure)  and 
posterior  extend  between  the  optic  thalami.     (Fig.  217.) 

The  lateral  ventricle  is  bounded  above  by  the  corpus  callo- 
sum; internall_y  by  the  septum  lucidum,  which  separates  it 
from  its  fellow  on  the  opposite  side  ;  below,  principally  b}'  the 
corpus  striatum,  optic  thalamus,  and  a  band  of  white  ner- 
vous matter,  the  fornix,  which  is  continuous  i)osteriorly  with 
the  corpus  callosum.  Extending  outwards  from  each  lateral 
ventricle  are  horn-shaped  cavities  or  cornua.  The  anterior 
extends  outwards,  curving  round  the  corpus  striatum  and 
running  into  the  frontal  lobe.     The  middle  extends  into  the 


ANATOMY    OF    THE    BRAIN. 


809 


spb.eno-temporal  lobe,  passii^^  behind  the  optic  thalamus, 
then  curvino-  around  the  crus  cerel)ri,  and  running-  deep  into 
the  lobe.  In  the  floor  of  this  cornu  are  three  parts,  which 
are  here  worthy  of  notice:  the  hippocampus  major,  pes 
hippocampi,  and  pes  accessorius.     (Fig.  217.)     The  hippo- 


FiG.  220. 


CLR 


ccn{ 


Te^tnenttt/. 


Cei-cbclc 


CCH,  cortex  of  the  cerebral  hemispheres,  the  con  vohitions  of  which  are  seen  to  be 
connected  by  arcuate  connecting  fibres;  Cft,  cortex  of  cerebellmn  :  Ci?,  corona  ra- 
diata,  consisting  of  fibres  extending  from  the  cortex  cerebri  to  Z.Vand  CN  the  len- 
ticular and  caudate  nuclei  of  the  corpus  striatum,  and  to  OT,  the  optic  thalamus. 
The  posterior  extremity  of  the  optic  thalamus  presents  two  enlargements,  the  corpus 
geniculatum  externum  and  internum,  which  is  seen  to  be  connected  with  the  optic 
tracts.  The  letters  Op.  Tr.  are  placed  on  a  bind  of  fibres  that  are  believed  to  run 
directly  from  the  cortex  cerebri  to  the  cortex  cerebelli ;  SC,  stria  cornea,  or  tjenia 
semicircularis;  i?A',  red  nucieus  of  tegmentum  ;  A^,  nates  ;  r.teslis;  /*,  pineal  gland; 
6,  fibres  passing  directly  i'uto  the  tegmentum  from  the  cortex  cerebri;  Fa  C,  the 
band  of  fibres  to  the  right  of  these  letters  are  part  of  the  superior  peduncle  of  the 
cerebellum. 


cnwpits  major  is  an  elonoated  rounded  wiiite  eminence, 
which  courses  the  floor  of  the  vcnti-icle,  ending  in  an  irreg- 
ular enlarged  extremity,  the  pes  hippocampi.  This  body  is 
continuous  with  the  gyrus  fornicatus,  and  is  curved  upon 
itself,  so  that  the  white  matter  is  external.     The  pes  acces- 


810  THE    BRAIN. 

sorius  or  eminentia  collateralis  (Fi^.  217)  is  a  white  emi- 
nence situated  between  the  hipitocampus  major  and  the  hip- 
pocampus minor  of  tlie  posterior  cornu.  The  posterior 
cornu  extends  dow^nwards  and  backwards  into  the  occipital 
lobe.  On  its  floor  is  an  eminence  called  the  hippocampus 
minor  Man}'  other  parls  of  interest  are  referred  to,  and 
shown  in  the  accompanying  cuts. 

The  distribution  of  the  fibres  in  the  brain  is  one  of  great 
physiological  interest.  According  to  Meynert^  the  cells  of 
the  same  convolution  are  connected  through  their  polar  pro- 
longations with  each  other;  by  arcuate  fibres  with  the  cells 
of  different  convolutions  (Fig.  220,  CCH);  and  with  the 
convolutions  of  the  opposite  side  by  fil)res  passing  the  most 
part  through  the  corpus  callosum.  To  tiie  corpus  striatum 
fibres  of  the  corona  radiata  {C'li)  run  from  the  whole  area 
of  the  cortex  to  the  lenticular  body  ;  others,  the  striae  cornea 
(^S'C),  run  from  the  temporal  lobe  to  the  anterior  part  of  the 
corpus  striatum  ;  others  run  to  the  olfactory  bulb  {0),  To 
the  optic  thalamus,  fibres  proceed  from  the  frontal  lobe, 
passing  between  the  lenticular  and  caudate  nuclei  (a),  and 
from  tlie  temporal  lobes,  walls  of  the  fissure  of  Sylvius,  the 
gyrus  fornicatus,  and  optic  i  racts  A  special  band  ( Op.  Tr.) 
is  supposed  to  run  from  the  cortex  to  the  cerebellum.  The 
course  of  many  other  special  fibres  has  been  referred  to  in 
previous  pages,  or  will  be  referred  to  hereafter.] 

Sec.  1.    On  the  Phenomena  exhibited  by  an  Animal 
deprived  of  its  cerebral  hemispheres. 

A  frog  from  which  the  cerebral  lobes  have  been  removed, 
even  though  all  the  rest  of  the  i»rain  has  been  left  intact, 
seems  to  possess  no  volition.  The  apparent I3'  spontaneous 
movements  which  it  executes  are  so  few  and  seldom  that  it 
is  much  more  rational  to  attribute  those  wiiich  do  occur  to 
the  action  of  some  stimulus  which  has  escaped  observation, 
than  to  su[)pose  that  they  are  the  products  of  a  will  acting 
only  at  long  intervals  and  in  a  feeble  manner. 

By  the  application,  however,  of  a[)propriate  stimuli,  such 
an  animal  can  be  induced  to  perform  all  tlie  movements 
which  an  entire  frog  is  capable  of  executing.  It  can  be 
made  to  swim,  to  leap,  and  to  crawl.  When  placed  on  its 
back,  it   immediately  regains  its  natural   position.     When 

^  Carpenter's  Physiology,  1876,  p.  896,  et.  seq. 


THE    BRAINLESS    FROG.  811 

placed  on  a  board,  it  does  not  fall  from  the  board  when  the 
latter  is  tilted  up  so  as  to  displace  the  animal's  centre  of 
gravity  :  it  crawls  up  the  board  until  it  o;ains  a  new  position 
in  which  its  centre  of  gravity  is  restored  to  its  proper  place. 
Its  movements  are  exactly'  those  of  an  entire  frog,  except 
that  they  need  an  external  stimulus  to  call  them  forth.  They 
inevitably  follow  when  the  stimuhis  is  applied  ;  they  come 
to  an  end  when  the  stimulus  ceases  to  act.  B3'  continually 
varying  the  inclination  of  a  board  on  which  it  is  placed,  the 
frog  may  be  made  to  continue  crawling  almost  indefinitely  ; 
but  directly  the  board  is  made  to  assume  such  a  position 
that  the  body  of  the  frog  is  in  equilibrium,  the  crawling 
ceases;  and  if  the  position  be  not  disturbed  the  animal  will 
remain  impassive  and  quiet  for  an  almost  indefinite  time. 
Wlien  thrown  into  water,  the  creature  begins  at  once  to 
swim  about  in  the  most  regular  manner,  and  will  continue 
to  swim  till  it  is  exhausted,  if  there  be  nothing  present  on 
whicli  it  can  come  to  rest.  If  a  small  piece  of  wood  be 
placed  on  the  water  the  frog  will,  when  it  comes  in  contact 
with  the  wood,  crawl  upon  it,  and  so  come  to  rest.  Such  a 
frog,  if  its  flanks  be  gently  stroked,  will  croak;  and  the 
croaks  follow  so  regularly  and  surely  upon  the  strokes  that 
the  animal  ma}-  almost  lie  played  upon  like  a  musical  in- 
strument. Moreover,  the  aiovements  of  the  animal  are 
influenced  b}'  light  ;  if  it  be  urged  to  move  in  any  particu- 
lar direction,  it  will  avoid  in  its  progress  objects  casting  a 
a  strong  shadow.  In  fact,  even  tu  a  careful  observer,  the 
differences  between  such  a  frog  and  an  entire  frog  which 
was  simply  very  stupid  or  very  olistinate,  would  appear 
slight  and  unimportant  except  in  one  point,  viz.,  tiiat  the 
animal  without  its  cerebral  hemispheres  was  obedient  to 
every  stimulus,  and  that  each  stimulus  evoked  an  appro- 
priate movement,  whereas  with  the  entire  animal  it  would 
be  impossible  to  predict  whether  any  result  at  all,  and  if  so 
what  result,  would  follow  the  application  of  this  or  that 
stimulus.  Both  are  machines;  but  the  one  is  a  machine 
and  nothing  more,' the  other  is  a  machine  governed  and 
checked  by  a  dominant  volition. 

jSow  such  movements  as  crav.iing,  leaping,  swimming, 
and,  indeed,  to  a  greater  or  less  extent,  all  bodily  move- 
ments, are  carried  out  by  means  of  co-ordinate  nervous 
motor  impulses,  influenced,  arranged,  and  governed  l)y  co- 
incident sensory  or  aft'erent  impulses.  We  have  already 
seen  that  muscular  movements  are  determined  by  the  mus- 


812  THE    BRAIN. 


ciilar  sense  ;  they  are  also  directed  by  means  of  sensory 
impulses  passing  centripetally  along  the  sensory  nerves  of 
the  skin,  the  eye,  the  ear,  and  other  organs.  Independently 
of  the  afferent  impulses,  which  acting  as  a  stimulus  call 
forth  the  movement,  all  manner  of  other  afferent  impulses 
are  concerned  in  the  generation  and  co-ordination  of  the 
resultant  motor  impulses.  Every  bodily  movement  such  as 
those  of  which  we  are  speaking  is  the  work  of  a  more  or 
less  complicated  nervous  mechanism,  in  which  there  are  not 
only  central  and  efferent,  but  also  afferent  factors.  And, 
putting  aside  the  question  of  consciousness,  with  which  we 
have  here  no  occasion  to  deal,  it  is  evident  that  in  the  frog 
deprived  of  its  cerebral  hemispheres  all  these  factors  are 
present,  the  afferent  no  less  than  the  central  and  the  effer- 
ent. The  machinery  for  all  the  necessary  and  usual  bodily 
movements  is  present  in  all  its  completeness.  The  share, 
therefore,  which  the  cerebral  hemispheres  take  in  executing 
the  movements  of  which  the  entire  animal  is  capable,  is 
simi)ly  that  of  putting  this  machinery  into  action.  The  re- 
lation which  the  higher  nervous  changes  concerned  in  voli- 
tion  bear  to  this  machinery  is  not  unlike  that  of  a  stimulus. 
We  might  almost  speak  of  the  will  as  an  intrinsic  stimulas. 
Its  operations  are  limited  I)}'  the  machinery  at  its  comman<l. 
The  cerebral  hemisi)heres  in  their  action  can  only  give  shai)e 
to  a  bodily  movement  by  throwing  into  activity  particular 
parts  of  the  nervous  machinery  situated  in  the  lower  en- 
cephalic structures;  and  precisely  the  same  movement  may 
be  initiated  in  their  absence,  by  applying  such  stimuli  as 
shall  throw  precisely  the  same  parts  of  that  machinery  into 
the  same  activity. 

Very  marked  is  the  contrast  between  a  frog  which,  though 
deprived  of  its  cerebral  hemispheres,  still  retains  the  optic 
lobes,  cerel)ellum  and  medulla  oblongata,  and  one  which 
possesses  a  spinal  cord  only.  The  latter  when  placed  on  its 
back  makes  no  attempt  to  regain  its  noi-mal  position  ;  in 
fact,  it  may  be  said  to  have  completely  lost  its  normal  posi- 
tion, for  even  when  placed  on  its  feet  it  does  not  stan<l  with 
its  fore  feet  erect,  as  does  the  other  anitnal,  but  lies  flat  on 
the  ground.  When  thrown  into  water,  instead  of  swim- 
ming it  sinks  like  a  lump  of  lead.  When  pinched,  or  other- 
wise stimulated,  it  does  not  crawl  or  leap  forwards  ;  it  simply 
throws  out  its  limbs  in  various  ways.  When  its  flanks  are 
stroked  it  does  not  croak;  and  when  a  board  on  which  it  is 
placed  is  inclined  sufficiently  to  displace  its  centre  of  gravity 


THE    BRAINLESS    FROG.  813 

it  makes  no  effort  to  regain  its  balance,  but  falls  off  the  board 
like  a  lifeless  mass.  Though,  as  we  have  seen,  there  is  in  all 
parts  of  the  spinal  cord  of  tiie  frog  a  large  amount  of  co- 
ordinating machinery,  it  is  evident  that  a  great  deal  of  the 
more  complex  machinery  of  this  kind,  especially  all  that 
which  has  to  deal  with  the  body  as  a  whole,  and  all  that 
which  is  concerned  vvith  equilibrium  and  is  specially  gov- 
erned by  the  higher  senses,  is  seated  not  in  the  si)inal  cord 
but  in  the  brain  and  medulla  oblongata.  We  sliall  pres- 
ently see  that  in  the  frog  a  great  deal  of  this  more  complex 
machinery  is  concentrated  in  the  optic  lobes.  The  point, 
however,  to  which  we  wish  now  to  call  special  attention  is 
that  the  nervous  machinery  required  for  the  execution,  as 
distinguished  from  the  origination,  of  bodily  movements 
even  of  tiie  most  complicated  kind,  is  i)resent  after  com- 
plete removal  of  the  cei'ebral  hemispheres,  though  these 
movements  may  require  tlie  co-operation  of  highly  differen- 
tiated afferent  impulses.^ 

Our  knowledge  of  the  piienomena  presented  by  the  bird 
or  mammal  from  which  the  cerebral  hemispheres  Imve  been 
removed  is  not  so  exact  as  in  tlie  case  of  the  frog.  We  may 
however  assert  that  volition  is  absent,  though  movements 
apparently  spontaneous  in  cliaracter  are  more  common  with 
the  mammal  than  with  the  iiv)g,  as  might  be  expected,  see- 
ing that  the  more  complicated  brain  of  the  former  affords, 
even  in  the  absence  of  the  cerebral  hemispheres,  much  more 
opportunity  for  the  origination  of  stimuli  within  the  nervous 
sysiem  itself,  and  for  the  \)\a.y  of  stimuli  however  originat- 
ing, than  does  that  of  the  latter. 

AVhen  the  cerebral  hemispheres  are  removed  from  a  bird 
the  animal  is  able  to  maintain  a  completely  normal  posture, 
and  that  too  when  the  corpora  striata  and  optic  thalami  are 
taken  away  at  the  same  time.  It  will  balance  itself  on  one 
leg,  after  the  fashion  of  a  bird  which  has  in  a  natural  way 
gone  to  sleep.  In  fac-t,  the  ai'pearnnce  and  behavior  of  a 
birtl  which  has  been  deprived  of  its  cerebral  hemispheres  are 
strikingly  similar  to  those  of  a  bird  sleepy  and  stupid.  Left 
alone  in  [)erfect  quiet,  it  will  remain  impassive  and  motion- 
less for  a  long,  it  may  be  for  an  almost  indefinite  time. 
When  stirred,  it  moves,  shifts  its  position;  and  then  on 
being  left  alone  returns  to  a  natural,  easN'  posture.  Placed 
on  its  side  or  its  back  it  will  regain  its  feet ;  thrown  into  the 

Of.  Goltz,  Functionen  d.  Nervencentren  des  Frosches,  1869. 


814  THE    BRAIN. 

air,  it  flies  with  considerable  precision  for  some  distance  le- 
jbre  it  returns  to  rest.  It  frequently  tucks  its  head  under 
its  wings,  and  if  b}-  judicious  feeding  it  has  been  kept  alive 
for  some  time  after  the  operation,  it  may  be  seen  to  clean 
its  featliers  and  to  pick  up  corn  or  to  drink  water  presented 
to  its  beak.^  It  may  be  induced  to  move  not  only  by  ordi- 
nary stimuli  applied  to  the  skin,  but  also  by  sudden  sharp 
sounds,  or  flashes  of  light ;  and  it  is  evident  that  its  move- 
ments are  to  a  certain  extent  guided  by  visual  sensations, 
for  in  its  flight  it  will,  though  imperfectly,  avoid  obstacles. 
Save  that  all  signs  of  distinct  volition  are  absent,  that  all 
satisfactory  indications  of  intelligence  are  wanting,  and  tiiat 
the  movements  are  on  the  whole  clumsy,  resembling  rather 
those  of  a  stupid  drows}'  bird  than  those  of  one  quite  wide 
awake,  there  is  very  little  to  distinguish  such  a  bird  from 
one  in  full  })ossession  of  its  cerebral  hemispheres. 

Even  in  a  mammal,  during  tlie  few  hours  which  intervene 
between  the  removal  of  tlie  hemispheres  and  death,  very 
much  the  same  phenomena  ma}'  be  observed.  The  rabbit, 
or  rat,  operated  on  can  stand,  run,  and  leap;  placed  on  its 
side  or  back,  it  at  once  regains  its  feet.  Left  alone,  it  re- 
mains as  motionless  and  impassive  as  a  statue,  save  now 
and  then  when  a  passing  impulse  seems  to  stir  it  to  a  sud- 
den but  brief  movement.  Such  a  rabbit  will  remain  for 
minutes  togetlier  utterly  heedless  of  a  carrot  or  cabbage  leaf 
placed  just  before  its  nose,  though  if  a  morsel  be  placed  in 
its  mouth  it  at  once  Ijegins  to  gnaw  and  eat.  When  stirred 
it  will,  with  perfect  ease  and  steadiness,  run  or  leap  for- 
ward ;  and  obstacles  in  its  course  are  very  frequently,  with 
more  or  less  success,  avoided.  It  will  often  follow  by  move- 
ments of  the  head  a  bright  light  held  in  front  of  it  (provided 
that  the  optic  nerves  and  tracts  have  not  been  injured  during 
the  operation),  and  starts  when  a  shrill  and  loud  noise  is 
made  near  it.  When  pinched  it  cries,  often  with  a  long  and 
seem.ingly  plaintive  scream.  Evidently  its  movements  are 
guided,  and  may  be  originated  by  tactile,  visual,  and  audi- 
tory sensations.'^     But  there  is  no  evidence  that  it  possesses 

'  Bischofl"  and  Voit,  Sitzungsberichte  Acad.  Wiss.  Miinchen,  1863, 
pp.  479,  469;  1868,  p.  105. 

2  Here  we  come  upon  a  difficulty  which  we  shall  meet  with  again  in 
the  present  chapter.  Are  we  justified  in  speaking  of  "sensation"  in 
cases  where  we  have  reason  to  think  that  consciousness  is  absent ;  or 
where,  as  in  the  present  instance,  we  have  no  evidence  to  show  whether 
consciousness  is  present  or  not  ?     In   treating  of  the  senses  we  called 


THE    BRAINLESS    MAMMAL.  815 

either  visual  or  other  perceptions,  v^hile  there  is  almost  clear 
proof  that  the  sensations  it  experiences  give  rise  to  no  ideas. 
Its  avoidance  of  ohjects  depends  not  so  raucli  on  the  form 
of  these  as  on  their  interference  with  light.  No  image, 
whether  pleasant  or  terrible,  whether  of  fooci  or  of  an  enemy, 
produces  an  effect  on  it,  other  than  that  of  an  object  reOect- 
ing  more  or  less  light.  And  though  the  plaintive  character 
of  the  cry  which  it  gives  forth  when  pinched  suggests  to  the 
observer  the  existence  of  passion,  it  is  probable  that  this  is 
a  wrong  interpretation  of  a  vocal  action  ;  the  cry  appears 
plaintive  simply  because,  in  consequence  of  the  complete- 
ness of  the  reflex  nervous  machinery,  and  the  absence  of 
the  usual  restraints,  it  is  prolonged.  The  animal  is  able  to 
execute  all  its  ordinary  bodily  movements,  but  in  its  per- 
formances nothing  is  ever  seen  to  indicate  the  retention  of 
an  educated  intelligence. 

These  phenomena  are  witnessed  in  some  mammals  at  least 
not  only  after  the  cerebral  convolutions  have  been  removed, 
but  also  when  the  corpora  striata  and  optic  thalami  aie 
taken  away  at  the  same  time,  so  that  the  Itrain  is  reduced 
to  the  corpora  quadrigemina  and  cerebellum  witli  the  crura 
cerebri  and  pons  Varolii.  In  removing  the  corpora  striata, 
however,  various  forced  movements,  of  which  we  shall  speak 
presently',  frequently  make  their  appearance,  and  interfere 
with  the  observation  of  the  phenomena  we  have  just  de- 
scribed ;  and  it  is  stated  by  some  observers  that,  even  when 
these  do  not  occur,  the  scope  of  the  various  movements  of 
which  the  animal  remains  capable  is  much  limited. 

Yulpian  insists^  that  all  the  phenomena  above  described  may 
be  observed  in  the  total  absence  both  of  the  corpora  striata  and 
optic  thalami,  at  least  in  rodents.     Many  authors,  how^ever,  state 

attention  to  the  fact  that  we  must  suppose  in  the  ease,  for  instance,  of 
vision,  the  visual  periphery  organ  to  be  connected  with  a  visual  central 
organ  in  such  a  way  that  the  sensory  impulses  originating  in  the  former 
become  modified  in  thedatter  before  they  affect  consciousness.  In  the 
pei'ipheral  organ,  and  along  the  nerve  of  sense,  the  afiection  of  the 
nervous  tissue  may  be  spoken  of  as  a  sensory  impulse ;  but  after  the  afiec- 
tion has  traversed  the  central  organ  and  become  modified  it  is  no  longer 
a  simple  sensory  impulse.  We  must,  then,  either  call  it  a  sensation, 
irrespective  of  whether  any  change  of  consciousness  intervenes  or  not,  or 
we  must  give  it  a  new  name.  Not  wishing  to  introduce  a  new  name,  we 
have  ventured  to  use  the  word  "sensation"  in  a  sense  which  neither 
affirms  nor  denies  the  coexistence  of  consciousness. 
'  Syst.  Nerv.,  Ie9.  xxiv. 


816  THE    BRAIN. 


that  dogs  difrer  from  rodents,  inasmuch  as  in  dogs  lesions  of  the 
corpora  striata  always  entail  loss  of  co-ordinotion.  When  we 
come  to  study  the  functions  of  the  cerebral  hemispheres  in  par- 
ticular we  shall  have  occasion  to  dwell  on  the  danger  of  drawing 
conclusions  from  the  phenomena  exhibited  by  an  animal  imme- 
diately after  a  grave  operation  on  its  central  nervous  system. 
The  facts  described  above  in  reference  to  mammals  refer  exclu- 
sively to  the  period  immediately  following  the  removal  of  the 
hemispheres  ;  and  though  they  clearly  show  that  complex  co-or- 
dinate movements  may  then  be  carried  on,  they  cannot  be  trusted 
as  disclosing  to  us  the  exact  condition  of  a  mammal  under  such 
circumstances.  We  have  yet  to  learn  the  details  of  the  behavior 
of  a  mammal  deprived  of  the  whole  of  both  cerebral  hemispheres 
and  yet  enjoying  the  full  functional  activity  of  the  rest  of  its 
brain. 

With  the  removal  of  that  part  of  the  brain  whicli  lies  be- 
tween the  hemispheres  and  tlie  medulla  a  large  number  of 
these  co-ordinate  movements  disappear.  The  animal  can 
no  longer  balance  itself,  it  lies  heli)less  on  its  side,  and 
though  various  movements  of  a  complex  character,  includ- 
ing cries,  may  be  produced  by  appropriate  stimuli,  they  are 
much  more  limited  than  when  these  cerebral  structures  are 
intact. 

We  may,  therefore,  state  that  in  the  higher  animals,  in- 
cluding mammals,  as  in  the  frog,  the  body,  after  the  removal 
of  the  cerebral  hemispheres,  is  capable  of  executing  all  the 
ordinary  movements  which  the  animal  in  its  natural  life  is 
wont  to  perform,  though  these  movements  necessitate  the 
co-operation  of  various  afferent  impulses  ;  and  that,  there- 
fore, the  nervous  machinery  for  tiie  execution  of  these  move- 
ments lies  in  some  part  of  the  l)rain  other  than  the  cerebral 
hemispheres.  We  have  reasons  for  thinking  that  it  is  sit- 
uated in  the  structures  formino^  the  uiiddle  or  hind  brain. 


Sec.  2.  The  Mechanisms  of  Co-ordinated  Movements. 

When  in  a  pigeon  the  horizontal  membranous  circular 
canal  of  the  internal  ear  is  cut  through,  the  bird  is  observed 
to  be  continually  moving  its  head  froui  side  to  side.  If  one 
of  the  vertical  canals  be  cut  through,  tiie  movements  are  up 
and  down.  The  peculiar  movements  are  not  witnessed 
when  the  bird  is  perfectly  quiet,  but  they  make  their  ap- 
pearance whenever  it  is  disturbed,  and  attempts  in  any  way 
to  stir.     When  one  side  only  of  the  head  is  operated  on,  the 


THE    SEMICIRCULAR    CANALS.  817 

conclilion  after  awhile  passes  away.  When  tlie  canals  of 
both  sides  have  been  divided,  it  becomes  much  exaggerated, 
and  remains  permanently.  And  it  is  then  found  that  these 
peculiar  movements  of  the  head  are  associated  with  what 
appears  to  be  a  complete  want  of  co-ordination  of  all  bodily 
movements.  If  the  bird  be  thrown  into  the  air,  it  flutters 
and  falls  down  in  a  helpless  and  confused  manner ;  it  ap- 
pears to  have  totally  lost  the  power  of  orderly  flight.  If 
placed  in  a  balanced  position,  it  may  remain  for  some  time 
quiet,  generally  with  its  head  in  a  peculiar  posture;  but 
directly  it  is  disturbed,  the  movements  which  it  attempts  to 
execute  are  irregular  and  fall  short  of  their  purpose  It  has 
great  ditticulty  in  picking  up  food  and  in  drinking;  and  in 
general  its  behavior  very  much  resembles  that  of  a  person 
who  is  exceedingly  dizzy. 

It  can  hear  perfectly  well,  and  therefore  the  symptoms 
cannot  be  regarded  as  the  result  of  an}'  abnormal  auditory 
sensations,  such  as  ''  a  roaring  "  in  the  ears.  Besides,  an}^ 
such  stimulation  of  the  auditory  nerve  as  the  result  of  the 
section,  would  speedily  die  awa}',  whereas  these  phenomena 
may  be  permanent. 

The  movements  are  not  occasioned  by  any  partial  paral- 
ysis, by  any  want  of  power  in  })articular  muscles  or  group 
of  muscles.  Nor,  on  the  other  hand,  are  they  due  to  any 
uncontrollable  imi)ulse  ;  a  very  gentle  pressure  of  the  hand 
suffices  to  stop  the  movements  of  the  head,  and  the  hand  in 
doing  so  experiences  no  strain.  The  assistance  of  a  very 
slight  support  enables  movements  otherwise  impossible  or 
most  difficult,  to  be  easily  executed.  Thus,  though  when 
left  alone  the  bird  has  great  difficulty  in  drinking  or  picking 
up  corn,  it  will  continue  to  drink  or  eat  with  ease  if  its  beak 
be  plunged  into  water  or  into  a  heap  of  barley  ;  the  slight 
sujiport  of  the  water  or  of  the  grain  b-eing  sufficient  to  steady 
its  movements.  In  the  same  way,  it  can,  even  without 
assistance,  clean  its  feathers  and  scratch  its  head,  its  beak 
and  foot  being  in  these  operations  guided  by  contact  with 
its  own  body. 

After  the  operation  the  head  of  the  animal  frequently  as- 
sumes a  peculiar  position,  being  twisted  and  inclined  in 
various  ways,  sometimes  hanging  down  on  the  breast  with 
the  neck  so  distorted  that  the  right  eye  looks  to  the  left  side 
and  vice  versa,  sometimes  turned  back  over  the  shoulder  so 
that  one  eye  looks  direct!}'  upwards  ;  the  exact  attitude  dif- 
fering apparently  according  as  this  or  that  canal  has  been 


818  THE    BRAIN. 

injured.  And  Goltz^  has  called  attention  to  the  fact  that 
pigeons  whose  canals  have  l)een  left  intact  but  whose  heads 
have  been  artificially  secured  in  similar  abnormal  positions 
are  inca|)able  of  orderly  flight,  and  in  tiieir  general  behavior 
closely  resemble  animals  whose  canals  liave  been  destroyed. 
Injury  to  the  bony  canals  alone  is  insufficient  to  produce 
the  symptoms  ;  the  membranous  canals  themselves  must  be 
divicied  or  destroyed. 

E.  Cyon^  thus  describes  the  effects  of  dividing  the  several 
canals.  When  the  horizontal  (exterior)  canal  is  cut,  the  move- 
ments of  the  head  are  from  side  to  side  round  an  axis  passing 
vertically  through  the  head.  When  the  posterior  vertical  canal 
is  cut  the  head  is  moved  up  and  down  round  an  axis  passing  from 
ear  to  ear.  When  the  anterior  (superior)  vertical  canal  is  cut 
the  movement  of  the  head  is  in  a  diagonal  direction,  a  combina- 
tion of  an  up-and-down  and  a  side-to-side  movement.  When  one 
canal  on  one  side  only  is  divided  the  effects  are  very  transient, 
and  they  are  also  transient,  disappearing  on  the  second  or  third 
day,  even  when  all  three  canals  are  divided,  provided  that  the 
operation  is  confined  to  one  side  of  the  head.  When  the  same 
canal,  horizontal  or  vertical,  is  divided  on  ])oth  sides  of  the  head, 
the  symptoms  are  more  lasting,  ])ut  may  after  some  days  wholly 
or  almost  wholly  disappear.  When  different  canals  are  divided 
on  the  two  sides  of  the  head,  i.  e,,  when  the  operation  is  bilateral 
and  unsymmetrical,  the  effects  become  permanent. 

In  mammals  (rabbits)  section  of  the  canals  produces  a  loss  of 
co-ordination  similar  to  that  witnessed  in  birds  ;  but  the  move- 
ments of  the  head  are  not  so  marked,  peculiar  oscillating  move- 
ments of  the  eyeballs  (nystagmus),  differing  in  direction  and  char- 
acter according  to  the  canal  or  canals  operated  upon,  becoming, 
however,  very  prominent.  In  the  frog  no  deviations  of  the  head 
are  seen,  but  there  is,  as  in  other  animals,  a  loss  of  co-ordination 
in  the  movements  of  the  body. 

Cyon  has  noticed  that  in  pigeons  after  section  of  the  canals  on 
both  sides  of  the  head,  the  leg  is  frequently  folded  up  under  the 
body  in  a  peculiar  way,  as  if  it  were  broken  ;  but  otherwise  there 
are  no  signs  of  any  paralysis. 

How  are  we  to  explain  these  remarkable  phenomena  ? 
Let  us  for  awhile  turn  aside  to  ourselves  and  examine  the 
co-ordination  of  the  movements  of  our  own  bodies.  When 
we  appeal  to  our  own  consciousness  we  find  that  our  move- 
ments are  governed  and  guided  by  what  we  may  call  a  sense 
of  equilibrium,  by  an  appreciation  of  tiie  position  of  our  body 

'  Pfliiger's  Archiv,  iii  (1870),  p.  172. 

^  These  pour  le  Doctorat  en  Mfedecine,  Paris,  1878. 


THE    SEMICIRCULAR    CANALS.  819 


and  its  relations  to  space.  When  this  sense  of  equilihrium 
is  disturbed  we  say  we  are  dizzy,  and  we  th6n  stagger  and 
reel,  being  no  longer  able  to  co-ordinate  the  movements  of 
our  bodies  or  to  adapt  them  to  the  position  of  things  around 
ns.  What  is  the  origin  of  this  sense  of  equilibrium?  By 
what  means  are  we  able  to  appreciate  the  position  of  our 
body  ?  There  can  be  no  doubt  that  this  appreciation  is  in 
large  measure  the  product  of  visual  and  tactile  sensations; 
we  recognize  the  relations  of  our  body  to  the  things  around 
us  in  great  measure  by  sight  and  touch  ;  we  also  learn  much 
by  our  muscular  sense.  But  there  is  something  besides 
these.  Neitlier  sight  nor  touch  nor  muscular  sense  would 
help  us  when,  placed  perfectly  flat  and  at  rest  on  a  horizon- 
tal rotating  table,  with  the  eyes  shut  and  not  a  muscle  stir- 
ring, we  attemi)ted  to  determine  wliether  the  table  and  we 
with  it  were  moved  or  not,  or  to  ascertain  how  much  it  and 
we  were  turned  to  the  right  or  to  tlie  left.  Yet  under  such 
circumstances  we  are  not  only  conscious  of  a  cliange  in  our 
position,  but  according  to  Crum  Brown^  and  others  wc  can 
pass  a  tolerably  successful  judgment  as  to  the  angle  tiirough 
which  we  have  been  moved.  What  are  the  data  on  which 
we  are  able  to  form  such  a  judgment?  It  is  possible  that 
the  mere  displacement  of  blood  or  of  the  more  fluid  parts  of 
the  tissues  in  various  regions  of  the  l»ody,  by  giving  rise  to 
aflTections  of  general  sensibility,  may  contribute  to  these 
data  :  but  the  peculiar  features  of  the  semicircular  canals 
suggest  almost  irresistibly  that  they  are  special  agents  in 
this  matter.  The  three  canals  are,  as  we  know,  placed  in 
the  head  in  planes  nearly  at  right  angles  to  one  another. 
Hence  the  pressure  of  the  endolymph  on  the  walls  of  the 
canal  (including  the  macuhie  of  the  ampullae)  in  any  given 
position  of  the  head,  and  variations  of  that  pressure  due  to 
movements  of  the  head,  would  be  different  in  the  three 
canals :  a  sonorous  wave,  on  the  other  hand,  would  affect 
all  the  ampulhe  equally.  If  we  suppose  that  the  pressure  of 
the  endolympli  or  variations  in  that  pressure  can  give  rise 
to  afferent  impulses  -which,  though  passing  up  to  the  brain 
along  the  auditory  nerve,  are  not  of  the  nature  of  auditory 
impulses,  we  have  found  the  data  for  which  we  are  seeking  ; 
for  it  is  quite   possible  to  conceive  that  the  impulses  thus 

'  Journ.  Anat.  Phys.,  1874,  p.  327;  see  also  Maeh.  Lehre  v.  d.  Be- 
wearungs-Eniplincl.,  1875;  Ereuer,  Wien.  Med.  Jahb.,  1874,  p.  72;  1875, 
p.  87. 


820  THE    BRAIN. 

o^enerated  in  the  ampullar  by  movements  of  the  liead,  should 
hy  becoming  transformed  into  sensations  enter  into  the 
judgment  which  we  form  of  the  movements  which  have  given 
rise  to  thenj. 

When  a  person  under  the  circumstances  mentioned  above  is 
rotated  for  some  time,  the  sense  of  rotation  ceases  to  be  felt  ;  but 
on  the  rotation  ceasing  a  sense  of  being  rotated  in  the  opposite 
direction  is  set  up ;  a  complementary  or  more  strictly  a  rebound 
sensation  is  caused.  Regarding  the  sensation  as  due  to  the  move- 
ment of  the  fluid  in  the  canals,  Crum  Browni  supposes  that  the 
effect  is  difterent  according  as  the  flow  is  from  the  ampulla  into 
the  canal,  or  from  the  canal  into  the  ampulla,  and  that  thus  we 
are  able  to  recognize  the  direction  of  the  rotation,  whether  posi- 
tive or  negative,  ex.  gr.,  to  the  right  or  to  the  left,  and  so  on. 
Hence  the  existence  of  six  ampulke,  two  for  each  of  the  three 
axes  of  rotation  ;  and  Crum  Brown  asserts  that  in  man  and  all 
animals  which  he  has  examined  the  two  exterior  canals  of  the 
two  ears  are  very  nearly  in  the  same  plane,  and  the  su]ierior 
canal  of  one  ear  very  nearly  in  the  same  plane  as  the  posterior 
canal  of  the  other. 

But  if  am[)ullar  sensations,  if  we  may  so  call  them,  thus 
enter  into  our  appreciation  of  the  position  of  our  body  and 
tlius  form,  in  part,  the  basis  of  our  sense  of  eqnilibrium,  it 
is  obvious  that  wiien  tliese  are  absent  or  deranged,  the  sense 
of  equilihrinm  will  be  affected  and  the  co-ordination  of  move- 
ments interfered  with.  And  this  seems  to  be  the  most  sat- 
isfactory explanation  of  the  phenomena  attendant  on  injury 
to  the  semicircular  canals.  We  are  not  perhaps  yet  in  a 
position  to  explain  the  whole  matter  in  a  complete  manner; 
there  may  be  much  divergence  of  opinion  as  to  the  exact 
way  in  which  the  ampnllar  impulses  are  generated,  and  as 
to  the  exact  manner  in  which  injury  to  the  canals  pro(hices 
its  effects,  whether  by  causing  the  simple  absence  of  normal 
impulses  or  by  generating  abnormal  inflnences  ;  but  it  is 
difficult  to  withstand  the  general  conclusion  that  the  am- 
pullae have  in  some  way  or  other  to  do  with  the  sense  of 
equilibrium  and  with  tlie  co-ordination  of  movements,  and 
that  the  remarkable  effects  of  injuring  them  are  connected 
with  this  function. 

Some  authors^  have  adopted  the  former  view,  that  the  phenom- 
ena are  due  to  the  mere  absence  of  the  normal  ampullar  sensa- 

^  Goltz,  op.  cit. 


THE    SEMICIRCULAR    CANALS.  821 


tions,  the  usual  pressure  of  the  endolymph  failing  on  account  of 
the  removal  of  that  fluid.  A  difliculty  is  presented  to  this  view 
by  the  fact  that  the  canals  are  all  continuous ;  and  hence  if  the 
effects  of  section  are  simply  due  to  loss  of  fluid,  and  consequent 
absence  of  the  usual  pressure  and  of  the  variations  in  that  pres- 
sure, the  section  of  one  canal  ought  to  produce  tlie  same  effect  as 
that  of  all  of  them  ;  but  this  is  not  the  case. 

On  the  other  hand  Cyon  insists  very  strongly  that  mere  re- 
moval not  only  of  the  perilymph  but  also  of  the  endolymph  is 
insufficient  to  give  rise  to  the  symptoms.  He  states  that  he  has 
removed  the  endolymph  from  the  whole  labyrinth  b}- very  careful 
puncture  of  the  vestibule  without  producing  any  effects,  but  that 
section  of  the  membranous  walls  of  the  emptied  canals  is  imme- 
diately effective.  He  regards  the  symptoms  as  due  to  irritation 
caused  by  the  section. 

Tomaszewicz-  also  urges  that  the  effects  of  section  are  the  less 
pronounced  the  more  carefully  the  operation  is  performed.  He 
indeed  refuses  altogether  to  admit  the  existence  of  any  such  func- 
tion as  that  we  are  discussing,  and  regards  the  permanent  want 
of  co-ordination  which  follows  upon  extensive  injur}-  to  the  canals 
as  due  to  miscliief  set  up  as  a  secondary  result  in  the  cerebellum 
or  other  regioas  of  the  brain.  Other  observers  insist  most 
strongly  that  the  phenomena  of  inco-ordination  may  be  most 
fully  developed  without  the  slightest  secondary  mischief  to  the 
brain. 

The  injury  which  causes  the  loss  of  co-ordination  need  not  be 
confined  to  the  peripheral  organs  of  the  auditory  nerve.  Section 
of  the  auditory  trunk  produces  similar  effects. 

According  to  Cyon,  however,  the  loss  of  co-ordination  which 
follows,  in  the  rabbit,  upon  section  of  both  auditory  nerves  dis- 
appears "  almost  wholly  "  after  some  time.  If  this  is  really  the 
case,  without  any  regeneration  of  the  divided  nerves  taking  place, 
it  is  clear  that  whatever  normal  ampullar  impulses  may  be  gener- 
ated in  the  intact  canals,  these  must  play  far  too  subordinate  a 
part  in  maintaining  equilibrium  to  permit  us  to  regard  their  mere 
absence  as  the  cause  of  such  disorder  ;  for  we  can  hardly  imagine 
that  an  animal  could  learn  to  do  without  such  peculiar  and  im- 
portant normal  impulses,  as  on  that  view  of  the  question  these 
are  supposed  to  be  ;  and,  consequently,  are  driven  to  look  upon 
the  symptoms  arising  from  injur}^  to  the  canals  as  due  to  irrita- 
tion. Tomaszewicz^  also  finds  that  animals  ""in  successful 
cases  -  exhibit  none  of  the  phenomena  of  inco-ordination  after 
section  of  both  auditory  nerves. 

We  compared  the  condition  of  a  pigeon  after  injur}^  to 
the  semicircular  canals  to  that  of  a  person  who  is  dizzy,  and, 

^  Op.  cit. 

2  Hofmann  u.  Scliwalbe's  Bericlit,  Literatur,  1877,  p.  203. 

3  Op.  ch. 

69 


822  THE    BRAIN. 

indeed,  one  great  characteristic  of  vertigo  or  dizziness  is  an 
inability  on  tlie  part  of  the  snhject  to  maintain  a  due  equi- 
librinm;  he  cannot  co-ordinate  his  movements  properly  or 
adapt  them  to  the  circumstances  around  him,  and  in  conse- 
quence staggers  and  reels.  Vertigo  may  be  brought  about 
in  various  ways.  It  may  be  the  result  simply  of  unusual 
and  powerful  visual  sensations,  such  as  tliose  produced  by 
water  falling  rapidly  from  a  great  height,  or  by  objects 
moving  swiftly  across  the  field  of  vision.  It  may  arise  from 
changes  taking  place  in  the  brain  itself,  and  is  a  common 
symptom  of  many  maladies,  and  of  the  action  of  many  poi- 
sons. As  is  well  known,  a  most  severe  vertigo  may  be  at 
once  produced  by  rapidly  rotating  the  body.  All  cases  of 
vertigo,  however  produced,  have  this  common  subjective 
feature,  that  one  or  more  of  the  sets  of  sensations  which 
form  the  basis  of  our  appreciation  of  the  relation  of  our 
body  to  external  things  disagree,  and  are  in  conflict  with 
the  rest  of  the  sensations  which  go  to  make  up  the  same  ap- 
preciation. Thus  in  the  vertigo  after  rapid  rotation  of  the 
body,  while  we  seem  to  see  the  whole  world  whirling  round 
ns,  this  conclusion  is  contradicted  by  other  sensations.  Cor- 
responding to  tliis  snbjt'ctive  feature  of  vertigo  is  the  objec- 
tive feature  of  the  failure  of  motor  coordination  ;  and  there 
can  be  no  doubt  that  the  tvv'o  are  connected  together  as 
cause  and  effect.  The  exact  manner  in  which  the  vertigo  is 
developed,  i.  e.,  the  sequence  and  relation  of  the  various 
factors  of  it,  will  naturally  vary  according  to  the  nature  of 
the  exciting  cause,  and  the  course  of  events  appears  to  be 
not  only  different  in  diflferent  forms,  but  in  many  cases  com- 
plex. When  vertigo  comes  on  from  rapidly  rotating  the 
body  with  the  eyes  open,  an  element  of  discord  is  introduced 
by  the  eyeballs  not  keeping  pace  with  the  movements  of  the 
head  but  following  irregularly,  executing  the  oscillatory 
movements  known  as  nystagmus,  movements  which  continue 
after  the  body  has  come  to  rest,  and  then  give  rise  to  the 
false  sensation  that  external  objects  are  moving  rapidly. 
But  in  this  vertigo  of  rotation  there  are  othetei  factors  at 
work,  for  the  dizziness  comes  on,  though  less  readily,  when 
the  eyes  are  kept  shut  all  the  time.  It  has  been  suggested 
that  false  ampullar  sensations  arise  from  the  rotation  of  the 
body  exciting  the  semicircular  canals.  But  even  admitting 
this  as  a  contribution  to  the  total  effect,  it  seems  probable, 
as  Purkinje  suggested,  that  changes  in  the  brain  due  to  the 
displacement  of  the  blood  or  even  of  the  brain-substance 


VERTIGO.  823 

itself  caused  by  the  too  rapid  rotation,  are  at  work.  It  is 
difficult  otlierwise  to  explain  the  unconsciousness  which  may 
ensue  if  the  rotation  be  rapid  and  long-continued  ;  and  the 
vertigo  resulting  from  various  poisons  seems  to  be  distinctly 
of  central  origin. 

Vertigo,  as  in  the  so-caUed  Meniere's  malady,  is  frequently  as- 
sociated with  disease  of  the  semicircular  canals  ;  but  it  must  be 
remembered  that  the  canals  are  frequently  diseased  without  any 
vertigo  appearing.  According  to  Cyon'  and  Tomaszewicz^  vt- rtigo 
by  rotation  may  be  readily  induced  in  rabbits  after  section  of  both 
auditory  nerves,  a  result  which  indicates  that  the  semicircular 
canals  can  have  little  share  in  this  form  of  vertigo. 

Whether  we  accept  the  view  of  ampullar  sensations  just 
discussed  or  not,  and  whatever  be  the  exact  share  which 
false  sensations  take  in  the  causation  of  vertigo,  this  at  all 
events  is  clear,  that  afferent  impulses  of  various  kinds  so 
far  contribute  to  the  building  up  of  the  coordinating 
mechanisms  that  changes  in  these  impulses  go  far  to  throw 
the  mechanisms  into  disorder,  or  at  least  to  impair  their 
})roper  working.  It  is  not  necessary  that  these  afferent  im- 
pulses should  directly  affect  consciousness  (or,  to  speak 
more  correctly,  should  affect  tiiat  complete  consciousness 
which  is  associated  with  volition),  and  so  develop  into  dis- 
tinct perceptions.  We  have  seen  that  a  bird  from  which 
the  cerebral  hemispheres  have  been  removed  is  perfectly 
al»le  to  fly;  and  that,  theret'oie,  the  co-ordinating  nervous 
mechanism  necessary  for  flight  is  situated  in  the  parts  of 
the  brain  lying  behind  the  cerebral  hemispheres.  We  have 
also  dwelt  on  the  fact  that  all  the  chief  cc-oidinating  mech- 
anisms of  the  frog  lie  in  the  hind  parts  of  the  brain  ;  yet  in 
the  frog,  as  in  the  bird,  and  we  may  add,  as  in  the  mammal, 
injur}'  to  the  hinder  parts  of  the  brain  produces  loss  of  co- 
ordination whether  the  hemispheres  be  [)resent  or  not.  Now 
we  have  no  satisfactory  reasons  for  either  asserting  or  deny- 
ing that  what  we  call  consciousness,  i.  e.^  a  distinct  con- 
sciousness similar  to  our  oun  consciousness,  exists  in  ani- 
mals deprived  of  their  cereltral  hemispheres.  When  signs 
of  volition  are  present,  we  may  safely  take  these  signs  as 
indications  of  con.sciousness  also;  but  we  are  not  justified 
in  saying  that  all  consciousness  is  absent  when  satisfactory 
signs  of  volition  are  wanting.     We  cannot  form  any  just 

'  Op.  cit.  ^  Op.  cit. 


824  THE    BRAIN. 

jiid<^nient  on  the  matter  without  some  more  trustworthy  nnd 
objective  tokens  of  consciousness  than  we  at  present  possess. 
But  what  we  may  safely  assert  is,  that  the  co-ordinating 
meclianism,  tiie  retention  of  wiiich  is  so  striking  a  feature 
of  an  animal  deprived  of  its  cerebral  hemispheres,  is  con- 
structed out  of  divers  afferent  impulses  of  various  kinds 
arriving  at  the  co-ordinating  centre  from  various  parts  of 
the  body,  that  in  fact  tlie  co  ordination  taking  place  at  the 
centre  is  the  adjustment  of  etlerent  to  afferent  impulses. 
Many  if  not  all  of  these  afferent  impulses  are  such  that  in 
the  presence  of  consciousness  they  would  give  rise  to  per- 
ceptions and  ideas  ;  but  we  have  no  reason  for  thinking  that 
the  comi)lete  development  of  the  afferent  impulse  into  a  per- 
ception or  an  idea  is  always  necessar}'  to  the  carrying  out 
of  co-ordination.  We  may  say  that  vve  have  a  sense  of 
equilibrium  by  means  of  tlie  semicircular  canals,  and  when 
that  sense  is  deranged  we  feel  giddy  and  cannot  stand.  We 
have  no  reason,  however,  for  thinking  that  the  failure  to 
keep  ujjright  is  (lue  to  the  feeling  of  giddiness,  in  the  sense 
of  being  a  direct  result  of  the  condition  of  the  conscious- 
ness On  the  contrary,  since  the  peculiar  movements  char- 
acteristic of  vertigo  may  take  [)lace  in  the  absence  of  con- 
sciousness without  the  vertigo  being  actually  felt,  we  may 
witii  security  assert  that  the  failure  to  stand  uprigiit  and  the 
feeling  of  giddiness  are  both  concomitant  effects  of  the  same 
disarrangement  of  the  co-ordinating  mechanism. 

It  cannot  Ite  too  much  insisted  u|)on  that  for  ever^'  bodily 
movement  of  any  complexity  afferent  impulses  are  as  essen- 
tial as  the  executive  efferent  impulses.  Our  movements,  as 
we  have  already  urged,  are  guided  not  only  by  the  muscu- 
lar sense,  but  also  by  contact  sensations,  auditory  sensa- 
tions, visual  sensations,  and  visual  peiceptions  (for  the 
remarks  made  above  concerning  the  relations  of  the  co-ordi- 
nating mechanism  to  consciousness  do  not  exclude  the  pos- 
silulity  of  consciousness  affecting  the  mechanism  ;  indeed, 
not  onl}'  may  perceptions  enter  into  the  causation  of  ver- 
tigo, but  even  an  imaginary  idea  may  be  the  sole  exciting 
cause  of  this  condition);  and  wiien  we  say  "  they  are  guided," 
we  mean  that  without  the  sensations  the  movements  become 
im|)ossible.  In  studying  vision  we  saw^  repeatedly  that  the 
movements  of  the  eyes  were  directly  dependent  on  vision, 
and  every  ballroom  affords  almndant  evidence  of  the  ties 
between  sensations  of  sound  and  motions  of  the  limbs.  So 
essential,  in  fact,  are  afferent  impulses  to  the  development 


CO-ORDINATING    MECHANISMS.  825 

of  complex  bodily  movements,  that  we  are  almost  justified 
in  considering  every  sueii  movement  in  the  light  of  a  reflex 
action  made  u[)  of  afferent  and  efferent  impulses  and  central 
actions,  and  set  going  by  the  influence  of  some  dominant 
aflerent  impulse,  or  by  the  direct  action  of  those  nervous 
changes,  whose  psyducal  correlative  is  what  we  call  the  will, 
on  the  centre  itsell".  All  day  long  and  every  day  multitudi- 
nous afferent  impulses,  from  e^-e,  and  ear,  and  skin,  and 
muscle,  and  other  tissues  and  organs,  are  streaming  into 
our  nervous  system  ;  and  did  each  afferent  impulse  issue  as 
its  correlative  aflferent  motor  impulse,  our  life  would  be  a 
prolonged  convulsioji.  As  it  is,  I»y  the  checks  and  counter- 
ciiecks  of  cei-ebral  and  spinal  activities,  all  these  impulses 
are  drilled  and  marshalled,  and  kept  in  hand  in  orderly 
array  till  a  movement  is  called  for;  and  thus  we  are  able  to 
execute  at  will  the  most  complex  bodily  manoeuvres,  know- 
ing only  li'hy,  and  unconscious  or  but  dimly  conscious  hoiv^ 
we  carry  them  out. 

We  have  ventured  to  use  the  phrase  ''co-ordinating  cen- 
tre," but  it  must  be  understood  that  we  have  no  right  to  at- 
tach more  than  a  general  meaning  to  the  words.  We  can- 
not, at  present  at  least,  define  such  a  centre  in  the  same  way 
that  we  can  the  vaso  motor  or  lespiratory  centre.  When 
the  optic  lobes  as  well  as  the  cerebral  hemispheres  are  re- 
moved from  the  trog,  the  power  of  balancing  itself  is  lost; 
when  such  a  frog  is  thrown  off  its  balance  by  inclining  the 
plane  on  which  it  is  placed,  it  falls  down.  The  special  co- 
ordinating mechanism  for  balancing  must  therefore  in  this 
animal  be  situated  in  the  optic  lobes;  but  after  removal  of 
these  organs  the  animal  is  still  capable  of  a  great  variety  of 
co-ordinate  movements;  unlike  a  frog  retaining  its  spinal 
cord  only,  it  can  swim  and  leai),  and  when  placed  on  its 
back  immediately  regains  the  normal  position.  The  cere- 
bellum of  the  frog  is  so  small,  and  in  removing  it  injiuyis 
so  likely  to  be  done  to  the  underlying  parts,  that  it  becomes 
diflicnlt  to  say  how  much  of  the  co-oi'dination  apparent  in  a 
frog  possessing  cerebellum  and  medulla  is  to  be  attributed 
to  the  former  or  to  the  latter ;  probably,  however,  the  [)art 
played  by  the  former  is  small.  In  the  mammal,  as  we  have 
stated,  removal  of  the  whole  middle  and  hind  brain  does 
away  with  the  most  marked  of  these  co-ordinating  mechan- 
isms. Removal  of  the  pons  Yarolii  alone  has  the  same 
effect.  Injury  to,  or  disease  of,  the  more  sui)erficial  parts 
of  the  corpora  quadrigemina,  or  of  the  cerebellum,  does  not 


826  THE    BRAIN. 

appear  to  influence  the  movements  of  the  body  at  laroje  to 
any  striking  extent ;  but  there  are  many  pathological  cases, 
as  well  as  experimental  observations,  tending  to  associate 
the  co-ordinating  mechanisms  of  which  we  are  speaking  with 
the  deeper  parts  of  the  cerebellum.  It  would  be  hazardous, 
in  the  present  state  of  our  knowledge,  to  make  any  definite 
statement  concerning  the  share  taken  l>v  these  several  cere- 
bral structures  in  the  various  co-ordinations. 

The  results  of  experiments  are  in  many  ways  conflicting,  but 
still  more  conflicting  and  still  less  trustworthy  are  the  results  of 
pathological  observations.  In  this  and  in  so  many  other  parts 
of  physiology  the  so-called  "experiments  of  nature,"  as  seen  at 
the  bedside,  are  extremely  useful  in  suggesting  and  correcting 
experimental  inquiries,  but  they  prove  broken  reeds  when  reli- 
ance is  placed  on  them  alone.  There  is  hardly  a  thesis  in  cere- 
bral physiology  in  respect  of  which  a  long  array  of  "cases'"  may 
not  be  quoted  strikingly  supporting  the  views  enunciated,  and  a 
long  array  as  flatly  contradicting  them. 

Forced  Movements. 

All  investigators  who  have  performed  experiments  on  the 
brain,  have  observed  as  the  result  of  injury  to  various  parts 
of  it  remarkable  compulsory  movements.  One  of  the  most 
common  forms  is  that  in  which  the  animal  rolls  incessantly 
round  the  longitudinal  axis  of  its  own  body.  This  is  espe- 
cially common  after  section  of  one  of  the  crura  cerebri, 
more  particularly  of  the  external  and  superior  parts,  or  after 
unilateral  section  of  the  pons  Varolii,  but  has  also  been 
witnessed  after  injury  to  the  medulla  oblongata  and  corpora 
quadrigemina.  Sometimes  the  animal  rotates  towards  and 
sometimes  away  from  the  side  operated  on.  Another  form 
is  that  in  which  the  animal  executes  '•  circus  movements," 
i.  e.,  continually  moves  round  and  round  in  a  circle,  some- 
times towards  and  sometimes  away  from  the  injured  side. 
This  may  be  seen  after  several  of  the  above-mentioned  ope- 
rations, hut  is  perhaps  particularly  common  after  injuries  to 
the  corpora  striata  and  optic  thalami.  There  is  a  variety  of 
the  circus  movement  said  to  occur  frequently  after  lesions 
of  the  nates,  in  which  the  animal  moves  in  a  circle,  with  the 
longitudinal  axis  of  its  body  as  a  radius,  and  the  end  of  its 
tail  for  a  centre.  And  this  form  again  may  easily  pass  into 
a  simply  rolling  movement.  In  yet  another  form  the  animal 
rotates  over  the  transverse  axis  of  its  body,  tumbles  head 


FORCED    MOVEMENTS.  827 

over  heels  in  a  series  of  somersaults  ;  or  it  may  run  inces- 
santly in  a  straiglit  line  backwards  or  forwards  until  it  is 
stop[)ed  by  some  obstacle.  These  latter  forms  of  forced 
movements  are  frequently  seen  after  injury  to  the  corpora 
striata  ;  and  Xotlinagel  speaks  of  a  limited  portion  of  the 
grax'  matter  of  the  corpus  striatum  as  the  nodufi  cursorius^ 
the  injection  of  ciiromic  acid  into  whicii  produces  in  the 
rabbit  the  straight-forward  running.  Lastly,  many,  if  not 
all,  these  various  forced  movements  may  result  from  injuries 
which  appear  to  be  limited  to  tiie  cerel)ral  hemisplieres. 

Attempts  have  been  made  to  explain  the  rotator}'  move- 
ments by  reference  to  unilateral  paralysis  or  to  spasm  of 
various  muscles  of  the  body  caused  by  the  cerebral  injury; 
and  in  the  case  of  the  ''circus"  movements  with  partial 
hemiplegia,  which  follow  upon  injury  to  the  cor|)ora  striata 
or  other  parts,  the  explanation  that  the  animal  in  progress- 
ing forward  naturally  bears  on  its  paralyzed  or  weak  side 
seems  a  valid  one;  but  the  movements  may  frequently  be 
witnessed  in  the  complete  absence  of  either  paralysis  or 
spasm,  and  cannot  therefore  be  always  so  explained.  On 
the  other  hand,  if  the  views  urged  just  now  concerning  the 
nature  of  the  co-ordinating  mechanisms  of  the  brain  are  true, 
it  is  evident  t'nat  they  atford  a  general  explanation  of  the 
phenomena,  though  our  present  knowledge  will  not  permit 
us  to  explain  the  genesis  of  each  particular  kind  of  move- 
ment. Such  gross  injuries  as  are  involved  in  dividing  cere- 
bral structures  or  in  injecting  coirosive  substances  into  the 
midst  of  cerebral  organs,  must  of  necessity,  either  by  irri- 
tation or  otherwise,  seriously  alfect  the  transmission  not 
only  of  afferent  impulses  in  their  cerebral  course,  but  also 
of  central  impulses,  inhibitory  and  the  like,  passing  from 
one  part  of  the  brain  to  another ;  and  must  therefore  seri- 
ously affect  the  due  working  of  the  general  co-ordinating 
mechanisms.  The  fact  that  an  animal  can,  at  any  moment, 
by  an  effort  of  its  ovvn  will,  rotate  on  its  axis  or  run  straight 
forwards,  shows  that  the  nervous  mechanism  for  the  execu- 
tion of  those  movements  is  ready  at  hand  in  the  brain, 
waiting  only  to  be  discharged  .  and  it  is  easy  to  conceive 
how  such  a  discharge  might  be  affected  either  b}-  the  sub- 
stitution of  some  potent  intrinsic  afferent  impulse  for  the 
will  or  by  some  misdirection  of  the  volitional  impulses. 
Persons  who  have  experienced  similar  forced  movements  as 
the  result  of  disease  report  that  they  are  frequently  accom- 
panied, and  seem  to  be  caused,  by  disturbed  visual  or  other 


828  THE    BRAIN. 

sensations ;  they  say  they  fall  forward  because  the  ground 
appears  to  sink  away  beneath  their  feet.  Without  trusting 
too  closely  to  the  interpretations  the  subjects  of  these  dis- 
orders give  of  their  own  feelings,  we  may  at  least  conclude 
tiiat  the  disorderly  movements  are  due  to  a  disorder  of  the 
co-ordinating  mechanism,  which  in  many  cases  is  itself  tiie 
result  of  disordered  sensory  impulses,  and  not  to  any  par- 
alytic or  other  failing  of  the  simple  muscular  instruments 
of  the  nervous  system.  And  this  view  is  supported  by  the 
fact  tliat  many  of  these  forced  movements  are  accompanied 
by  a  peculiar  and  wholly  abnormal  position  of  the  eyes, 
which  alone  might  perhaps  explain  many  of  the  phenomena. 


Sec  8.  The  Functions  of  the  Cerebral  Convolutions. 

All  the  older  observers,  Flourens  and  others,  agreed  that 
when  the  cerebral  hemispheres  were  gradually  removed, 
piece  by  [)iece  or  slice  by  slice,  no  obvious  effects  manifested 
themselves,  either  in  the  intelligence  or  volition  of  tlie  ani- 
mal, when  the  first  portions  only  were  taken  away  ;  but  that, 
as  the  removal  was  continued,  the  animal  became  more  and 
more  dull  and  stupid,  until  at  last  hoth  intelligence  and  vo- 
lition seemed  to  be  entirely-  lost.  It  has  been  frecpieutly 
observed  that  after  wounds  of  the  skull  large  portions  of 
the  brains  of  men  might  be  removed  without  any  maiked 
effect  on  the  psychical  condition  of  the  patients.  The  brain 
when  exposed  was  found  not  to  be  sensitive  ;  and  ordinary 
stimuli  applied  to  the  surface  of  the  convolutions  of  ani- 
mals failed  in  the  hands  of  most  experimenters  to  produce 
any  clearly  recognizal)le  effect.  Hence  it  became  very  com- 
mon to  deny  the  existence  of  any  localization  of  functions 
in  the  convolutions  of  the  hemisphere,  and  to  speak  of  the 
brain  as  "acting  as  a  whole,"  whatever  that  might  mean. 
On  the  other  hand,  there  was  clear  evidence  that  not  only 
did  disease  of  the  superficial  gra}'  matter  of  the  hemispheres 
cause  delirium,  as  in  meningitis,  but  sometimes  convulsions 
either  of  an  epileptic  character  or  localized  to  particular 
groups  of  muscles.^     Hitzig  and  Fritsch'^  were  the  first  to 

^  Hughlings-Jackson,  London  Hosp.  Reports,  1864;  Clinical  and 
Physiol.  Researches,  1873. 

'■^  Reichert  u.  Du  Bois-Reymond's  Archiv,  1870,  p.  300.  See  also 
Hitzig,  Das  Gehirn,  Berlin,  1874. 


CEREBRAL    CONVOLUTIONS. 


829 


sliow  that  the  local  application  of  the  constant  oralvanic  cur- 
rent to  particular  convolutions  and  to  particular  parts  of 
convolutions  gave  rise  to  definite  co-ordinate  movements  of 
various  groups  of  muscles.     Thus  while  the  stimulation  of 


Fig. 221. 


The  Areas  of  the  Cerebral  Convolutions  of  the  Dog,  according  to  Hitzig  and 
Fritsch. 

(1)  A  The  area  for  the  muscles  of  the  neck. 

(2)  _p.  "  "          extension  and  adduction  of  the  fore  liiub. 

(3)  -f-  "  '*           flexion  and  rotation  of  the  fore  limb. 

(4)  ^  "  "           hind  limb. 

Running  transversely  towards  and  separating  (1)  and  (2)  from  (.3)  and  (4)  is  seen 
the  crucial  sulcus- 

(5)  f\     The  facial  area. 

one  spot  (Fig.  221)  caused  movements  in  the  muscles  of  the 
neck,  another  caused  extension  with  adduction  of  the  fore 
leg,  a  third  movements  of  the  hind  leg,  a  fourth  movements 
of  the  eye  and  other  parts  of  the  face.  In  fact,  tiicy  and 
Ferrier,^  who  using  chiefly  the  interrupted  or  faradaic  cur- 
rent, repeated  and  extended  their  observations,  were  al>le 
to  map  out  tlie  convolutions  of  the  front  and  middle  parts 
of  the  hemisphere  of  tiie  dog  (Figs.  221,  222)  cat,  monkey 


West  Riding  Reports,  vol. 
Brain,  London,  1876. 


iii,  1S73.     See  also  his  Functions  of  the 


830 


THE    BRAIN. 


(Fios.  223,  224),  and  other  animals,  into  a  number  of  pre- 
cisely limited  areas,  the  stimulation  of  each  area  producing 


The  Areas  of  the  Cerebral  Convolutions  of  the  Dog,  according  to  Ferrirr. 
O.  The  olfactory  lobe.     A.  The  fissure  of  Sylvius.    B.  The  crucial  sulcus. 

Faradaic  stimulations  of  the  areas  indicated  by  the  several  circles  produce  the  fol- 
lowing results  • 

(1)    The  hind  leg  is  advanced  as  in  walking. 
(3)'  Lateral  or  wagging  motion  of  the  tail. 

(4)  Retraction  and  adduction  of  the  opposite  fore  limb. 

(5)  Elevation  of  the  shoulder  of,  and  extension  forwards  of,  the  opposite  fore 

limb. 

(7)  Closure  of  the  opposite  eye,  caused  by  combined  action  of  the  orbicular  and 

zygomatic  muscles. 

(8)  Retraction  and  elevation  of  the  opposite  angle  of  the  mouth. 

(9)-  The  mouth  is  opened  and  the  tongue  moved;  sometimes  barking  is  produced. 

(11)  Retraction  of  the  angle  of  the  mouth  . 

(12)  Opening  of   the  eyes  and  dilation  of  the  pupils;  the  eyes  and  then  the  head 

turning  to  the  opposite  side. 

(13)  The  eyeballs  move  to  the  opposite  side. 

(14)  Pricking  or  sudden  retraction  of  the  opposite  ear. 

(15)  Torsion  of  the  nostril  on  the  same  side. 

(16)  Elevation  of  the  lip  and  dilation  of  the  nostril  (?). 

a  distinct  and  limited   movement,  while  stimulation   of  a 
large  surface  produced  general  convulsions.    The  movements 


^  There  is  in  the  dog  no  movement  comparable  to  that  resulting  from 
stimulating  (2)  (Figs.  223,  224)  in  the  monkey.     (Ferrier.) 


^  Corresponding  to  (9)  and  (10)  in  the  monkey. 


CEREBRAL    CONVOLUTIONS. 


sn 


were  so  precise  that  they  answered  each  to  the  spot  stimu- 
lated almost  as  completely'  as  a  note  answers  to  a  ke}'  struck 
on  the  piano. 

Fifi.  223. 


Figs.  223  and  224.— Side  and  Upper  Views  of  the  Brain  of  Man,  with  the  Areas  of  the 
Cerebral  Convolutions,  according  to  Ferrier. 

The  figures  are  constructed  by  marking  on  the  brain  of  man,  in  their  respective  situa- 
tions thA  areas  of  the  brain  of  the  monkey,  as  determined  by  experiment,  and  the  descrip- 
tion of  the  effects  of  stimulating  the  various  areas  refers  to  the  brain  of  the  monkey. 

(I)  (On  the  postero-parietal  [superior  parietal]  lobule.)  Advance  of  the  opposite 
hind  limb  as  in  walking. 

(2),  (3),  (4)  (Around  the  upper  extremity  of  the  fissure  of  Rolando.)  Complex 
movements  of  the  opposite  leg  and  arm,  and  of  the  trunk,  as  in  swimming, 

(a),  (6),  (c),  {d)  (On  the  postero-parietal  [posterior  central]  convolutions.)  Indi- 
vidual and  combined  movements  of  the  fingers  and  wrist  of  the  opposite 
hand.    Prehensile  movements. 

(5)  (At  the  posterior  extremity  of  the  superior  frontal  convolution.)  Extension 
forward  of  the  opposite  arm  and  hand. 

A  relationship  has  also  been  observed  between  the  brain-sur- 
face and  the  secretion  of  saliva,  the  beat  of  the  heart,  the  condi- 


832 


THE    BRAIN. 


tion  of  tbe  pupil,  the  action  of  vaso-motor  nerves,  and  other  or- 
ganic functions.     Eulenburg  and  Landois^  find  tliat  extirpation 


Fig.  224. 


(G)    (On  the  upper  part  of  the  aiitero-parietalor  ascending  frontal  [anterior  cen- 
tral] convolution.)    Supination  and  flexion  of  the  opposite  forearm. 

(7)  (On  tliu  median  portion  of  the  same  convolution.)    Retraction  and  elevation 

of  the  opposite  angle  of  the  mouth  by  means  of  the  zygomatic  muscles. 

(8)  (Lower  down  on  the  same  convolution.)    Elevation  of  the  ala  nasi  and  upper 

lip  with  depression  of  the  lower  lip,  on  the  opposite  side. 
(9),  (10)    (At  the  inferior  extremity  of  the  same  convolution,  Broca's convolution.) 
Openingof  themouth  with  (9)  i)rotrusion  and  (10)  reiraction  of  the  tongue. 
Region  of  Aphasia.    Bilaleral  aclion. 


Virchow's  Archiv,  68  (1876),  p.  245. 


CEREBRAL    CONVOLUTIONS.  833 


(11)  (B'tween  CIO)  and  the  inferior  extremity  of  the  postero-pnrietal  convolu- 

tion.)   Retraction  of  the  opposite  angle  of  tlie  mouth,  the  liead  turned 
i-li-'liliy  to  one  side. 

(12)  (On  the  jmsterior  portions  of  tlie  superior  and  middle  frontal  convolutions.) 

The  eyes  open  widely,  the  pupils  dilate,  and  the  head  and  eyes  turn  to- 
wards the  opposite  side. 
(13),  (13')    (On  the  supra-marginal  lohule  and  angular  gyrus.)    The  eyes  move  to- 
wards the  opposite  side  with  an  upward  (13)  or  downward  (13')  deviation. 
The  pupils  generally  contracted.    (Centre  of  vision.) 
(14)     (On  the  infra-marginal  or  superior  [tirst]  temporo-sphenoidnl  convolution.) 
Pricking  of  tlie  opposite  ear,  the  head  and  eyes  turn  to  the  opposite  side, 
and  the  pupils  dilate  largely.     (Centre  of  hearing.) 
Ferrier  moreover  places  the  centres  of  taste  and  smell  at  the  extremity  of  the 
temporo-spheuoidal  lobe,  and  that  of  touch  in  the  gyrus  uncinatus  and  hippocam- 
pus major. 

of  the  motor  areas  for  the  extremities  causes  a  rise  of  temperature 
(lastiuij;  in  some  cases  for  months)  in  the  corresponding  limbs  ; 
and  Hitzig  had  previously  observed  the  same  thing.'  Balogh- 
describes  in  the  dog  and  rabbit  areas  in  the  cerebral  surface 
stimulation  of  which  causes  acceleration  of  the  heart's  beat,  and 
other  areas  stimulation  of  which  slows  the  heart.  Bochefon- 
taine^  observed  that  stimulation  of  the  cerebral  surface  in  the 
neighborhood  of  the  crucial  sulcus  produced  a  rise  of  arterial 
pressure  with  alternating  acceleration  and  retardation  of  the 
heart's  beat.  Among  other  results  of  stimulating  the  same  and 
other  regions  of  the  surface  he  witnessed  increased  ti  )W  of  saliva, 
contraction  of  the  spleen,  bladder,  uterus,  etc.,  and  dilation  of 
the  pupil ;  the  last  effect  might  follow  ui^on  stimulation  of  almost 
any  point  of  the  cerebral  surface.  But  on  these  points  the  results 
of  various  observers  are  by  no  means  constant.*  Haemorrhage 
into  the  lung  has  been  observed  in  the  rabbit  to  follow  upon 
stimulation  of  the  cerebral  surface.^ 

These  experiments,  wiiich  have  not  only  been  confirmed 
l)y  many  observers,  but  may,  with  due  care,  be  successfully 
repeated  by  any  one,  clearly  show,  in  spite  of  some  discord- 
ance among  various  authors  as  to  the  exact  pt)sition  aud 
extent  of  the  several '•  areas,"  that  tliere  is  a  connection 
between  electric  stimulation  of  certain  areas  of  the  brain- 
surface  and  certain  bodily  movements  ;  but  the  exact  nature 


'  Cf.  however  Vtilpian,  Archives  de  Phvsiol.,  1876,  d.  814;  Kuessner, 
Ardi.  f.  Psych.,  viii  (1878),  p.  432. 

■^  Hofiiiaiui  and  Scliwalbe's  Bericht,  1876,  p.  38. 

^  Archives  de  Physiol.,  iii  (1876),  p.  140. 

*  Brown-Sequard,  Archives  de  Piiys.,  ii  (1875),  p.  864,  Eckhanl, 
Beitriige,  vii  (1876),  199. 

s  Xothnagel,  Cbl.  Med.  Wiss.,  1874,  p.  209. 


834  THE    BRAIN. 

of  this  connection  is  at  present  very  obscure.  The  areas  in 
question  have  been  spoken  of  by  some  authors  as  "motor 
centres."  Such  a  term  is  liowever  niisleadiug,  since  it  sug- 
gests that  the  brain-surface  in  a  given  area  is  largely  occu- 
pied in  giving  rise  to  the  co-ordinate  nervous  impulses  which 
carry  out  tlie  movement  resulting  from  stimulation  of  the 
area,  just  as  the  respiratory  centre  for  instance  is  occupied 
in  giving  rise  to  the  co-ordinate  respiratory  impulses;  but 
it  is  absurd  to  suppose  tiiat  comparatively  large  areas  of 
such  valuable  material  as  we  must  needs  suppose  the  gray 
matter  of  the  convolutions  to  be,  should  be  taken  up  in,  so 
to  speak,  menial  works,  such  for  instance  as  that  of  dis- 
charging the  nervous  impulses  requiied  for  bending  or  for 
straightening  the  arm.  Besides,  we  know  that  an  animal 
can  be  made  to  execute,  in  the  total  absence  of  the  cerebral 
hemisi)heres,  the  various  co  ordinate  movements  which  "csult 
from  the  stimulation  of  the  cerebral  areas  ;  co-ordination  in 
fact  is,  as  we  have  already  shown,  effected  in  parts  of  the 
brain  other  tlian  the  surface  of  the  cerebral  hemispheres; 
and  all  that  tl»e  areas  in  question  do  is  to  make  use  in  some 
way  or  other  of  these  lower  co-ordinating  mechanisms.  If 
on  the  other  hand  it  is  admitted  tiiat  the  movements  which 
result  from  stimulation  of  an  area  form  merely  a  small  and 
insignificant  part  of  the  total  effects  of  stimulation,  the 
other  changes  brought  about  being  profound  but  invisible 
and  as  yet  unrecognizable,  the  use  of  the  term  ^' motor  cen- 
tre" is  ^till  more  objectionable.  That  the  latter  view  is,  of 
the  two,  the  more  i)robable  seems  indicated  by  the  fact  that 
over  lai-ge  i)Oi'tions  of  the  brain-suiface  electric  stimulation 
produces  no  movements ;  these  portions  are  wholly  devoid 
of  "motor  centres."  The  real  interest  in  fact  in  the  results 
of  electric  stiuiulation  of  the  brain-surface  attaches  not  so 
much  to  tl.e  question  as  to  which  are  the  exact  movements 
resulting  from  the  stimulation  of  tliis  or  that  area,  as  to  the 
broad  fact  that  different  results  follow  upon  stimulation  of 
different  regions,  thus  serving  to  indicate  that  there  is  after 
all  a  "localization  of  functions"  in  the  brain-surface.  Ex- 
periments have  i)een  made  with  the  view  of  attacking  the 
problem  by  another  method,  viz.,  by  watching  the  results 
following  upon  the  removal  of  particular  parts  of  the  brain  ; 
but  the  statements  of  observers  are  in  this  respect  so  op- 
posed that  a  dogmatic  statement  is  at  present  impossible. 

In  trying  to  appreciate  the  true  meaning  of  the  experiments 
on  electric  stimulation  of  the  brain-surface  the  followiu&f  facts 


CEREBRAL    CONVOLUTIONS.  "         835 


deserve  attention.  Xot  only  do  the  phenomena  continue  when 
the  animal  is  under  opium  and  chloroform,  provided  that  the 
anaesthesia  is  not  too  profound,  and  not  only  do  they  require  for 
their  development  electric  currents  of  a  considerable  stren^ith, 
mechanical  and  chemical  stimulation  being  unable  to  produce 
them,  but  the  results  of  stinuilatiou  are  the  same,  Avhen  the  sur- 
face of  the  convolution  operated  on  is  highly  congested,  and  even 
when  it  has  become  completely  dried  up,  or  after  it  has  been 
washed  with  strong  nitric  acid.  The  results,  moreover,  remain 
unchanged  when  the  area  experimented  upon  is  isolated  from  the 
surroLuiding  gray  matter,  by  plunging  a  cork-borer  for  some  dis- 
tance into  the  brain  round  it  ;  and  even  when  the  brain-substance 
is  removed  to  some  depth  down  by  means  of  the  cork-borer,  and 
the  electrodes  plunged  into  the  blood  which  tills  up  the  cylindri- 
cal hole  thus  made.^  The}' remain  the  same  when  the  surface 
stimulated  is  disconnected  physiologically  though  not  physically 
from  the  deeper  parts,  by  a  horizontal  incision  carried  some  lit- 
tle distance  from  the  surface.-  And  though  the  area,  stimula- 
tion of  which  gives  rise  to  a  definite  movement,  is  always  lim- 
ited, yet  it  is  not  constant  in  ditlerent  individuals,  and  frequently 
a  large  and  deep  sulcus  may  be  seen  running  through  its  very 
midst. ^  All  these  facts  suggest  that  the  results  are  due  to  the 
escape  of  the  current  from  the  surface  to  which  the  electrodes 
are  applied  to  deeper  underlying  portions  of  the  brain,  the  escape 
taking  place  along  definite  lines  determined  by  the  electrical  con- 
ductivity of  the  brain-substance.  And  Burdon  Sanderson*  states 
that  local  stimulation  of  the  white  matter  immediately  surround- 
ing a  corpus  striatum  produces  localized  movements  quite  simi- 
lar to  those  caused  by  stimulation  of  the  corresponding  cerebral 
surface  ;  from  which  it  may  be  inferred  that  when  tlie  surface 
appears  to  be  stimulated,  it  is  really  the  corpus  striatum  which 
is  alfected  physiologically  by  the  stimulus.  Albertoni  and  Mi- 
chieli'  however  found  that  several  weeks  after  the  removal  of  an 
area  stimulation  of  the  scar  or  its  immediate  neighborhood  no 
longer  produces  the  particular  movements  characteristic  of  the 
area.  Unless  it  can  be  shown  that  the  injury  in  such  cases  pro- 
duces marked  changes  in  the  electrical  conductivity  of  the  brain- 
substance,  this  observation  ma}-  be  taken  as  indicating  that  the 
fibres  passing  downwards  from  the  area  to  deeper  parts  of  the 
brain,  have  through  degeneration  become  incapable  of  conveying 
the  impulses  set  going  by  the  application  of  the  current  to  the 
brain-surface  ;  that  the  connection  between  the  area  and  the 
deeper  parts  is  not  a  physical  one,  depending  on  the  escape  of  the 
current,  but  a  physiological  one,  dependent  on  the  existence  of 

^  Hermann,   Pfliiger's  Archiv,  x   (1875),     77.        Bnmu,   Eckbard's 
Beitriige,  vii  (1874),  127. 

-  Burdon  Sanderson,  Proc.  Roy.  Soc,  xxii  (1875),  368. 

^  Hermann,  op.  cit.  *  Op.  cit. 

^  Hofmann  and  Schwalbe's  Bericht,  1876,  p.  30. 


836  THE    BRAIN. 


fibres  passing  from  the  area  to  some  more  central  mechanism  and 
capable  of  producing  their  special  effects  when  stimulated  in  any 
part  of  their  course. ' 

At  all  events,  these  various  experiments  show  that  the  fact  of 
certain  movements  following  upon  stimulation  of  certain  areas, 
is  in  itself  no  satisfactory  proof  that  those  areas  are  to  be  con- 
sidered as  ''  motor  centres."  They  are  not  fundamentally  incon- 
sistent with  the  hypothesis  that  such  centres  exist ;  for  tlie  fibres 
proceeding  from  the  centres  to  the  corpus  striatum  or  to  other 
organs,  might,  when  artilicially  stimulated,  produce  the  same 
effect  as  when  they  were  the  channels  of  impulses  originating  in 
the  centres  in  a  normal  manner,  just  as  cardiac  inhibition  may 
be  brought  about  by  artificial  stimulation  of  the  vagus,  though 
in  ordinary  life  it  occurs  through  the  activity  of  the  medullary 
cardio-inhibitory  centre.  They  are  not  inconsistent  with  the 
hypothesis,  but  they  affVjrd  it  very  little  positive  support. 

On  the  other  hand,  if  these  circumscribed  areas  of  superficial 
gray  matter  are,  as  they  have  by  some  been  supposed  to  be,  motor 
centres  in  the  sense  of  being  necessary  for  the  volitional  or  psy- 
chical initiation  of  movements  corresponding  to  those  produced 
by  artificial  stimulation,  particular  sets  of  vohmtary  movements 
ought  to  disappear  when  particular  areas  are  removed  or  other- 
wise rendered  functionally  incapable. 

Similarly,  if  the  phenomena  attendant  on  stimulation  of  these 
"motor"  areas  are  to  be  interpreted  as  proving  a  localization  of 
function,  we  ought  to  expect  that  in  those  regions  of  the  cerebral 
surface  in  which  stimulation  produces  no  movements  and  wluch 
have  accordingly  been  called  "  sensory  "  (a  term,  however,  dis- 
tinctly open  to  objection),  the  remov^al  of  particular  areas  would 
give  rise  to  loss  or  ini'pairment  of  particular  cerebral  functions 
even  though  no  derangement  of  muscular  activity  was  manifested. 

In  respect  to  the  ''  motor  "  areas,  not  only  Hitzig  and  Terrier, 
but  many  subsequent  inquirers,  have  observed  that  removal  or 
destruction  of  an  area  is  followed  by  an  inability  to  execute  the 
movements  assigned  to  the  area,  or  at  least  by  a  difficulty  in 
carrying  them  out.  Ferrier  attributes  the  paralysis  thus  pro- 
duced to  an  absence  or  impairment  of  volitional  or  psychical 
initiation.  Hitzig,-  on  the  other  hand,  is  inclined  to  interpret 
the  imperfection  of  tlie  movements  as  due  to  a  loss  of  muscular 
sense  or  "muscular  consciousness;"  and  Xothnagel,^  who  in- 
jected minute  quantities  of  chromic  acid  into  limited  areas  of  the 
cerebral  surface,  observed  motorial  anomalies,  which  he  also  was 
inclined  to  regard  as  due  to  a  loss  or  impairment  of  the  muscular 
sense.  Nothnagel,  however,  made  the  important  observation 
that  the  symptoms  after  awhile  disappeared  ;  and  in  this  he  has 
been  corroborated  by  subsequent  observers.     Ferrier  appears  to 

^  For  a  discussion  of  this  point  see  Report  by  Dobbs,  Journ.  Anat. 
and  Phys.,  Jan.,  1878. 

'i  Op.  cit.  3  Virchow's  Archiv,  13d.  57  (1873),  p.  184. 


CEREBRAL    CONVOLUTIONS.  837 


have  kept  his  raiimals  alive  for  a  few  days  only  at  the  utmost, 
and  to  have  ceased  his  observations  before  adequate  recovery  had 
taken  place.  Hermann'  removed  from  do^s  cerebral  areas,  stimu- 
lation of  which  gave  localized  movements,  and  found  that  the 
paralysis  which  immediately  followed  the  operation,  after  some 
days  wholly  disappeared.  Carville  and  Duret'  obtained  the  same 
results,  ancl  they  showed  that  the  restitution  of  power  could  not 
be  due  to  a  vicarious  action  of  the  same  centre  of  the  other  hemi- 
sphere, since  after  recovery  from  a  left-sided  paralysis  due  to  an 
operation  on  the  right  hemisjihere,  subsequent  operation  on  the 
same  centre  of  the  left  hemisphere  produced  the  usual  effect  on 
the  right  side,  but  did  not  cause  a  return  of  the  paralysis  on  the 
left  side.  They  could  only  reconcile  their  results  with  the  "'motor 
centre"  theory  by  supposing  that  when  a  centre  was  destroyed, 
other  portions  of  "the  same  hemisphere  took  up  its  functions,  an 
hypothesis  which  is  in  itself  opposed  to  the  ^'localization''  theory. 
Moreover,  paralysis  more  readily  makes  its  appearance  in  opera- 
tions on  the  areas  for  the  fore  leg  and  hind  leg  than  in  those  on 
other  areas  ;  thus  Albertoni  and  Michieli^  removed  the  centre  for 
the  movements  of  the  jaw  and  tongue  without  any  paralysis  in 
those  organs.  But  the  most  serious  objections  to  the  theory  of 
"motor"  centres  in  any  of  the  forms  in  which  it  has  yet  been 
brought  forward,  are  furni;?hed  by  the  observations  by  Goltz*  on 
dogs.  He  removed  parts  of  the  cerebral  surface  by  washing  the 
nervous  substance  away  with  a  stream  of  water,  a  method  which 
has  the  advantage  of  causing  comparatively  Uttle  bleeding,  and 
affording  considerable  localization  of  the  injury  ;  and  he  found 
that  the  operation  was  followed  at  first  by  more  or  less  paralysis. 
He  failed,  however,  to  find  any  exact  correspondence  between  the 
areas  destroNed  and  the  groups  of  mascles  affected,  the  paralysis 
manifesting" itself  most  readily  in  the  fore  and  hind  limbs,  and 
generally  to  a  certain  extent  in  both  together.  ^Moreover,  and 
this  is  the  important  point,  the  paralysis  in  a  short  time  wholly 
disappeared  whatever  the  portions  of  brain  removed.  Both  the 
amount  of  mischief  done,  and  the  speed  and  completeness  with 
which  recovery  took  place,  depended  not  on  the  locality  operated 
on,  but,  as  older  observers  found,  on  the  quantity  of  brain-sub- 
stance removed.  After  recover}'  from  one  operation,  a  second 
removal  of  brain-substance  reproduced  th(;  same  phenomena  as 
the  previous  one  ;  and,  though  at  first  sight  this  might  be  taken 
as  supporting  Carville  and  Duret's  theory  of  a  vicarious  action 
of  other  parts  of  the 'same  hemisphere,  the  impossibility  of  such 
a  view  is  proved  by  the  fact  that  Goltz  was  able  to  remove  the 

^  Op.  cit.  ,  ^  Archives  de  Physiol,  ii  (1875),  p.  352. 

^  Op.  cit.  Cf.  also  Liissana  and  Lenioiffiie,  Archives  de  Physiologie, 
iv  (1877),  p.  119  et  seq.  Lnciani  and  Tamburini,  Sni  Centri  Psico- 
sensori  Corticali,  1879.  Dupuy,  Researches  into  the  Physiology  of  the 
Brain,  New  York,  1878. 

*  Ptliiger's  Archiv,  xiii  (1876),  p.  1 ;  xiv  (1877),  p.  412  ;  xx  (1879),  p.  1. 


838  THE    BRAIN. 

greater  part  of  the  gray  matter  of  one  hemisphere,  and  yet  re- 
covery of  muscular  power  eventually  took  place.  Goltz  argues 
that  all  the  temporary  phenomena  are  due  to  the  superficial  lesions 
exercising  inhibitory  influences  on  the  parts  of  the  brain  lying 
between  the  cerebral  convolutions  and  the  spinal  cord.  He  very 
aptly  compares  the  paralysis  caused  by  operations  on  the  surface 
of  the  cerebrum  to  the  paralysis  of  "the  lumbar  spinal  centres 
which  results  from  and  lasts  some  time  after  divison  of  the  spinal 
cord  in  the  dorsal  region.  In  one  case  in  which  he  removed  the 
greater  part  of  both  hemispheres  the  dog  lived  for  months,  and 
showed  eventually  no  signs  whatever  of  any  muscular  weakness  ; 
all  the  muscles  of  his  body  were  firm  and  well  built,  and  the  only 
permanent  failure  in  the  way  of  movement  was  a  certain  clumsi- 
ness ;  and  this  Goltz  argues  to  be  merely  the  result  of  a  deficiency 
of  tactile  sensibility,  which,  as  we  shall  see  presently,  is  a  strik- 
ing result  of  large  injuries  to  the  cerebral  hemispheres.  Goltz's 
experiments  are  "in  fact  absolutely  opposed  to  the  hypothesis  of 
"motor"  areas  in  any  part  of  the  brain-surface. 

Turning  now  to  the  second  fine  of  inquiry  indicated  above,  viz., 
whether  the  removal  of  particular  areas  of  the  brain-surface,  even 
in  those  regions  in  which  stimulation  evokes  no  visible  movements, 
interferes  with  the  production  or  development  of  particular  sen- 
sations or  otherwise  modifies  in  particular  ways  the  functions  of 
the  brain,  we  find  that  Ferrier  and  others  contend  for  the  ex- 
istence of  definite  areas  in  connection  with  the  various  senses, 
areas  which  may  accordingly  be  spoken  of  as  ''sensory."  Thus 
Ferrier  describes  a  "visual"  centre,  the  destruction  of  which 
entails  blindness  of  the  opposite  eye,  an  "auditory"  centre,  a 
"  tactile  "  centre,  centres  for  taste  and  smell,  and  even  a  centre 
for  hunger.  Further  inquiries  have  brought  to  light  a  number 
of  facts  which  deserve  special  attention,  and  which  have  been 
most  fully  studied  in  reference  to  vision.  The  older  observers, 
Flourens  and  others,  had  remarked  that  injury  to,  or  removal  of 
portions  of  the  cerebral  hemispheres  frequently  caused  blindness  ; 
this,  however,  appeared  to  be  of  a  temporary  character  only,  the 
animal,  at  a  later  period,  seeming  upon  a  superflcial  examination 
to  have  completely  regained  its  sight.  Goltz,'  however,  has 
called  attention  to  a  remarkable  imperfection  of  vision  which  is 
more  or  less  permanent  after  extensive  injuries  to  the  cerebral 
hemispheres,  but  which  without  care  might  escape  notice.  The 
salient  character  of  this  im])erfection  is  that  though  the  animal 
evidently  can  see,  and  uses  his  sight  successfully  in  avoiding  ob- 
stacles and  guiding  his  movements,  yet  what  he  sees  does  not 
produce  its  usual  effect  on  him  ;  he  obviously  fails  to  recognize 
many  things,  and  has  become  indifierent  to  scones  which  formerly 
affected  him  strongly.  Thus  a  dog  from  which  portions  of  the 
cerebral  hemispheres  have  been  removed,  fails  to  recognize  his 
food  by  sight ;  when  he  is  threatened  with  the  whip,  he  is  not 

1  Op.  cit. 


CEREBRAL  CON VOLUTIO.NS .  839 


cowed  ;  when  the  hand  is  held  out  for  his  paw  he  makes  no  re- 
spouse  ;  and  though  hefore  the  operation  he  became  violent!}-  ex- 
cited when  the  laboratory  servant  dressed  in  a  fantastic  irarb  was 
presented  to  him,  he  remains  after  the  operation  pertectly  indif- 
ferent to  the  same  image.  Another  striking  character  of  this 
imperfection  of  vision  is  that  recovery  from  it  to  a  considerable 
extent  is,  under  certain  circumstances,  possible  by  means  of  edu- 
cational exercise  :  the  dog,  which  at  tirst  could  not  recognize  his 
food  by  sight,  and  Avas  inditftrent  to  the  whip,  learns  after  awhile 
to  know  the  one  and  to  respect  the  other.  Xow  it  is  obvious  that 
two  interpretations  may  be  given  of  this  peculiar  imperfection  of 
vision.  The  usual  psychical  eftects  may  fiiil  simply  because  the 
sensory  impulses  are  unable  to  give  rise  to  sutliciently  well-de- 
fined sensations  or  perceptions  and  vision  consequently  remains 
misty,  as  if  things  were  seen  through  a  gauze,  and  possibl}-,  to 
adop"^!  Goltz's  suggestion,  with  all  their  colors  washed  out ;  under 
such  circumstances  the  dog  could  not  readily  recognize  meat  as 
meat,  nor  appreciate  the  fantastic  dress  of  the  laboratory  ser- 
vant. The  other  interpretation  supposes  that  the  failure  is  due 
to  the  absence  of  intellectual  foctors,  that  the  sensations  may  be 
intact,  but  from  the  break  in  the  cerebral  sul)stance  cease  to  give 
rise  to  ideas  or  to  excite  the  memory  of  past  experience.  The 
beneticial  effects  of  exercise  are  obviously  explicable  on  both  hy- 
potheses. Under  the  tirst  view,  the  dog,  still  possessing  intel- 
lectual powers,  simi)ly  learns  to  make  use  of  his  imperfect  sensa- 
tions, just  as  he  would  do  if  the  inij^ierfect  vision  had  been  due  to 
simple  injury  or  disease  of  his  retina.  Under  the  second  view, 
new  ideas,  new  experience,  and  a  new  memory  are  formed  afresh  ; 
the  dog  learns  once  more  to  interpret  his  visual  sensations  in  the 
same  way  that  he  did  in  his  early  days.  The  tirst  view  is  the 
one  held  by  Goltz.the  second  view  is  maintained  l)y  Munk,'  who 
accordingly  speaks  of  the  imperfection  of  vision  of  which  we  are 
speaking  as  "'psychical"  blindness  in  contradistinction  to  a 
blindness  in  which  sensory  impulses  passing  along  the  ojitic  nerve 
altogether  fiiil  to  excite  visual  sensations  in  the  brain,  and  which 
we  may  speak  of  as  ''absolute"  blindness. 

Similar  but  less  striking  imperfections  of  the  other  senses 
were  observed  by  Goltz  as  attendant  on  removal  of  portions  of 
the  cerebral  hemispheres  ;  and  Munk,  in  accordance  with  the 
view  just  stated,  describes  a  psychical  deafness  and  ps3-chical 
failures  of  the  other  senses. 

Bearing  in  mind  tHe  distinctions  just  raised  we  maj'  retvn-n  to 
the  question  of  localization.  Munk-  insists  on  the  existence  of 
a  "'visual  area,"  seated  on  the  posterior  lobes,  but  differing  in 
position  from  and  of  much  wider  extent  than  that  of  Perrier. 

1  Yerhandl.  d.  phvsiol.  Gesell.  z.  Berlin,  1876-77,  Nos.  16,  17,35; 
1877-78,  Xos.  9,  10  ;"  1878-79,  4,  5,  18.  Archiv  f.  Anat.  u.  Phys.  (Phvs. 
Abth.),  1878,  pp.  162,  547,  599. 

2  Op.  cit.  . 


84:0  .  THE    BRAIN. 


He  maintains  not  only  that  removal  of  this  area  causes  blind- 
ness, without  necessarily  producing  any  other  change  in  the  ani- 
mal, but  also  that  parts  of  this  area  correspond  to  parts  of  the 
retina,  extirpation  of  small  portions  of  the  area  giving  rise  to 
blindness  in  particular  parts  of  the  retina,  the  retina  being  as  it 
were  projected  on  to  the  cerebral  surface,  so  that  a  partial  loss 
of  the  "visual  area"  gives  rise  to  a  functional  blind  spot,  so  to 
speak,  in  the  retina.  Thus  in  the  dog  the  retinal  area  of  distinct 
vision  he  regards  as  connected  with  the  central  parts  of  the  visual 
area  of  the  brain  of  the  opposite  side,  while  the  external  (tem- 
poral) parts  of  the  retina  are  connected  with  the  external  parts 
of  the  area  of  the  brain  of  the  same  side^  the  internal  (nasal)  parts 
with  the  internal  (median)  parts,  the  upper  parts  with  the  front, 
and  the  lower  parts  with  the  hind  parts  of  the  area  of  the  oppo- 
site side.  Tliese  results  of  circumscribed  ''  absolute"  blindness, 
he  states,  are  accompanied  by  psychical  blindness,  from  which 
the  animal  may  recover  by  due  practice  and  experience,  provided 
that  the  whole  visual  area  be  not  removed.  The  recovery  from 
psychical  blindness  Munk  interprets  as  being  carried  out  by  what 
may  be  crudely  spoken  of  as  the  deposition  of  new  visual  experi- 
ences in  the  rest  of  the  visual  area.  In  analogy  with  this  visual 
area  he  describes  an  auditor}^  area  differing  again  from  that  of 
Ferrier,  and  he  regards  the  whole  front  part  of  the  brain  as  form- 
ing a  large  "sensory"  area,  in  which  he  distinguishes  separate 
sensory  areas  (areas  of  tactile  sense,  of  muscular  sense,  and  gen- 
eral sensibility)  for  the  fore, limb,  the  hind  limb,  the  eye,  the 
head,  the  neck,  etc. 

Absolutel}^  opposed  to  Munk's  results  are  those  of  Goltz.  This 
author,  in  his  latest  as  in  his  earlier  researches,  insists  most 
stroniily  that  he  can  no. more  obtain  distinct  evidence  of  local- 
ization in  reference  to  sensation  than  in  reference  to  movements. 
When  in  a  dog  the  lesions  are  slight  the  recovery  from  imperfec- 
tions of  vision,  of  the  other  senses,  and  of  general  sensibility 
which  follow  immediately  on  the  operation  may  be  complete. 
When  a  larger  portion  of  brain  is  removed  the  peculiar  imper- 
fections discussed  above  become  striking,  and  the  so-called  psy- 
chical blindness,  togetiier  with  the  corresponding  imperfections 
of  the  other  senses,  may  become  permanent.  When  still  larger 
portions  are  removed,  as  in  the  case  of  the  dog  from  which  the 
greater  part  of  both  hemispheres  was  removed,  vision  becomes 
so  imperfect  that  though  the  animal  can  see,  since  he  avoids  ob- 
stacles in  his  path,  and  his  movements  are  obviously  guided  by 
vision,  still  to  a  superficial  observer  he  seems  completely  blind  ; 
a  match  may  be  struck  just  before  his  face  without  his  taking  any 
notice  of  it,  though  his  pupils  contract,  so  little  able  are  visual 
impulses  to  produce  any  cerebral  reactions.  Similar  phenomena 
were  witnessed  by  Goltz  with  regard  to  the  other  senses.  In  all 
cases  the  characters  of  the  result  depended  on  the  extent  of  the 
injury,  on  the  quantity  of  brain-substance  removed,  and  not  on 
the  locality  operated  on  ;  the  amount  of  amelioration  of  the  so- 


CEREBRAL    CONVOLUTIONS.  841 


called  psychical  blindness  possible  by  practice  and  experience 
being  determined  partly  by  the  amount  of  damage  done  to  vision 
itself,  and  partly  by  the  degree  to  which  the  general  intellect  of 
the  animal  had'^been  impaired  by  the  operation.  Goltz  thinks 
that,  perhaps,  destruction  of  the  parietal  lolies  has  the  greater 
effect  on  tactile,  and  destruction  of  the  posterior  lobes  the  greater 
effect  on  visual  sensations,  but  he  can  tind  no  well-marked  local- 
ized areas.  The  dog,  according  to  him,  from  which  a  large  por- 
tion of  the  cerebral  hemispheres  has  been  removed,  is  a  dog  re- 
duced to  idiocy  by  a  cutting  oft'  of  the  higher  elaborations  of  all 
the  sensory  impulses  which  reach  him,  and  by  a  curtailing  of  his 
general  psychical  activity  ;  and  he  is  brought  to  this  condition 
step  by  step,  as  more  and  more  of  his  cerebral  substance  is  re- 
moved. 

Besides  the  experimental  evidence  just  discussed  we  iiave 
also  })athological  indications  of  the  connection  of  certain 
movements  with  a  particular  convolution.  The  condition 
known  as  aphasia,  using  tliat  word  in  its  general  sense,  in- 
cluding its  several  varieties,  as  meaning  the  loss  of  articulate 
speech,  is  so  often  associated  with  disease  of  the  posterior 
portion  of  the  third  frontal  convolution  (Figs.  223,  224)  (9) 
(10),  that  it  l)ecomes  impossible  not  to  admit  that  there 
must  be  some  causal  connection  between  this  part  of  the 
brain  and  speech.  In  the  vast  niajority  of  cases  the  disease 
is  on  the  left  side  of  the  brain  and  occurs  in  company  with 
right  hemiplegia,  but  cases  have  been  recorded  where  the 
right  side  of  the  brain  was  affected. 

Seeing  that  articulate  speech  is  a  thing  learned  b}'  use,  it  has 
been  suggested  that  in  most  persons  one  side  of  the  brain  only 
has  been  educated  for  this  purpose,  and  hence  that  one  side  only 
of  the  brain  is  employed  ;  that  we  are,  in  fact,  left-brained  in 
respect  to  speech  in  the  same  way  that  we  are  right-handed  in 
respect  to  many  bodily  movements  ;  and  this  view  is  apparently 
supported  by  the  fact  that  the  left  side  of  the  brain  is  on  the 
whole  larger  and  more  convoluted  than  tlie  right  side  ;^  but  the 
question  of  the  dual  action  of  the  two  cerebral  hemispheres  is  too 
dark  a  subject  to  enter, into  here. 

It  is  obvious  that  loss  of  speech  may  arise  from  a  variet}^  of 
causes.  It  may  be  due  to  simple  paralysis  of  the  hypoglossal, 
and  other  nerves  concerned  in  speech.  It  may  be  occasioned  by 
an  imi)erfection  in  the  co-ordinating  mechanism  by  which  the 
efttirent  impulses  are  marshalled  just  previous  to  their  exit  from 
the  central  nervous  system.     Or  it  may  be  caused  by  a  break  in 

1  This  statement  bv  Gratiolet  has,  however,  been  opposed  by  Ecker 

and  others;  but  cf.  Boyd  (Phil.  Trans.,  1861,  p.  261). 


842  THE    BRAIN. 


the  nervous  chain  connecting  the  idea  of  the  word  with  this 
co-ordinate  motor  mechanism  of  expression.  Lastly,  the  fault 
may  lie  in  the  generation  of  the  idea  itself.  It  is  the  two  latter 
forms  of  aphasia  which  appear  to  he  connected  with  the  cerebral 
convolution  spoken  of  above.  The  cases  are  strikingly  parallel 
to  that  of  the  dog  just  mentioned. 


Sec.  4.    The  Functions  of  other  Parts  of    the  Brain. 

Although  much  has  been  written,  and  many  experiments 
performed,  in  reference  to  the  various  parts  of  the  brain, 
the  views  which  have  thereby  l)een  worked  out  are  for  the 
most  part  neither  satisfactory  nor  consistent ;  indeed,  the 
proper  method  to  study  the  l>rain  is  probably  to  trace  out  a 
cerebral  operation  along  its  chain  of  events  rather  than  to 
seek  to  attach  readily  definable  functions  to  the  cerebral 
anatomical  components. 

A  fundamental  difficulty  meets  us  at  the  threshold  of  every  in- 
quiry into  the  particular  function  of  any  part  of  the  brain.  When 
an  organ,  such  for  instance  as  the  corpus  striatum,  is  removed 
by  the  knife,  or  placed  hors  de  combat,  or  thrown  into  an  abnormal 
condition  by  the  injection  of  corrosive  fluids,  or  by  haemorrhage, 
or  by  other  pathological  changes,  we  have  no  right  to  infer  that 
the  negative  phenon^iena,  loss  of  volition,  of  sensation,  etc.,  which 
make  their  appearance,  prove  that  in  its  normal  condition  the 
organ  in  question  is  a  seat  or  a  main  tract  of  volition,  loss  of  sen- 
sation, etc.  This  may  be  the  explanation  of  the  experiment  or 
malady  ;  but  it  may  not.  Whatever  may  prove  in  the  end  to  be 
the  nature  of  nervous  inhibition,  it  is  clear  that  inhibitor}'  actions 
are  important  factors  in  the  production  of  nervous  phenomena. 
In  almost  every  instance  in  which  we  have  treated  of  a  nervous 
mechanism  we  have  had  to  deal  with  inhibition,  i.  e.,  with  a 
nervous  action  interfering  with  another  nervous  action.  Indeed 
the  nervous  phenomena  of  the  heart,  of  the  vasomotor  system,  of 
the  respiratory  centre,  and  of  the  spinal  cord  generally  become  a 
confused  mtdlcy  if  we  refuse  to  admit  that  certain  effects  are  due 
to  the  action  of  one  part  of  a  nervous  mechanism  inhibiting  (or 
conversely  increasing)  the  actions  of  another  part.  But  if  this 
be  the  case  in  such  comparatively  simple  nervous  mechanisms, 
we  have  every  reason  to  expect  that  inhibitory  actions  play  a 
distinguished  part  in  the  operations  of  the  far  more  complex 
nervous  machinery  of  the  brain.  This  being  granted,  it  is  ob- 
vious that  any  interference,  by  experiment  or  disease,  with  the 
normal  working  of  the  brain,  may  act,  as  far  as  inhibition  is  con- 
cerned, in  two  different  ways.  In  the  first  place  the  interference 
may  place  /ior.s  de  combat  a  part  of  the  brain  which  previously 
was  exerting  an  inhibitory  influence  on  another  perhaps  quite 


FUNCTIONS  OF  PARTS  OF  THE  BRAIN.     843 


distant  part,  just  as  section  of  the  vagi  in  the  dog  relieves  the 
heart  from  the  cardio-inliibitory  inliuenees  of  the  medulla  ob- 
longata ;  and  the  part  of  the  brain  thus  freed  from  its  wonted 
restraint  may  fall  into  disorderly  action.  Obviously  in  such  a 
case  the  real  seat  of  the  disorder  is  in  this  part  and  not  in  the 
(distant)  inhibitory  part  directlj'^  operated  on.  In  the  second 
place  the  interference  itself,  the  injury  to  the  nervous  elements 
caused  by  the  knife,  or  the  cautery,  or  by  the  sequent  intlamma- 
tory  processes,  or  by  the  irritation  of  disease,  may  act  as  a  stim- 
ulus discharging  impulses  which  exert  an  inhibitory  influence  on 
it  may  be  distant  organs.  And  when  we  consider  the  delicacy 
and  activity  of  the  elements  of  the  central  nervous  system,  it  is 
not  surprising  that  the  effects  of  even  a  simple  incision  should 
be  profound  and  should  last  some  considerable  time.  Goltz  has 
called  attention,  in  this  respect,  to  the  effects  of  dividing  in  the 
dog  the  spinal  cord  in  the  dorsal  region.  Immediately  after  the 
operation  retlex  movement  in  the  hand,  legs,  and  other  parts 
connected  with  the  lumbar  cord  are  entirely  absent,  and  their  ab- 
sence continues  for  a  considerable  period,  the  dog  in  this  respect 
presenting  a  marked  contrast  to  the  frog.  In  time,  however,  as 
the  wound  in  the  spinal  cord  heals  up,  reflex  movements  make 
their  appearance,  and  as  we  have  already  seen  (p.  780),  are  abun- 
dant and  manifold.  In  such  a  case  we  must  either  suppose  that 
in  the  normal  dog  the  reflex  movements  of  the  hind  limbs,  etc., 
require  for  their  development  the  presence  and  activity,  not  only 
of  the  lumbar  cord  but  also  of  parts  of  the  cerebro-spinal  axis 
lying  higher  up,  and  that  such  reflex  movements  as  do  eventually 
appear  after  section  of  the  dorsal  cord  are  new  achievements 
gradually  forced,  so  to  speak,  on  the  lumbar  cord  in  consequence 
of  its  isolated  position  ;  or  we  must  admit  that  the  section  of  the 
dorsal  cord  has  produced  for  the  time  being  a  profound  inhibitory 
action  on  the  lumbar  cord  below.  The  latter  view  is  as  much  in 
consonance  with,  as  the  former  view  is  opposed  to,  all  other 
physiological  experience.  But  if  we  admit  the  latter  view,  then 
we  may  fairly  ask,  why  should  not  section  of,  or  injury  to,  or  dis- 
ease of  parts  of  the  still  more  highly  organized  "brain  produce 
similar  inliibitory  effects  in  other  parts  of  the  cerebral  machinery  V 
If,  however,  we  admit  this,  it  follows  that  great  caution  is  neces- 
sary in  explaining  the  results  of  any  operation  on  the  brain. 
Difliculties  such  as  these  are  more  likel}'  to  occur  in  cases  of  dis- 
ease than  even  in  those  of  operative  interference  ;  and  it  is  this 
which  renders  caution  so  necessary  in  the  physiological  handling 
of  clinical  facts. ' 

We  may,  therefore,  be  permitted  to  summarize  very  briefly 
what  is  actuallv  known. 


Cf.  Brown-Sequard,  Archives  de  Physiol.,  iv  (1877),  p.  409,  et  seq. 


844  THE    BRAIN. 


Corpora  Striata  and  Optic  Thalami, 

The  preceding  discussions  enable  us  to  lay  down  two 
broad  propositions  :  (1.)  The  functions  of  tlie  cerebral  convo- 
lutions are  eminently  psychical  in  nature  ;  these  parts  of  the 
brain  intervene,  and  as  far  as  we  can  judge,  intervene  only, 
in  those  operations  of  the  nervous  system  in  which  an  intel- 
ligent consciousness  and  volition  play  a  part.  (2.)  The 
hinder  paits  of  the  brain,  viz.,  the  corpora  quadrigemina, 
crura  cerebri,  pons  Varolii,  cerebellum,  and  medulla  oblon- 
gata, are  capable  by  themselves  of  cari'ying  into  execution 
complex  movements,  the  co-ordination  of  which  implies  very 
considerable  elalioi-ation  of  afferent  impulses;  they  can  do 
this  even  in  the  case  of  such  mammals  as  the  rabbit  and  the 
rat,  in  the  total  absence  of  the  cerebral  hemisplieres,  corpora 
striata,  and  optic  thalami.  Tiicse  two  latter  bodies,  often 
s})oken  of  as  ''  the  basal  ganglia,"  are  undoubtedly  the  great 
means  of  communication  between  the  cereljral  hemispheres 
on  the  one  hand  and  the  crura  cerebri  on  the  other.  Though 
some  fibres^  do  pass  from  the  crura  by  or  through  the  gan- 
glia to  the  cerebral  convolutions  without  being  connected 
with  the  nerve-cells  of  those  ganglia,  tiie  great  mass  of  the 
peduncular  fibres  are  probably  connected  with  the  superfi- 
cial gray  matter  of  the  hemispheres  in  an  indirect  manner 
only,  tiie  lower  or  anterior  fibres  (criisla)  passing  first  into 
the  coipora  striata,  and  the  upper  or  posterior  fibres  (ler/- 
mejitum)  into  the  optic  thalami.  This  anatomical  disposi- 
tion would  lead  us  to  suppose  that  these  bodies  have  impor- 
tant functions  in  mediating  between  the  psychical  operations 
of  the  cerebral  convolutions  on  the  one  hand  and  the  sen- 
sori-motor  machinery  of  the  middle  and  hind  brain  on  the 
other;  and  tlie  separate  courses  taken  by  the  peduncular 
fil)res  would  further  lead  us  to  expect  that  the  functions  of 
the  corpora  striata  diifer  fundamentally  from  those  of  the 
optic  thalami. 

When  in  the  human  subject  a  lesion  occurs  involving  both 
these  bodies  on  one  side  of  the  brain,  the  result  is  a  loss  of 
sensation  in,  and  voluntary  power  over,  the  opposite  side  of 
the  body  and  face,  a  so-called  hemiplegia,  wdiich  may  be  ab- 
solutely complete  without  any  impairment  whatever  of  the 
intellectual   faculties.     The  will  and  the  power  to  receive 

^  Quain's  Anatomy,  8th  ed.,  ii,  555. 


CORPORA    STRIATA.  845 


impressions  are  present  in  their  entirety,  but  neither  efferent 
nor  afferent  irapnlses  can  make  their  way  to  or  from  the 
peripheral  organs  and  the  cerebral  convolutions.  The  injury 
to  the  basal  ganglia  blocks  the  way.  In  the  great  majority 
of  cases  the  am^^sthesia  (or  loss  of  sensation)  and  akinesia 
(or  loss  of  movem.ent)  are  sibsolutely  confined  to  the  op- 
posite side  of  the  body;  and  the  cases  in  which  a  lesion  of 
the  l)asal  ganglia  of  one  side  of  the  brain  affects  the  same 
side  of  the  body  or  both  sides  must  be  regarded  as  excep- 
tional, and  explicable  as  the  results  of  the  action  of  one  side 
ot  the  brain  on  the  other  side  either  of  the  brain  or  of  some 
region  of  the  cerebro-spinal  axis.  The  results  of  experi- 
ments on  animals  agree  entirely  with  the  general  experience 
of  pathologists,  that  lesions  of  the  corpora  striata  and  optic 
thalami  produce  their  effect  on  the  opposite  side  of  the  body. 
Whatever  be  the  view  taken  concerning  the  decussations  of 
sensor}'  and  motor  impulses  in  the  spinal  cord,  it  must  be 
admitted  that  both  kinds  of  impulses  cross  over  completely 
somewhere  during  their  transmission  to  and  from  the  basal 
ganglia  and  the  peripheral  organs. 

When,  however,  we  have  admitted  that  these  bodies  act, 
as  it  were,  the  part  of  middlemen  between  the  cerebral  con- 
volutioiis  and  the  rest  of  the  brain,  we  have  gone  almost  as 
far  as  facts  will  support  ns.  We  are  not  at  present  in  a  posi- 
tion to  state  dogmatically  what  is  the  nature  of  the  media- 
tion which  either  body  respectively  effects.  A  very  tempt- 
ing hypothesis  is  one  which  suggests  that  the  corpora  striata 
are  conceriied  in  the  downward  transmission  and  elal)ora- 
tion  of  efferent  volitional  impulses,  and  the  optic  thalami  in 
a  similar  upward  transmission  and  elaboration  of  afferent 
sensory  impulses  ;  and  there  are  many  facts  which  may  be 
nrged  in  favor  of  this  view  which  was  first  developed  and 
expounded  by  Carpenter  and  Todd.  So  much  acceptance, 
indeed,  has  it  found  that  many  pathologists  regard  it  as 
established,  and  speak  confidently  of  the  corpora  striata  as 
motor,  and  the  optic  thalami  as  sensory,  ganglia.  A  careful 
review,  however,  of  all  the  facts  leads  to  the  conclusion  that 
this  division  of  functions  has  not  yet  been  clearly  proved. 

The  pathological  evidence  in  this  case,  were  it  sharply  defined 
and  accordant,  would  be  of  unusual  value  ;  but  it  is  neither  the  one 
nor  the  other.  A  number  of  cases,  indeed,  may  be  cited  to  show 
not  only  that  lesions  ot  a  corpus  striatum  may  be  accompanied 
by  akinesia  without  anaesthesia,  but  that  lesions  of  an  optic 
thalamus  may  cause  anaesthesia  without  actual  akinesia ;  that 

71 


816  THE    BRAIN. 


is,  without  any  furtlier  interference  with  the  execution  of  vol- 
untary movements  than  is  occasioned  by  the  loss  of  the  co-ordi- 
nating sensations.  Of  these  two  classes  of  cases  the  latter  is  the 
more  valuable,  since  all  clinical  experience  shows  that  any  lesion 
more  readily  interferes  with  volitional  movements  than  with  the 
reception  of  sensory  impressions.  Convulsions  are  not  common 
when  the  lesions  are  conlined  to  these  bodies  ;  but  when  wit- 
nessed they  can  generally  be  referred  to  the  corpora  striata  rather 
than  to  the  o])tic  thalami ;  like  the  paralysis,  the  convulsions  are 
generally  limited  to  the  opposite  side  of  the  body,  though  feeble 
movements  may  occasionally  be  seen  on  the  same  side  as  well. 
On  the  other  hand,  numerous  cases  have  been  recorded  where  an 
injury  apparently  confined  to  one  corpus  striatum  has  had  as 
part  of  its  results  ansesthesia  of  the  opposite  side  of  the  body  ; 
and  others,  where  disease  apparently  confined  to  an  optic  thal- 
amus, has  caused  loss  of  movement  as  well  as  of  sensation. 

Experiments  on  animals,  though  very  valuable  as  regards  the 
investigation  of  movements,  are  imperfect  means  of  studying  the 
phenoniena  of  conscious  sensations.  AVe  have  already  seen  that 
crude  unelaborated  sensatioUvS  ma}^  originate  in  an  animal  de- 
prived of  its  cerebral  hemispheres  ;  and  it  becomes  a  matter  of 
great  difficulty  to  disentangle  the  evidences  of  these  primitive 
sensations  from  those  of  the  higher  psychical  perceptions.  More- 
over we  do  not,  at  present,  at  all  know  to  what  an  extent  the 
larger  development  of  the  cerebral  hemispheres  in  man  has  in- 
fluenced the  ordinary  functions  of  the  other  parts  of  the  brain. 
It  may  be  that  important  functions  which  in  the  rabbit  belong 
to  the  middle  and  hind  brain  have,  in  man,  almost  disappeared 
in  order  to  make  these  structures  more  useful  servants  of  the 
cerebral  hemispheres.  It  may  be,  however,  that  the  greater 
activity  of  the  convolutions  has  simply  increased  the  ordinary 
labors  of  the  middle  and  hind  brain.  We  cannot  at  present  say 
which  eftect  has  resulted  ;  but  meanwhile  great  caution  ought  to 
be  exercised  in  drawing  inferences  from  experiments  on  a  rabbit 
or  on  a  dog,  as  to  what  are  the  functions  of  the  corresponding 
parts  of  the  human  brain. 

Ferrier'  observed  that  when  the  corpora  striata  were  stimu- 
lated with  an  interrupted  current,  convulsive  movements  of  the 
opposite  side  of  the  body  took  place  ;  the  animal,  when  the 
stimulus  was  powerful,  being  thrown  into  complete  pleuros- 
thotonus,  the  side  of  the  body  opposite  to  the  side  of  the  brain 
stimulated  being  forcibly  drawn  into  an  arch  ;  the  locahzed  move- 
ments observed  by  Burdon  Sanderson  (p.  835),  were  lost  in  the 
general  convulsions  caused  by  the  galvanic  current  aftecting  a 
large  portion  of  the  organ.  When,  on  the  other  hand,  the  optic 
thalami  were  similarly  stimulated,  no  such  convulsions  were  ob- 
served. On  this  point  Carville  and  Duret's-  observations  are  in 
accordance  with  those  of  Ferrier  ;  and  the  results,  as  far  as  they 

'  Op.  ch.  2  Op.  cit. 


CORPORA    STRIATA.  847 


go,  appear  at  first  sight  to  \ye  in  accordance  with  the  theory  of 
the  exclusively  motor  functions  of  the  corpora  striata,  and  the 
exclusively  sensory  functions  of  the  optic  thalami.  But  it  would 
obvious)}'  be  rash  to  draw  any  such  conclusion  directly  from 
them,  since,  if  the  optic  thalamus  is  concerned  in  the  transmis- 
sion and  elaboration  of  sensory  impulses,  the  application  of  the 
galvanic  current  to  it  ought,  by  discharging  a  number  of  sensory 
nupulses,  to  give  rise  to  movements  of  some  kind  or  other,  and 
not  to  be  characterized  by  the  absence  of  all  effects.  Moreover 
any  such  inference  is  opposed  by  the  results  of  Nothnagel's'  ex- 
periments. This  observer  destroyed  by  injection  of  chromic 
acid  both  nuclei  lenticulares  (the  extra-ventricular  portions  of 
the  corpora  striata)  of  the  rabbit,  with  the  result  of  bringing  the 
animal  almost  exactly  into  the  same  condition  as  if  both  its  cere- 
bral hemispheres  had  been  removed.  When,  on  the  other  hand, 
by  the  help  of  a  special  instrument,  he  succeeded  in  destroying 
both  optic  thalami  Avithout  any  otber  injury  to  the  brain,  no  ob- 
vious effects  followed  ;  there  were  no  signs  of  either  loss  of  voli- 
tion or  of  sensation,  nothing  in  fact  could  be  noticed  except  a 
rather  peculiar  disposition  of  the  limbs.  When  the  nuclei  len- 
ticulares were  destro\'ed  there  was  no  apparent  loss  of  sensation, 
that  is  to  say  the  animal  readily  moved  wlien  stimulated  by 
pinching  tbe  skin,  etc.  ;  but  it  was  impossible  to  tell  whetber 
sensory  impulses  reached  the  cerebral  convolutions,  since  no 
manifestations  whatever  of  the  condition  of  the  convolutions 
were  possible.  The  animal  might  have  felt  acutely,  and  yet  have 
been  unable,  from  tbe  loss  of  the  appropriate  motor  tracts,  to 
express  itself;  or  it  might  have  been  as  incapable  of  the  higher  i)sy- 
chical  feeling  as  it  was  of  executing  spontaneous  movements.  The 
phenomena  resulting  from  destruction  of  the  nuclei  lenticulares 
admit  of  no  clear  proof  in  either  direction.  The  fact,  however, 
that  voluntary  movements  continued  as  usual  after  complete  de- 
struction of  the  optic  thalami  gocs  far  to  prove  that,  in  the  rabbit 
at  least,  these  bodies  are  not  the  only  means  by  which  sensory 
impulses  pass  to  the  cerebral  convolutions.  Even  admitting 
(and  indeed  in  the  case  of  man  we  know  that  the  general  anaes- 
thesia following  upon  lesions  of  the  optic  thalami  is  not  neces- 
sarily accompanied  by  blindness  or  loss  of  an}-  other  special  sense) 
that  visual  and  other  specitic  impulses  still  reached  tbe  rabbit's 
convolutions,  and  that,  in  consequence  of  the  co-ordinating  mech- 
anisms of  the  hinder  brain  being  still  intact,  the  co-ordination  of 
the  animal's  movements  might"  still  have  been  carried  out,  yet 
the  initiation,  and  hence  the  general  character  of  those  move- 
ments, must  have  been  influenced  by  the  total  absence  of  all  psy- 
chical tactile  sensations.  Apparently,  however,  this  was  not  the 
case  ;  the  movements  did  not  in  any  wa}-  betray  the  loss  of  any 
factors. 


'  Op.  cit.     Ibid.  Bd.  58  (1873),  p.  420;   Bd.  60  (1874),  p.  129;   Bd. 
62  (1875),  p.  201. 


848  THE    BRAIN. 


Lussana  and  Lemoigne,  who  regard  the  optic  thalami  as 
motor  centres  for  the  lateral  movements  of  the  anterior  limbs  (a 
lesion  of  one  optic  thalamus  paralyzing  tiie  adduction  of  the 
fore  limb  of  the  corresponding  and  the  abduction  of  that  of  the 
opposite  side),  saw  no  evidence  of  any  loss  of  general  sensibility 
or  any  signs  of  pain  to  result  from  injuries  to  these  bodies,  and 
no  movements  to  result  from  stimulation  of  otber  than  their  deep 
parts.  After  a  lesion,  however,  of  the  optic  thalamus  of  one 
side  the}'  invariably  found  blindness  in  the  opposite  eye. 

Carville  and  Duret^  found  that  in  the  dog  section  of  the  in- 
ternal capsule,  or  expansion  of  tibrts  passing  between  the  nucleus 
lenticularis  and  optic  thalamus,  in  the  anterior  part  of  its  course 
where  it  passes  between  the  nucleus  lenticularis  and  the  nucleus 
caudatus,  led  to  hemiplegic  loss  of  voluntary  movement  on  the 
opposite  side,  though  stimulation  of  the  paralyzed  limb  still  gave, 
rise  to  reflex  movements.  When  the  section  was  carried  through 
ths  posterior  part  of  the  expansion,  between  the  nucleus  lenticu- 
laris and  optic  thalamus,  the  loss  of  voluntary  movement  on  the 
opposite  side  of  the  bod}'  was  accompanieil  b}-  loss  of  sensation 
i.  e.,  when  the  paralyzed  limbs  were  pinched  no  responsive  re- 
flex movements  followed.  It  is  hazardous,  however,  to  draw 
from  these  experiments  an}'  positive  conclusions. 

Nothnagel-^  observed  that  in  the  rabbit  voluntary  movements 
still  persisted  after  destruction  of  both  nuclei  caudati ;  in  this 
respect  these  portions  of  the  corpora  striata  presented  a  marked 
contrast  to  the  nuclei  lenticulares.  Nevertheless  destructi(m  of 
one  nucleus  caudatus  frequently  induced  a  certain  amount  of  pa- 
ralysis of  the  opi)osite  side  of  the  body,  which  disappeared  after 
removal  of  the  nucleus  caudatus  of  the  other  side  ;  and  as  we  iiave 
already  stated,  destruction  or  injury  to  a  particular  part  of  the 
nucleus  caudatus,  viz.,  the  so-called  nodus  cursorius,  gave  rise 
to  remarkable  forced  movements,  which  made  their  appearance 
even  after  the  previous  removal  of  the  nuclei  lenticulares.  Tbe 
injection  of  chromic  acid  into  other  parts  of  the  nucleus  cauda- 
tus also  frequently  caused  for  awhile  forced  movements,  either 
straight  forward,  or  of  the  circus  kind,  which  ditfered  from  those 
witnessed  by  older  observers  in  the  operations  on  the  corpora 
striata  after  removal  of  the  hemispheres,  inasmuch  as  they  were 
executed  by  an  animal  still  possessing  intelligence,  and  frequently- 
striving  to  avoid  obstacles. 

It  is  impossible  at  present  to  give  a  satisfactory  explanation  of 
all  tiiese  varied  and  frequently  inconsistent  phenomena,  but  it 
may  be  worth  while  to  return  again  to  the  possibility  of  consid- 
ering some  at  least  of  the  phenomena  as  inhibitory  effects.  The 
fact  that  the  paralysis,  curvature  of  the  body,  and  the  circus 
movements  resulting  from  lesion  of  one  nucleus  caudatus  or  uu- 

'*  Fisiologia  dei  centri  nervosi  encefalici,  1871,  and  Archives  de 
Phvsiologie,  iv  (1877),  p.  119  et.  seq. 

2'  Op.  cit.  3  Op.  cit. 


CORPORA    QUADRIGEMINA.  849 

cL'Us  lenticularis,  disappear  when  the  same  bod}'^  on  the  other  side 
iis  removed,  warns  us  against  too  hastily  assuming  that  a  loss  or 
diminution  of  voluntary  power  means  nothing  more  than  a  break 
in  the  transmission  of  volitional  impulses;  it  may  mean  that,  but 
it  may  mean  also  the  development  of  nervous  actions  having 
inhibitory  effects.  In  the  experiment  of  Carville  and  Duret, 
quoted  above,  pinching  the  left  hind  limb  after  section  of  the  right 
internal  capsule  produced  no  retlex  action  whatever.  Xow  it  is 
absurd  to  suppose  that  in  this  case  the  retlex  centre  was  removed, 
or  any  part  of  a  veritable  reflex  chain  broken,  because,  as  we 
know,  pinching  the  hind  limb  will  produce  a  reflex  movement, 
provided  oidy  a  portion  of  the  lumbar  cord  be  left  intact  and 
functional.  There  nmst  in  this  case  have  been  inhibition  of  the 
lumbar  reflex  centres  ;  and  if  of  these,  why  not  of  otber  centres, 
reflex  or  automatic  V 

Cotyora  Q uadrige min a . 

We  have  already  seen  that  the  centre  of  co-ordination  for 
the  movements  of  the  eyeballs  (p.  717)  and  that  for  the  con- 
traction of  the  pui)il  (p.  <i67),  lie  in  the  neighborhood  of  the 
nates  or  anterior  tubercles  of  the  corpora  quadrigemina. 
These  two  centres  are  associated  together  in  such  a  way 
that  when  the  eyeballs  are  voluntarily  directed  inwards  and 
downwards,  as  for  near  vision,  the  pupils  are  at  the  same 
time  coulracted;  and  when  the  eyeballs  are  directed  up- 
wards and  returu  to  parallelism,  the  pupils  are  dilated  to  a 
correspondiug  extent;  when  both  eyeballs  are  moved  to- 
gether sideways  the  pupils  remain  unchanged.  We  have 
seen  (p.  717)  that  the  various  movements  of  the  eyeballs  may 
be  brought  about  by  direct  stimulation  of  particular  parts 
of  the  nates,  and  are  then  also  accompanied  by  the  appro- 
priate changes  in  the  pupils.  The  association,  therefore,  of 
the  movements  of  the  pupil  and  of  the  ocular  muscles  is  not 
simple  psychical  in  nature,  but  is  dependent  on  the  close 
connection  of  their  respective  centres.  From  the  fact  of 
the  movements  of  the  eyeball  and  pupil  being  so  readil}' 
and  variously  excited  by  stimulation  of  the  nates,  it  has  been 
inferred  that  the  centres  for  these  movements  lie  in  those 
bodies  ,^  it  would  ap[>ear,  however,  that  what  may  be  called 
the  real  or  immediate  centres  of  these  movements  lie  be- 
neath the  corpora  quadrigemina,  in  the  front  part  of  the 
floor  of  the  aqueduct  of  Sylvius,  and  therefore  are  affected 
in  an  indirect  manner  only  when  the  corpora  quadrigemina 
are  stimulated. 

,      1  Adamuk,  Cbt.  raed.  Wiss.,  1870,  p.  65. 


850  THE    BRAIN. 


The  more  exact  determination  by  Hensen  and  Voelkers  of  the 
topography  of  the  centres  for  the  movements  of  the  eyeball  and 
pupil  (see  p.  <571)  explains  the  results  of  Knoll  who  found,  in  o])- 
position  to  Flourens,  Budge,  and  others,  that  retiex  contraction 
of  the  pupils  remained  even  after  removal  of  the  corpora  quadri- 
gemina,  and  helps  to  clear  up  the  discrepancy  between  Adamuk' 
and  Knoll  as  to  dilation  of  pupil  being  produced  by  stimulation 
of  the  testes  or  of  the  nates.  Hensen  and  A'oelkers  found  their 
experiments  untrustworthy  so  long  as  they  merely  stimulated 
the  corpora  quadrigemina  ;  it  was  not  until  they  divided  these 
bodies  and  stimulated  the  underlying  parts  that  their  results  be- 
came uniform. 

Flourens  observed  that  unilateral  extirpation  of  tlie  cor- 
pora quadrigemina  in  m.ammals  or  of  the  optic  lobes  in 
birds  produced  l)lindness  in  the  opposite  eye;  and  tlie  same 
result  has  been  gained  by  many  subsequent  observers.'^ 
We  have  seen,  moreover,  that  both  frogs,  birds,  and  mam- 
mals continue  to  receive  and  within  limits  to  react  upon 
visual  impressions  after  the  total  removal  of  tlie  cerebral 
hemispheres.  From  these  facts  we  infer  that  visual  sensory 
impulses  become  transformed  into  visual  sensations  in  the 
c  )rpora  quadrigemina;  or,  in  other  words,  that  these  ner- 
vous structures  are  centres  of  sight.  But  they  are  so  in  a 
limited  sense  only.  We  have  seen  that  destruction  or  in- 
jury of  the  cerebral  hemispheres  profoundly  affects  vision. 
In  the  absence  of  the  cerebral  convolutions,  a  crude  vision, 
devoid  of  distinct  visual  percei)tions,  is  probably  all  that  is 
possible.  The  processes  constituting  distinct  and  perfect 
vision  in  fact  begin  in  the  retina,  and  are  partially  elabo- 
rated in  the  corpora  quadrigemina,  possibly  in  the  optic 
thalami,^  but  do  not  become  completely  developed  until  the 
cerebral  convolutions  have  been  called  into  operation. 

In  those  animals  [ex.  (jr.^  rabbits)  in  which  unilateral  destruc- 
tion of  the  corpora  quadrigemina  entails  blindness  of  the  oppo- 
site e3'e,  and  3'et  does  not  affect  at  all  the  visual  sensory  impulses 
originating  in  the  eye  of  the  same  side,  it  is  obvious  that  a  com- 
plete decussation  of  the  sensory  impulses  must  take  place  before 
the  centre  is  reached. 

The  question  however  whether  the  decussation  of  fibres  (and 
consequently  of  impulses)  in  the  optic  chiasiua  is  complete  or 
incomplete,  whether  the  optic  tract  of  one  side  is  the  continua- 
tion of  all  the  fibres  in  the  optic  nerve  of  the  opposite  side  or 

'  Op.  cit.  2  McKendrick,  Trans.  Koy.  Soc.  Ed.,  1873. 

Lussana  and  Lemoigne,  op.  cit. 


CORPORA    QUADRIGEMINA.  851 


whether  it  is  composed  of  representatives  of  the  optic  nerves  of 
both  sides,  is  one  which  has  been  much  debated,  both  from  an 
anatomical  and  a  pliysiological  standpoint.  As  regards  mam- 
mals, the  results  of  experiment  and  observation  ditfer  according 
to  the  animal  employed.'  In  the  rabbit  the  decussation  appears 
to  be  complete  ;  destruction  of  the  corpora  quadrigemina  on  one 
side  causes  degeneration  of  the  opposite  optic  nerve  but  not  at 
all  of  that  of  the  same  side,  and  removal  of  one  retina  degener- 
ation of  the  opposite  optic  tract  but  not  at  all  of  that  of  the  same 
side,  while  longitudinal  section  of  the  chiasma  causes  total  blind- 
ness. In  the  dog,  destruction  of  one  retina  gives  rise  to  strands 
of  degeneration  in  both  optic  tracts,^  and  Xicati^  has  in  the  cat 
succeeded  in  dividing  the  chiasma  without  destroying  vision  ; 
from  which  it  is  inferred  that  in  these  animals  the  decussation  is 
incomplete.  Munk"s  experiments  (see  p.  840)  are  also  in  favor 
of  an  incomplete  decussation  in  the  dog,  since  destruction  of  the 
visual  area  on  one  side  interferes  with  the  sight  of  both  eyes. 
In  man  Mandelstamm^  has  argued  from  the  various  forms  of 
hemiopia  (in  which  portions  only  of  the  retinas  are  insensible  to 
light)  that  the  decussation  is  complete  ;  but  the  concurrence  of 
hemiopia  in  both  eyes  with  hemianthesia,  or  hemiplegia,  and 
other  symptoms  indicating  disease  of  one  side  of  the  brain  only, 
has  generally,  though  not  perhaps  conclusively,  been  held  to 
prove  that  in  man  the  decussation  is  incomplete  :  and  Gowers' 
quotes  a  case  where  hemiopia  of  both  sides  resulted  from  disease 
limited  to  one  optic  tract,  and  brings  other  evidence  in  favor  of 
the  view  that  the  decussation  is  incomplete. 

Flourens  and  subsequent  observers  noticed  that  injury  or 
removal  of  the  corpora  quadrigemina  on  one  side  frequently 
caused  forced  movements,  and  that  removal  of  the  whole 
mass  led  to  oreat  want  of  co  ordination.  These  results  are 
quite  in  harmony  with  the  fact  mentioned  above  (p.  825) 
concerning  the  co-ordinating  functions  of  the  optic  lobes  in 
frogs.  But  at  present  we  have  no  exact  knowledge  con- 
cerning the  nature  of  the  coordination,  and  what  relations 
are  borne  in  this  respect  by  the  corpora  quadrigemina  to 
the  cerebellum,  crura  cerebri,  and  pons  Varolii. 

Flourens  in  many  cases  entirely  removed  the  corpora  bigemina 
from  birds  without  any  inco  ordination  or  disturbance  of  move- 

^  Biesiadecki,  Molescliott's  Untersnch.,  viii  (1862),  156.  Mandel- 
stamm,  Cbt.  Med.  Wiss.,  1873.  p.  339  ;  and  Archiv  fiir  Ophthalmol.,  xix 
(1873),  p.  39.  Gudden,  Archiv  f.  Ophthalmol.,  xx  (1874 1,  p.  249. 
Michel,  ibid.,  xix  (1873),  pp.  29-375. 

2  Gudden,  op.  cit.  ^  Archives  de  Phvsiolog.,  v,  1878,  p.  658. 

*  Op.  ch.  5  (;ijt  f  ^xed.  Wiks.  (1878),  p.  562. 


852  THE    BRAIN. 


ments  resulting,  though  they  M^ere  seen  by  McKendrick  in  pig- 
eons, and  by  Ferrier  in  rabbits  and  monkeys.  It  has  been  urged 
however  by  many  (Schifl')  that  when  such  phenomena  do  occur 
after  removal  of  the  corpora  quadrigemina,  they  are  the  result  of 
coincident  injury  to  the  underlying  crura  cerebri.  Adamuk' 
observed  in  rabbits  that  galvanic  stimulation  of  the  posterior 
tubercles,  in  contrast  to  the  anterior  tubercles,  produced  move- 
ments of  the  animal,  though  Knoll  observed  no  such  eflfect.  Ter- 
rier- saw  various  movements  follow  upon  stimulation  of  the  sur- 
face of  the  corpora  quadrigemina  with  the  interrupted  current, 
riourens  found  that  while  mechanical  stimulation  of  the  surface 
of  these  bodies  produced  no  effect,  deep  puncture  caused  various 
movements,  wdiich  he  attributed  to  stimulation  of  the  crura  cere- 
bri beneath.  This  suggests  that  the  movements  caused  by  gal- 
vanic stimulation  are  due  to  escape  of  current,  and  we  here  meet 
with  the  same  difficulty  that  was  experienced  in  dealing  with  the 
cerebral  convolutions.  Ferrier  states  that  with  even  a  moder- 
ately strong  current  the  movements  may  be  so  violent  as  to  merge 
into  a  general  opisthotonus.  He  also  observed  that  stimulation 
of  the  posterior  tubercles  was  followed  by  marked  and  distinct 
cries,  aff'ording  a  curious  parallel  to  the  croaking  produced  by 
retiex  stimulation  in  frogs,  the  seat  of  which  is  in  the  optic  lobes. 
Lussana  and  Lemoigne^also  observed  a  cry  invariably  to  follow 
upoQ  section  of  the  corpora  quadrigemina  and  superior  peduncles 
of  the  cerebellum  (processus  cerebelli  ad  testes),  though  no  loss 
of  sensibility  could  be  detected  as  resulting  from  the  operation. 
These  observers  assert  that  section  of  the  superior  peduncles 
paralyzes  the  muscles  of  the  trunk  of  the  opposite  side  and  thus 
leads  to  the  vertebral  column  being  arched  towards  the  same  side, 
and  to  ''circus"  movements.  According  to  Valentin,  Budge, 
and  others,  stimulation  of  the  corpora  quadrigemina,  or  of  the 
optic  lobes,  produces  movements  in  the  oesophagus,  stomach,  and 
other  parts  of  the  alimentary  canal,  and  in  the  uinnary  bladder. 
In  such  cases  the  stimulation  must  have  an  indirect  effect  on  the 
centres  of  the  above  movements,  which,  as  we  have  seen,  are 
situate  in  the  medulla  and  lumbar  cord  respectively.  Danilew- 
sky,  Jr.,*  and  Ferrier  have  observed  changes  in  the  blood-pres- 
sure and  respiration  follow  upon  stimulation  of  the  corpora 
quadrigemina,  as  of  other  parts  of  the  brain.  Martin  and 
Booker^  ffnd  in  the  frog  in  the  optic  lobes  and  in  the  rabbit  be- 
neath the  posterior  corpora  quadrigemina,  close  to  the  aqueduct 
of  Sylvius,  a  respiration-regulating  centre,  stimulation  of  which 
accelerates  inspiration  and  diminishes  or  inhibits  expiration. 


1  Op.  cit.  2  Op.  cit. 

3  Op.  cit.  *  Pfliiger's  Archiv.  (1875),  p.  128. 

'"  JoLirn.  Physiol,  i  (1878),  p.  370. 


CEREBELLUM.  853 


CereheUum. 

We  have  already  referred  to  the  cerebellum  as  being  prob- 
ably concerned  in  the  co-ordination  of  movements.  Flou- 
rens  observed  that  when  a  small  portion  of  the  cerol)ellum 
was  removed  from  a  pigeon,  the  animal's  gait  !)ecame  un- 
steady ;  when  larger  portions  were  taken  away  its  move- 
ments became  much  more  disorderly,  and  when  the  whole 
of  the  organ  was  removed  an  almost  total  loss  of  co-ordina- 
tion supervened.  Other  observers  have  obtained  similar 
results  in  other  animals;  and  it  has  in  general  been  found 
that  lateral  or  unsymmetrical  lesions  and  incisions  produce 
a  greater  effect  than  those  which  are  median  or  symmetrical. 
Section  of  the  middle  peduncle  on  one  side  almost  invari- 
ably gives  rise  to  a  foiced  movement,  the  animal  rolling  rap- 
idly round  its  own  longitndinnl  axis  :  the  rotation  is  gener- 
ally though  not  always  towards  the  side  operated  on  ;  and 
is  accompanied  by  nystagmus,  i.  e.^  by  peculiar  rolling 
movements  of  the  eyes  sugu^estive  of  vertigo  ;  frequently 
one  eye  is  moved  in  one  direction,  ex.  gr.^  inwards  and 
downwards,  and  the  other  in  a  diffeient  or  oj)posite  direc- 
tion, ex.  gr..  outwards  and  upwards.  Tlie  clinical  evidence 
is  discordant,  for  though  unsteadiness  of  gait  has  been  fre- 
quently witnessed  in  cases  of  cerebellar  disease,  many  his- 
tories liave  been  recorded  in  whie-h  extensive  disease,  amount- 
ing at  times  to  almost  complete  destruction,  of  the  cerebel- 
lum has  existed  without  any  obvious  disturbance  of  the 
co-ordination  of  movements.  Still  the  experimental  evi- 
dence is  so  strong,  that  we  must  consider  the  cerebellum  as 
an  important  organ  of  co-ordination,  though  we  are  unal)le 
at  present  to  define  its  functions  more  exactly.  It  is  prob- 
al»le,  but  not  proved,  that  its  functions  are  especially  con- 
nected with  the  afferent  impulses  proceeding  from  the  semi- 
circular canals. 

Observers  are  not  agreed  as  to  how  far  the  loss  of  co-ordination 
which  follows  upon  lesion  or  removal  of  part  of  the  cerebellum 
is  temporary  or  permanent.  Flourens  found  that  when  the  por- 
tion removed  was  small,  the  disorderly  movements  which  at  first 
appeared  eventually  vanished,  but  when  a  large  portion  w^as  re- 
moved the  loss  of  oo-ordimition  became  permanent.  These  results 
are  capable  of  interpretation  on  the  view  that  the  co-ordinating 
mechanisms  are  situated  in  the  deeper  structures,  and  hence, 
while  completely  removed  by  the  deeper  incisions,  are  only  tem- 
porarily paralyzed  by  the  shock  of  the  slighter  o})erations.  Hitzig 

72 


854  THE    BRAIN. 


and  Ferrier  find  that  injury  to  or  removal  of  the  lateral  lobe  pro- 
duces the  same  forced  movements  as  section  of  the  middle  pe- 
duncle. Flourens  and  others  have  observed  that  while  lateral 
injury  <iave  rise  to  lateral  movements,  injury  to  the  anterior  or 
posterior  median  portions  caused  the  animal  to  fall  forwards 
and  backwards  respectively.  Nothnao;er  has  been  led  from  his 
experiments  on  rabbits  to  the  conclusion  that  the  lesions  which 
determine  a  loss  of  co-ordination  are  those  which  result  in  a  solu- 
tion of  continuity  in  the  structures  uniting  the  two  sides  of  the 
organ,  the  mere  loss  of  lateral  parts,  even  amounting  to  an  entire 
half,  having,  according  to  him,  no  such  effect.  Ferrier  finds 
that  stimulation  of  the  cerebellar  surface  by  the  interrupted 
current  causes  in  monkeys,  dogs,  and  cats  movements  of  both 
eyes  with  associated  movements  of  the  head  and  limbs,  and  to  a 
certain  extent  of  the  pupils.  The  eyes  moved  horizontally,  or 
vertically,  or  obliquely,  symmetrically  or  unsymmetrically,  with 
or  without  rotation,  according  as  the  electrodes  were  applied  to 
one  or  other  portion  of  the  surfiice.  In  fact  the  results  were  to 
a  certain  extent  similar  to  those  obtained  by  Adamuk  on  stim- 
ulating the  corpora  quadrigemina,  but  they  cannot  be  wholly 
explained  as  simply  due  to  escape  of  current,  if,  as  Hitzig"^  as- 
serts, very  similar  phenomena  may  be  witnessed,  not  only  with 
weaker  currents,  but  even  on  mechanical  stimulation.^ 

Nothnagel'  also  finds  that  mechanical  stimulation  of  even  the 
surface  of  the  cerebellum  gives  rise,  without  signs  of  pain  being 
felt,  to  movements  chiefiy  of  the  trunk  and  extremities  and  of 
those  muscles  which  are  governed  by  the  facial,  hypoglossal,  and 
fifth  nerves.  These  movements,  which  are  developed  somewhat 
slowly,  manifest  themselves  first  on  the  side  operated  on,  and 
then  ceasing  on  that  side  make  their  appearance  on  the  opposite 
side. 

Lastly,  we  may  observe  that  Flechsig  (see  p.  795)  on  anatom- 
ical grounds  connects  a  definite  portion  of  the  lateral  columns  of 
the  spiuEil  cord  with  the  cerebellum. 

Purkinje  observed  long  ago  that  when  a  constant  current  of 
sufficient  strength  was  sent  through  the  head  from  ear  to  ear,  a 
feelingof  giddiness  was  experienced  ;  external  objects  appearing 
to  rotate  in  the  directi<m  of  the  current,  from  right  to  left,  for  in- 
stance, when  the  anode  was  placed  at  the  right  ear,  while  at  the 
same  time  the  subject  himself  leant  towards  the  anode.  Hitzig^ 
has  more  fully  investigated  and  described  the  phenomena.  When 
the  current  is  sufficiently  strong,  remarkable  movements  of  the 
eyes  are  seen  to  take  place  on  the  current  being  made.  These 
are  varied  and  partake  somewhat  of  the  nature  of  nystagmus. 
They  consist  of  a  rapid  snatching  movement  in  the  direction  of 
the  current,  and  a  slower  return  in  the  contrary  direction,  the 

'  Virchow's  Archiv,  Bd.,  68  (1876),  p.  33.  _^       '^^^  Op.  cit. 

^  Cf.,  however,  Scliwalin,  Eekliard's  Beitrage,  viii  (1878),  p.  149. 
♦  Op.  cit.  ^  Op.  cit. 


CEREBELLUM.  855 


eyes  oscillating  between  the  two.  Sometimes  the  two  eyes  move 
together,  sometimes  the}'  are  dissociated.  That  neither  the  feel- 
ing of  vertigo  nor  the  movements  of  the  body  are  dependent  on 
abnormal  visual  sensations  caused  by  the  ocular  movements,  is 
shown  by  the  fact  that  they  occur  when  the  eyes  are  shut,  and 
also  in  blind  people ;  and  indeed  the  feeling  of  vertigo  may  be  in- 
duced by  a  current  too  feeble  to  cause  an}'  abnormal  movements 
of  the  eyeballs.  The  application  of  the  current  when  the  eyes 
are  shut  gives  rise  to  a  sensation  similar  to  that  of  sitting  or  stand- 
ing in  a  carriage  which  is  being  turned  over  in  the  direction  of 
the  current,  from  right  to  left  when  the  anode  is  placed  at  the 
right  ear.  When  the  current  is  broken,  there  is  a  rebound  ot  the 
phenomena  in  an  opposite  direction.  The  person  now  leans  to- 
wards the  kathode,  and  external  objects  seem  to  revolve  from  the 
kathode  to  the  anode.  All  these  phenomena  are  best  explained 
by  supposing  that  the  current  interferes  with  the  cerebral  co-ordi- 
nating mechanism,  from  which  result,  as  efferent  effects,  the  com- 
pensating movements  of  the  bod}'  and  of  the  eyes,  the  change  in 
the  mechanism  at  the  same  time  so  affecting  consciousness  as  to 
produce  a  feeling  of  vertigo.  AVhether  the}'  are  due  to  an  ane- 
lectrotonic  and  katelectrotonic  condition  of  the  ampullar  fibres 
of  the  respective  auditory  nerves,  or  are  caused  by  the  action  of 
the  current  on  cerebellar  or  other  structures,  must  be  left  for  the 
present  undecided. 

Attempts  have  been  made  to  connect  the  cerebellum  with 
the  sexual  functions  ;  but  there  is  no  satisfactory  evidence 
of  any  such  relation.  As  we  shall  see  later  on,  the  nervous 
centres  connected  with  the  sexual  and  generative  organs  r.re 
seated,  in  the  case  of  dogs  at  least,  and  [)rol)ably  of  all  ani- 
mals, in  the  lumbar  spinal  cord  ;  and  all,  or  nearly  all.  sex- 
ual phenomena  may  be  witnessed  in  animals,  the  linnbar 
spinal  cords  of  which  have  been  isolated  by  section  from 
the  restof  the  cereliro-sjunal  system.  Galvanic  stimulation 
of  the  cerel)ellum  produces  no  change  in  the  generative  or- 
gans, and  when  erection  of  the  penis  is  caused  l)y  emotions, 
ihe  tract  connecting  the  cerebral  convolutions  with  the  erec- 
tion centre  in  the  spinal  Cord  passes  straiglit  along  the  crura 
cerebri  and  medulla,  foi"  Eckhard'  has  observed  tliat  stimu- 
lation of  these  parts  in  the  dog  will  produce  erection. 

Eckhard  has  brought  forward  facts  to  show  that  lesions  of  cer- 
tain parts  of  the  cerebellum,  like  those  of  certain  parts  of  the 
medulla  oblongata,  cause  either  diabetes  or  simple  hydruria. 

According  to  Budge,  stimulation  of  the  cerebellum  produces 
peristaltic  movements  in  the  oesophagus  and  stomach  ;  andSchiif 

'  Beitrage,  vii  (1873),  p.  67. 


856  THE    BRAIN. 


observed  inflammation  of  the  intestine  with  haemorrhage  after 
lesions  of  the  peduncles  of  the  cerebellum. 


Crura  Cm^ebi^i  and  Pons  VaroHi. 

Though  from  tlie  gray  matter  abundant  in  both  tliese  or- 
gans we  may  infer  that  they  possess  important  functions, 
we  hardl}^  know  more  concerning  them  than  that  the  former 
serve  as  the  great  means  of  communication  between  the 
spinal  cord  and  the  higher  parts  of  tiie  brain,  and  tliat  both 
are  intimately  connected  with  the  co-ordination  of  move- 
ments, since  either  forced  or  disorderly  movements  are  the 
frequent  results  of  section  of  either  of  them  ;  and  as  we 
have  seen,  the  i)ossession  of  tiiese  parts,  in  the  absence  of 
the  cerebral  hemispheres,  and  even  of  tiie  corpora  striata 
and  optic  thalami,  is  sutficient  to  carry  out  the  most  com- 
plex bodily  movements. 

Since  the  paralysis  of  the  face  seen  in  cases  of  hemiplegia 
from  disease  of  tiie  corpus  striatum  is  on  the  same  side  as 
that  of  the  body,  it  follows  that  the  impulses  proceeding 
along  the  cranial  nerves  crossover  like  those  of  the  spinal 
nerves.  Hence  wjien  paralysis  of  the  face  occurs  on  the 
opposite  side  to  that  of  the  body,  it  may  be  inferred  tliat 
the  injury  or  disease  has  atfccted  tiie  cranial  nerve  (or 
nerves)  in  a  part  of  its  course  before  decussation  lias  taken 
place  :  and  pathological  observations  support  this  view,  uni- 
lateral disease  or  injury  of  the  pons  Varolii  not  unfrequently 
involving  the  facial  nerve  of  the  same  side  in  its  compara- 
tively superficial  course,  and  so  causing  paralysis  of  the 
muscles  of  the  same  side  of  the  face  as  the  disease,  and  the 
opposite  side  to  the  paralysis  of  the  limbs.  It  is  probable 
that  the  decussation  which  we  have  seen  to  begin  in  the 
spinal  cord,  is  gradually  completed  as  the  impulses  pass 
through  the  medidla  and  pons  Varolii  ^  Against  the  view 
of  those  who  maintain  that  volitional  im[)ulses  cross  sud- 
denly and  completely'  at  the  decussation  of  the  pyramids, 
may  be  urged  the  fact  that  a  longitudinal  section  through 
the  decussation  does  not  entail  loss  of  voluntary  movements 
on  both  sides  of  tlie  body,  ns  it  ought  to  do  if  the  volitional 
impulses  crossed  completely  at  this  spot.  Moreover,  ac- 
cording to  Yulpian,  the  loss  of  voluntaiy  movement  wliich 

1  Cf.  Balighian,  Eckhard's  Beitriige,  viii  (1878),  p.  193. 


MEDULLA    OBLONGATA.  857 


follows  upon  a  unilateral  section  of  the  medulla  is  not  con- 
fined entirely  to  one  side  of  tlie  body. 


Medulla  Oblongata. 

We  have  so  often  spoken  of  this  link  between  the  brain 
and  tlie  si)inal  cord,  that  it  is  liardly  necessary  here  to  do 
more  than  recall  the  fact,  tiiat  the  majority  of  the  '"centres" 
for  various  oro-anic  functions  ai'e  situated  in  it. 

Tliese  we  may  briefly  recapitulate  as  follows  :  1.  The  re- 
spiratory centre  (p.  470),  with  its  neighboring  convulsive 
centre  (p.  490).  2.  The  vaso-motor  centre  (p.  2TS).  3.  The 
cardio-inhibitory  centre  {\).  250).  4.  The  diabetic  centre, 
or  centre  for  the  production  of  artificial  diabetes  (p.  551). 
5.  Tiie  centre  for  deglutition  (p.  379).  6.  The  centre  for 
the  movements  of  the  Q?sophagus  and  stomach  (p.  383),  with 
its  allied  vomiting  centre  (p.  391).  7.  The  centre  for  reflex 
excitation  of  the  secretion  of  the  saliva  (p.  347),  with  which 
may  be  associated  the  centre  through  which  the  vagus  in- 
fluences the  secretion  of  pancreatic  juice  ( [>.  360),  and  pos- 
sibly of  the  other  digestive  juices. 

In  the  frog,  as  we  have  urged  (p.  813),  the  medulla  is  un- 
doubtedly largely  concerned  in  the  co-ordination  of  move- 
ments, and  it  is  exceedingly  probahle  that  in  the  mammal 
also  a  considerable  portion  of  v.-ork  of  this  kind  falls  to  its 
lot. 

In  conclusion,  we  may  call  attention  to  the  fact,  that  of 
the  whole  brain  certain  parts  respond  easily,  by  various 
movements  in  different  parts  of  the  body,  to  mechanical  or 
other  stimuli  applied  directly  to  them,  while  others  will  not. 
The  former  are  consequently  spoken  of  as  sensitive,  and 
together  form  what  has  been  called  an  excito-motor  centre  ; 
they  are  the  (deep  parts  of)  the  cor[)ora  quadrigemina,  the 
crura  cerebri,  tlie  [)ons  Varolii,  the  (deep  parts  of)  the  cere- 
bellum, and  the  medulla.  The  latter  are  spoken  of  as  insen- 
sitive ;  they  are  the  cerebral  hemispheres  together  with  the 
corpora  striata  and  optic  thalami  (and  the  superficial  por- 
tions of  the  cerebellum  and  corpora  quadrigemina).  In 
view  of  the  results  obtained  by  electrical  stimulation  of  the 
cerebral  convolutions  and  other  parts,  this  distinction  can- 
not however  be  regarded  as  important. 


858  THE    BRAIN. 


Sec.  5.    On  the  Rapidity  of  Cerebral  Operations. 

We  have  already  seen  (p.  783)  that  a  considerable  time  is  taken 
up  in  a  purely  reflex  act,  such  as  that  of  winking,  though  this  is 
perhaps  the  most  rapid  form  of  reflex  movement.  When  the 
movement  which  is  executed  in  response  to  a  stimulus  involves 
mental  operations  a  still  loncer  time  is  needed  ;  and  the  interval 
between  the  application  of  the  stimulus  and  the  commencement 
of  the  muscular  contraction  varies  according  to  the  nature  of  the 
mental  labor  involved. 

The  simplest  case  is  that  in  which  a  person  makes  a  signal  im- 
mediately that  he  perceives  a  stimulus,  ex.  (/r.,  closes  or  opens  a 
galvanic  circuit  the  moment  that  he  feels  an  induction-shock 
applied  to  the  skin,  or  sees  a  flash  of  light,  or  hears  a  sound.  J3y 
arrangements  similar  to  those  employed  in  measuring  the  velocity 
of  nervous  impulses,  the  moment  of  the  application  of  the  stimu- 
lus and  the  moment  of  the  making  of  the  signal  are  both  recorded 
on  the  same  travelling  surface,  and  the  interval  between  them  is 
carefully  measured.  This  interval,  which  has  been  called  by 
Exner  "the  reaction  period,"  consists  of  three  portions:  (1),  the 
passage  of  atferent  impulses  from  the  peripheral  sensory  organ  to 
the  central  nervous  system,  including  the  possible  latent  period 
of  the  generation  of  the  impulses  in  the  sensory  organ  ;  (2),  the 
transformation,  by  the  operations  of  the  central  nervous  system, 
of  the  afterent  into  efterent  impulses  ;  and  (3),  the  passage  of  the 
efterent  impulses  to  the  muscles,  including  the  latent  period  of 
the  muscular  contractions.  If  the  time  required  for  the  flrst  and 
third  of  these  events  be  deducted  from  the  whole,  the  "reduced 
reaction  period,"  as  it  may  be  called,  gives  the  time  taken  up 
exclusively  by  the  operations  going  on  in  the  central  nervous 
system. 

The  reaction  period,  both  reduced  and  unreduced,  varies  ac- 
cording to  the  nature  and  disposition  of  the  peripheral  organs 
stimulated.  The  reaction  period  of  vision  has  long  been  known 
to  astronomers.  It  was  early  found  that  wiien  two  observers 
were  watching  the  appearance  of  the  same  star,  a  considerable 
discrepancy  e'xisted  between  their  respective  reaction  periods  ; 
and  that  the  diflerence,  forming  the  basis  of  the  so-called  "per- 
sonal equation,"  varied  from  time  to  time,  according  to  the  per- 
sonal conditions  of  the  observers.  Thus  the  difterence  between 
the  celebrated  astronomers  Struve  and  Bessi-l  varied  between  the 
years  1814  and  1831  from  .01  to  1.02  sec,  the  reaction  period  of 
Struve  being  so  much  longer  than  that  of  Bessel.  These  figures, 
however,  ai-o  not  to  be  compared  with  those  which  will  be  given 
immediately,  inasmuch  as  several  complications  were  introduced 
by  the  method  of  observation. 

Exner'  has  carefully  determined  the  reaction  period  of  himself 

1  Pfliiger's  Archiv,  vii  (1873),  p.  601. 


RAPIDITY    OF    CEREBRAL    OPERATIONS.  859 


and  others  with  different  stimuh,and  under  various  circumstances. 
When  the  stimuhis  was  an  induction-shock  thrown  into  the  skin 
of  the  k^ft  hand,  the  siiznal  beinp;  made  with  tlie  right  hand,  the 
reaction  period  varied  from  .1337  sec.  in  Exner  himself  to  .3576, 
or  even  to  .1)952,  in  an  obtuse  individual.  When  the  stimulus 
was  applied  in  different  wa3's,  the  signal  always  being  made  with 
the  right  hand,  the  results  in  Exuer's  own  case  were  as  follows  : 

Direct  electrical  stimulation  of  the  retina,  .         .     .1139 
Electric  shock  on  tiie  left  hand,   ....     .1283 

Sudden  noise,        . 1360 

Electric  shock  on  the  forehead, 1374 

''  on  the  right  hand,  .  .  .  .1390 
Visual  impression  from  an  electric  spark,  .  .  .1506 
Electric  shock  on  the  toe  of  the  left  foot,     .         .     .1749 

Hence  tactile  sensations,  produced  by  the  stimulus  of  an  elec- 
tric shock  applied  to  the  skin,  are  followed  by  a  shorter  reaction 
period  than  are  auditory  sensations  ;  but  the  period  of  these  is  in 
turn  shorter  than  that  of  visual  sensations  produced  by  luminous 
objects,  though  the  shortest  period  is  that  of  visual  sensations 
produced  by  direct  electrical  stimulation  of  the  retina.  Hirsch 
had  previously  arrived  at  similar  results,  and  Bonders'  had  simi- 
larly determined  the  reaction  period  or  physiological  time,  as  he 
termed  it,  to  be,  roughly  speaking,  for  feeling  ^th,  for  hearing 
^th,  and  for  sight  ^^th  of  a  second.  With  Dietl  and  Yintschgau' 
the  reaction  period  for  tactile  sensations  from  the  middle  finger 
of  the  right  hand  was  respectively  .1371  sec.  and  .1532  sec.  Von 
Wittich^  found  the  reaction  period  to  be  .167  sec,  when  the  ap- 
plication of  a  constant  current  to  the  tongue  produced  a  gustatory 
sensation.  Vintschgau  and  Honigschmied*  determined  the  reac- 
tion period  of  taste  to  be  for  salines  .1598  sec,  for  sugar  .1639, 
acids  .1676.  and  quinine  .2351.  Even  with  the  same  stimulus, 
the  reaction  period  will  vary  according  to  circumstances,  such  as 
the  time  of  year,  weather,  etc.,  and  according  to  the  condition  of 
the  individual.  Exner  found  that  while  strong  tea  had  no  ob- 
vious eftect,  two  bottles  of  Rhine  wine  lengthened  the  period  from 
.1904  to  .2969.  Dietl  and  Vintschgau,^  as  the  result  of  an  elabo- 
rate inquiry,  came  to  the  conclusion  that  while  opium  had  a  tem- 
porar}-  lengthening  effect,  coffee  produced  a  much  more  striking 
and  lasting  shortening  of  the  period,  while  the  effect  of  wine 
(champagne)  varied  according  to  the  quantit}'  drunk  and  the  ra- 
pidity with  which  it  was  take'n  ;  a  small  quantity  shortened,  but 
a  large  quantity  (a  bottle  drunk  rapidly)  lengthened  the  period. 

The  calculations  involved  in  "  reducing  ""  the  reaction  period 

^  Eeichert  and  Du  Bois-Revmond's  Archiv,  1868,  p.  657. 

2  Pfliiger's  Archiv,  xvi  (1878),  p.  316. 

'  Zt.  rat.  Med.  (3),  xxxi,  p.  113. 

*  Pfliiger's  Archiv,  x  (1875),  p.  1.  5  Qp.  cit. 


860  THE    BRAIN. 


are  obviously  open  to  much  error  ;  Exner's  own  reduced  period 
was  .08:28,  that  of  the  obtuse  individual  quoted  above  .3050  and 
.9420  ;  that  is  to  say,  an  intelliij;ent  ])erson  takes  less  than  j'fjth  of 
a  second  to  ])erceive  and  to  will.  If  the  whole  reaction  period 
of  the  case  when  the  retina  was  directly  stimulated  be  deducted 
from  the  period  of  the  case  when  a  luminous  object  was  used  to 
create  visual  impressions,  the  difference  (.0337  sec.)  would  indi- 
cate the  latent  period  of  luminous  stimulation  of  the  retina  ;  but 
it  is  doubtful  whether  any  great  dependence  can  be  placed  on  such 
a  calculation. 

In  all  the  above  instances  a  single  stimulus  was  used,  and  all 
that  the  person  experimented  on  had  to  do  w^as  to  perceive  the 
stimulus,  and  to  make  an  effort  in  accordance.  If,  however,  the 
stimulus,  instead  of  being  applied  to  a  part  of  the  body  deter- 
mined by  previous  arrangement,  as  for  instance  to  the  left  foot, 
were  applied  either  to  the  left  or  the  right  foot,  without  the  per- 
son being  told  which  it  was  to  be,  and  it  was  arranged  that  he 
should  make  a  signal  when  the  left  foot,  but  not  when  the  right 
foot  was  stimulated,  additional  mental  exertions  would  be  neces- 
sary ;  and  Bonders'  found  that  in  such  a  case  the  reaction  period 
was  considerably  prolonged.  The  following  table  gives  the  dif- 
ference between  a  simple  reaction  period  and  one  in  which  a  men- 
tal decision  has  to  be  carried  out  before  the  voluntary  effort  to 
make  the  signal  is  initiated,  i.  e. ,  gives  the  time  required  for  the 
person  to  ''make  up  his  mind"  in  accordance  with  the  nature  of 
the  sensation  wdiich  he  receives  ;  this  it  will  be  seen  is,  roughly 
speaking,  from  3th  to  2',th  of  a  second. 

Dilemma  between  two  spots  of  the  skin,  right  and  left 

foot  stimulated  by  an  induction-shock,      .         .         .     .006 

Dilemma  of  visual  sensations  between  two  colors,  sud- 
denly presented  to  the  view  ;  signal  to  be  made  on 
seeing  one  but  not  on  seeing  the  other,     .         .         .     .184 

Dilemma  between  two  letters ;  signal  to  be  made  on 
seeing  one  only,  .......     .106 

Dilemma  between  live  letters  ;  signal  to  be  made  on 
seeing  one  only,  .......     .170 

Dilemma  of  auditory  sensations  ;  two  vowels  suddenly 

sung  ;  signal  to  be  made  on  hearing  one  only,         .     .056 

Dilemma  between  five  vowels  ;  signal  to  be  made  on 
hearing  one  only,       ..." 088 

Sec.  6.    The  Cranial  Nerves. 

Though  we  have  incidentally  dwelt  on  the  functions  of  all 
these  nerves,  it  may  be  as  well  to  recapitulate  them  somewhat 
briefl}',  giving  at  the  same  time  a  very  general  outline  of 
their  physiological  anatomy. 

'  Op.  ch. 


CRANIAL    NERVES.  861 

1.  OJfarlory  TNcrve  of  Smell). — [The  olfactory  tracts  are 
prolongations  of- the  cei-ebral  substance  Accordino;  to  the 
observations  (»f  Henle  and  Meynert  each  tract  arises  in  a 
tubercular  eminence,  which  is  situated  in  the  posteiior  in- 
ferior portion  of  the  anterior  cerebral  lobe,  internal  to 
and  connected  with  the  island  of  Reil.  These  eminences 
are  called  the  ''optic  tubercles,''  and  are  connected  with 
each  other  by  commissural  fibres.  The  olfactoiy  tracts  are 
composed  of  both  white  and  gray  matter;  the  former  occu- 
pies the  inferior  and  lateral  portions.  Each  tract  (Fig.  199) 
terminates  in  an  oblong  ganglion,  which  is  called  the  olfac- 
tory bulb.  The  i)ulb  rests  upon  the  cribriform  plate  of  the 
ethmoid  bone,  and  in  this  position  gives  off  the  nervous 
filaments,  which  constitute  what  are  strirlly  speaking,  the 
true  olfactory  nerves.  The  distrilnition  of  these  nerves  has 
been  referred  to  in  previous  pages  (pp.  748-749).] 

2.  Optic  CSerye  of  Sight). — [The  optic  tracts  arise  from  the 
corpora  (piadrigemina  and  geniculata  and  the  optic  thalami. 
The  fibres  have  been  traced  to  the  crura  cerel)ri,  and  the 
anterior  portion  of  the  floor  of  the  aqueduct  of  Sylvius. 
The  optic  tracts  (Fig.  21(5)  run  forward  beneath  the  cere- 
brum, and  when  they  reach  tlie  olivary  process  of  the  sphe- 
noid bone  unite  to  form  the  optic  commissure  or  chia.^m. 
The  optic  nerves  arise  from  tlie 
anterior  part  of  the  commissure, 
enter  the  orbit  through  the  optic 
foramina,  pierce  the  external  coats 
of  the  eyeball,  and  l)ec;)me  ex- 
panded to  form  the  retinre. 

Within  the  commissure  the  fii»res      -.>^v-         -^^^'^^^^c/.^j,...u^a. 


of  the  o[)tic  tract  pursue  divergent 

Commissure. 


^  "  /.    .  1         o,  -    1  v.uiirse  of  P'ibres  in  the  Optic 

courses,     borne  or  the  fibres  de- 


cussate; otliers  continue  to  the 
retina  on  the  same  side  :  otliers  c^'oss  over  to  the  opposite 
side  and  return  to  the  optic  thalamus,  and  thus  form  (inter- 
cerebral)  or  commissural  fibres  between  the  optic  thalami  ; 
other  fibres  (inter  retinal)  probably  run  through  one  optic 
nerve  across  to  tiie  other  between  the  retinae.] 

3.  Oculo-motor. — [The  oculo-motor  serves  arise  from  the 
crura  cerebri  immediately  anterior  to  the  pons  Varolii  (Fig. 
216;.  The  fil)res  of  each  nerve  have  their  deep  origin  in  a 
gray  nucleus  in  the  floor  of  the  aqueduct  of  Sylvius.     This 


862  THE    BRAIN. 

nucleus  is  continuous  with  the  nucleus  in  which  the  root  of 
tiie  fourth  nerve  originates,  and  is,  therefore,  often  spoken 


The  Nerves  of  the  Orbit  seen  from  the  Outer  Side.  1,  section  of  the  frontal  bone; 
imnu'diately  beliind  the  numeral  is  the  frontal  sinus,  and,  in  front,  the  integument; 
2,  the  superior  maxillary  bone;  the  section  in  front  of  the  numeral  exhibits  the 
niiixillary  sinus  ;  3,  part  of  the  sphenoid  bone  ;  4,  tlie  levator  palpebrse  and  superior 
rectus  muscles;  5,  thn  superior  oblique  muscle;  6,  the  inferior  oblique  muscle  ;  7,  the 
ocular  half  of  the  external  rectus  muscle  drawn  forwards ;  8,  the  orbital  half  of  the 
external  rectus  muscle  turned  downwards.  On  this  muscle  the  sixth  nerve  is  seen 
dividing  into  branches;  9,  the  inferior  rectus  muscle;  10,  the  optic  nerve;  11,  the 
internal  carotid  artery  emerging  from  the  cavernous  sinus;  12,  the  ophthalmic 
artery  ;  13,  the  third  nerve  ;  14,  the  branch  of  the  third  nerve  to  the  inferior  oblique 
muscle.  Between  this  and  the  sixth  nerve  (8)  is  seen  the  branch  which  sujjplies  the 
inferior  rectus;  its  branch  to  the  ophthalmic  ganglion  is  seen  proceeding  from  the 
upper  side  of  the  trunk  of  the  nerve,  at  the  bottom  of  the  orbit;  15,  the  fourth  nerve  ; 
16,  the  trunk  of  the  filth  nerve;  17,  the  Gassiirian  ganglion;  18,  the  opiithalmic 
nerve;  19,  the  superior  maxillary  nerve;  20,  the  iuferi'jr  maxillary  nerve;  21,  the 
frontal  nerve;  22,  its  division  into  branches  to  supply  the  integument  of  the  fore- 
head; 23,  the  lachrymal  nerve  ;  24,  the  nasal  nerve;  the  small  nerve  seen  in  the  bi- 
furcation of  the  nasal  and  frontal  nerve  is  one  of  the  branches  of  the  upper  divi- 
sion of  the  thiid  nerve  ;  25,  the  nasal  nerve  passing  over  the  internal  rectus  muscle 
to  the  anterior  ethmoidal  foramen  ;  20,  the  infra-trochlear  nerve  ;  27,  a  long  ciliary 
branch  of  the  nasal  ;  another  long  ciliary  branch  is  seen  proceeding  from  the  lower 
aspect  of  the  nerve  ;  28,  the  long  root  of  the  ophthalmic  ganglion,  proceeding  from 
the  nasal  nerve,  and  receiving  the  sympathetic  root,  which  joins  it  at  an  acute  angle; 
29,  the  ophthalmic  ganglion,  giving  off  from  its  forepart  the  short  ciliary  nerves  ;  30, 
the  globe  of  the  eye. 

of  as  the  common  nucleus  of  the  two  nerves.     Each  nucleus 
is  connected  with  the  opposite  side  of  the  brain  by  fibres 


CRANIAL    NERVES.  863 

which  pass  throno;h  the  corpus  striatum  of  tlie  opposite 
side,  and  decussate  beneath  the  floor  of  the  aqueduct  of 
Sylvius.  Some  of  the  fibres  from  the  corpora  striatum  proba- 
bly remain  on  the  same  side  without  decussatino-. 

From  its  superficial  point  of  origin  this  nerve  passes  along 
the  cavernous  sinus,  receiving  some  sensory  filaments  from 
the  fifth.  It  enters  the  orbit  through  the  sphenoidal  fissure. 
(Fig.  22G)  ].  It  is  the  motor  nerve  to  the  levator  palpebrte 
snperioris  and  all  the  muscles  of  the  eye,  except  the  obliquus 
superior  and  the  rectus  externus.  Eti'erent  nerve  for  the 
contraction  of  the  pupil  and  for  the  muscles  of  accommoda- 
tion. Hence  when  the  nerve  is  divided  or  otherwise  para- 
lyzed the  upper  eyelid  falls  (  ptosis) ;  the  eye,  which  is  turned 
outwards,  is  capable  of  partial  movements  only,  viz.,  such 
as  can  be  produced  by  the  rectus  externus  and  obliquus  su- 
perior;  when  the  head  is  moved  the  eye  moves  with  it,  tiie 
inferior  oblique  not  being  able  to  execute  the  usual  compen- 
sating movements  of  the  eyeball;  the  j^upil  is  dilated,  and 
the  eye  cannot  accommodate  for  near  distances. 

The  root  of  the  nerve  shows  recurrent  sensibility,  due  to  fibres 
from  the  fifth,  but  is  otherwise  a  purely  motor  nerve. ^ 

4.  Trochlear  or  FafJwtir. — [The  trocblearis  or  patheticns 
nerve  is  the  smallest  of  all  the  cranial  nerves.  This  nerve 
arises  from  the  upper  surface  of  the  valve  of  Vieussens,  be- 
hind the  corpora  quadrigemina  (  Fig.  216).  The  larger  pro- 
portion of  fibres  run  transversely  across  the  valve  of  Vieus- 
sens and  decussate  with  those  of  the  nerve  of  the  opposite 
side;  other  fil)i'es  remain  on  the  same  side  as  the  nerve. 
These  fibres  have  their  origin  in  a  gray  nucleus  situated  in 
the  floor  of  the  aqueduct  of  Sylvius,  immediately  behind  and 
adjoining  the  nucleus  of  the  oculo-motor  nerve  ;  and  also  in 
a  nucleus  which  is  located  near  the  nucleus  of  the  fifth 
nerve  in  the  upper  part  of  the  floor  of  the  fourth  ventricle. 
It  passes  along  the  cavernous  sinus,  and  enters  the  orbit 
through  the  sphenaidal  fissure  (Fig.  22()).]  It  is  the  motor 
nerve  to  the  obliquus  superior.  When  the  nerve  is  paralyzed, 
no  marked  difference  is  observed  in  the  position  of  the  eye, 
but  the  patient  sees  double  when  he  attempts  to  look  straight 
forward  or  towards  the  paralyzed  side  ;  the  images,  however, 
coalesce  when  he  turns  his  head  to  the  sound  side.     When 

^  SchifF,  Lehrb.,  p.  376. 


864  THE    BRAIN. 

tlie  head  is  moved  from  side  to  side  tiie  eye  moves  with  it, 
the  usual  compensating  movement  of  the  eye  which  accom- 
panies tlie  movements  of  the  head  failing  in  consequence  of 
the  superior  oblique  not  acting. 

It  is  a  purely  motor  nerve,  but  receives  recurrent  fibres  from 
the  fifth. 

5.  Tjngeminus. — [The  fifth  or  trigeminus  is  the  largest 
of  the  cranial  nerves.  It  arises  from  the  side  of  the  j)ons 
Varolii  (Fig.  21(>)  by  two  i-oots,  which  are  separated  by  a 
narrow  band  of  fibres.  The  anterior  or  smaller  root  is 
motor;  the  posterior  root  is  sensory,  The  fibres  have  their 
deep  origin  principally  in  a  gray  nucleus  in  the  extreme  side 
of  the  floor  of  the  fourth  ventricle,  and  immediately  beiiind 
the  nuclei  of  the  oculo-motorius  and  patlieticus  nerves. 
Some  of  the  fibres  terminate  in  the  nuclei  or  decussate 
with  tiiose  of  the  opposite  side  ;  others  have  been  traced 
through  the  superior  peduncles  of  the  cerebellum  of  the 
same  side  to  tlie  tubercula  quadrigemina.  These  nerves 
run  forwards  from  their  superficial  poini  of  origin  to  the 
Gasserian  ganglion  (Fig.  227),  which  rests  on  the  petrous 
portion  of  the  temporal  bone.  At  this  point  tiie  sensory 
root  spreads  out  in  the  ganglion  ;  but  the  motor  root  passes 
by,  forming  no  connection  with  it.  The  sensory  fibres  pass 
through  the  ganglion,  being  reinforced  by  fibres  from  the 
ganglionic  cells,  and  form  three  branches  or  trunks:  the 
ophthalmic,  superior  maxillary,  and  inferior  maxillary. 
The  two  former  are  sensory ;  the  latter  is  joined  by  the 
motor  root,  and  is,  therefore,  both  sensory  and  motor.  The 
ophthalmic  branch  entei-s  the  orbit  through  the  sphenoidal 
fissure.  The  superior  maxillary  passes  through  the  foi-amen 
rotundum  inlo  the  spheno-maxillary  fossa,  where  it  sends  ofi" 
a  tract  to  the  spheno-palatine  ganglion,  then  passes  through 
a  groove  in  the  floor  of  the  orbit  and  emerges  at  the  infra- 
orbital foramen.  The  inferior  maxillary  division  passes 
through  the  foramen  ovale,  then  gives  oflf  several  l)ranches  to 
the  otic  ganglion  and  passes  on  to  its  points  of  distribution.] 

It  is  a  mixed  etterent  and  afl'erent  nerve,  with  distinct  mo- 
tor and  sensory  roots,  the  latter  bearing  the  ganglion  of 
Gasser. 

Efferent  Fibres:  Motor  fibres  to  the  muscles  of  mastica- 
tion, temporal,  masseter,  two  pterygoids  (mylo-hyoid,  an- 
terior belly  of  digastric),   to  the  tensor  palati,  and  tensor 


CRANIAL    NERVES. 


865 


t_ympani ;  vaso-raotor  fibres  to  various  parts  of  tlie  head  and 
face;  secretory  fii>res  to  the  lachi-vmal  o-land,  and  according 
to  Some  authors  to  the  parotid  and  snhinaxillary  glands  by 
fibres  joining  the  facial.     Trophic  (?)  fibres  to  eye,  nose,  and 

[Fig.  227. 


Genpral  Plan  of  the  Bramlit  s  of  the  Fifth  Pair  (alter  a  sketdi  hy  Charles  Bell). 
l^^.  1,  li-sser  root  of  the  fifth  p;iir;  2,  greater  root  J)a^i^il].<J  fui  wards  into  the  Gasse- 
rian  ganglion  ;  S,  placid  on  the  hone  above  the  ophthaliuir  nerve,  which  is  seen  di- 
viding into  the  supra-orbital,  lachrymal,  and  nasal  branches,  tlie  latter  connectfd 
with  the  ophthalmic  ganglion;  4,  placed  on  the  bone  close  to  the  foramen  rotiindiim, 
marks  the  superior  maxillary  division,  which  is  connected  below  with  the  spheno- 
palatine gaii.ulion,  and  passes  forwards  to  the  infra-orbiial  foramen;  5,  placid  on 
the  bone  over  the  foramen  ovale,  marks  the  submaxillary  nerve,  giving  off  the  an- 
terior auricular  and  muscular  branches,  and  continued  by  the  inferior  dental  to  the 
lower  jaw,  and  by  the  gustatory  to  the  tongue;  a,  the  submaxillary  gland,  the  sub- 
maxillary ganjilion  placed  r.bove  it  in  connection  with  the  gustatory  nerve;  6,  the 
chorda  tympani ;  7,  the  facial  nerve  issuing  fiom  the  stylo-mastoid  foramen.] 


other  parts  of  fnce,  see  p.  Cll . 
tion  of  the  pupil,  see  p.  (HO. 


Efl[erent  fibres  for  the  dila- 


8(J6  THE    BRAIN. 

Afferent  Fibres  :  General  nerve  of  sensation  of  the  skin 
of  head  and  face,  and  of  the  mncous  membrane  of  the 
mouth,  except  the  back  part  ot  the  tongue,  tiie  posterior 
pillars  of  the  fauces,  and  a  large  part  of  the  pharynx,  these 
parts  being  supplied  by  the  glo.iso-pharyngeal  and  vagus; 
the  back  of  the  head  is  chielly  sup[>lied  by  branches  from 
the  cranial  nerves,  and  the  external  meatus  and  concha  are 
supplied  chiefly  by  the  auricular  branch  of  the  vagus. 
Nerve  of  si)ecial  sense  of  taste  for  the  front  part  of  the 
tongue,  see  p.  757. 

6.  Abduceri,'^. — [The  abducens  nerve  emerges  from  the 
brain  at  the  [)Osterior  border  of  the  pons  Varolii  (Fig.  216). 
The  fibres  have  their  pi'incii)al  source  of  origin  in  a  gray 
nucleus  in  the  widest  part  of  the  floor  of  the  fourth  ventricle 
near  the  median  line.  The  nerve,  after  emerging  from  the 
brain,  passes  along  the  cavernous  sinus,  where  it  receives, 
filaments  fi'om  the  sym[)athetic  and  sensory  filaments  from 
the  ophthalmic  branch  of  the  fifth.  It  then  passes  through 
the  sphenoidal  fissure  to  the  external  rectus  muscle  of  the 
eye.]  It  is  the  motor  nerve  to  the  rectus  extern  us.  When 
the  nerve  is  divided  or  otherwise  paralyzed,  the  eye  is 
turned  inwards. 

The  abducens  is  joined  by  fibres  coming  from  the  cervical  sym- 
pathetic ;  when  this  nerve  is  divided  in  the  neck,  the  action  of 
the  muscle  is  weakened. 

7.  Facial. — [The  facial  nerve  arises  from  the  groove  be- 
tween the  olivary  and  restiform  bodies,  just  below  the  pons 
Varolii  (Fig.  2Ui).  The  fibres  have  their  deep  origin  prin- 
cipally in  a  gray  nucleus  in  the  floor  of  the  fourth  ventricle, 
which  is  a  common  seat  of  origin  for  both  the  facial  and 
abducens  nerves.  The  facial  fibres  arise  from  the  external 
portion  of  the  nucleus,  and  the  abducens  arises  from  the  in- 
ternal portion,  so  that  they  form  a  sort  of  loo[),  being  ap- 
parently continuous  with  each  other  through  the  nucleus. 
Some  of  the  fibres  extend  from  the  nucleus  to  the  brain  on 
the  same  side  ;  others  decussate  freely  in  tlie  median  line 
with  fihres  coming  from  the  opposite  nucleus,  and  run  to 
the  nucleus  or  are  continued  up  to  the  brain  on  the  opi)Osite 
side  to  whi(;h  they  originated. 

The  facial  nerve,  after  it  emerges  from  the  ])rain,  passes 
in  company  with  the  auditory  nerve   into  the  internal  audi- 


CRANIAL    NERVES. 


867 


tory  meatus.  Then  leaving  the  auditory  nerve  it  enters  the 
aqueductus  FaUopii  and  makes  its  exit  tlironojli  the  styh)- 
mastoid  foramen.  It  then  s[)reads  out  between  tlie  lobules 
of  the  parotid  gland,  its  branches  diverging  like  a  fan.  and 


Fig.  2-2S. 


w§n 


The  I  istributiou  of  the  Facial  Nerve,  and  the  Branches  of  the  Tervieal  Plexus  1, 
the  facial  nerve,  escaping  from  the  stylo-m-istoid  foramen,  and  crossing  the  ramus  of 
the  lower  jaw  ;  the  parotid  ■j,h\ud  has  been  removed  in  order  to  show  the  nerve  more 
distinctly;  2,  the  posterior  auricular  branch;  the  digastric  and  stylo-mastoid  fila- 
ments are  seen  near  the  origin  of  this  branch  ;  3,  temporal  branches,  communicating 
with  (4)  the  branches  of  the  frontal  nerve;  5,  facial  branches,  communicating  with 
(6)  the  infra-orbital  nerve;  7,  farial  branches,  communicating  with  (8)  the  mental 
nerve;  9,  cervico-facial  branches,  communicating  with  ilO)  the  superficialis  colli 
nerve,  and  foiminga  plexus  (11)  over  the  submaxilhiry  gland.  The  distribution  of 
the  branches  of  the  facial  in  a  radiated  direction  over  the  side  of  the  face,  consti- 
tutes the  pes  anseriuus;  12,  the  auricularis  magnus  nerve,  one  of  the  ascending 
branches  of  the  cervical  plejcus;  1.3,  the  occipitalis  minor,  ascending  along  the  pos- 
terior border  of  the  sterno-mastoid  muscle  ;  14,  the  superficial  and  deep  descending 
branches  of  the  cervical  plexus  ;  15,  the  spinal  accessory  nerve,  givinn  oft'  a  branch 
to  the  external  surface  of  the  trapezius  muscle;  16,  the  occipitalis  major  nerve,  the 
posterior  branch  of  the  second  cervical  nerve. 


is  distributed  principally  to  tlie  muscles  of  the  face  (Fig. 
228).]  It  is  the  motor  nerve  to  the  muscles  of  the  face; 
hence  nerve  of  expression.     Supplies  also  stylo-hyoid,  pos- 


868  THE    BRAIN. 

terior  bell}^  of  the  dig^astric,  buccinator,  stapedius,  muscles 
of  the  external  ear,  platysma,  some  muscles  of  the  palate, 
viz.,  the  levator  palati,  and  probably  others.  Secretory  nerve 
of  sul)maxillarv  and  parotid  inland.  Receives  afferent,  [)os- 
sibly  efferent  fibres  from  trigeminus,  and  also  from  vagus. 
According  to  Vulpian,  contains  vaso-motor  fibres  for  the 
tongue  and  side  of  the  face.  The  effects  of  paralysis  of 
the  facial,  from  the  inabibty  of  the  orbicularis  to  close  the 
e3^e,  the  drawing  of  the  face  to  the  sound  side,  and  the 
smoothness  of  the  paralyzed  side,  are  very  striking. 

8.  Auditory  Nerve. — -[The  auditory  nerve  arises  by  two 
roots  from  the  postei'ior  median  fissure  of  the  medulla  ob- 
longata, below  the  lower  border  of  the  pons  Varolii.  (Fig. 
216.)  In  the  floor  of  the  fourth  ventricle,  below  its  widest 
part,  are  a  number  of  transverse  white  striae.  (Fig.  218.) 
These  are  the  fibres  of  the  posterior  root,  which  arise  from 
a  gray  nucleus  beneath  them,  which  is  connected  with  the 
white  substance  of  the  cerebellum.  These  fihres  pass  out- 
wards, winding  around  the  restiform  body.  The  deep  or 
anterior  root  is  traced  to  the  borders  of  the  calamus  scrip- 
torius,  and  into  the  cerebellum  especially.  This  root  passes 
inwards  around  the  restiform  body  to  meet  the  other  root, 
and  thus  embraces  this  part  of  the  medulla.  Some  of  the 
fibres  decussate  in  the  floor  of  the  fourth  ventricle. 

This  nerve  accompanies  the  facial  into  the  internal  audi- 
tory meatus,  and  at  the  bottom  of  it  divides  into  the  cochlear 
and  vestibular  branches,  which  supply  the  internal  ear.  The 
cochlear  branch  is  distributed  to  the  cochlea;  the  vestil)ular 
branch  to  tiie  sacculi  and  semicircular  canals.  Within 
the  meatus  the  auditory  nerve  receives  several  filaments 
from  the  facial.]  It  is  the  special  nerve  of  heai'iug  ;  afl'erent 
nerve  for  impulses  other  tlian  auditory  proceeding  from  the 
semicircular  canals. 

9.  Glossopharyngeal.  —  [The  glosso-pharyngeal  nerve 
arises  by  four  or  five  bundles  of  fil»res  from  the  up|)er  part 
of  the  medulla  oblongata,  posterior  to  the  olivary  body. 
(Fig.  216.)  Tiiese  fibies  have  their  deep  origin  in  a  nucleus, 
which  is  situated  below  and  beneath  the  nucleus  of  the  audi- 
tory nerve.  The  nucleus  of  the  glosso-pharyngeal  is  a  con- 
tinuation of  the  same  series  of  cells  which  give  origin  to 
the  spinal  accessory  and  pneumogastric  nerves.  T!»e  nerve 
makes  its  exit   from  the  cranium  through  the  jugular  fora- 


CRANIAL    NERVES.  869 

men  in  company  witli  the  pneumogastric  and  spinal  acces- 
sor}' nerves.  In  its  passage  the  nerve  presents  two  ganglia 
on  its  trunk,  the  jugular  and  petrosal.  From  tlie  petrosal 
ganglion  fibres  arise  whicli  connect  the  nerve  with  the  pneiimo- 
gastiic.  facial,  and  sympathetic  nerves.  It  sends  a  special 
brancli  to  the  ear,  called  the  tympanic  Itranch.  It  divides 
into  two  principal  branches,  one  of  which  is  distributed  to 
the  pharynx  and  parts  immediately  surrounding;  the  other 
going  10  the  tongue  (Fig.  229;.]  Motor  nerve  for  levator 
palati,  azygos  uvulae,  st\  lo-pharyngeus,  constrictor  faucium 
medius  ;  the  motor  functions  of  this  nerve  have  been  dis- 
puted. Special  nerve  of  taste  for  the  back  of  the  tongue. 
General  nerve  of  sensation  for  the  root  of  the  tongue,  the 
soft  palate,  th&-  pharynx  (being  here  associated  with  tiie 
vagus),  tliC  Eustachian  tube,  and  the  tympanum. 

10.  Pneumogastric. —  Vagus. — [The  pneumogastric  nerve 
arises  by  ten  or  twelve  bundles  of  fibres  iiehiud  the  olivary 
body  and  below  tlie  point  of  origin  of  the  glossopharyngeal 
nerve.  (Fig.  216.)  These  fibres  haA'e  their  deep  origin  in  a 
gra}'  nucleus,  which  is  situated  below  the  nucleus  of  the 
glosso-pharyngeal,  with  its  upper  portion  piojecting  some- 
wiiat  above  it.  The  nucleus  is  exposed  in  the  floor  of  the 
ventricle.  The  fibres  proceed  from  the  nucleus  downwards 
and  outwards  through  the  medulla  oblongata,  and  emei'ge  at 
the  point  above  stated.  It  makes  its  exit  from  the  cranium 
through  the  jugular  foramen.  Before  its  exit  the  trunk 
presents  a  gangliform  eidargemeut  (ganglion  jugulare), 
through  which  it  rtceives  fibres  from  the  spinal  accessor}^ 
(accessory  portion),  facial,  gh/sso-pharyngeal,  and  sympa- 
thetic. After  its  exit  it  presents  a  second  enlargement 
(ganglion  inferius),  through  which  it  is  connected  with  the 
spinal  accessory  (accessory  portion),  hypoglossal,  loop  of 
tlie  first  and  second  cervical,  and  sympathetic  nerves. 

The  nerve  passes  down  the  neck  in  the  sheath  of  the  great 
bloodvessels,  and  is  dislrilnited  to  the  diti'erent  parts  below 
mentioned.] 

Efferent  Fibres:  Motor  nerve  for  the  muscles  of  the 
pharynx,  for  the  movements  of  the  oesophagus  (see  p.  883;, 
of  the  stomach  (see  p.  3S(>),  of  tlie  intestines  (see  p.  881  , 
for  the  muscles  of  the  larynx,  possibly  for  the  plain  mus- 
cular fibres  of  the  trachea  and   bronchial  divisions.     Vaso- 

73 


870 


Distribution  of  the  Pneumogastric  or  Tenth  Pair  of  Nerves  on  the  Left  Side.— After 
HiRSCHFELD  and  Leveille. 

1,  Gasserian  ganglion  of  tifth  nerve;    2,  internal  carotid  artery;   3,  pliaryngeal 
branch  of  pneumogastric;  4,  glosso-pharyngeal  nerve;   5,  lingual  nerve  (fi(th)  ;  6, 


CRANIAL    NERVES.  871 


spinal-acces«orY  nerve;  7,  middle  constrictor  of  pharj'nx  ;  8,  internal  jnsular  vein 
(cut);  9,  superior  laryri-ieal  nerve;  10,  ganglion  of  trunk  of  pneumogastric  nerve; 
11,  hypoglossal  nerve  (cut),  on  liyoglossus ;  12,  ditto  (cut),  eoiumuuicating  with  eighth 
and  first  cervical  nerve;  IS,  external  laryngeal  nerve;  14,  second  cervical  nerve 
looping  with  first ;  15,  j)haryngpal  plexus  on  inferior  constrictor;  16,  superior  cervi- 
cal ganglion  of  sympathetic  ;  17,  superior  cardiac  nerve  of  pneuuiogastric;  18,  third 
cervical  nerve;  19,  thyroid  body;  20,  fourth  cervical  nerve;  21,  left  recurrent  lar- 
yngeal nerve  ;  22,  spinal  accessory, communicating  with  cervical  nerves;  23,  trachea; 
24,  middle  cervical  ganglion  of  sympathetic;  25,  middle  cardiac  nerve  of  pneuuio- 
gastric; 26,  phrenic  iierve(cut);  27,  left  carotid  artery  (cut) ;  28,  trachea!  plexus  ;  29, 
phrenic  nerve(cut);  30,  inferior  cervical  ganglion  of  sympathetic;  31,  pulmonary 
plexus  of  pneumogastric;  32,  arch  of  thoracic  aorta;  33,  oesophageal  plexus;  34, 
vena  azygos  superior;  35,  vena  azygos  minor;  36.gangliated  cord  of  sympathetic] 

motor  fibres  for  lungs."  Inhihilory  nerve  of  the  heart.  Tro- 
pliic  111  ties  for  lungs  and  heart  (see  [).  P)1<S). 

Atfereiit  Fibres :  Sensory  nerve  of  the  respiratory  pns- 
sages,  and  of  the  pharynx.  a?sophagus,  and  stomach.  Affer- 
ent nerve,  augmenting  and  inhibiting,  of  the  respiratory 
centre  (see  p.  472).  afferent  inhibitory  nerve  (depressor 
branch)  <>^  the  metlullaiy  vaso-motor  centre  (see  |).  207), 
afierent  nerve  producing  salivary  secretiim  (see  p.  351  ),  in- 
hibiting i)ancreatic  secretion  (see  p.  360). 

According  to  Steiner,-  the  vagus  in  the  rabbit  may  be  easily 
dissected  into  two  strands,  an  outer  one  containing  the  afferent, 
and  an  inner  one  containing  the  efferent  fibres, 

1 1.  Spinal  Acct'^Hory. — [The  spinal  accessory  nerve  arises 
by  eigiit  or  ten  filaments  from  the  lateral  tract  of  the  cord, 
belov/  the  point  of  origin  of  the  pneumogastric  The  spinal 
accissory  nerve  consists  of  two  portions,  the  accenHory  and 
.spt/ial.  (Fig.  216.)  The  accessory  i)ortion  joins  the  pneu- 
mogastric nerve,  as  has  been  previously  stated.  The  fibres 
have  their  deep  origin  in  a  gray  nucleus,  in  the  lower  part 
of- the  medulla  and  upper  part  of  the  spinal  cord,  which  is 
continuous  aliove  with  the  nucleus  of  the  pneumogastric,  and 
below  with  the  remains  of  the  anterior  cornu.  The  nerve 
makes  its  exit  from  the  cranium  through  the  jugular  foramen.] 

Motor  nerve  to  the  sterno  mastoid  and  trai)ezius  mus- 
cles. It  receives  recurrent  sensory  fibres  from  the  cervical 
nerves.  P*art  of  the  spinal  accessory  blends  with  the 
I)neumogas!ric,  and  the  efferent  effects  (such  as  the  move- 
ments of  the    larynx,   pharynx,  etc.,   and    cardiac   inhibi- 


^  Michaelson,  Mitth.  a.  d.  Konigsberger  physiol.  Lab.  (1878),  p.  85. 
2  Arch.  f.  Anat.  u.  Phys.  (Phys.  Abth.),  1878,  p.  216. 


872  THE    BRAIN. 

tion)  of  the  united  trunk  seem  to  be  largely  due  to  tlie 
spinal  accessory  fibres  contained  in  them.  It  is  stated, 
however,  that  division  of  the  spinal  accessory,  before  it  joins 
the  pnenmogastric,  does  not  entirely  do  away  with  either 
swallowing  or  the  movements  of  the  larynx.  In  the  move- 
ments of  the  oesophngus  and  stomach,  brought  about  by  the 
vagus  acting  as  an  efierent  nerve,  tlie  accessory  fil)res  seem 
to  have  no  share.  Tlie  cardiac  inhibitory  fibres  seem  to  be 
distinctly  of  accessory  origin. 

12.  BijpogloHHaL — [The  hypoglossal  nerve  arises  by  twelve 
or  fifteen  bundles  from  the  groove  between  the  anterior  pyra- 
mid and  the  olivary  body,  in  a  line  corresponding  to  the 
anterolateral  groove  in  the  cord.  The  fiitros  have  their 
deep  origin  in  an  elongated  gray  nucleus  situated  in  the 
floor  of  tlie  fourth  ventricle  at  its  inferior  part,  near  the 
median  line  and  internal  to  the  nucleus  of  the  spinal  acces- 
sory, pneumogasti'ic,  and  glosso  pharyngeal  nerves.  The 
nerve  makes  its  exit  from  the  ci'anium  through  the  anterior 
condyloid  foramen.]  Motor  nerve  for  the  muscles  of  the 
tongue,  and  for  all  tlie  muscles  connected  with  the  hyoid 
bone,  except  the  digastric,  stylohyoid,  mylohyoid,  and 
middle  constrictor  of  the  pharynx  ;  it  also  supplies  the 
sterno  thyroid.  It  receives  sensory  fibi-es  fi'om  the  fifth  and 
vagus,  and  is  also  connected  with  the  three  upper  cervical 
nerves  as  well  as  with  the  sympathetic. 

There  is  probably  some  intimate  connection  existing  be- 
tween the  hypoglossal  nerve  roots  and  the  gray  matter  of 
the  olivary  bodies. 

To  Charles  Bell  is  due  the  merit  of  having  made  the  funda- 
mental discovery  of  the  distinction  between  motor  and  sensory 
fibres.  Led  to  this  view  by  reflecting  on  the  distribution  of  the 
nerves,  he  experimentally  verified  his  conclusions  by  observing 
that  -while  mechanical  irritation  of  a  posterior  root  gave  rise  to  no 
movements  in  the  muscles  to  which  the  nerv^e  was  distributed,  these 
were  very  evident  when  the  anterior  root  was  pricked  or  pinched. 
He  printed  his  views  for  private  circulation  in  1(S11  under  the 
the  title  of  Idea  of  a  New  Anatomy  of  the  Brain,  and  communi- 
cated them  to  the'  Royal  Society  in  July,  1821,  in  a  pa])er  On  the 
Arrangement  of  the  Nerves.  In  1(S22  Magendie'  showed  that  sec- 
tion of  the  posterior  root  caused  loss  of  sensation  and  section  of 


.Journal  de  Physiol.,  ii,  p.  21 


CRANIAL    NERVES.  873 


the  anterior  root  loss  of  motion  :  an  observation  no  less  epoch- 
making  than  that  of  Bell.  Mageudie  \vas,  however,  led  by  the 
phenomena,  which  we  can  now  explain  as  due  to  recurrent  sensi- 
bility or  reflex  action,  to  believe  that  the  distinction  between  the 
two  roots  was  partial  only  ;  and  it  was  not  till  Johannes  Mliller^ 
some  years  afterwards  conducted  experiments  on  frogs  and  made 
use  of  galvanic  stimulation,  that  the  doctrine  of  motor  and  sensory 
nerves  became  thoroughly  established.  The  next  great  step  was 
the  establishment  of  tlie  theory  of  Heflex  Action.  Although  this 
important  function  of  nerv(»us  centres  was  recognized  dimly  by 
older  observers,  such  as  Whytt,'-  more  closely  detined  by  Pro- 
chaska,^  and  clearly  grasped  by  Johannes  Midler  in  1833,'  it  was 
independently  discovered  in  1832  by  Marshall  Hall  ;^  and  it  was 
owing  to  the  enthusiastic  labors  of  the  latter  observer  that  the 
new  doctrine  was  rapidly  accepted  and  developed.  Among 
the  more  important  labors  since  that  Lime  may  be  mentioned 
the  remarkable  book  of  Flourens,*^  the  work  of  Longet,'  and 
the  researches  of  Schiff,'  Brown-Sequard,^  and  others.  The  work 
of  Goltz  "  on  the  frog,  though  small,  contains  manj^  valuable 
facts  and  suggestions  ;  and  an  admirable  summary  of  the  whole 
physiology  of  the  nervous  system  is  given  by  A'ulpian,'-  to  whom 
also  we  are  indebted  for  many  valuable  observations.  The  chief 
of  the  more  recent  inquiries  have  been  mentioned  in  the  text. 


'*  Physiology,  Engl,  ed.,  i,  (»91. 

^  On  the  Vital  and  other  Involnntary  Movements  of  Animals,  1751. 

^  Lehrsiitze  ans  dei  Pliysiol.,  1797. 

'^  In  the  tirst  edition  of  his  Phvsiology. 

^  More  fully  in  Phil.  Trans.,  1833. 

^  Rech.  Exp,  sur  les  Proi)rie:es  et  les  Fonctions  dn  Systeme  Nerveux, 
1st  ed.,  in  1824;  2d,  much  enlarged  and  containing  many  new  facts,  in 
1842. 

'  Anat.  et  Phvs.  du  Svsteme  Nerveux,  1841. 

8  Lehrb.  d.  Physiol.,  1858. 

^  Rech.  et  Exp.  sur  la  Phy».  de  la  moelle  epin.,  1846,  and  numerous 
subsequent  papers. 

'°  Beitriige  z.  Lehre  v.d.  Functionen  der  Xervencentren  des  Frosches, 
1869. 

"  Leyons  sur  la  Phvs.  generale  et  comparee  du  Svsteme  Nerveux, 
1866. 


874 


SPECIAL    MUSCULAR    MECHANISMS, 


CHAPTER  YII. 
SPECIAL  MUSCULAR  MECHAXLSMS. 

l^The  Phydrjlogical  Analomy  of  the  Larynx. 

The  larynx  is  a  memhrano  cirtilauiiious  chainher,  Isroader 
above  than  below,  and  situtili'd  m  I  lie  anterior  median  })()!•- 
tion  of  the  neck.  It  consis's  of  a  number  of  cartilages, 
which  are  articulated  with   cnch   other,  connected  b}-  liga- 

Fio.  2:50. 


\V^  ^     ^1^^^.z        __ 


Median  S  ctiui  nf  M.  \ith,  No?e,  Pharyux,  an  1  Larynx,  a,  soptnm  of  nose;  below 
It,  section  of  lianl  palate;  6,  tongue;  c,  section  of  v^-hini  poiidnhim  palati ;  rf,  (f,  lips  ; 
u,  uvula  ;  r,  aiiteriur  arch  or  pillar  of  fauces;  t,  posterior  arcli  ;  /,  tonsil ;  />,  pharynx  ; 
h,  hyoid  hone;  k,  thvroid  carlilaj^e;  n,  cricoid  cartilaj^e  ;  a,  epi;;lottis;  r,  glottis;  1, 
posterior  oj»ening  of  tlie  nares;  3,  isthmus  fauciiim  ;  4.  superior  op.niing  of  larynx  ; 
h,  passage  into  oesophagus  ;  6,  mouth  of  right  Eustachian  tulje. 


nient.  moved  l)y  a  number  of  muscles,  and  lined  by  a  mucous 
membrane. 

The  principal  cartilages  are  the  thyroid,  cricoid,  the  two 
arytenoid,  and  the  epiglottis. 


ANATOMY  OF  THE  LARYNX.  875 

Tlie  thyroid  cartilage  is  the  largest,  and  consists  of  two 
quadrilateral  plates  or  aire,  which  are  continuous  with  each 
other  in  front,  where  they  foi-m  the  prominence  called  the 
pomuHi  Adanii.  The  posterior  liorders  of  the  thyroid  car- 
tilage serve  as  a  point  of  attachment  of  the  stylo-pharyngeus 
and  palato-pharyngeus  muscles.  The  upper  part  of  each  of 
these  horder^teiminatcs  in  a  superior  cornu.  which  articulates 
with  the  hyoid  hone;  the  lower  portion  terminates  in  the 
inferior  cornn,  which  arlic  dates  with  the  cricoid  cartilage. 
The  upper  border  between  thecoriiua  is  connected  with  the 
hyoid  hone  by  the  thyr( -hyoid  membrane.  The  lower 
border  is  connected  with  the  cricoi<l  cartilage  by  the  thyro- 
cricoid  membrane  at  the  median  line,  and  at  the  sides  by 
the  cricothyroid  muscles. 

The  cricoid  cartilage  is  situated  below  the  thyroid  car- 
tilage with  its  broad  portion  posteriorly.  At  the  upper  part 
of  its  broad  portion  are  two  Mnooth  sur'aces  on  which  the 
arytenoid  cartilages  articulate. 

The  arytenoid  cartilages  are  pyiamidal  in  foiin,  and  artic- 
ulate on  the  upper  surface  of  the  cricoid.  Eacii  t-artilage 
has  an  external,  posterior  and  internal  (median,  surlaci-.  an 
apex  and  a  l»ase.  The  apex  is  pointed  backwards  and  in- 
wai"ds,  and  is  suvmounted  by  a  small  cartilaginou.s  tubercle, 
called  the  cartilage  of  Santorini  (  Fig  288  \  The  base,  which 
articulates  with  the  cricoid  cartilage,  presents  at  its  external 
internal  angle  a  projection  called  the  procrssi/.s-  vocalis.  At 
the  posteri(r  internal  angle  is  a  second  projection,  called  the 

The  superior  (»pening  of  the  larynx  is  formed  anteriorly 
by  the  e|)ii>lottis.  posteriorly  by  the  apices  of  the  arytenoid 
cartilages,  and  laterally  iiy  t  he  ar\  teno-e[)iglottidean  folds 
stretching  between  these  points.  The  inferior  opening  cor- 
responds to  the  inferior  border  of  the  ci-icoi(l  cartilage. 
Between  these  points  is  the  carity  of  the  lar\  nx,  which  has 
stretching  across  its  sides  the  vocal  cords.  The  vocal  cords 
consist  of  two  pairs:  the  superior  or  false  voc:d  cords  are 
membrano  ligamentous  l»ands  which  extend  from  the  I'eced- 
ing  angle  of  the  thyroid  to  the  external  surfaces  of  the  aiy- 
tenoid  cartilages;  the  inferioi-  or  true  vocal  cords  (c/?o?'(/a 
vocaies)  are  membrano-ligamentous  bauds  whicli  s' retch 
aci'oss  the  cavity  of  the  larynx  from  the  lecediug  angle  of 
the  thyroid  to  tlie  processus  V(K-ales  of  the  arytenoid  carti- 
lages. Between  the  borders  of  the  true  and  false  vocal 
cords  is  an  elliptical  opening,  the  ventricle:^  which  leads  to  a 


876 


SPECIAL    MUSCULAR    MECHANISMS. 


space  running:  upwards  and   heliind  the  false  vocal  cords, 
called  the  .saccultiti  larynciU.     The  nuicoiis  membrane  lining 


Fig  231 


Fig.  232. 


Fig.  231. — View  of  the  Larynx  and  part  of  the  Trachea  from  behind,  with  Ihemu!^- 
cles  dissected  ;  A,  the  body  of  the  hyoid  bone  ;  e,  epiglottis;  t,  the  posterior  borders 
of  the  thyroid  cartilage;  c,  the  median  ridge  of  the  cricoid;  a,  upper  part  of  the 
arytenoid  ;  s,  placed  on  one  of  the  oblique  fasciculi  of  the  arytenoid  muscle;  b.  left 
posterior  crito-arytenoid  muscle;  ends  of  the  incomplete  cartilaginous  rings  of  the 
trach»'a ;  /,  fibrous  membrane  crossing  the  back  of  the  trachea  ;  n,  muscular  fibres 
exposed  in  a  part  (from  Quain's  Anatomy). 

Fig.  232. — V^iew  of  the  Larynx  from  above.  1,  aperture  of  glottis;  2,  arytenoid 
cartilages;  3,  vocal  cords  ;  4,  posterior  cricoarytenoid  muscles;  5,  lateral  crico-ary- 
teiioid  muscle  of  right  sidi-,  that  of  left  side  removed  ;  6,  arytenoid  muscle  ;  7,  thyro- 
arytenoid muscle  of  left  fide,  that  of  right  side  removed  ;  8,  thyroid  cartilage;  9, 
cricoid  cartilage;  13,  posterior  crico-arytenoid  ligament.  With  the  exception  of  the 
aiytenoid  muscle,  this  diagram  is  a  copy  from  Mr.  Willis's  figure. 

Fig.  233. — View  of  the  upper  part  of  the  Larynx  as  seen  by  means  of  the  Laryn- 
goscope during  the  Utterance  of  a  Grave  Note,  c,  epiglottis;  s,  the  cartilages  of 
Santorini;  «,  arytenoid  cartilages;  z,  base  of  the  tongue  ;  ^^,  the  posterior  wall  of 
the  pharynx. 

this  sac  contains  a  great  number  of  follicular  glands,  which 
discharge  a  mucous  secretion  for  the  purpose  of  lubricating 
the  true  vocal  cords. 


THE    VOICE.  877 

Between  tlie  true  vocal  cords  is  an  opening  which  is  called 
the  rima  gJo/fidix.  The  form  of  the  glottis  varies  very  much 
hoth  in  the  inspiratory  and  expiratory  acts,  and  in  the  act 
of  phonation. 

The  muscles  of  the  larynx  are  divided  anatomically  into 
the  intrinsic  and  extrinsic.  The  former  are  nine  in  num- 
ber, four  of  them  being  in  pairs.  They  are  the  essential 
muscles  concerned  in  the  movements  of  the  arvtenoid  carti- 
lages and  chorda  vocales.  Their  points  of  oiigin  and  in- 
sertion are  referred  to  on  p.  880.  The  extrinsic  muscles 
connect  the  larynx  with  adjacent  parts,  and  are  for  the 
most  part  concerned  in  the  elevation  and  depression  of  the 
organ. 

The  larj-nx  is  lined  with  a  mucous  membrane,  wdiich  is 
continuous  above  with  that  lining  the  pharynx  and  mouth, 
and  below  with  that  lining  the  trachea.  Above  the  chorda 
vocales  it  is  lined  with  pavement  epithelium,  excepting  at 
the  lower  anterior  portion,  where  it  is  ciliated  ;  below  the 
chorda  vocales  the  epithelium  is  of  a  ciliated  cobimnar 
variety.  The  mucous  membrane  contains  many  mucous 
glands,  which  are  pretty  uniformly  distributed  ;  they  are 
however  A'ery  abundant  in  the  part  of  the  membrane  lining 
the  sacculus  laryngis.] 


Sec.  1.   The  Yotce. 

A  blast  of  air,  driven  by  a  more  or  less  prolonged  expi- 
ratory movement,  throws  into  vibrations  two  elastic  mem- 
branes,— the  chordse  vocales.  These  impart  their  vibrations 
to  the  column  of  air  above  them,  and  so  give  rise  to  the 
sound  which  we  call  the  voice.  Since  the  sound  is  generated 
in  the  vocal  cords,  we  may  speak  of  them  and  of  those  parts 
of  the  larynx  which  decidedly  affect  their  condition  as  con- 
stituting the  essential  vocal  api)aratus  ;  while  the  chamber 
above  the  vocal  cords,  comprising  the  ventricles  of  the 
lar3^nx,  with  the  false  vocal  cords,  the  pharynx  and  the  cavity 
of  tlie  mouth.  t!ie  latter  varying  much  in  form,  constitute  a 
subsidiary  apparatus  of  the  nature  of  a  resonance-tul^e, 
modifying  the  sound  originating  in  the  vocal  cords.  In  the 
voice,  as  in  other  sounds,  we  distinguish:  (1)  Loudness. 
This  depends  on  the  strength  of  the  expiratory  blast.  (2) 
Pitch.  This  depends  on  the  length  and  tension  of  the  vocal 
cords.     Their  length  may  be  regarded  as  constant,  or  vary- 

74 


878 


SPECIAL    MUSCULAR    MECHANISMS. 


ins:  only  witli  age.  It,  consequently  determines  the  rang:e 
only  of  the  voicp,  and  not  tlie  particular  note  given  out  at 
any  one  time.     The  shrill  voice  of  the  child  is  determined 


Fig.  234. 


^K 


The  Larynx  as  seen  by  means  of  the  Laryngoscope  in  different  conditions  of  (he 
Glottis  (from  Quaiu's  Anatomy). — After  Czermak. 

A,  while  singing  a  high  note;  ^,  in  quiet  breathing;  C,  during  a  deep  inspiration. 
The  corresponding  diagrammatic  figures  A',  B',  C",  illustrate  the  changes  in  position 
of  the  arytenoid  cartilages,  and  the  form  of  the  rima  vocalis  and  rima  respiratoria 
in  the  above  three  conditions. 

/,  the  base  of  the  tongue  ;  e,  the  upper  free  part  of  the  epiglottis  ;  e',  the  tubercle 
or  cushion  of  the  epiglottis;  ph,  part  of  the  anterior  wall  of  the  pharynx  behind 
the  larynx  ;  w,  swelling  in  the  aryteno-epiglottidean  fold  caused  by  the  cartilage  of 
Wrisberg;  s,  swelling  caused  by  the  cartilage  of  Santorini ;  a,  the  summit  of  the 
arytenoid  cartilage;  cv,  the  true  vocal  cords;  cvs,  the  false  vocal  cords;  tr,  the  tra- 
chea with  its  rings  ;  6,  the  two  bronchi  at  their  commencement. 


b\7  the  shortness  of  the  cords  in  infancy,  and  the  voices  of 
a  soprano,  tenor,  and   barytone  are   all   dependent  on  the 


THE    VOICE.  879 

respective  lengths  of  their  vocal  cords.  The'w  tension  is  on 
the  contrary  variable  ;  and  the  chief  problems  connected 
with  the  voice  refer  to  variations  in  the  tension  of  the  vocal 
cords.  (3)  Quality.  This  depends  on  the  number  and 
character  of  the  overtones  accompanying  any  fundamental 
note  sounded,  and  is  determined  by  a  variety  of  circum- 
stances, chief  among  which  is  the  physical  quality  of  the 
cords. 

The  vocal  cords,  attached  in  front  to  the  thyroid  cartilage, 
end  behind  in  the  processus  vocales  of  the  arytenoid  carti- 
lages. Hence  a  distinction  has  been  drawn  between  the 
rima  vocalis,  i.  e.,  the  opening  bounded  laterally  b}-  the  vocal 
cords,  and  the  rima  respiratoria,  or  space  between  the  ary- 
tenoid cartilages  behind  the  processus  vocales  ;  these  names 
however  are  not  free  from  objections.  In  quiet  breathing 
(Fig.  234,  B)  the  two  form  together  a  Y-shaped  space,  which, 
as  we  have  seen  (p.  432^,  in  deep  inspiration  is  widened  into 
a  rhomboidal  opening  by  the  divergence  of  the  processus 
vocales  (Fig.  234,  C).  When  a  note  is  about  to  be  uttered, 
tlie  vocal  cords  are  YiV  the  approximation  of  the  processus 
vocales  brought  into  a  position  parallel  to  each  other,  and 
the  whole  rima  is  narrowed  (Fig.  284,  A).  By  their  parallel- 
ism and  by  the  narrowness  of  the  interval  between  them 
the  cords  are  rendered  more  sus'.*eptible  of  being  thrown 
into  vibration  by  a  moderate  blast  of  air.  The  problems 
we  have  to  consider  are.  first,  by  what  means  are  the  cords 
brought  near  to  each  other  or  drawn  asunder  as  occasion 
demands ;  and,  secondly,  by  what  means  is  the  tension  of 
the  cords  made  to  vary.  We  may  speak  of  these  two  ac- 
■  tions  as  narrowing  or  widening  of  the  glottis,  and  tighten- 
ing or  relaxation  of  tlie  vocal  cords. 

Narrowing  of  the  Glottis. — The  change  of  form  of  the 
glottis  is  best  understood  when  it  is  borne  in  mind  that  each 
arytenoid  cartilage  is,  when  seen  in  horizontal  section  (Fig. 
234 ),  somewhat  of  the  form  of  a  triangle,  with  an  internal 
or  median,  an  external,  and  a  posterior  side,  the  {)rocessus 
vocalis  being  placed  in  the  anterior  angle  at  the  junction  of 
the  median  and  external  sides.  When  the  cartilages  are  so 
placed  that  the  processus  vocales  are  approximated  to  each 
other,  and  the  internal  snrfaces  of  the  cartilages  nearly 
parallel,  the  glottis  is  narrowed.  When  on  the  contrary  the 
cartilages  are  wheeled  round  on  the  pivots  of  their  articu- 
lations, so  that  the  processus  vocales  diverge,  and  the  inter- 


880  SPECIAL    MUSCULAR    MECHANISMS. 

nal  surfaces  of  the  cartilages  form  an  angle  with  each  otiier, 
the  glottis  is  wirlened. 

There  are  several  muscles  forming  together  a  gronp,  which 
has  been  called  by  Henle  the  sphincter  of  the  larynx.  These 
are  (1)  the  thyro-ary  epiglofticui<^  proceeding  from  the  inner 
surface  of  the  thyroid  cartilage  anrl  from  tlie  arytenoid  epi- 
glottidean  ligament,  and  sweeping  round  the  outer  ridge  of 
the  arytenoid  cartilage  of  its  own  side  to  be  inserted  into 
the  processus  muscularis  of  the  arytenoid  cartilage  of  tiie 
other  side;  (2)  the  fhyi^o-aryfenoide.s  extcrnus^  passing  from 
the  re-entrant  angle  of  the  thyroid  cartilage  to  be  inserted 
into  the  outer  edge  of  the  arytenoid  cartilage  of  the  same 
side;  (3)  tlie  thyro  arytenoidea  internus^  passing  from  the 
angle  of  the  thyroid  cartilnge  to  the  processus  vocalis  and 
outer  side  of  the  arytenoid  cartilnge;  (4)  the  orytenoideun 
( podicui<)^  passing  transversely  from  one  arytenoid  cartilage 
to  another.  All  these  muscles,  when  they  act  together, 
grasp  round  the  glottis  and  tend  to  close  it  up  ;  and  eacli  of 
them,  acting  alone,  has,  with  the  exception  of  the  last- 
named  (arytenoidens),  the  same  effect.  In  addition  to  tliese, 
the  crico  arytenoideuH  Iaterali.s^w]\'n:h  passes  from  the  lateral 
border  of  the  cricoid  cartilage  ujjwards  and  backwai'ds  to 
the  outer  angle  of  the  arytenoid,  by  pulling  this  outer  angle 
forwards  throws  the  processus  vocalis  inwards,  and  so  also 
narrows  the  glottis. 

Widening  of  the  Glottis. — The  cHco-ay^ytenoideus  posticus^ 
passing  from  the  posterior  surface  of  the  cricoid  cartilage 
to  the  outer  angle  of  the  arytenoid  cartilnge  behind  the  at- 
tachment of  the  lateral  crico-arytenoideus.  pulls  back  this 
outer  angle,  and  so  causing  the  processus  vocalis  to  move 
outwards,  widens  the  glottis.  The  aryfenoideus  poi^tlciiH^ 
acting  alone,  lias  a  similar  etfect. 

Tightening  of  the  Vocal  Cords. — The  crico-thyroideus 
pulls  the  thyroid  downwards  and  forwards,  and  so  increases 
the  distance  between  that  cartilnge  and  the  arytenoids  when 
the  latter  are  fixed.  Supposing  then  the  arytenoidens  and 
crico-arytenoideus  posticus  to  fix  the  arytenoids,  the  effect 
of  the  contraction  of  the  crico  th^roideus  would  be  to  tighten 
the  vocal  cords. 

Slackening  of  the  Vocal  Cords. — This  is  effected  by  the 
whole  of  the  sphincter  group  just  mentioned,  but  more  es- 


THE    VOICE.  881 

pecially  by  the  thyro-aryteiwidei  externus  and  internus ; 
these  acting  alone,  supposing  the  arytenoid  cartilages  to  he 
fixed,  would  pull  the  thyroid  cartilage  upwards  and  hack- 
wards,  and  so  shorten  the  distance  between  the  processus 
vocales  and  that  body. 

Thus  almost  every  movement  of  the  larynx  is  effected  not 
by  one  muscle  only  but  by  several,  or  at  least  by  more  than 
one,  acting  in  concert.  The  movements  which  give  rise  to 
the  voice  are  pre-eminently  comi)ined  and  co-c^rdinate  move- 
ments. When  we  remember  how  a  very  slight  variation  in 
the  tension  of  the  vocal  cords  must  give  rise  to  a  marked 
difference  in  the  [)itch  of  the  note  uttered,  and  yet  what  a 
multitude  of  fine  differences  of  pitch  are  at  the  command 
of  a  singer  of  even  moderate  ability,  it  appears  exceedingly 
probable  that  the  various  muscular  combinations  required 
to  j)rodnce  the  possible  variations  in  pitch  are  of  such  a 
kind  that  frequently  a  part  only,  possibly  a  few  fibres  only, 
of  a  particular  muscle,  may  be  thrown  into  contraction, 
while  all  the  rest  of  the  muscle  remains  quiet.  Taking  into 
view  moreover  the  great  range  of  pitch  possessed  by  even 
common  voices,  as  compared  with  the  possible  variations  of 
tension  of  wdiich  the  vocal  cords  in  their  natural  length  are 
capable,  it  has  been  suggested  that  some  of  the  fibres  of  the 
thyro-ar3tenoideus  internus,  wiiich  |)assing  either  from  tiie 
thyroid  or  from  the  arytenoid  appear  to  end  in  the  vocal 
cords  themselves,  may,  b\'  fixing  particular  points  of  the 
cords,  so  to  speak,  ••  stop  "  them  :  and  by  thus  artificially 
shortening  the  length  actually  thrown  into  vibration,  pro- 
duce higher  notes  than  the  cords  in  their  natural  length  are 
capal)le  of  producing.  It  has  been  also  suggested  that  the 
processus  vocales  may  overlap  each  other,  and  therel)y 
shorten  the  length  of  cord  available  for  vibration.^ 

These  various  muscles  are  supi)lied  by  the  vagus  nerve, 
or  rather  by  spinal  accessory  fibres  running  in  the  vagus 
trunk.  The  superior  laryngeal  is  the  afferent  nerve  sup- 
plying the  mucous  mem'orane,  but  it  also  contains  the  motor 
fibres  distributed  to  the  crico-thyroid  muscle;  hence  when 
this  nerve  is  divided  on  one  side  the  corresponding  vocal 
cord  is  relaxed  and  high  notes  become  impossil)le.  It  is 
worthy  of  notice  that  this,  the  chief  tensor,  and  therefore 
the  most  important,  muscle  of  the  larynx,  has  a  separate 
and  distinct  nervous  supply. 

^  Cf.  Riihlmann,  Wien.  Sitzungsbericht,  Ixix  (1874),  p.  257. 


882  SPECIAL    MUSCULAR    MECHANISMS. 


According  to  some  authors,  the  ar3^tenoideiis  posticus  also  re- 
ceives its  nervous  supply  from  this  nerve  ;  but  this  is  denied  by 
Schech.^ 

The  inferior  laryngeal  or  recurrent  branch  supplies  all  the 
other  muscles.  When  this  nerve  is  divided  the  voice  is  lost, 
since  the  approximation  and  parallelism  of  the  vocal  cords 
can  no  longer  be  effected.  When  in  a  living  animal  both 
recurrent  nerves  are  divided,  the  glottis  is  seen  to  become 
immobile  and  partiall}^  dilated,  tlie  vocal  cords  assuming 
the  position  in  which  they  are  found  in  tlie  body  after  death, 
and  which  may  be  considered  as  the  condition  of  equilibrium 
between  the  dilating  and  constricting  muscles.  During  for- 
cible inspiration  the  glottis  passes  from  this  condition  in  the 
direction  of  more  complete  dilation  ;  during  forcible  expi- 
ration, the  change  is  one  of  constriction.  When  the  pe- 
ripheral portion  of  one  recurrent  nerve  is  stimulated,  the 
vocal  cord  of  the  same  side  is  approximated  to  the  middle 
line;  when  both  nerves  are  stimulated,  the  vocal  cords  are 
l)rought  together  and  the  glottis  is  narrowed.  Though  the 
nerve  is  distributed  to  both  dilating  and  constricting  mus- 
cles, the  latter  overcome  the  former  when  the  nerve  is  arti- 
ficially stimulated.  In  the  complete  closure  of  the  glottis, 
which  is  so  important  a  part  of  the  act  of  coughing  (p.  498), 
the  group  of  muscles  which  we  have  spoken  of  as  consti- 
tuting a  sphincter  is  thrown  into  forcible  contractions  by 
the  recurrent  laryngeal  nerve. 

Though  fundamentally  a  voluntary  act,  the  utterance  of 
a  given  note  is  not  effected  by  the  direct  passage  of  simple 
volitional  impulses  down  to  the  laryngeal  muscles.  So 
complex  and  co-ordinate  a  movement  as  that  of  sounding 
even  a  simple  and  natural  note,  requires  a  co-ordinating 
nervous  mechanism  in  which,  as  in  other  complex  muscular 
actions,  afferent  impulses  play  an  important  part.  Auditory 
sensations,  if  not  as  important  for  an  accurate  manage- 
ment of  the  voice  as  are  visual  sensations  for  the  movements 
of  the  eye,  are  yet  of  prime  importance.  This  is  recognized 
when  we  say  that  such  and  such  a  one  whose  power  over 
his  laryngeal  muscles  is  imperfect,  "  has  no  ear." 

The  "falsetto  "  voice  is  one  not  at  present  clearly  understood. 
According  to  some  authors  the  vocal  cords  are  seen  to  be  wide 
apart  when  falsetto  notes  are  uttered,  and  not  close  and  parallel 

^  Zt.  f.  Biol.,  ix,  p.  258. 


SPEECH.  883 


as  in^  the  ordinary  voice.  Hence  for  the  development  of  these 
notes  a  stronger  blast  of  air  and  a  greater  effort  are  required. 
When,  as  in  ordinar}^  full  voice,  the  glottis  is  very  narrow,  the 
trachea  and  bronchi  serve  the  purpose  of  a  resonance  chamber  ; 
hence  such  a  voice  is  spoken  of  as  a  "  chest  "  voice.  In  the  falsetto 
voice,  where  the  vocal  cords  are  wide  apart,  this  function  of  the 
air-tubes  is  in  abej-ance.  This  view  is  combated  by  Yacher/ 
who,  from  observations  on  himself,  has  come  to  the  conclusion 
that  the  glottis  is  narrowed  in  both  kinds  of  notes,  the  cords 
vibrating  along  their  whole  length  in  the  chest  notes,  and  along 
their  anterior  portions  only  in  the  high  falsetto  notes.  Accord- 
ing to  him,  therefore,  the  high  notes  are  the  result  of  a  ''•stop- 
ping" of  the  vocal  cords,  but  whether  this  is  effected  by  the  ac- 
tion of  the  thyro-arytenoideus  internus  spoken  of  above,  must  be 
left  at  present  uncertain.  .Johannes  Miiller  was  of  oi)inion  that 
in  the  falsetto  notes  the  edges  only  of  the  vocal  cord  vibrate, 
while  in  the  chest  notes  the  whole  width  of  each  cord  is  involved. 
It  is  exceedinglj'  probable  that  the  falsetto  notes  are  produced  by 
some  muscular  manoeuvre,  since  they  may  by  exercise  be  uttered 
with  comparative  ease.  The  change  from  the  chest  to  the  fal- 
setto range  is  an  abrupt  one,  and  the  combined  range  may  be 
very  extensive,  as  in  the  case  of  persons  who  can  carry  on  a  duet, 
singing  alternatelv,  for  instance,  in  a  tenor  (chest)  and  a  soprano 
(falsetto)  voice.  According  to  Yacher  the  rima  respiratoria  is 
always  completely  closed  during  singing,  whether  chest  or  fal- 
setto notes,  and  not  as  Mandl  thought  in  the  latter  only. 

The  ventricles  of  Morgagni  are  apparently  of  use  in  giving  the 
vocal  cords  sufficient  room  for  their  vibrations.  The  purpose  of 
the  false  vocal  cords  is  not  exactly  known.  Some  authors  think 
that  in  the  falsetto  voice  the}-  are  brought  down  into  contact  with, 
and  thus  serve  to  stop,  the  true  vocal  cords. 

At  the  age  of  puberty  a  rapid  development  of  the  larynx  takes 
place,  leading  to  a  change  in  the  range  of  the  voice.  T'he  pecu- 
liar harshness  of  the  voice  when  it  is  thus  "  breaking  "  seems  to 
be  due  to  a  temporary,  congested,  and  swollen  condition  of  the 
mucous  membrane  of  the  vocal  cords  accompanying  the  active 
growth  of  the  whole  larynx.  The  change  in  the  mucous  mem- 
brane may  come  on  quite  suddenly,  the  voice  '"breaking"  for 
instance  in  the  course  of  a  night. 


.   Sec.  2.    Speech. 

Vowels. 

Every  sound,  or  every  note  (for  all  vocal  sounds  when 
considered  by  themselves  are  musical  sounds),  caused  by 
the  vibrations  of  the  vocal  cords,  besides  its  loudness  due 

*  De  la  Yoix,  Paris,  1877. 


884  SPECIAL    MUSCULAR    MECHANISMS. 

to  tile  force  of  the  expiratory  blast,  and  its  pitch  due  to 
the  tension  of  the  cords,  has  a  quality  of  its  own.  due  to 
the  number  and  relative  prominence  of  the  overtones  which 
accompany  the  fundamental  tone.  Some  of  these  features 
which  make  up  the  quality  are  imposed  on  the  note  ity  the 
nature  of  the  vocal  cords,  but  still  more  arise  from  various 
modifications  which  the  relative  intensities  of  the  overtones 
undergo  through  the  resonance  of  the  cavity  of  the  mouth 
and  tliroat.  Whenever  we  hear  a  note  sounded  by  the  lar- 
ynx we  are  able  to  recognize  in  it  features  which  enable  us 
to  state  that  one  or  other  of  the  "  vowels  "  is  being  uttered. 
Vowel  sounds  are  in  fact  only  extreme  cases  of  quality,  ex- 
treme prominence  of  certain  overtones  brought  about  by  the 
shape  assumed  by  the  buccal  and  pharyngeal  passages  and 
orifices,  as  the  vibrations  pass  through  them.  Each  vowel 
has  its  appropriate  and  causative  disposition  of  these  parts. 
When  i  ( ee  in  feet)  is  sounded,  the  sounding-tube  of  the 
'upper  air-passages  is  made  as  short  as  ])ossible,  the  larynx 
is  raised  and  the  lips  are  retracted,  the  whole  cavity  of  the 
mouth  taking  on  the  form  of  a  bi'oad  flask  with  a  narrow 
neck.  During  the  giving  out  of  e  (a  in  fat)  the  shape  of 
the  mouth  is  similar,  but  somewhat  longer.  For  the  pro- 
duction of  a  (as  in  father)  the  moutii  is  widely  open,  so  that 
the  buccal  cavit}'  is  of  the  shape  of  a  funnel  with  the  ai)ex 
at  the  i)harynx.  With  o,  the  buccal  cavity  is  again  flask- 
shaped,  witli  the  mouth  more  closed  than  in  a,  but  the  lips, 
instead  of  being  retracted  as  in  i  and  e,  are  somewhat  pro- 
truded, so  that  the  sounding-tube  is  prolonged.  The  greatest 
length  of  the  tube  is  reached  in  u  (oo),  in  which  the  larynx 
is  depressed  and  tlie  lips  protruded  as  much  as  possible. 
While  the  two  latter  vowels  are  being  uttered,  the  general 
form  of  the  l)uccal  cavity  is  that  of  a  tiask  with  a  short  neck 
and  a  small  opening,  the  orifice  being  smaller  for  u  than 
for  0. 

Each  of  these  various  "vowel "  forms  of  the  mouth  possesses 
a  note  of  its  own,  one  towards  which  it  acts  as  a  resonance 
chamber.  Thus,  if  several  tuning-forks  of  various  pitch  be  held 
while  sounding  before  a  mouth  wdiich  has  assumed  the  jjarticular 
form  necessary  for  sounding  U,  it  will  be  found  that  the  resonance 
will  be  particularly  great  with  the  fork  having  the  pitch  of  the 
bass  ft-flat.  Similarly  the  pitch  of  the  treble  h  will  be  more  in- 
tensified by  the  mouth  moulded  to  sound  O,  the  octave  6,  above 
the  treble,  will  correspond  to  A,  another  octave  higher  to  E,  and 
still  an  octave  higher  to  I.  And  it  is  the  experience  of  singers 
that  each  vowel  is  sung  with  peculiar  ease  on  a  note  having  a 


SPEECH.  885 


prominent  overtone  corresponding  to  the  tone  proper  to  the  mouth 
when  moulded  to  utter  the  vowel.  The  precise  nature  of  the 
vowel  sounds,  however,  requires  further  investigation.^ 

As  the  vibrations  are  travelling  through  the  pharyngeal 
and  buccal  cavities,  the  })osterior  nares  are  closed  bv  the 
soft  palate  ;  and  it  may  be  shown,  by  holding  a  flame  before 
tlie  nostril,  that  no  current  of  air  issues  from  tlie  nose  when 
a  vowel  is  properh'  said  or  sung.  When  the  posterior  nares 
are  not  effectually  closed  the  sound  acquires  a  nasal  ciiar- 
acter.  The  same  iiapi)ens  when  the  anterior  nares  are  closed, 
as  when  the  nose  is  held  between  the  fingers,  the  nasal 
chamber  then  foiming  a  cavity  of  resonance. 


Consonants. 

Towels  are,  as  their  name  implies,  the  only  real  vocal 
sounds  ;  it  is  only  on  a  vowel  that  a  note  can  be  said  or 
sung.  Our  speecli,  however,  is  made  up  not  only  of  vowels, 
but  also  of  consonants,  i.  e.,  of  sounds  which  are  produced 
not  by  the  vibrations  of  the  vocal  c  n-ds,  but  b}-  the  expira- 
tory blast  being  in  various  ways  interrupted,  or  otherwise 
modified  in  its  course  through  the  throat  and  mouth. 

The  distinction  between  the  two  is,  however,  not  an  abso- 
lute one,  since,  as  we  have  seen,  the  characters  of  the  several 
vowels  depend  on  the  form  of  tlie  mouth,  and  in  the  pro- 
duction of  some  consonants  (B.  I),  M.  X,  etc.)  vibrations 
of  tlie  vocal  cords  form  a  necessary,  though  adjuvant,  factor. 

Consonants  have  been  classified  according  to  the  place  at 
which  the  characteristic  interruption  or  modification  takes 
place.     Thus  it  may  occur  : 

1.  At  the  lips,  by  the  movement  or  position  of  the  lips  in 
reference  to  each  other  or  to  the  teeth,  giving  rise  to  labial 
consonants. 

2.  At  the  teetii,  by  the  movement  or  position  of  the  front 
part  of  the  tongue  in  reference  to  the  teeth  or  the  hard 
palate,  giving  rise  to  denial  consonants. 

3.  In  tlie  throat,  by  the  movement  or  position  of  the  root 
of  the  tongue  in  reference  to  the  soft  palate  or  phar}nx, 
giving  rise  to  guttural  consonants. 

^  Cf.  Jenkin  and  Ewing,  Nature,  1878,  p.  167,  et  seq. 


886  SPECIAL    MUSCULAR    MECHANISMS. 

Among  the  dentals  again  may  be  distinguished  the  den- 
tals commonly  so  called,  sucli  as  T,  the  sibilants  such  as  S, 
and  the  lingual  L,  all  differing  in  the  relative  position  of 
the  tongue,  teeth,  and  palate. 

Consonants  may  also  be  classified  according  to  the  char- 
acter of  the  movements  which  give  rise  to  them.  Thus  they 
may  be  either  explosive  or  continuous. 

1.  Explosives. — In  these  the  characters  are  given  to  the 
sound  by  the  sudden  establishment  or  removal  of  the  appro- 
priate interruption.  Thus,  in  uttering  the  labial  P,  the  lips 
are  first  closed,  then  an  expiratory  current  of  air  is  driven 
against  them,  and,  upon  their  being  suddenly  opened,  the 
sound  is  generated.  Similarly,  the  dental  T  is  generated 
by  the  sudden  removal  of  the  interruption  caused  by  the 
approximation  of  the  tip  of  the  tongue  to  the  front  of  tlie 
hard  palate,  and  the  guttural  K  by  tlie  sudden  removal  of 
the  interruption  caused  \)y  tlie  approximation  of  the  root  of 
the  tongue  to  the  soft  palate. 

The  lahial  B  differs  from  P,  inasmuch  as  it  is  accompanied 
by  vibrations  of  the  vocal  cords  (that  is,  a  vowel  sound  is 
uttered  at  the  same  time),  and  these  vibrations  continue 
after  the  removal  of  the  interruption.  Hence  B  is  often 
spoken  of  as  being  uttered  with  voice  and  P  without  voice ; 
and  D  and  G  (hard)  with  voice  bear  the  same  relation  to  T 
and  K  without  voice. 

The  continuous  consonants  may  further  be  divided  into: 

2.  Aspirates. — In  these  the  sound  is  generated  by  a  rush 
of  air  through  a  constriction  formed  by  the  partial  closure 
of  the  lips,  or  b}'  the  raising  of  the  tongue  against  the  hard 
or  soft  palate,  etc.  Thus  F  is  sounded  when  the  lips  are 
brought  into  partial,  and  not  as  in  P  and  B  into  complete, 
approximation,  and  a  current  of  air  is  di-iven  through  the 
narrowed  opening.  F  is  uttered  without  any  accompanying 
vibration  of  the  vocal  cords,  i.  e.,  v/ithout  voice.  With  voice 
it  becomes  Y. 

The  sibilant  S  is  formed  by  a  rush  of  air  past  an  obstruc- 
tion caused  l)v  the  partial  closure  of  the  teeth,  the  front  of 
the  tongue  being  depressed  at  tlie  same  time  ;  and  S  accom- 
panied with  vibrations  of  the  vocal  cords  becomes  Z. 

In  Sh  the  dorsal  surface  of  the  tongue  is  raised  so  as  to 
narrow  the  passage  between  that  organ  and  the  palate  for 
a  considerable  portion  of  its  length. 


SPEECH.  887 

Th  is  formed  b}*  placing  the  tongue  between  the  two  par- 
tially open  rows  of  teeth  ;  and  the  hard  and  soft  Th  bear  to 
each  other  the  same  relation  as  do  P  and  B. 

L  is  produced  wiien  the  passage  is  closed  in  the  middle 
by  pressing  the  tip  of  the  tongue  against  the  hard  palate, 
and  the  air  is  allowed  to  escape  at  the  sides  of  the  tongue. 

When  the  constriction  in  an  aspirate  is  formed  by  the 
approximation  of  the  root  of  the  tongue  to  the  soft  palate, 
we  have  the  guttural  CH  (as  in  loch)  without  voice,  and  GH 
(as  in  lough)  with  voice. 

3.  Besonajits. — In  these,  all  of  which  must  have  vibra- 
tions of  the  vocal  cords  as  a  basis,  the  usual  passage  through 
the  mouth  is  closed  either  in  a  labial,  dental,  or  guttural 
fashion,  and  the  peculiar  character  is  given  to  the  sound  by 
the  nasal  chambers  acting  as  a  resonance  cavity.  Thus  in 
M  the  passage  is  closed  b}-  the  approximation  of  the  lips, 
in  N  by  the  approximation  of  the  tongue  to  the  hard  pal- 
ate, and  in  NG  by  the  approximation  of  the  root  of  the 
tongue  to  the  soft  palate. 

4.  The  various  forms  of  R  are  often  spoken  of  as  vibra- 
tory^ the  characteristic  sounds  being  caused  by  the  vibration 
of  some  or  other  of  the  parts  forming  a  constriction  in  the 
vocal  passage.  Thus  the  ordinary  R  is  produced  by  vibra- 
tions of  the  point  of  the  tongue  elevated  against  the  hard 
palate,  the  guttural  R  by  the  vibrations  of  the  uvula  or 
other  parts  of  the  walls  of  the  pharynx;  and  in  some  lan- 
guages there  seems  to  be  an  R  produced  by  the  vibrations 
of  the  lips. 

H  is  caused  by  the  rush  of  air  through  the  widely  open 
glottis.  When,  in  sounding  a  vowel,  the  sound  coincides 
with  a  sudden  change  in  the  position  of  the  vocal  cords 
from  one  of  divergence  to  one  of  approximation,  the  vowel 
is  pronounced  with  the  i<piritus  a.sper.  When  the  vocal 
cords  are  brought  together  before  the  blast  of  air  begins, 
the  vowel  is  pronounced  with  the  spiritua  lenis.  The  Arabic 
H  is  produced  by  closing  the  rima  vocalis,  the  epiglottis 
and  false  vocal  cords  being  depressed,  and  sending  a  blast 
of  air  through  the  rima  respiratoria. 

On  many  of  the  above  points,  however,  there  are  great 
ditierences  of  opinion,  the  discussion  of  which  as  well  as  of 
other  more  rare  consonantal  sounds  would  lead  us  too  far 
away  from  the  purpose  of  this  book.     The  following  tabular 


888 


SPECIAL    MUSCULAR    MECHANISMS. 


statement  must  therefore  be   regarded   as   introduced   for 
convenience  only. 


Explosives. 

Labials^ 

without  voice, 

.     P. 

ii. 

with  voice,  . 

.     B. 

Dentals, 

without  voice, 

.     T. 

i  <. 

with  voice,  . 

.     D. 

Gutturals 

,  without  voice, 

.    K. 

u 

with  voice,  . 

.     G  (hard). 

Aspirates. 

Labials, 

without  voice, 

.     F. 

Ci, 

witli  voice,  . 

.    V. 

Dentals, 

without  voice, 

.     S,L,Sh,Th(hard). 

b( 

with  voice,  . 

.     Z,  Zh(ino2*n-e,  the 
Frenchj),Th(soft). 

Gutturals. 

,  without  voice, 

.     CH  (as  in  loch). 

u 

with  voice,  . 

.     GH  (as  in  lough). 

Resonants. 

Labial, 

.     M. 

Dental, 

. 

.     N. 

Guttural, 

.     NG. 

Vibratory. 

Labial, 

not  known  in 

European  speech. 

Dental, 

R  (common). 

Guttural, 

R  (guttural). 

Whispering  is  speech  witliout  any  employment  of  the 
vocal  cords,  and  is  etiected  chiefly  by  the  lips  and  tongue. 
Hence  in  whispering  the  distinction  between  consonants 
needing  and  those  not  needing  voice,  such  as  13  and  P,  be- 
comes for  the  most  part  lost. 


Sec.  3.   Locomotor  Mechanisms. 

The  skeletal  muscles  are  for  the  most  part  arranged  to  act 
on  the  bones  and  cartilages  as  on  levers,  examples  of  the  first 
kind  of  lever  being  rare,  and  those  of  the  third  kind,  where 
the  power  is  applied  nearer  to  the  fulcrum  than  is  the  weight, 
being  more  common  than  the  second.  (Fig.  285.)  This 
arises  from  the  fact  that  the  movements  of  the  body  are  chiefly 
directed  to  moving  comparatively  light  weights  througli  a 
great  distance,  or  through  a  certain  distance  with  great  pre- 
cision, rather  than  to  moving  heavy  weights  through  a  short 
distance.  The  fulcrum  is  generally  supplied  by  a  {perfect 
or  imperfect)  joint,  and  one  end  of  the  acting  muscle  is  made 
fast  by  being  attached  either  to  a  fixed  point,  or  to  some 
point  rendered  fixed  for  the  time  being  liy  the  contraction 
of  other  muscles.  There  are  few  movements  of  the  body 
in  which  one  muscle  only  is  concerned  ;  in  the  majority  of 


LOCOMOTOR    MECHANISMS. 


889 


cases  several  muscles  act  together  in  concert ;  nearly-  all  our 
movements  are  co-ordinate  movements.  Where  gravity  or 
the  elastic  reaction  of  tlie  parts  acted  on  does  not  afford  a 
sufficient  antagonism  to  the  contraction  of  a  muscle  or  group 

[Fig.  23.5. 


Illustration  of  the  Third  Kind  of  Lever.     F,  fulcriini  ;  P,  power;  W,  weight.] 

of  muscles,  the  return  to  the  condition  of  equilibrium  is 
provided  for  hy  the  action  either  elastic  or  contractile  of  a  set 
of  antagonistic  muscles;  this  is  seen  in  the  case  of  the 
face. 


The  erect  posture,  in  which  the  weight  of  the  body  is 
borne  by  the  plantar  arches,  is  the  result  of  a  series  of  con- 
tractions of  tlie  muscles  of  the  trunk  and  legs,  having  for 
their  object  the  keeping  the  body  in  such  a  position  that  the 
line  of  gravity  falls  within  the  area  of  the  feet.  That  this 
does  require  muscular  exertion  is  sliown  by  the  facts,  that 
a  person  when  standing  perfectly  at  rest  in  a  completely 
balanced  position  falls  when  he  becomes  unconscious,  and 
that  a  dead  body  cannot  be  set  on  its  feet.  The  line  of 
gravity  of  the  head  falls  in  front  of  the  occipital  articula- 
tion, as  is  shown  by  the  nodding  of  the  head  in  sleep.  The 
centre  of  giavity  of  the  combined  head  and  trunk  lies  at 
about  the  level  of  the  ensiform  cartilage,  in  front  of  the 
tenth  dorsal  vertebra,  and  the  line  of  gravity  drawn  from 
it  passes  l)ehind  a  line  joining  the  centres  of  the  two  hip- 
joints,  so- that  the  erect  body  would  fall  backward  were  it 
not  for  the  action  of  the  mfuscles  passing  from  the  thighs  to 
the  pelvis  assisted  by  the  anterior  ligaments  of  the  hip- 
joints.     The  line  of  gravit\'   of  the  combined  head,  trunk, 


890 


SPECIAL    MUSCULAR    MECHANISMS. 


and  tliiiijhs  fall  moreover  a  little  behind  the  knee-joints,  so 
that  some,  though  little,  muscular  exertion  is  required  to 
prevent  tiie  knees  from  being  bent.  Lastly,  the  line  of  grav- 
it}^  of  the  whole  body  passes  in  front  of  the  line  drawn  be- 
tween the  two  ankle-joints,  the  centre  of  gravity'  of  the  whole 
bod>^  being  placed  at  the  end  of  the  sacrum  ;  hence  some 
exertion  of  the  muscles  of  the  calves  is  required  to  prevent 
the  body  falling  forwards. 

In  walking,  there  is  in  each  step  a  moment  at  which  the 
body  rests  vertically  on  the  foot  of  one,  say  the  left  leg, 
while  the  other,  the  right  leg,  is  inclined  ol^liquely  beliind 
with  the  heel  raised  and  the  toe  resting  on  the  ground. 
(Fig.  237,  2.)     The  right  leg,  slightly  flexed  to  avoid  contact 

[Fig.  236. 


with  the  ground,  is  then  swung  forward  like  a  pendulum  (4), 
tiie  length  of  the  swing  or  step  being  determined  by  the 
length  of  the  leg;  and  tlie  right  toe'  is  brought  to  the  ground. 
On  this  right  toe  as  a  fulcrum,  the  body  is  moved  forward, 
the  centre  of  gravity  of  the  bod}^  describing  a  curve  the  con- 
vexity of  which  is  upward,  and  the  right  leg  necessarily  be- 
coming straight  and  rigid.  As  the  body  moves  forward,  a 
point  will  be  reached  similar  to  that  vvitii  which  we  sui)posed 
the  step  to  be  started,  the  body  resting  vertically  on  the 
left  foot,  and  the  right  leg  being  directed  behind  in  an  oblique 
position.  The  movement  on  the  right  foot  however  carries 
tlie  body  beyond  this  point,  and  in  doing  so  swings  the  left 
leg  forward  until  it  is  the  length  of  a  step  in  advance  of  its 


'  This  indicates  perhaps  what  shoirid  be  done  rather  than  the  actual 
practice ;  most  people  put  the  heel  to  the  ground  first,  the  contact  with 
the  toe  coming  later. 


LOCOMOTOR    MECHANISMS.  891 

previous  position,  and  its  toe  in  turn  forms  a  fulcrum  on 
wliich  the  bod>',  and  with  it  the  right  leg,  is  again  swung  for- 
ward. Hence  in  successive  steps  tlie  centre  of  gravity,  and 
with  it  tlie  top  of  the  head,  dee-cribes  a  series  of  consecutive 
curves,  with  their  convexities  upwards,  ver}'  similar  to  the 
line  of  flight  of  many  birds. 

Since  in  standing  on  both  feet  the  line  of  gravity  falls 
between  the  two  feet,  a  lateral  displacement  of  the  centre 
of  gravity  is  necessary  in  order  to  balance  the  body  on  one 
foot.  Hence  in  walking  tlie  centre  of  gravity  describes  not 
only  a  series  of  vertical,  but  also  a  series  of  horizontal 
curves,  inasmuch  as  at  each  step  the  line  of  gravity  is  made 
to  fall  alternately  on  each  standing  foot.  While  the  left 
leg  is  swinging,  the  line  of  gravity  fiiUs  within  the  area  of 
the  right  foot,  and  the  centre  of  gravity  is  on  the  right  side  of 
the  pelvis.  As  the  left  foot  liecomes  the  standing  foot,  the 
centre  of  gravity  is  shifted  to  the  left  side  of  the  pelvis. 
The  actual  curve  described  by  the  centre  of  gravity  is  there- 
fore a  somewhat  complicated  one,  being  composed  of  verti- 
cal and  horizontal  factors.  The  natural  step  is  the  one 
which  is  determined  by  the  length  of  the  swinging  leg,  since 
this  acts  as  a  pendulum  ;  and  hence  the  step  of  a  long- 
legged  person  is  naturally  longer  than  that  of  a  person  with 
short  legs.  The  length  of  the  step  however  may  be  dimin- 
ished or  increased  by  a  direct  muscular  effort,  as  when  a  line 
of  soldiers  keep  step  in  spite  of  their  having  legs  of  differ- 
ent lengths.  Such  a  mode  of  marching  must  obviouslv  be 
fatiguing,  inasmuch  as  it  involves  an  unnecessar}^  expendi- 
ture of  energy. 

In  slow  walking  there  is  an  appreciable  time  during  which, 
while  one  foot  is  already  in  position  to  serve  as  a  fulcrum, 
the  other,  swinging,  foot  has  not  yet  left  the  ground.  In 
fast  walking  this  period  is  so  much  reduced,  that  one  foot 
leaves  the  ground  the  moment  the  other  touches  it ;  hence 
there  is  practically  no  period  during  which  both  feet  are  on 
the  ground  together. 

When  the  body  is  swung  forward  on  the  one  foot  acting 
as  a  fulcrum  with  such  energy  that  this  foot  leaves  tiie 
ground  before  the  other,  swinging,  foot  has  reached  the 
ground,  there  heing  an  interval  during  which  neither  foot  is 
on  the  ground,  the  person  is  said  to  be  running,  not  walking. 

In  jumping  this  propulsion  of  the  body  takes  place  on 
both  feet  at  the  same  time  ;  in  hopping  it  is  effected  on  one 
foot  onl}'. 


892  SPECIAL    MUSCULAR    MECHANISMS. 

The  locomotion  of  four  footed  animals  is  necessarily  more 
complicated  than  that  of  man.  The  simple  walk,  sucii  as 
that  of  the  horse,  is  executed  in  four  times,  with  a  diagonal 
succession;  thus,  right  fore  leg,  left  hind  leg,  left  fore  leg, 
riglit  hind  leg.  In  the  amble,  such  as  tliat  of  the  camel, 
the  two  feet  of  the  same  side  are  put  down  at  one  and  the 
same  time,  this  movement  being  followed  l)y  a  similar  move- 
ment of  the  other  two  legs  ;  it  corresponds  therefore  very 
closely  to  human  walking.  In  the  trot,  which  corresponds 
to  human  running,  the  two  diagonally  opposite  feet  are 
brought  to  the  ground  at  the  s:une  time,  and  the  body  is 
propelled  forwards  on  them.  Of  the  gallop  and  canter  there 
are  many  varieties,  and  the  movements  become  very  com- 
plicated.^ 

The  other  problems  connected  with  the  action  of  the  va- 
rious skeletal  muscles  of  the  body  are  too  special  to  be  con- 
sidered here. 

'  See  MarcY,  La  Machine  Animale  (1876). 


BOOK    IV. 

THE  TISSUES  AND   MECHANISMS  OF 
REPRODUCTIOX. 

Many  of  the  individual  constituent  parts  of  the  body  are 
capable  of  reproduction,  i.e.,  they  can  give  rise  to  parts 
like  themselves ;  or  they  are  capable  of  regeneration,  i.  e., 
their  places  can  be  taken  by  new  parts  more  or  less  closel3'- 
resembling  themselves.  The  elementary  tissues  undergo 
during  life  a  very  large  amount  of  regeneration.  Thus  the 
old  epithelium  vScales  which  fall  awav  from  the  surface  of 
the  body  are  succeeded  by  new  scales  from  the  underlying 
layers  of  the  epidermis  ;  old  blood-corpuscles  give  place  to 
new  ones  ;  worn-out  muscles,  or  those  which  have  failed 
from  disease,  are  renewed  by  the  accession  of  fresh  fibres ; 
divided  nerves  orow  as^ain  :  broken  bones  are  united  ;  con- 
nective  tissue  seems  to  disappear  and  appear  almost  without 
limit;  new  secreting  cells  take  the  place  of  the  old  ones 
which  are  castotf :  in  fact,  with  tlie  exception  of  some  cases, 
such  as  cartilage,  and  these  doubtful  exceptions,  all  those 
fundamental  tissues  of  the  body  which  do  not  form  part  of 
highly  differentiated  organs  are,  within  limits  fixed  more 
hy  bulk  than  bj^  anything  else,  capable  of  regeneration. 
That  regeneration  by  substitution  of  molecules,  which  is  the 
basis  of  all  life,  is  accompanied  b}'  a  regeneration  by  sub- 
stitution of  mass. 

In  the  higher  animals  regeneration  of  whole  organs  and 
members,  even  of  those  whose  continued  functional  activity 
is  not  essential  to  the  well-being  of  the  bod}',  is  never  wit- 
nessed, though  it  may  be  seen  in  the  lower  animals  ;  the 
digits  of  a  newt  ma}^  be  restored  by  growth,  but  not  those 
of  a  man.  And  the  repair  which  follows  even  partial  de- 
struction of  highly  differentiated  organs,  such  as  the  retina, 
is  in  the  higher  animals  very  imperfect. 

In  tlie  higher  animals  the  reproduction  of  the  w^iole  indi- 
vidual can  be  effected  in  no  other  waj'  than  by  the  process 
of  sexual  generation,  through  which  the  female  representa- 
tive element  or  ovum  is.  under  the  influence   of  the  male 


894      TISSUES    AND    MECHANISMS    OF    REPRODUCTION. 

representative  or  spermatozoon,  developed   into   an   adult 
individual. 

AVe  do  not  purpose  to  enter  here  into  any  of  the  mor- 
phological problems  connected  with  the  series  of  changes 
through  which  the  ovum  becomes  the  adult  being;  or  into 
the  obscure  biological  inquiry  as  to  liow  the  simple,  all  but 
structureless,  ovum  contains  within  itself,  in  potentiality, 
all  its  future  developments,  and  as  to  what  is  the  essential 
nature  of  the  tnale  action.  These  problems  and  questions 
are  fully  discussed  ele^ewhere  ;  they  do  not  properly  enter 
into  a  work  on  physiology,  except  under  tl^e  view  that  all 
biological  problems  are,  when  pushed  far  enough,  physio- 
logical problems.  We  shall  limit  ouiselves  to  a  brief  survey 
of  the  moi*e  important  physiological  phenomena  attendant 
on  the  impregnation  of  tiie  ovum,  and  on  the  nutrition  and 
birth  of  the  embryo. 

\^The  Physiological  Anatomy  of  the  Organs  of  Generation. 

The  female  organs  of  generation  are  anatomically  divided 
into  the  internal  and  external  organs.  The  latter  comprise 
the  labia  majora  and  minora,  tiie  clitoris,  the  hymen,  the 
meatus  urinarius,  the  vulvo-vaginal  glands,  and  the  mucous 
and  sebaceous  glands  which  are  distributed  in  the  mucous 
membrane  covering  the  parts.  The  external  organs  i)lay  a 
A'^ery  subsidiary  part  in  the  function  of  reproduction,  and 
they  will  be  passed  by  with  this  brief  notice. 

The  internal  organs  con  prise  the  vagina,  uterus,  Fal- 
lopian tubes,  and  ovaries. 

The  vagina  is  a  musculo-membranoug  canal,  about  four  to 
six  inches  long,  directed  obliquel}'  upwards  and  backwards, 
and  extending  from  the  hymen  to  the  cervix  uteri,  where  it 
is  attached  at  a  point  a  short  distance  above  the  os  uteri. 
Its  walls  consist  of  an  external  coat  of  longitudinal  muscular 
fibres,  a  middle  erectile  coat,  and  an  internal  mucous  coat. 
Tlie  mucous  membrane  is  continuous  below  with  that  cov- 
ering the  external  genitals,  and  al)ove  with  the  mucous 
meml)rane  lining  the  uterus.  The  anterior  and  posterior 
surfaces  are  marked  by  longitudinal  folds  or  raj)he,  from 
which  a  number  of  transverse  folds  are  given  off.  This  mem- 
brane is  provided  with  mucous  glands,  and  is  thickly  cov- 
ered with  sensitive  papilhe. 

The  uterus  is  a  flattened,  pyriform,  muscular  organ  (Fig. 
237).     Anatomically  it  is  divided  into  the  fundus,  neck,  and 


ANATOMY    OF    THE    ORGANS    OF    GENERATION.       805 


cervix.  The  neck  indicates  the  point  of  division  between 
the  lower  constricted  portion,  which  is  the  cervix,  and  the 
upper  expanded  portion,  the  fundus.  The  cervix,  which 
extends  from  the  neck  to  the  end  of  the  organ,  projects  into 

Fig.  237. 


Diagrammatic  View  of  the  Uterus  and  its  Appendages,  as  seen  from  behind  (from 
Qiiain).  J^— The  uterus  and  upper  part  of  tbe  vagina  have  been  laid  open  by  re- 
moving the  posterior  wall;  the  Fallopian  tube,  round  ligament,  and  ovarian  liga- 
ment have  been  cut  short,  and  the  broad  ligament  removed  on  the  left  side;  u,  the 
upper  part  of  the  uterus;  c,  the  cervix  opposite  the  os  internum;  the  triangular 
shape  of  the  uterine  cavity  is  shown,  and  the  dilatation  of  the  cervical  cavity  with 
the  rugse,  termed  arbor  vitse ;  v,  upper  part  of  the  vagina ;  od,  Fallopian  tube  or  ovi- 
duct; the  narrow  communication  of  its  cavitv  with  that  of  the  cornu  of  the  uterus 
on  each  side  is  seen  ;  /,  round  ligament ;  lo,  ligament  of  the  ovary  ;  o,  ovary  ;  /,  wide 
outer  part  of  the  right  Fallopian  tube;  fi,  its  fimbriated  extremity;  po,  parovarium  ; 
h,  one  of  the  hydatids  frequently  found  connected  with  the  broad  ligament. 


the  vagina,  at  which  point  it  is   raarked  by  a  transverse 
fissure,  called  the  on  uteri. 

The  cavity  of  the  uterus  is  somewhat  triangular  in  shape, 
and  very  much  flattened  antero-posteriorly.  The  inferior  angle 
of  the  cavity  is  continuous  with  the  canal  running  through 
the  cervix  to  the  vagina.  Tlie  superior  angles  are  called  the 
cornua;  at  the  bottom  of  each  is  an  oritice  of  a  Fallopian 
tube.  The  uterus  is  comi)osed  of  three  coats:  a  serous 
(formed  by  the  peritoneum  ).  a  muscular,  and  a  mucous  coat. 
The  mucous  coat  is  continuous  with  that  lining  the  Fal- 
lopian tubes  and  vagina.  It  is  covered  with  columnar 
ciliated  epithelium,  and,  if  examined  with  a  lens,  the  open- 


896       TISSUES    AND    MECHANISMS    OF    REPRODUCTION. 


ingsof  the  mucous  follicles  will  be  seen  to  be  very  profusely 
distributed  over  the  surface.  If  a  vertical  section  be  made 
as  in  Fig.  238,  the  tubules  will  be  seen  to  be  arranged  per- 
pendicularly to  the  surface,  having  a  wavy  course.  In  the 
impregnated    uterus  they   become    much   swollen    and  en- 


Section  of  the  Lining  Membrane  of  a  Human  Uterus  at  the  Period  of  Commencing 
Pregnancy,  showing  the  arrangement  and  otiier  peculiarities  of  the  glands,  d,  d,  d, 
with  their  orifices,  a,  a,  a,  on  the  internal  surface  of  the  organ.  Twice  the  natural 
size. 


larged.  The  mucous  membrane  lining  the  cervix,  on  account 
of  its  peculiar  appearance,  is  called  the  arbor  vitse  uterinus. 

The  Fallopian  tubes  (Fig.  237)  are  about  four  inches  in 
length,  and  extend  from  the  cornua  of  the  uterus  to  the 
ovaries,  where  they  end  in  enlarged  expanded  extremities, 
the  margins  of  whicii  are  covered  b}'  long  slender  processes, 
one  of  them  being  connected  to  the  ovary.  This  portion  of 
the  tul)e  is  called  the  fimbriated  extremity.  The  tubes  are 
composed  of  a  serous,  muscular,  and  mucous  la3^er.  The 
mucous  membrane  is  covered  with  ciliated  columnar  epithe- 
lium. 

The  ovaries  (Fig.  237)  are  flattened  ovoidal  bodies,  whicli 
are  situated  one  on  each  side  of  the  uterus,  and  inclosed 
in  the  folds  of  the  broad  ligaments.  They  are  connected 
with  the  uterus  by  a  ligament,  and  with  the  Fallopian  tube 
by  one  of  its  fimbriae.  They  consist  of  a  fibrous  coat  {tu- 
nica albugiiiea)  which  incloses  the  stroma  of  the  organ. 
(Fig.  231).)  This  is  composed  of  a  soft  vascular  fibrous 
tissue,  having  imbedded  in  it  a  number  of  small  bodies, 
called  Graafian  vesicles,  which  are  in  divers  stages  of  de- 
velopment. These  vesicles  commence  their  development  in 
the  deeper  portions  of  the    ovary,   and  as  they  approach 


ANATOMY  OF  THE  ORGANS  OF  GENERATION.   897 


maturity  gradually  make  their  way  to  the  surface,  where  they 
project  as  prominences,  and  their  capsule  finally  rupturing 
discharge  their  contents  into  the  F'allopian  tube.  Each 
vesicle  consists  of  an  external  coat  formed  by  tlie  ovary,  an 
internal  coat  or  capsule,  and  within  tliis  a  layer  of  cells, 
which  constitutes  the  membrana  granulosa.     The  interior  of 

Fig. 239. 


View  of  a  S-?ctioii  of  the  Prepared  Ovary  of  the  Cat.— After  Schrox.    6-1, 

1,  outer  covering  and  free  border  of  the  ovary  ;  1',  attached  border  ;  2,  the  ova- 
riau  stroma,  presenting  a  fibrous  and  vascular  structure  ;  3,  granular  substance  ly- 
ing external  to  the  fibrous  stroma  ;  4,  bloodvessels;  5,  ovigernis  iu  their  earliest 
stages  occupying  a  part  of  the  granular  layer  near  the  surface  ;  6,  ovigerms  which 
have  begun  to  enlarge  and  to  pass  more  deeply  into  the  ovary  ;  7,  ovigerms  round 
which  the  Graafian  follicle  and  tunica  granulosa  are  now  formed,  and  which  have 
passed  somewhat  deeper  into  the  ovary  and  are  surrounded  by  the  fibrous  stroma; 
8,  more  advanced  Graafian  follicle  with  the  ovum  imbedded  in  the  layer  of  cells 
constituting  the  proligerous  disk ;  9,  the  most  advanced  follicle  containing  the 
ovum,  etc.;  9',  a  follicle  from  which  the  ovum  has  accidentally  escaped;  10,  corpus 
luteum. 


the  vesicle  consists  of  an  albuminous  fluid,  in  which  is  sus- 
pended the  ovule. 

The  Male  Generative  Organs. — The  same  physiological 
interest  is  not  centred  in  the  male  organs  of  generation,  as 
in  those  of  the  female,  the  principal  interest  being  con- 
centrated upon  the  organs  which  secrete  the  male  fluid  by 
which  the  ovule  is  impregnated.  Our  remarks  will  therefore 
be  almost  entirely  confined  to  the  organs  concerned  in  the 
secretion  of  this  fluid. 

The  male  organs  comprise  the  penis  or  organ  of  copula-. 


89(S       TISSUES    AND    MECHANISMS    OF    REPRODUCTION. 

tion,  the  prostate  and  Cowper's  alands,tlie  testicles,  and  vasa 
delerentia  and  vesiculae  seminales. 

The  prostate  gland  surrounds  the  neck  of  the  bladder  and 
commencement  "of  tiie  urethra  (Fig.  240).  It  secretes  a 
milky  fluid,  which  is  conveyed  by  the  prostatic  ducts  to  the 
floor  of  the  uretlira.  Cowper's  glands  are  two  small  glands 
which  are  situated  between  the  layers  of  the  deep  perineal 
fascia  at  the  anterior  part  of  the  membranous  urethra.    They 


Fig.  240 


Fig.  241. 


Fig.  240.— The  Base  of  the  Male  Bladder,  with  the  Vesiculse  Seminales  and  Pros- 
tate Gland.— After  HaLler. 

1,  the  urinary  bladder;  2,  the  longituliual  layer  of  muscular  fibres  ;  .3,  the  pros- 
tate gland;  4,  membranous  portion  of  the  urethra  ;  5,  the  ureters;  6,  bloodvessels; 
7,  left;  8,  right  vas  deferens  ;  9,  left  seminal  vesicle  in  its  natural  position;  10,  ductus 
ejaculatorius  of  the  left  side  traversing  the  prostate  gland  ;  11,  right  seminal  vesicle 
injected  and  unraveled  ;  12,  13,  blind  pouches  of  vesiculs;  14,  right  ductus  ejacula- 
torius travensing  the  prostate. 

Fig.  241.— a,  lobules  ;  b,  vasa  recta;  c,  mediastinum  ;  d,  vasa  efferentia;  e,  body  of 
epididymis;  /,  rete  testes;  g,  globus  minor;  h,  vas  deferens;  i,  tunica  albugineaand 
its  interlobular  reflections  ;  I,  globus  major. 

secrete  a  viscid  fluid,  which  is  conveyed  by  ducts  to  the  floor 
of  the  urethra. 

The  testes  or  testicles  are  two  small  flattened  ovoidal 
glands,  which  are  situated  in  a  musculo-membranous  pouch, 
called  the  scrotum,  and  suspended  by  tlie  spermatic  cords. 
Each  testicle  consists  of  two  parts  :  the  gland  proper  and 
the  epididymis.  The  gland  (Fig.  241)  is  composed  of  an 
outer  fibrous  coat,  the  tunica  albuginea,  this  being  covered 


ANATOMY    OF    THE    ORGANS    OF    GENERATION.       899 

b\'  a  serous  membrane,  tlie  tunica  vaginalis.  The  substance 
of  the  gland  consists  of  a  number  of  pyramidal  lobular 
divisions,  which  are  situated  with  their  bases  towards  the 
surface.  Each  lobule  is  composed  of  several  convoluted 
tuhuli  ^eminiferi,  and  are  separated  from  adjoining  lobules 
by  prolongation  of  fibrous  tissue  from  the  tunica  albuginea. 
The  tubules  are  composed  of  a  homogeneous  basement 
membrane,  which  is  lined  by  granular  nucleated  epithelium, 
in  the  apices  of  the  lobules  they  have  a  straight  course  and 
form  the  vasa  recta.  They  then  enter  the  fii)rou9  tissue  of 
the  mediastinum  (Fig.  241),  and  form  a  plexus  of  tubes 
called  the  rete  /^.s/is,  which  end  in  the  upper  part  of  the 
mediastinum  as  the  vasa  efferentia,  and  these  becoming  very 
mucii  convoluted  foim  the  glohua  major  or  head  of  the  epi- 
didymis. The  tubules  of  the  globus  major  unite  to  form  a 
single  tube,  which  is  very  much  convoluted,  and  constitutes 
the  body  and  gtobuf<  minor  of  the  epididymis,  and  is  then 
continued  from  the  globus  minor  to  the  base  of  the  bladder 
as  the  excretory  duct  or  va>i  d^^ferena. 

Tlie  vas  deferens  commencing  at  the  globus  minor  ascends 
in  the  posterior  part  of  the  spermatic  cord  through  the  sper- 
matic canal  into  the  pelvis,  where  it  runs  to  the  base  of  the 
bladder  and  becomes  enlarged,  sacculated,  and  narrowed, 
and  joins  with  the  duct  of  the  vesicula  seminalis  to  form  a 
common  ejaculatory  duct.  The  walls  of  the  vas  deferens 
are  composed  of  fibrous  and  muscular  tissue,  which  is  lined 
by  a  mucous  membrane  with  columnar  epithelium. 

The  veaiculx  seminalen  are  two  ebmgated  sacculated 
bodies,  placed  external  to  the  vasa  defereutia.  The  struc- 
ture of  the  seminal  vesicles  is  similar  to  that  of  the  vasa 
deferentia,  consisting  of  a  fibro-muscular  wall  lined  with  a 
mucous  membrane,  which  is  covered  by  granular,  nucleated, 
polygonal  epithelium  cells.  These  organs  serve  as  recep- 
tacles for  the  seminal  fluid  secreted  by  the  testes,  and  at  the 
same  time  produce  a  secretion  of  their  own  which  is  added 
to  it.  The  ejaculatory  ducts,  which  are  formed  by  the  union 
of  the  ducts  of  the  vasa  deferentia  and  vesiculre  seminales, 
open  into  the  prostatic  portion  of  the  urethra.  Their  coats 
are  thinner,  but  have  essentially  the  same  structure  as  the 
vasa  deferentia,  with  which  they  are  continuous. 

The  seminal  fluid  is  a  complex  secretion,  being  composed 
of  the  anatomical  elements  or  spermatozoa,  which  are  formed 
in  tlie  testes,  and  of  the  secretions  of  the  vasa  deferentia, 
vesicular  seminales,  the  prostate  and  Cowper's  glands,  and 


900      TISSUES    AND    MECHANISMS    OF    REPRODUCTION. 

the  mucous  glands  of  tlie  urethra.  The  seminal  fluid  is  of 
a  thick,  whitish,  striated  appearance,  and  if  examined  mi- 
croscopically is  seen  to  contain  innumerable  bodies  which 
are  in  active  motion.  These  are  the  spermatozoids,  and 
are  the  essential  male  elements  concerned  in  the  fecundation 
of  the  ovule.  Each  of  these  bodies  (Fig.  242)  consists  of 
a  flattened  ovoidal  head,  having  at  its  base  a  tapering 
caudate  appendage  in  active  vibratile  motion.     These  ana- 

Fici.  242. 


\y 


A,  Spermatozoa  from  the  Human  Vas  Deferens.— After  Kolliker. 
1,  magnified  3-50  diameters ;  2,  magnified  800  diameters;  a,  from  the  side;  b,  from 
above. 
B,  Spermatic  Cells  and  Spermatozoa  of  the  Bull  undergoing  development. — After 

KOLLIKER.     450-1. 
1,  spermatic  cells,  with  one  or  two  nuclei,  one  of  them  clear ;  2,  3,  free  nuclei,  with 
spermatic  filaments  forming;  4,  the  filaments  elongated  and  the  body  widened  ;  5, 
filaments  nearly  fully  developed. 

tomical  elements  were  at  first  considered  animalcula,  but 
they  are  now  looked  upon  as  free  masses  of  protoplasm 
with  ciliary  appendages,  which  endows  them  with  the  power 
of  migration. 

The  spermatozoa  are  developed  from  the  nuclei  of  vesi- 
cles which  are  formed  in  the  tubules  of  the  testes.  The 
nuclei  are  metamorphosed  into  the  heads  of  the  spermato- 
zoa, the  ciliar}-  appendages  being  afterwards  developed  as  a 
sort  of  outgrowth.  Ditterent  stages  of  the  development 
and  other  interesting  features  are  shown  in  the  above  fig- 
ure.] 


MENSTRUATION. 


901 


CHAPTER    I. 

MENSTRUATION. 

From  pubert.y,  which  occurs  at  from  13  to  IT  years  of 
age,  to  the  climacteric,  which  arrives  at  from  45  to  50  years 
of  age,  the  human  female  is  subject  to  a  monthly  discharge 
of  ova  from  the  ovaries,  accompanied  by  special  changes, 
not  only  in  those  organs,  but  also  in  the  Fallopian  tubes  and 
uterns/as  well  as  by  general  changes  in  the  body  at  large, 
the  whole  constituting  ^'  menstruation."  The  essential  event 
in  menstruation  is  the  escape  of  an  ovule  frcm  its  Graatian 
follicle  (Fig.  248).  The  whole  ovary  at  this  time  becomes 
congested,"and  the  ripe  follicle  bulging  from  the  surface  of 
the  ovary  is  grasped  by  the  trumpet-shaped  fringed   open- 


[FiG.  -243. 


Fig.  244. 


Fig.  243.— Section  of  the  Graafian  Follicle  of  a  Mammal,  after  Von  Baer.  1.  Stroma 
of  the  ovary  with  bloodvessels.  2.  Peritoneum.  3  and  4.  Layers  of  the  external 
coat  of  the  Graafian  follicle.  5.  Merabrana  granulosa.  6.  Fluid  of  the  Graafian  fol- 
licle.   7.  Granular  zone,  or  discus  proligerus,  containing  the  ovule  (8). 

Fig.  244.— Ovule  of  the  Sow,  after  Barry.  1.  Germinal  spot.  2.  Germinal  vesicle. 
3.  Yolk.    4.  Zona  pellucida.    5.  Discus  proligerus.    6.  Adherent  granules  or  cells.] 


ing  of  the  Fallopian  tube,  itself  turgid  and  congested;  by 
what  meclianism  this  is  elTeded  is  not  exactly  known.  The 
most  projecting  portion  of  the  wall  of  the  follicle,  which 
has  previously  become  excessively  thin,  is  now  ruptured, 
and  the  ovule,  which  having  left  its  earlier  position,  is  lying 
close  under  the  projecting  surface  of  the  follicle,  escapes, 
together  with  the  cells  of  the  discus  proligerus  (Fig.  244), 
into  the  Fallopian  tube.  Thence  it  travels  downwards,  very 
slowly,  by  the  action  probably  of  the  cilia  li-Jiing  the  tube, 
though  possibly  its  progress  mav  occasionally  be  assisted 
by  the  peristaltic  contractions  of  the  muscular  walls.     The 

7G 


902 


MENSTRUATION. 


stay  of  the  ovule  in  the  Fallopian  tube  may  extend  to  sev- 
eral (lays.  There  is  an  effusion  of  blood  into  the  ruptured 
follicle,  which  is  sul)sequently  followed  by  histological 
changes  in  the  coats  of  the  follicle  resulting  in  a  corpus 
luteuin^  {¥\g.  245).  The  discharge  of  the  ovule  is  accom- 
panied not  only  by  a  congestion  or  erection  of  the  ovary 
and  Fallopian  tube,  but  also  by  marked  changes  in  the 
uterus,  especially  in  the  uterine  mucous  membrane.  While 
the  whole  organ  becomes  congested  and  enlarged,  the  mu- 
cous membrane,  and  especially  the  uterine  glands,  are  dis- 
tinctly h3-pertrophied.  The  swollen  internal  surface  is 
thrown  into  folds  which  almost  obliterate  the  cavity;  and  a 
hsemorrhagic  discharge,  often  considerable  in  extent,  con- 
stituting the  menstrual  or  catamenial  flow,  takes  place  from 
the  greater  part  of  its  surface.  The  blood  as  it  passes 
through  the  vagina  becomes  somewhat  altered  by  the  acid 
secretions  of  that  passage,  and  when  scanty  coagulates  but 
slightly ;  when  the  flow,  however,  is  considerable,  distinct 
clots  may  make  their  appearance.  It  is  not  certain  that 
menstruation,  in  the  human  subject  at  all  events,  is  always 
accompanied  by  a  discharge  of  an  ovule  ;  indeed  cases  have 


[^  The  following  tabular  statement  by  Dalton  expresses  the  principal 
differences  between  the  corpus  luteum  of  the  non-pregnant  and  pregnant 
female : 


Corpus  Luteum  of  Men- 
struation. 


Corpus  Luteum  of 
Pregnancy. 


At  the  end  of .  Three-quarters  of  an  inch  in  diameter;  central  clot  red- 


three  weeks. 
One  mouth, 


Two 


iths, 


Six  months, 


Nine  months, 


dish  ;  convoluted  wall  pale 
Smaller ,     convoluted    wall 

bright  yellow ;    clot   still 

reddish. 
Reduced  to  tlie  condition  of 

an  insio-nificant  cicatrix. 


Absent. 


Absent. 


Larger ;  convoluted  with 
bright  yellow;  clot  still 
reddish. 

Seven-eighths  of  an  incli  in 
diameter;  convoluted  wall 
bright  yellow ;  clot  per- 
fectly decolorized. 

Still  as  large  as  at  end  of 
second  month  ;  clot  fibri- 
nous ;  convoluted  wall 
paler. 

One-half  an  inch  in  diam- 
eter ;  central  clot  con- 
verted into  a  radiating 
cicatrix  ;  the  external 
wall  tolerably  thick  and 
convoluted,  but  without 
any  bright-yellow  color.] 


MENSTRUATION. 


903 


been  recorded  in  which  menstruation  continued  after  what 
appeared  to  be  complete  removal  of  both  ovaries.  And  it 
seems  probable,  also,  that  under  certain  circumstances,  e.r. 
gr.,  coitus,  a  discharge  of  an  ovule  may  take  place  at  other 
times  than  at  the  menstrual  period.  Since,  however,  the 
time  during  which  both  the  ovule  and  the  spermatozoon 
may  remain  in  the  female  passages  alive  and  functionally 
capal)le  is  considerable,  probably  extending  to  some  days, 
coitus  effected  either  some  time  after  or  some  time  before 
the  menstrual  escape  of  an  ovule  might  lead  to  impregna- 
tion and  subsequent  development  of  an  embryo  ;  hence  the 
fact  that  impregnation  may  follow  upon  coitus  at  some  time 

[Fig.  24-^. 


Successive  stages  of  the  formation  of  the  Corpus  Luteum  in  the  Graafian  Follicle 
of  the  Sow,  as  seen  in  vertical  section  ;  at  a  is  shown  the  state  of  the  follicle 
immediately  after  the  expulsion  of  the  ovule,  its  cavity  being  filled  with  blood, 
and  no  ostensible  increase  of  its  epithelial  lining  having  yet  taken  place  ;  at  6,  a 
thickening  of  this  lining  has  become  apparent;  at  e  it  begins  to  present  folds,  which 
are  deepened  at  d,  aud  the  clot  of  blood  is  absorbed  jaori  passu,  and  at  the  same  time 
decoloi-ized ;  a  continuance  of  the  same  process,  as  shown  at  e,f,  g,  h,  forms  the  cor- 
pus luteum,  with  its  delicate  cicatrix.] 

after  or  before  menstruation,  is  no  veiy  cogent  argument  in 
favor  of  the  view  that  such  a  coitus  has  caused  an  indepen- 
dent escape  of  an  oyule.  The  escape  of  the  ovule  is  said 
to  precede,  rather  than  coincide  with  or  follow,  the  cata- 
raenial  flow/  If  no  spermatozoa  come  in  contact  with  the 
ovule  it  dies,  the  uterine  membrane  returns  to  its  normal 
condition,  and  no  trace  of  the  discharge  of  an  ovule  is  left, 
except  the  corpus  luteum  in  the  ovary. 


'  Williams,  Proc.  Eoy.  Soc,  xxiii,  439. 


904  MENSTRUATION. 


According  to  many  authors  the  uterine  mucous  membrane  is 
actually  shed  during  menstruation,  and  subsequently  entirely 
regenerated.  According  to  their  view  the  hfemorrhagic  discharge 
is  due  to  a  positive  ''solution  of  continuity."  In  animals  no 
discharge  of"  blood,  or  a  very  scanty  one,  takes  place  at  "heat " 
or  "■rut;"  hence  this  point  cannot  be  settled  by  comparative 
studies  ;  and  in  the  human  subject  the  interval  which  must 
necessarily  elapse  between  death  and  examination,  is  sufficiently 
long  to  render  investigation  very  difficult.  Williams^  has  brought 
forward  strong  evidence  in  favor  of  an  actual  loss  of  substance 
taking  place.  'According  to  him,  menstruation  is  accompanied 
by  a  rapid  growth  and  subsequent  rapid  degeneration  of  the  mu- 
cous membrane,  for  a  depth  reaching  down  to  that  layer  of  mus- 
cular fibres  which  passes  among  the  deeper  parts  of  the  uterine 
glands.  The  growth  and  degeneration  begin  at  an  abrupt  line 
near  the  cervix,  and  spread  towards  the  fundus.  The  decay 
lays  bare  small  bloodvessels,  from  which  the  haemorrhage  takes 
place. 

It  is  obvious  that  in  these  phenomena  of  menstruation 
we  have  to  deal  with  complicated  reflex  actions  affecting 
not  only  the  vascular  supply  but,  appaienth'  in  a  direct 
manner,  the  nutritive  changes  of  the  organs  concerned. 
Our  studies  on  the  nervous  action  of  secretion  render  it 
easy  for  us  to  conceive  in  a  general  way  how  tlie  several 
events  are  l)rought  about.  It  is  no  more  difficult  to  suppose 
that  the  stimulus  of  the  enlargement  of  a  Graafian  follicle 
causes  nutritive  as  well  as  vascular  clumges  in  the  uterine 
mucous  membrane,  than  it  is  to  suppose  that  the  stimulus 
of  food  in  the  alimentary  canal  causes  those  nutritive 
changes  in  tiie  salivary  glands  or  pancreas  which  constitute 
secretion.  In  the. latter  case  we  can  to  some  extent  trace 
out  the  chain  of  events ;  in  the  former  case  we  hardly  know 
more  than  that  the  maintenance  of  the  lumbar  cord  is  suffi- 
cient, as  far  as  tiie  central  nervous  system  is  concerned,  for 
the  carrying  on  of  the  work.  In  the  case  of  a  dog  observed 
b}'  Goltz,'^  ''heat"  or  menstruation  took  place  as  usual, 
though  the  spinal  cord  had  been  completely  divided  in  the 
dorsal  region  while  the  animal  was  as  yet  a  mere  puppy. 

The  operation  was  performed  in  December,  1873.  In  the  fol- 
lowing May  the  animal  was  in  excellent  health,  and  there  was 
not  the  slightest  indication  that  any  functional  connection  be- 

'  Proc.  Roy.  Soc,  xxii,  297.  See  also  his  8 true.  Muc.  Memb.  of  Ute- 
rus, 1875. 


2  Pflijger's  Archiv,  ix  (1874),  p. 


IMPREGNATION.  905 


tween  the  dorsal  and  lumbar  portions  of  the  spinal  cord  had  been 
re-established.  At  the  end  of  that  month  "  heat  "  came  on,  at- 
tended by  all  the  ordinary  phenomena  psychical  as  well  as  phys- 
ical. Impregnation  was  effected  and  the  animal  became  gravid. 
The  pregnancy,  Uke  the  heat,  was  marked  b}'  all  the  usual  signs  ; 
the  mammary  glands  enlarged,  and  the  usual  mental  accompani- 
ments of  the'^  condition  were  present.  Finall}^  one  living  and 
two  dead  puppies  were  born,  the  first  without  and  the  latter  two 
with  assistance  ;  the  mother  however  sank  soon  afterwards  from 
puerperal  peritonitis.  The  post-mortem  examination  showed 
that  there  had  been  no  regeneration  of  the  divided  spinal  cord ; 
the  two  portions  were  separated  by  more  than  a  centimeter. 

In  tliis  case  the  connection  between  tiie  ovar}-  on  the  one  hand 
and  the  mammary  gland,  brain,  etc.,  on  the  other,  must,  if  a 
nervous  one.  have  been  furnished  by  the  abdominal  sympathetic. 
We  may  however  suppose  that  the  nexus  was  a  chemical  one  ; 
that  the  condition  of  the  ovar}'  and  uterus  effected  a  change  in 
the  blood,  wliich  in  turn  excited  the  mammary  gland  to  increased 
action  and  produced  special  changes  in  the  brain. 


CHAPTER   II. 

IMPREGXATIOK. 

In  coitus  the  discharge  of  the  semen  containing  tlie  sper- 
matozoa is  most  probably  effected  b\'  means  of  the  peri- 
staltic contractions  of  the  vesiculae  seminales  and  vasa  defer- 
entia.  assisted  by  rhythmical  contractions  of  tlie  bulbo- 
cavernosus  muscle,  the  whole  being  a  reflex  act,  the  centre 
of  which  appears  to  be  in  tiie  lumbar  spinal  cord.  Goltz^ 
has  shown  that  in  the  do2,  emission  of  semen  can  be  brousfht 
about  by  stimulation  of  the  glans  penis  after  complete  di- 
vision of  the  spinal  cord  in  the  dorsal  region.  The  emission 
of  semen  is  preceded  by  an  erection  of  tlie  penis.  This  we 
have  already  seen,  p.  274,  is  in   part  at  least  due  to  an  in- 

'  Pfliiger's  Archiv,  viii  (1874),  p.  460. 


906  '  IMPREGNATION. 

creased  vascular  supply  brouglit  about  by  means  of  the 
nervi  erigentes  ;  it  is  probable,  however,  that  the  condition 
is  further  secured  by  a  compression  of  the  efferent  veins  of 
the  corpora  cavernosa  by  means  of  smooth  muscular  fibres 
present  in  those  bodies.  The  semen  being  received  into  the 
female  organs,  which  are  at  the  time  in  a  state  of  turgescence 
resembling  the  erection  of  the  penis,  but  less  marked,  the 
spermatozoa  find  their  way  into  the  Fallopian  tubes,  and 
here  (probably  in  its  upper  part)  come  in  contact  with  the 
ovule. ^  In  the  case  of  some  animals  impregnation  may  take 
place  at  the  ovary  itself.  The  passage  of  the  spermatozoa 
is  most  probably  effected  mainly  by  their  own  vibratile  ac- 
tivity; but  in  some  animals  a  retrograde  peristaltic  move- 
ment travelling  from  the  uterus  along  the  Fallopian  tubes 
has  been  observed;  this  might  assist  in  bringing  the  semen 
to  the  ovule,  but  inasmuch  as  these  movements  are  probably 
parts  of  the  act  of  coitus  and  impregnation  may  be  deferred 
till  some  time  after  that  event,  no  great  stress  can  be  laid 
upon  them. 

The  ascent  of  the  spermatozoa  is  certainly  puzzling  if  the  cilia 
of  the  Fallopian  tubes,  which  act  from  above  downwards,  con- 
tinue their  activity  after  the  escape  of  the  ovule.  The  sperma- 
tozoa directly  they  come  in  contact  with  the  ovule  become  mo- 
tionless ;  this  suggests  that  the  final  cause  of  their  activity  is  to 
enable  them  to  reach  the  ovule. 

As  the  result  of  the  action  of  the  spermatozoa  on  the 
ovule,  the  latter  instead  of  dying  as  when  impregnation 
fails,  awakes  to  great  nutritive  activity  accompanied  by  re- 
markable morphological  changes  ;  it  enlarges  and  develops 
into  an  embryo. 

[Preceding  the  time  of  the  occurrence  of  the  entrance  of  tlie 
spermatozoon  into  the  egg,  certain  anatomical  changes  have 
been  observed  to  occur,  and  in  order  to  thoroughly  under- 
stand these,  as  well  as  the  changes  which  follow  in  the  ovum, 
it  will  be  first  necessary  to  review  the  anatomy  of  the  egg. 

The  ovule  is  a  minute  cell,  the  wall  being  formed  by  a 
structureless,  transparent  membrane,  called  the  zona  pellu- 
cida,  or  vitelline  membrane.  Within  this  is  the  yolk,  or 
vitellus,  which  consists  of  a  granular  semifluid  mass,  having 
suspended   in   it  a  nucleus  or  germinal  vesicle,  containing 

[^  The  uniinpregnated  egg  is  called  the  ovule  in  contradistinction  to  the 
ovum  or  impregnated  egg.] 


IMPREGNATION. 


907 


B.7iucleoIus  or  germinal  spot.     The  germinal  vesicle  consists 
of    a  very  delicate   transparent    homooeneons   membrane, 
which    incloses   a  fluid   with  granules,   and    suspended    in 
it,  an  eccentric  nucleolus  of  a  granular 
and  fibrillated  structure. 

Previous  to  the  occurrence  of  the  im- 
pregnation of  the  ovule  a  very  interesting 
series  of  changes  have  been  ol>served  to 
take  place.  According  to  Balfour.^  tlie 
first  interesting  point  to  be  noticed  is 
the  migration  of  the  germinal  vesicle 
towards  the  cell  wall.  The  vesicular 
wall  then  becomes  wavy  and  gradually 
disappears,  while  at  the  same  time  the 
nucleolus  or  germinal  spot  has  under- 
gone metamorphosis,  so  that  what  re- 
mains of  these  structures  is  a  spindle- 
shaped  mass.  One  extremit\'  of  this 
mass  gradually  projects  through  the 
cell  wall  and  is  thrown  off  as  a  polar 
vesicle.  From  the  other  remaining  por- 
tion a  second  polar  vesicle  is  formed, 
the  part  of  the  mass  then  remaining  in 
the  ovule  being  permanent,  and  is  called 
the  female  pronucleus.  The  next  change 
observed  is  the  appearance  of  a  zone, 
of  radial  stride  around  the  p'ronucleus 
and  its  migration  to  the  centre  of  the 
egg.  The  spermatozoon  then  penetrates 
the  wall  of  the  ovule,  probably  at  the 
point  of  the  formation  of  the  polar  ves- 
icles. The  tail  of  the  spermatozoon  be- 
comes absorbed,  and  the  head  is  meta- 
morphosed into  the  male  pronucleus. 
From  the  male  pronucleus  a  nund^er  of 
radiating  striae  are  given  off  in  all  directions,  and  it  then 
migrates  towards  tjie  female  pronucleus,  and  afterwards 
fuses  with  it,  forming  a  single  or  cleavage  nucleus. 

Cleavage  or  segmentation  of  the  vitellus  then  begins  (Fig. 
246),  ii3'  which  process  the  nucleus  thus  formed  divides  into 
two  parts,  each  taking  with  it  half  of  the  vitelline  mass.  These 
two  divide  into  four,  and  these  four  into  eight,  and  so  on 


Diagrams  of  the  Va- 
rious Stages  of  Cleavage 
of  the  Yolk.— After  Dal- 

TOX. 


^  See  Quarterly  Journal  of  Microscopy,  October,  1878. 


908 


IMPREGNATION. 


Fio.  247 


Impregnated  Egg, 
with  Comiuenceraent 
of   Formation  of   Em 


indefinitely  until  nn  agglomerate  ranss  of  nncleated  cells  re- 
sults, each  of  which  contains  a  part  of  the  cleavage  nucleus. 
This  mass  of  cells  is  called  the  mulberry  mass,  and  the  cells 
constituting  it  arrnnge  themselves  ai)out  the  interior  of  the 
zona  pellucida  and  form  the  blastodermic  vehicle  or  mem- 
hrane.  This  membrane  then  splits  up  into  two  layers,  the 
external  and  internal;  a  third  or  middle  layer  being  aftei'- 
vvards  formed  between  them. 

Immediately  after  the  formation  of  the  two  la^'ers  of  blas- 
toderm, an  opaque  rounded  collection  of  ^mall  cells  occurs, 
called  the  area,  germinativa  or  embryonic 
spot.  (Fig.  247.)  This  spot  then  becomes 
elongated,  and  in  its  longitudinal  axis  the 
first  trace  of  the  embryo  appears  as  a  faint 
line,  termed  the  primitire  trace,  this  being 
in  the  midst  of  a  clear  elongated  mass  of 
cells,  the  area  pellucida,  which  is  itself 
surrounded  b}^  a  more  opaque  zone. 

In  front  of  the  primitive  trace  two  folds 
are  formed  from  which  a  groove  is  pro- 
longed backwards  in  a  line  with  the  primi- 
tive trace.  These  folds  gradually  extend 
bryo;  showing  the  area  along  the  entire  length  of  the  groove,  and 
germinativa  or  embry-  form  the  laminae  c/or.va/e'.s.w-hich  by  grovving, 
ouic  spot,  the  area  pel-  project  more  and  more  above  the  groove, 

lucida,  and  the  priiui-   ^       ,  in  i  •  i       ii 

r  and  gradual  va|)proaching  each  otlier,coa- 

tive  groove  or  trace.—    "'    ^^  &  .'11  ^  i  i  •    i 

After Daltox.  lescc  and  inclose  the  neural  canal,  which 

will  afterwards  contain  the  cerebrospinal 
axis.  At  about  the  same  period  corresponding  to  the  de- 
velopment of  the  dorsal  laminte  similar  laminae  are  given  ofiT 
from  the  under-surface  of  the  blastoderm.  These  are  the 
lamina  ventrale.^,  which,  by  gradually  enlarging  and  finally 
coalescing,  inclose  the  abdominal  cavity.  Beneath  the  floor 
of  the  gi'oove  above  described  a  delicate  whitish  collection 
of  cells  appears.  This  is  the  chorda  dormlis  or  notocliord, 
around  which  are  afterwards  developed  the  bodies  and  pro- 
cesses of  the  vertebra. 

During  this  period  other  changes  have  also  taken  place. 
The  cephalic  and  caudal  extremities  have  become  flexed  and 
form  the  cei)halic  and  caudal  /?t^J^?6r^8  ;  and  the  embryo  also 
being  curved  ujjon  itself  laterally,  the  vitelline  mass  appears 
separated  from  it  by  a  constriction.  This  constriction  gradu- 
ally increasing,  finally  separates  the  vitelline  mass  as  a  vesic- 
ular body,  it  being  connected  with  the  body  of  the  embryo 
by  the  vitelline  duct.  (Fig.  248.)    The  vesicular  body  thus 


IMPREGNATION. 


909 


formerl  is  called  tlie  umbilical  reside.  This  at  first  commu- 
nicates with  the  intestinal  cavity,  but  as  development  pro- 
ceeds the  duct  of  communication  hecosnes  closed  and  tlie 
vesicle  is  merely  attached  by  a  pedicle,  and  finally  disappears 
altogether.     At  the  time  of  the  development  of  the  bloodves- 

Fio.  248. 


(/T^^AV 


Diagraminat  if  Section  showing  the  Relation  in  a  Mammal  and  in  Man  between  the 
Primitive  Alimentary  Canal  and  the  Membranes  of  the  Ovum.  Ttie  stage  rt-pre- 
sented  in  this  diagram  corr^^sponds  to  that  of  the  fifteenth  or  seventeenth  day  in 
tlie  human  embryo,  previous  to  tlie  expansion  of  the  allautois  :  c,  the  villous  cho- 
rion; a,  the  amnion  ;  rt',  the  place  of  convergence  of  the  amnion  and  reflection  of  the 
false  amnion,  a"  a",  or  outer  or  corueus  layer ;  e,  the  head  and  trunk  of  the  embryo, 
comprising  the  primitive  vertebris  and  cere.bro-spinal  axis;  i,  i,  the  simple  alimen- 
tary canal  in  its  upper  and  lower  portions;  v,  the  yolk-sac  or  umbilical  vesicle;  vi, 
the  vitelline  duct ;  u,  the  aflaiitois  connected  by  a  pedicle  with  the  anal  portion  of 
the  alimentary  cai:al. 


sels,  vessels  appear  on  the  surface  of  the  umbilical  vesicle, 
constituting  tlie  vascular  area,  the  chief  vessels  being  the 
omphalo-mes>enteric  arteries  and  veins.  The  vessels  of  the 
vascular  area  absorb  tlie  nutritive  material  contained  within 
the  vesicle  and  convey  it  to  the  embryo  for  its  sustenance. 


910 


IMPREGNATION. 


Slioi'tly  after  the  occurrence  of  the  commencement  of  the 
formation  of  tlie  umbilical  vesicle,  douhle  folds,  formed  of  the 
external  layer  of  the  blastoderm,  are  given  off  from  the  cepha- 
lic and  caudal  extremities  and  laterally,  which  curve  around 
over  the  dorsal  surface  of  the  embryo,  where  they  meet  and  co- 
alesce, and  their  point  of  junction  becoming  al)sorl)ed,  form 
the  amniotic  cavity.  (Figs.  248,  249,  250,\nd  252.)  The 
outer  layer  of  the  fold,  or  false  amnion,  gradually  expands 
and  covers  the  whole  of  the  internal  surface  of  the  vitelline 
membrane,  which  it  ultimately  replaces;  the  inner  layer,  or 
true  amnion,  is  continuous  with  the  skin  of  the  embryo  at 


Fig.  249. 


Fig.  250. 


a,  Chorion  with  villi.  The  villi  are  shown  to  be  best  developed  in  the  part  of  the 
chorion  to  which  the  allantois  is  extending;  this  portion  nltiniately  becomes  the 
placenta  ;  h,  space  between  the  two  layers  of  the  amnion  ;  c,  amniotic  cavity;  d,  sit- 
uation of  the  intestine,  showing  its  connection  with  the  umbilical  vesicle;  e,  um- 
bilical vesicle  ;  /,  situation  of  heart  and  vessels;  g,  allantois. — After  Todd  and  Bow- 
man. 


the  umbilicus,  and  closely  envelops  it.  The  amniotic  cavity 
or  sac  thus  formed  becomes  lilled  with  the  liquor  amnii, 
which  gradually  increases  in  quantity  as  pregnancy  ad- 
vances, up  to  about  the  fifth  or  sixth  month,  when  the  quan- 
tity gradually  decreases  up  to  the  time  of  labor. 

At  about  the  time  of  the  commencement  of  the  develop- 
ment of  the  amnion  a  new  organ,  the  allantois^  appears  as  a 
piriform  mass  of  cells  at  a  point  immediately  posterior  to 
the  vitelline  duct  and  projecting  through  the  same  opening. 
(Fig.  251.)  This  mass  of  cells  undergoes  rapid  growth, 
spreading  itself  between  the  true  and  false  amniotic  folds, 


IMPREGNATION. 


911 


finall}^  completely  inclosing  the  embryo  and  amnion  (Fig. 
252),  becoming  at  the  same  time  adjoined  to  the  false  am- 
nion, when  it  is  developed  into  the  true  chorion.  During 
the  process  of  the  development  of  the  allantois,  it  has  be- 
come ver}'  vascular ;  at  first  there  are  two  arteries  and  two 
veins,  afterwards  one  of  the  veins  disappears.  These  vessels 
constitute  the  umbilical  vessels,  forming  part  of  the  umbili- 
cal cord,  which  connects  the  allantois  with  the  embryo. 
During  the  development  of  the  allantois  it  presents  three 
distinct  anatomical  portions:   a  portion  which  becomes  con- 


FiG.  251. 


Fig.  252. 


Fig.  251.— Diagram  of  Fecuudated  Egg.  a,  umbilical  vesicle  ;  6,  amniotic  cavity; 
c,  allantois. — After  Dalton. 

Fig.  252. — Fecundated  Egg  with  Allantois  nearly  complete,  a,  inner  layer  of  am- 
niotic fold;  b,  outer  layer  of  ditto  ;  c,  point  where  the  amniotic  folds  come  in  con- 
tact. The  allantois  is  seen  penetrating  between  the  outer  and  inner  layers  of  the 
amniotic  folds.  This  figure,  which  represents  only  the  amniotic  folds  and  the  parts 
within  them,  should  be  compared  with  Figs.  249  and  250,  in  which  will  be  found  the 
structures  external  to  these  folds. 


stricted  off,  as  it  were,  from  the  rest  and  forms  the  urinnry 
bladder;  tne  outer  portion  forms  the  chorion,  the  interme- 
diate portion  forming  the  umbilical  cord. 

During  the  development  of  the  embryo  up  to  this  time, 
the  first  chorion  was  formed  by  villosities  formed  on  the 
vitelline  membrane;  and  following  that  by  villosities  de- 
veloped upon  the  false  amnion.  The  allantois  then  becom- 
ing developed,  completely  covers  the  internal  surface  of 
the  false  amnion,  which  then  gradually  disappears  as  a  dis- 
tinct structure.  The  true  chorion  is  then  formed  by  the 
allantois,  v\hich  becomes  covered  by  a  growth  of  a  mul- 
titude of  vascular  shaggj'  tufts  or  villi  (Fig.  253).  These 
villi  at  first  are  distributed  over  the  entire  surface  of  the 
organ,  but  they   soon  commence  disappearing,  except  at 


912 


IMPREGNATION. 


a  small  area  corresponding  to  the  attachment  of  the  pedicle 
wliich  connects  the  allantois  witli  the  emhryo.  At  this  point 
they  become  greatly  increased  in  number  and  also  in  size  and 
vascularity.  These  villi  are  composed  of  a  fibro  granular 
matrix,   in  which  are    numerous   capillary  loops,   and  are 


Fig.  2o3.— Entire  Human  Ovum  of  eighth  week,  sixteen  lines  in  length  (not  reck- 
oning the  tufts);  the  surface  of  the  chorion  partly  smooth  and  partly  rendered 
shaggy  by  the  growth  of  tufts. 

Fig.  254.— Portion  of  one  of  the  Foetal  Villi,  about  to  form  part  of  the  Placenta, 
highly  magnified  :  a,  a,  its  cellular  covering;  b,  b,  b,  its  looped  vessels  ;  c,  c,  its  basis 
of  connective  tissue. 


covered  with  a  layer  of  epithelial  cells  (Fig.  254).  This  por- 
tion of  the  chorion  forms  the  fuetal  portion  of  the  placenta.] 
No  sooner,  however,  have  these  changes  begun  in  the 
ovum  than  correlative  changes,  brought  about  probably  hy 
reflex  action,  but  at  present  most  obscure  in  their  causation, 
take  place  in  the  uterus.  The  mucous  membrane  of  this 
organ,  whether  the  coitus  resulting  in  impregnation  be  co- 


IMPREGNATION.  913 


incident  with  a  menstrunl  period  or  not,  becomes  congested, 
and  a  rapid  growth  tnkts  place,  characteiized  by  a  rapid 
proliferation  ot"  the  epithelial  and  subepithelial  tissues.  Un- 
like the  case  of  menstruation,  however,  this  new  growth 
does  not  give  way  to  immediate  decay  and  haemorrhage,  but 
remains,  and  may  be  distinguished  as  a  new  temporary 
lining  to   the  uterus,  the  so  called  decidua.     Into  this  de- 

[FlG.  255. 


First  stage  of  the  formation  of  the  Decidua  Reflexa  around  the  ovum.] 

cidua  the  ovum,  on  its  descent  from  the  Fallopian  tube,  in 
which  it  has  undergone  developmental  changes,  extending 
most  probably  as  far  at  least  as  the  formation  of  the  blas- 

[FiG.  256. 


More  advanced  stage  of  Decidua  Reflexa.] 

toderm,  if  not  fart.her,  is  received;  and  in  this  it  becomes 
imbedded,  the  new  growth  closing  in  over  it.  (Figs.  255, 
256.)  Meanwhile  the  rest  of  the  uterine  structures,  espe- 
cially tlie  muscular  tissue,  become  also  much  enlarged  ;  as 
pregnancy  advances  a  large  number  of  new  muscular  fibres 
are  formed.  As  the  ovum  continues  to  increase  in  size,  it 
bulges  into  the  cavity  of  the  uterus  carrying  with  it  the  por- 
tion of  the  decidua  which  has  closed  over  it.    Henceforward, 


914 


IMPREGNATION. 


accordingly,  a  distinction  is  made  in  the  now  well-developed 
decidua  between  the  de.cidua  reJJt'xa^  or  that  part  of  the 
memhrane  whicli  covers  the  projecting  ovutn,  and  the  de- 
cidua vera^  or  the  rest  of  the  membrane  lining  the  cavity  of 
the  uterus,  the  two  being  continuous  round  the  base  of  tiie 
projecting  ovum.  That  part  of  the  decidua  which  inter- 
venes between  the  ovum  and  the  nearest  uterine  wall  is  fre- 
quentlj^  spoken  of  as  the  decidua  serotina.  As  the  ovum 
develops  into  the  fcEtus  witii  its  meral)ranes,  the  decidua  re- 
flexa  becomes  pushed  against  the  decidua  vera;  about  the 
end  of  the  third  montii,  in  the  liuman  subject,  the  two  come 
into  complete  contact  all  over,  and  ultimately  the  distinc- 
tion between  them  is  lost.  In  the  regicm  of  the  decidua 
serotina  the  allantoic  vessels  of  the  foetus  develop  a  placenta. 
[In  the  earliest  stages  of  the  development  of  the  placenta, 


Fig.  2.")7. 


Section  of  a  portion  of  a  fully-f Hi.ied  Placenta,  with  the  part  of  the  Uterus  to 
which  it  is  attached,  a,  umbilical  cord  ;  b  b,  section  of  uterus,  showing  tlie  venous 
sinuses ;  c,  c,  c,  branches  of  the  umbilical  vessels ;  d,  d,  curling  arteries  of  the  uterus. 

the  delicate  villous  processes  of  the  chorion  insinuate  them- 
selves into  the  hypertrophied  follicles  of  the  decidua  sero- 
tina.    The  villi  then  undergo  a  rapid  increase  in  size  and 


NUTRITION    OF    THE    EMBRYO.  915 

vascularity,  becoming  branclied  into  secondary  and  tertiary 
ramifications  ;  while  at  the  same  time  corresponding  changes 
are  taking  place  in  the  follicles,  by  which  they  become  greatly 
increased  in  size  and  vascularity,  and  at  the  same  time  form- 
ing diverticula  in  which  are  imbedded  the  ramifications  of 
the  villi.  The  villi  and  follicles  thus  grow  simultaneously, 
and  finally  become  blended  with  each  other  and  are  no  longer 
separate  structures.  The  follicular  bloodvessels  first  form 
capillary  plexuses;  these  vessels,  however,  become  enlarged, 
forming  frequent  anastomoses,  and  finally  coalescing  to  form 
venous  sinuses  {  Fig.  257),  in  which  are  bathed  the  foetal  villi. 
There  is  no  continuity  established  between  the  maternal  and 
foetal  blood  ;  the  interchange  of  nutritive  material  necessary 
for  the  growth  and  development  of  the  foetus  takes  place 
through  the  delicate  walls  of  the  villi.] 

For  further  account  of  the  various  changes  by  which  these 
events  are  brought  about,  as  well  as  of  the  history  of  the 
embryo  itself,  we  must  refer  the  reader  to  anatomical  trea- 
tises. 


CHAPTER  III. 

THE  XUTRITIOX  OF  THE  EMBRYO. 

During  the  development  of  the  chick  within  the  hen's  egg 
tlie  nutritive  material  needed  for  the  growth  first  of  the 
blastoderm,  and  subsequently  of  the  embryo,  is  supplied  by 
the  yolk,  while  the  oxygen  of  the  air  passing  freely  through 
the  porous  shell,  gains  access  to  all  tlie  tissues  both  of  the 
embryo  and  yolk,  either  directly  or  by  the  intervention  of 
the  allantoic  vessels.  Tlie  mammalian  embryo,  during  the 
period  which  precedes  the  extension  of  the  allantoic  ves- 
sels into  the  cavities  of  the  uterine  walls  to  form  the  pla- 


916  NUTRITION    OF    THE    EMBRYO. 

centa,  must  be  nourished  by  direct  difTnsion,  first  from  tlie 
contents  of  the  Fallopian  tube,  and  subsequently  from  tlie 
decidua;  and  its  supply  of  oxygen  must  come  from  the 
same  sources.  All  analogy  would  lead  us  to  suppose  that, 
from  the  very  first,  oxidation  is  goino;  on  in  the  blastodermic 
and  embryonic  structures;  but  the  amount  of  oxygen  actu- 
ally drawn  from  without  is  probably  exceedingly  small 
in  the  early  stages,  seeing  that  nearly  the  whole  energy  of 
the  metabolism  going  on  is  directed  to  the  building  up  of 
structures,  the  expenditure  of  energy  in  the  form  of  either 
heat  or  external  work  being  extremely  small.  The  marked 
increase  of  bulk  which  takes  place  during  the  conversion  of 
the  mulberry  mass  into  the  blastodermic  vesicle,  shows  that 
at  this  epoch  a  relatively  speaking  large  quantity  of  water 
at  least,  and  probably  of  nutritive  matter,  must  pass  from 
without  into  the  ovum ;  and  subsequently^,  though  the 
blastoderm  and  embryo  may  for  some  time  draw  the  ma- 
tei'ial  for  their  continued  construction  at  first  hand  from  the 
yolk  sac  or  umbilical  vesicle,  both  this  and  they  continue 
prol)ably  until  the  allantois  is  formed  to  receive  fresh  ma- 
terial from  the  mother  by  direct  diffusion. 

As  the  thin-walled  allantoic  vessels  come  into  closer  and 
fuller  connection  with  the  maternal  uterine  sinuses,  until  at 
last  in  the  full}^  formed  placenta  the  former  are  freely  bathed 
in  the  blood  streaming  through  the  latter,  the  nutrition  of 
the  embryo  becomes  more  and  more  confined  to  this  si)ecial 
channel.  The  blood  of  the  foetus  flowing  along  the  umbilical 
arteries  effects  exchanges  with  the  venous  blood  of  the  mo- 
ther, and  leaves  the  placenta  by  the  umbilical  vein  richer  in 
oxygen  and  nutritive  material  and  poorer  in  carbonic  acid 
and  excretory  products  than  when  it  issued  from  the  foetus. 

As  far  as  the  gain  of  oxygen  and  the  loss  of  carbonic 
acid  are  concerned  these  are  the  results  of  simple  diffusion. 
Yenous  blood,  as  we  have  already  seen,  always  contains  a 
quantity  of  oxyhoemoglobin,  and  the  quantity  of  this  sub- 
stance present  in  the  blood  of  the  uterine  veins  is  sufficient 
to  supply  all  the  oxygen  that  the  embryo  needs;  the  blood 
of  the  foetus,  containing  less  oxygen  than  even  the  venous 
blood  of  the  mother,  will  take  up  a  certain  though  small 
quantity.  The  foetal  blood  travelling  in  the  umbilical  artery 
must,  in  proportion  to  the  extent  of  the  nutritive  changes 
going  on  in  the  embryo,  possess  a  higher  carbonic  tension 
than  that  in  the  umbilical  vein  or  uterine  sinus  ;  and  by  dif- 
fusion gets  rid  of  this  surplus  during  its  stay  in  the  placenta. 


FCETAL    RESPIRATION.  917 

The  biood  in  the  umbilical  arteries  and  veins  is,  therefore, 
relatively  speakinir.  venous  and  arterial  respectively,  though 
the  small  excess  of  ox\  haemoglobin  in  the  blood  of  the  um- 
bilical vein^  is  insufficient  to  give  it  a  distincth'  arterial 
color,  or  to  distinguish  it  as  sharply  from  the  more  venous 
blood  of  the  umbilical  artery,  as  is  ordinary  arterial  from 
ordinary  venous  blood.  Thus  the  fa?tus  breathes  b}-  means 
of  the  maternal  blood,  in  the  same  way  that  a  tisli  breathes 
by  means  of  the  water  in  which  it  dwells. 

The  blood  of  the  foetus,  according  to  Zuntz,'-  is  very  poor  in 
hsemoglobin  corresponding  to  its  low  oxygen  consumption.  When 
the  mother  is  asphyxiated,  the  fuetus  is  asphyxiated  too,  the  0x3^- 
gen  of  the  latter  passing  back  again  in  the  blood  of  the  former ; 
and  the  asphyxia  thus  produced  in  the  ftetus  is  much  more  rapid 
than  that  which  results  when  the  oxygen  is  used  up  by  the  tis- 
sues of  the  fuetus  alone,  *as  when  the  umbilicus  is  ligatured  and 
the  foetus  not  allowed  to  breathe. 

If  ox^'gen  and  carbonic  acid  thus  pass  by  dift'nsion  to  and 
from  the  mother  and  the  fcetus,  one  might  fairly  expect  that 
ditl'usible  salts,  proteids.  and  carbohydrates  would  be  con- 
veyed to  the  latter,  and  diflusible  excretions  carried  away  to 
the  former,  in  the  same  way  ;  and  if  fats  can  pass  directly 
into  the  portal  blood  during  ordinary  digestion,  there  can 
be  no  reason  for  doubting  tliat  this  class  of  food-stnifs  also 
wouH  find  its  way  to  the  foetus  through  the  placental  struc- 
tures. We  do  know  from  experiment  that  diti\isible  sub- 
stances will  pass  both  from  the  mother  to  the  foetus,  and 
from  the  f(Etns  to  the  mother  ;  but  we  have  no  definite 
knowledge  as  to  the  exact  form  and  manner  in  which,  during 
normal  intra-uterine  life,  nutritive  materials  are  conveyed  to 
or  excretions  conveyed  from  the  growing  young.  The  pla- 
centa is  remarkable  for  the  great  development  of  cellular 
structures,  apparently  of  an  epithelial  nature,  on  the  border- 
land between  the  maternal  and  fcetal  elements  ;  and  it  has 
been  suggested  that  these  form  a  temporary  digestive  and 
secretory  (excretory)  organ.  But  we  have  no  exact  knowl- 
edge of  what  actuail}'  does  take  place  in  these  structures. 
From  the  cotyledons  of  ruminants  may  be  obtained  a  white 
creamydooking  fluid,  which  from  many  features  of  its  chemi- 

^  Zweifel,  Arch,  fiir  Gynakologie,  ix,  Hft.  2. 
^  Ptliiger's  Archly,  xiy  (1877),  p.  605. 

77 


918  NUTRITION    OF    THE    EMBRYO. 

Cfil  composition  might  be  almost  spoken  of  as  a  "  uterine 
milk." 

Speaking  broadly,  the  foetus  lives  on  the  blood  of  its 
mother,  very  much  in  the  same  way  as  all  the  tissues  of  any 
animal  live  on  the  blood  of  the  body  of  which  ihey  are  the 
parts. 

For  a  long  time  all  the  embryonic  tissues  are  "proto- 
plasmic "  in  cliaracter  ;  that  is,  the  gradually  differentiating 
elements  of  the  several  tissues  remain  still  imbedded,  so  to 
speak,  in  undifferentiated  protoplasm ;  and  during  this 
period  there  must  be  a  general  similarity  in  the  metabolism 
going  on  in  various  parts  of  the  body.  As  differentiation 
l)ecomes  more  and  more  marked,  it  obviously  would  be  an 
economical  advantage  for  partially  elaborated  material  to 
be  stored  up  in  various  foital  tissues,  so  as  to  be  ready 
for  immediate  use  wdien  a  demand  arose  for  it,  rather  than 
for  a  special  call  to  be  made  at  each  occasion  upon  the 
mother  for  comparatively  raw  material  needing  subsequent 
preparatory  changes.  Accordingly,  we  find  the  tissues  of 
the  foetus  at  a  very  early  period  loaded  wMth  glycogen.  The 
muscles  are  especially  rich  in  this  sul)stance,  but  it  occurs 
in  other  tissues  as  well.  The  abundance  of  it  in  the  former 
may  be  explained  partly  by  the  fact  that  they  form  a  very 
large  proportion  of  the  total  mass  of  the  foetal  bod}^  and 
partly  by  the  fact  that,  while  during  the  presence  of  the 
glycogen  they  contain  much  undifferentiated  protoplasm, 
they  are  exactl}'  the  organs  which  will  ultimately  undergo 
a  large  amount  of  differentiation,  and  therefore  need  a  la»-ge 
amount  of  material  for  tiie  metabolism  which  the  differen- 
tiation entails.  It  is  not  until  the  later  stages  of  intra- 
uterine life,  at  about  the  fifth  month,  when  it  is  largely  dis- 
appearing from  the  muscles,  that  the  glycogen  begins  to  be 
deposited  in  the  liver.  By  this  time  histological  differen- 
tiation has  advanced  largely,  and  the  use  of  the  glycogen 
to  the  economy  has  become  that  to  which  it  is  put  in  the 
ordinary  life  of  the  animal;  hence  we  find  it  deposited  in 
the  usual  place  Besides  being  present  in  the  foetal,  glyco- 
gen is  found  also  in  the  placental  structures  ;  but  here 
probably  it  is  of  use,  not  for  the  foetus,  but  for  the  nutri- 
tion and  growth  of  the  placental  structures  themselves.  We 
do  not  know  how  much  carbohydrate  material  finds  its  way 
into  the  umbilical  vein  ;  and  we  cannot  therefore  state  what 
is  the  source  of  the  foetal  glycogen;  but  it  is  at  least  pos- 
sible, not  to  say  probable,  that  it  arises,  as  we  have  reason 


F(ETAL    CIRCULATION.  919 

(p.  555)  to  think  it  may,  from  a  splitting  up  of  proteid  ma- 
terial. 

Concerning  the  rise  and  development  of  the  functional 
activities  of  the  emln-yo,  our  knowledtre  is  almost  a  blank. 
We  know  scarcely  anything  about  tlie  various  steps  b}'  which 
tiie  primary  fundamental  qualities  of  the  protoplasm  of  the 
ovum  are  differentiated  into  the  complex  phenomena  wliicli 
we  have  attempted  in  this  book  to  expound.  We  can  liardly 
state  more  than  that  while  muscular  contractility  becomes 
early  developed,  and  the  heart  probably,  as  in  the  chick, 
heats  even  before  the  blood-corpuscles  are  formed,  move- 
ments of  the  foetus  do  not,  in  the  human  subject,  become 
pronounced  until  after  the  fifth  month  ;  from  that  time  for- 
ward they  increase  and  subsequently  become  ver}^  marked. 
They  are  often  spoken  of  as  reflex  in  character;  but  only  a 
preconceived  bias  would  prevent  them  from  being  regarded 
as  largely  automatic.  The  digestive  functions  are  naturally, 
in  the  absence  of  all  food  from  the  alimentary  canal,  in 
abeyance.  Though  pepsin  may  be  found  in  the  gastric 
membrane  at  about  the  fourth  month,  it  is  doubtful  whether 
a  truly  peptic  gastric  juice  is  secreted  during  intra-uterine 
life;  trypsin  appears  in  the  pancreas  somewhat  later,  but 
an  amylolytic  ferment  cannot  be  obtained  from  tiiat  organ 
till  after  birtli.^  Tlie  excretory  functions  of  tiie  liver  are 
developed  early,  and  about  the  third  month  bile-pigment 
and  i)ile-salts  fim]  their  way  into  the  intestine.  The  quan- 
tity of  bile  secreted  during  intra-uterine  life,  accumulates 
in  the  intestine  and  especially  in  the  rectum,  forming,  to- 
gether with  the  smaller  secretion  of  the  rest  of  the  canal, 
and  some  desquamated  epithelium,  the  so-called  meconium. 
Bile-salts,  both  unaltered  and  variously  changed,  the  usual 
bile-pigment,  and  cholesterin,  are  all  present  in  the  me- 
conium. The  distinct  formation  of  bile  is  an  indication 
that  the  products  of  fatal  metabolism  are  no  longer  wholly 
carried  off  by  the  maternal  circulation  ;  and  to  the  ex- 
cretory function  of  the  liver  are  now  added  those  of  the 
skin  and  kidney.  The  substances  escaping  by  these  or- 
gans find  their  way  into  the  allantois  or  into  the  amnion, 
according  to  the  arrangement  of  tlie  foetal  membranes  in 
difiTerent  classes  of  animals;  in  both  these  fluids  urea 
representatives  liave  been  found  as  welk  as  the  ordinary 
saline  constituents  ;  the  latter  may  or   may  not  have   been 

1  Langendorft:  Arch.  f.  Anat.  u.  Phys.  (Phys.  Abth.)  1879,  p.  90.  Cf. 
Moriggia,  Mrtleschott's  Untersuch.,  xi  (1875),  p.  455. 


920  NUTRITION    OF    THE    EMBRYO. 

actually  secreted.  From  the  allantoic  fluid  of  ruminants  the 
body  allantoin  has  heen  obtained,  and  human  and  other  am- 
niotic fluids  have  been  found  to  contain  urea. 

Zuntz,^  however,  argues  that  since  sodium  sulphindigolate  in- 
jected into  the  veins  of  the  mother  (rabbits)  is  readily  found  in 
the  fluid  of  tlie  amnion  but  not  in  any  part  of  the  body  of  the 
fcetus  (save  a  small  quantity  in  the  stomach  probably  derived 
from  amniotic  fluid  which  had  been  swallowed),  the  fluid  must 
be  discharged  from  the  maternal  structures  and  cannot,  at  all 
events,  be  regarded  as  wholly  a  secretion  from  the  foetus.  The 
sulphindigolate  also  made  its  way  into  the  amnion  when  the 
foetus  had  been  previously  killed.  The  urea  of  the  amniotic  fluid 
may  accordingly,  in  part  at  least,  have  escaped  by  difl'usion 
from  the  blood  of  the  mother. - 

The  date  at  which  pepsin  and  other  ferments  make  their  ap- 
pearance in  the  embryo  appears  to  differ  in  different  animals.^ 

About  the  middle  of  intra-uterine  life,  when  the  foetal  cir- 
culation (Fig.  258)  is  in  full  development,  the  blood  flowing 
along  the  umbilical  vein  is  carried  chiefly  l\v  the  ductus  veno- 
sus  into  the  infeiior  vena  cava  and  so  into  the  right  auricle. 
Thence  it  is  directed  by  the  valve  of  Eustachius  through  the 
foramen  ovale  into  the  left  auricle,  passing  from  which  into 
the  left  ventricle  it  is  driven  into  the  aorta.  Part  of  the 
umbilical  blood,  however,  instead  of  passing  directly  to  the 
inferior  cava,  enters  by  the  portal  vein  into  the  hepatic  cir- 
culation, from  which  it  returns  to  the  inferior  cava  by  the 
hepatic  veins.  The  inferior  cava  also  contains  blood  coming 
from  the  lower  liml)S  and  lower  truidc.  Hence  the  blood 
which  passing  from  the  right  auricle  into  the  left  auricle 
through  the  foramen  ovale  is  distributed  by  the  left  ventricle 
through  tlie  aortic  arch,  though  chiefly  blood  coming  direct 
from  the  placenta,  is  also  blood  which  on  its  wa}^  from  the 
placenta  has  passed  through  the  liver  and  blood  derived 
from  the  tissues  of  the  lower  part  of  the  body  of  the  foetus. 
The  blood  descending  as  foetal  venous  blood  from  the  head 
and  limbs  by  the  superior  vena  cava  does  not  mingle  with 
that  of  the  inferior  vena  cava,  but  falls  into  the  right  ven- 
tricle, from  which  it  is  discharged  through  the  ductus  ar- 
teriosus (Botalli)  into  the  aorta,  below  the  arch,  whence  it 
flows  partly  to  the  lower  trunk  and  limbs,  but  chiefly  by  the 

'  Pflui?er's  Archiv,  xvi  (1878),  p.  548. 

2  Cf.  Fehh'ng,  Arch.  f.  Gynak.,  xiv  (1879),  p.  221. 

^  Landendorff,  op.  cit.     Sevvall,  Journal  of  Physiol.,  i  (1878),  p.  321. 


FCETAL    CIRCULATION. 


921 


nmbilifal  arteries   to  the   placenta.     A  small  quantity  only 
of  the  contents  of  the  right  ventricle  finds  its  way  into  the 


Diagram  of  the  Fcetal  Circulation.  1,  the  umbilical  cord,  consisting  of  the  um- 
bilical vein  and  two  umbilical  arteries,  proceeding  from  the  placenta  (2) ;  3,  the  um- 
bilical vein  dividing  into  three  branches,  two  (4,  4)  to  be  distributed  to  the  liver,  and 
one  (5),  the  ductus  venosus,  wliich  enters  the  inferior  vena  cava  (6) ;  7,the  portal  vein, 
returning  the  blood  from  the  intestines,  and  uniting  with  the  right  hepatic  branch  ;  8, 
the  right  auricle  ;  the  course  of  the  blood  is  denoted  by  the  arrow  proceeding  from  8  to 
9,  the  left  auricle ;  10,  the  left  ventricle  ;  the  blood  following  the  arrow  to  t  he  arch  of 
the  aorta  (11),  to  bedistributfd  through  the  branches  given  off  by  the  arch  to  the  head 
and  upper  extremities;  the  arrows  12  and  13  represent  the  return  of  the  blood  from  the 
head  and  upper  extremities  through  the  jugular  and  subclavian  veins  to  the  supe- 
rior vena  cava  (14),  to  the  right  auricle  (8),  and  in  the  coarse  of  the  arrow  through 
the  right  ventricle  (15),  to  the  pulmonary  artery  (16) ;  17,  the  ductus  arteriosus,  which 


922  NUTRITION    OF    THE    EMBRYO. 


appears  to  be  a  proper  continuation  of  the  pulmonary  artery ;  the  offsots  at  eanh 
side  are  the  right  and  left  pulmonary  arteries  cut  olf.  The  ductus  arteriosus  joins 
the  descending  aorta  (18,  18),  which  divides  into  the  common  iliacs,  and  these  into 
the  internal  iliacs,  which  become  the  umbilical  arteries  (19),  and  return  the  blood 
along  the  umbilical  cord  to  the  placenta,  and  the  external  iliacs  (20),  which  are  con- 
tinued into  the  lower  extremities.  The  arrows  at  the  termination  of  these  vessels 
mark  the  return  of  the  venous  blood  by  the  veins  to  the  iuferior  cava.] 

lungs.  Now  the  blood  which  comes  from  the  placenta  by 
the  umbilical  vein  direct  into  the  right  auricle  is,  as  far  as 
the  fcEtus  is  concerned,  arterial  blood  ;  and  the  portion  of 
umbilical  blood  whicli  traverses  the  liver  probably'  loses  at 
this  epoch  vei\y  little  ox3gen  during  its  transit  through  tliat 
gland,  th.e  liver  being  at  tliis  period  a  simple  excretory 
ratlier  than  an  actively'  metabolic  organ.  Hence  the  blood 
of  the  inferior  vena  cava,  though  mixed,  is  on  tiie  whole  ar- 
terial blood;  and  it  is  this  blood  which  is  sent  by  the  left 
ventricle  through  the  arch  of  the  aorta  into  the  carotid  and 
subclavian  arteries,  Thus  the  head  of  the  foetus  is  provided 
with  blood  comparatively  rich  in  oxygen.  The  blood  de- 
scending from  the  head  and  upper  limbs  by  the  superior 
vena  cava  is  distinctly  venous;  and  this  passing  from  the 
right  ventricle  by  the  ductus  arteriosus  is  driven  along  tlie 
descending  aorta,  and  together  with  some  of  the  blood 
}3assing  from  the  left  ventricle  round  the  aortic  arch  falls 
into  the  uml)ilical  arteries  and  so  reaches  the  placenta.  The 
foetal  circulation  then  is  so  arranged,  that  while  the  most 
distinctly  venous  blood  is  driven  l>y  the  right  ventricle  back 
to  the  placenta  to  be  oxygenate<l,  the  most  distinctly  arte- 
rial (but  still  mixed)  l)Iood  is  driven  by  the  left  ventricle  to 
the  cerebral  structures,  which  have  more  need  of  oxygen 
tiian  the  other  tissues.  In  the  later  stages  of  pregnancy 
the  mixture  of  the  various  kinds  of  blood  in  the  right 
auricle  increases  pieparatory  to  the  changes  taking  place 
at  birth.  But  during  the  whole  time  of  intra-uterine  life 
the  amount  of  oxygen  in  the  blood  passing  from  the  aortic 
arch  to  the  medulla  oblongata  is  sufficient  to  prevent  any 
inspiratory  impulses  being  originated  in  the  medullary  re- 
spiratory centre.  This  during  the  whole  period  elapsing 
l)etween  the  date  of  its  structural  establishment,  or  rather 
the  consequent  full  development  of  its  irritability,  and  the 
epoch  of  birth,  remains  dormant;  the  oxygen-supply  to  the 
protoplasm  of  its  nerve  cells  is  never  brought  so  low  as  to 
set  going  the  respiratory  molecular  explosions.  As  soon, 
liowever,  as  the  intercourse  between  the  maternal  and  um- 


F(ETAL    CIRCULATION.  923 

bilical  blood  is  interrupted  by  separation  of  the  placenta  or 
bv  ligature  of  the  umbilical  cord,  or  when  in  any  other  way 
blood  of  sufficiently  arterial  quality  ceases  to  find  its  way  by 
the  left  ventricle  to  the  medulla  oblongata,  the  supply  of 
oxygen  in  the  respiratory  centre  sinks,  and  when  the  fall 
has  reached  a  certain  point  an  impulse  of  inspiration  is 
generated  and  the  foetus  for  the  first  time  breathes.  Through 
this  first  inspiratory  movement  the  thorax,  by  an  upward 
movement  of  the  ribs,  is  permanenth^  enlarged,  and  the 
bings  assume  that  condition  of  partial  distension  which  we 
studied  ^p.  420)  in  treating  of  respiration.^  When  the  first 
breath  is  taken,  as  under  normal  circumstances  it  is,  with 
free  access  to  the  atmosphere,  the  lungs  become  filled  with 
air,  and  the  scanty  supply  of  blood  which  at  the  moment 
was  passing  from  the  right  ventricle  along  the  pulmonary 
artery  returns  to  the  left  auricle  brighter  and  richer  in 
oxygen  than  ever  was  the  foetal  blood  before.  With  the 
diminution  of  resistance  in  the  pulmonary  circulation  caused 
by  the  expansion  of  the  thorax,  a  larger  supply  of  blood 
passes  into  the  pulmonary  artery  instead  of  into  the  ductus 
arteriosus,  and  this  derivation  of  the  contents  of  the  right 
ventricle  increasing  with  the  continued  respiratory  move- 
ments, the  current  through  the  latter  canal  at  least  ceases 
altogether,  and  its  channel  shortly  after  birth  becomes  ob- 
literated. Corresponding  to  the  greater  flow  into  the  pul- 
monary artery,  a  larger  and  larger  quantity  of  blood  returns 
from  the  pulmonary  veins  into  the  left  auricle.  At  the  same 
time  the  current  through  the  ductus  venosus  from  the  um- 
bilical vein  having  ceased,  the  flow  from  the  inferior  cava 
has  diminished;  and  the  blood  of  the  right  auricle  finding 
little  resistance  in  the  direction  of  the  ventricle,  which  now 
readily  discharges  its  contents  into  the  pulmonary  artery 
(where  as  we  have  seen  (p.  211)  the  mean  pressure  and  the 
peripheral  resistance  are  very  low),  but  finding  in  the  left 
auricle,  whicli  is  continually  being  filled  from  the  lungs,  an 
obstacle  to  its  passage  through  the  foramen  ovale,  ceases  to 
take  that  course,  and  the  foramen  speedily  becomes  closed. 
Thus  the  foetal  circulation,  in  consequence  of  the  respira- 
tory movements  to  which  its  interruption  gives  rise,  changes 
its  course  into  that  characteristic  of  the  adult. 

^  Bernstein,  Pfliiger's  Archiv,  xvii  (1878),  p.  617. 


924  PARTURITION. 

CHAPTER  IV. 

PARTURITION. 

In  spite  of  the  increasing  distension  of  its  cavity,  the 
uterns  remains  quiescent,  as  far  as  any  marked  muscular 
contractions  are  concerned,  until  a  certain  time  has  been 
run.  In  tlie  human  subject  the  period  of  gestation  gener- 
ally lasts  from  275  to  280  days,  i.  e.,  about  40  weeks,  the 
general  custom  being  to  expect  parturition  at  about  280 
days  from  tiie  last  menstruation.  Seeing  that,  in  many 
cases,  it  is  uncertain  whether  the  ovum  which  develops 
into  the  embryo  left  the  ovar}^  at  the  menstruation  pie- 
ceding  or  succeeding  coitus,  or,  as  some  have  urged,  inde- 
pendent of  menstruation,  by  reason  of  the  coitus  itself,  an 
exact  determination  of  the  duration  of  pregnancy  is  impos- 
sible. 

In  the  cow  the  period  of  gestation  is  about  280  days,  in  the 
mare  about  350,  sheep  about  150  days,  dog  about  60  days,  rabbit 
about  30  days. 

The  extrusion  of  the  fretus  is  brought  about  partly  by 
rhythmical  contractions  of  the  uterus  itself,  and  partly  by  a 
pressure  exerted  by  the  contraction  of  the  abdominal  mus- 
cles, similar  to  that  descril)ed  in  defecation.  The  contrac- 
tions of  the  uterus  are  the  first  to  appear,  and  their  first 
effect  is  to  bring  about  a  dilation  of  the  os  uteri ;  it  is  not 
till  the  later  stages  of  labor,  while  the  foetus  is  passing  into 
the  vagina,  that  the  abdominal  muscles  are  brought  into 
play. 

The  whole  process  of  parturition  may  be  broadly  consid- 
ered as  a  reflex  act,  the  nervous  centre  being  placed  in  the 
lumbar  cord.  In  a  dog,  whose  dorsal  cord  had  been  com- 
pletely severed  (see  p.  904)  parturition  took  place  as  usual; 
and  tlie  fact  that  in  the  human  sul)jeet  labor  will  progress 
quite  naturall}'  while  the  patient  is  unconscious  from  the 
administration  of  chloroform,  show-s  that  in  woman  also  the 
whole  matter  is  an  involuntary  action,  however  much  it  ma}"" 
be  assisted  by  direct  volitional  efforts.  That  the  uterus  is 
capable  of  being  thrown  into  contractions  through  reflex 
action,  excited  by  stimuli  applied  to  various  afferent  nerves, 
is  well  known.     The  contraction  of  the  uterus,  which  is  so 


UTERINE    CONTRACTIONS.  h2b 

necessary  for  tlie  prevention  of  tlie  licTniorrhnge  after  deliv- 
ery, may  frequently  be  hronglit  about  by  pressure  on  the 
abdomen,  by  the  introduction  of  foreign  bodies  into  tbe 
A'agina,  and  especially  by  the  application  of  tlie  child  to  the 
nipple.  But  we  are  not  thereby  justified  in  considering  the 
rhythmical  contractions  of  the  uterus  during  parturition  as 
simple  reflex  acts  excited  by  the  presence  of  the  foetus.  We 
are  utterly  in  the  dark  as  to  why  the  nterns,  after  remaining 
apparentl}'  perfectly  quiescent  (or  with  contractions  so  slight 
as  to  be  with  ditliculty  apiireciated)  for  months,  is  suddenly 
thrown  into  action,  and  within  it  may  be  a  few  hours  gets 
rid  of  tbe  burden  it  has  borne  with  such  tolerance  for  so  long 
a  time ;  none  of  the  various  hypotheses  which  have  been 
put  forward  can  be  considei'ed  as  satisfactory.  And  until  we 
know  what  starts  the  active  phase,  we  shall  remain  in  ignor- 
ance of  the  exact  manner  in  which  the  activity  is  brought 
about.  The  peculiar  rhythmic  character  of  the  contractions, 
each  ''pain  "  beginning  feebly,  rising  to  a  maxinuim,  then 
declining,  and  finally  dying  away  altogether,  to  be  succeeded 
after  a  pause  b}'  a  similar  pain  just  like  itself,  pain  following 
pain,  like  the  tardy  long-drawn  beats  of  a  slowly  beating 
heart,  suggests  that  the  cause  of  the  rhythmic  contraction  is 
seated,  like  that  of  the  rhythmic  beat  of  the  heart,  in  the 
organ  itself.  And  this  view  is  supported  by  the  fact  that 
contractions  of  the  uterus,  similar  to  those  of  parturition, 
have  been  observed  in  animals  even  after  complete  destruc- 
tion of  the  spinal  cord.  Nevertheless  general  evidence 
supports  the  conclusion  that,  in  a  normal  slate  of  things,  at 
all  events,  the  contractions  of  the  uterus,  like  those  of  the 
lymph-hearts,  are  largely  dependent  on  the  spinal  cord. 

The  action  of  the  abdominal  muscles,  on  the  other  hand, 
is  obviously  a  reflex  act  carried  out  b}'  means  of  the  spinal 
cord,  the  necessary  stimulus  being  supplied  by  the  pressure 
of  the  foetus  in  the  vagina,  or  by  the  contractions  of  the 
uterus.  Hence  the  whole  act  of  parturition  may  with  reason 
be  considered  as  a  reflex  one. 

Whether  it  be  whoJly  a  reflex  or  partly  an  automatic  one, 
the  act  can  readily  be  inhibited  by  the  action  of  the  central 
nervous  system.  Thus  emotions  are  a  very  frequent  cause 
of  the  progress  of  parturition  being  suddenly  stopped  ;  as  is 
well  known,  tlie  entrance  into  the  bedroom  of  a  stranger 
often  causes  for  a  time  the  sudden  and  absolute  cessation  of 
"labor"  pains,  which  previously  may  have  been  even  vio- 
lent.    Judging  from   the  analogy  of  micturition,  between 

78 


926  PARTURITION. 


which  and  parturition  there  are  many  points  of  resemblance, 
we  may  suppose  that  this  inhibition  of  uterine  contractions 
is  brought  about  by  an  inhibition  of  the  centre  in  the  lumbar 
cord. 

Experimental  investigations  into  the  movements  of  the  uterus 
have  been  carried  out  chietly  on  rabbits  and  dogs.  In  these  ani- 
mals, rhythmical  contractions  may  occur  spontaneously  or  be 
icduced  by  direct  stimulation  after  the  connections  of  the  uterus 
with  the  general  nervous  system  have  been  entirely  severed. 
The  application  of  the  interrupted  current  produces  a  local  con- 
traction frequently  accompanied  or  followed  by  a  general  move- 
ment of  the  whole  organ.  This  general  movement  may  fail  to 
make  its  appearance,  especially  in  an  unimpregnated  uterus  (and 
indeed  the  results  of  stimulating  the  uterus,  whether  directly  or 
indirectly,  are  for  some  reason  or  other,  remarkably  inconstant)  ; 
where  it  does  occur,  it  possesses,  like  an  artificially  produced 
heart-beat  (p.  240),  characters  resembling  those  of  a  reflex  act. 

Rhythmical  contractions  of  the  uterus  may  be  induced  by  di- 
rectly stimulating  the  spinal  cord  along  any  part  of  its  course  from 
the  medulla  oblongata  to  the  lumbar  region,  as  well  as  in  a  reflex 
manner  by  stimulation  of  the  central  ends  of  various  spinal 
nerves.^  Stimulation  of  the  cerebellum,  crura  cerebri,  and  other 
parts  of  the  brain  as  high  up  as  the  corpora  striata  and  optic 
thalami,  will  also  give  rise  to  uterine  contractions.-' 

The  movements  brought  about  by  direct  electric  stimulation  of 
the  central  nervous  system  are  more  energetic  when  the  electrodes 
are  applied  low  down,  near  the  lumbar  region  of  the  cord,  than 
when  they  are  applied  high  up,  and  such  contractions  as  are 
caused  by  direct  stimulation  of  various  parts  of  the  brain  are 
comparatively  feeble.  When  the  cord  is  divided  at  the  level  of 
the  tenth  dorsal  vertebra,  stimulation  of  the  cord  above  the  sec- 
tion gives  rise  to  no  movement.''  These  facts  support  the  conclu- 
sion that  the  uterine  centre  is  placed  in  the  lumbar  spinal  cord, 
and  that  the  movements  witnessed  when  parts  higher  up  are 
stimulated  are  due  to  the  lumbar  centre  being  thus  indirectly 
stimulated.  Rohrig  finds  that  reflex  movements  are  more  easily 
induced  by  central  stimulation  of  the  sciatic  or  crural  than  of 
the  brachial  or  other  nerves  of  the  anterior  part  of  the  body ; 
and  especially  energetic  movements  are  witnessed  when  the  cen- 
tral ends  of  "the  ovarian  nerves  are  stimulated.  The  same  ob- 
server states  that  the  contractions  of  the  uterus  which  (in  urarized 
unimpregnated  rabbits)  are  brought  about  by  an  asphyxiated 

1  Schlesinger,  Wien.  Med.  Jahrb.,  i  (1873),  Hft.,  4.  Cyon,  Pfluger's 
Archiv,  viii  (1874),  349.  Basch  and  Hofmann,  Wien.  Med.  Jahrb.,  1877, 
Hft.  4.     Rohrig,  V^irchow's  Archiv,  Bd.  76  (bS79),  p.  1. 

'^  Korner,  Studien  Phys.  Inst.  Breslau,  iii,  34. 

^  Rohrig,  op.  cit. 


PARTURITION.  927 


condition  of  the  blood,  b^- compression  of  the  aorta,  by  strychnia, 
picrotoxin  and  ergotin,  fail  to  appear  if  the  lumbar  cord  be  pre- 
viously destroyed.  These  agents  therefore  he  considers  produce 
their  effect  by  acting  not  directly  on  the  uterus  but  on  the  lumbar 
centre.  The  injection  of  ammonia,  or  ammonia  salts,  into  the 
blood  gives  rise  to  energetic  movements  even  after  complete  de- 
struction of  the  central  nervous  system.  Other  observers  have 
seen  contractions  result  from  asphyxia  after  removal  of  the  spinal 
centre. 

Basch  and  Hofmann^  distinguish,  in  the  dog,  two  paths  along 
which  efferent  impulses  may  pass  from  the  central  nervous  sys- 
tem to  the  uterus  ;  one,  a  sympathetic  tract,  consisting  of  nerves 
]iassing  from  the  inferior  mesenteric  ganglion  (Iving  in  the  dog  at 
the  extreme  end  of  the  aorta)  to  the  Iwpogastric  plexus,  and  the 
other,  a  spinal  tract,  consisting  of  branches  passing  from  the 
sacral  nerves  across  the  pelvis  to  the  same  plexus,  and  being  the 
representatives  in  the  female  of  Eckhard's  nervi  erigentes  in  the 
male  (see  p.  274).  Stimulation  of  the  former  produces  contrac- 
tions of  the  uterus,  cliiefly  circular  in  nature,  with  descent  of  the 
cervix,  and  dilation  of  ttie  os ;  when  the  latter  are  stimulated, 
the  uterus  is  shortened,  as  if  by  longitudinal  contractions,  the 
cervix  ascends,  and  the  os  is  closed.  Both  nerves  apparently  may 
take  part  in  a  contraction  brought  about  in  a  reflex  manner. 
When  one  tract  is  divided,  the  results  of  reflex  stimulation  resem- 
ble those  of  direct  stimulation  of  the  other  tract.  AVhen  both 
tracts  are  divided,  stimulation  of  the  central  end  of  a  spinal 
nerve,  such  as  the  sciatic,  is  without  eftect.  The  sacral  nerves 
sharing  in  this  spinal  tract  are  branches  from  the  first,  second, 
and  occasionally  the  third.  Ri^hrig-  also  finds  (in  the  rabbit)  tv/o 
efferent  paths  from  the  spinal  cord  to  the  uterus,  viz.,  the  uterine 
(sympathetic)  and  the  sacral  (spinal)  nerves  ;  but  he  makes  no 
marked  distinction  of  character  between  them :  he  regards  both 
sets  of  nerves  as  containing  also  afferent  fibres.  Basch  and  Hof- 
mann  further  assert  that  the  sympathetic  tract  contains  vaso- 
constrictor and  the  spinal  tract  vaso-dilator  nerves,  both  of  which 
may  be  thrown  into  action  in  a  reflex  manner,  the  former,  how- 
ever, more  readily  than  the  latter.  The  occurrence  of  contrac- 
tions in  consequence  of  an  asphyxiated  condition  of  the  blood, 
explains  why  when  pregnant  animals  are  asphj'xiated,  an  extru- 
sion of  the  foetus  frequently  takes  place.  There  is  no  evidence, 
however,  that  the  onset  of  labor  is  caused  by  a  gradual  diminution 
of  oxygen  in  the  blood-,  I'eaching  at  last  to  a  climax.  Xor  are 
there  suflicient  facts  to  connect  parturition  with  any  condition  of 
the  ovarj^  resembling  that  of  menstruation. 

After  the  expulsion  of  the  f(vtus,  the  foetal  placenta  sepa- 
rates from  the  uterine  walls,  and  is,  together  with  the  rem- 

1  Op.  cit.  2  Op.  cit. 


928 


THE    PHASES    OF    LIFE. 


nants  of  the  membranes,  expelled  after  it.  The  uterus  then 
falls  into  a  firm  tonic  contraction,  similar  to  that  of  the 
emi)tied  bladder,  by  which  means  haemorrhage  from  the  ves- 
sels torn  by  the  separation  of  the  placenta  is  avoided.  The 
lining  mem!)rane  of  the  nterns  is  gradually  restored,  the 
muscular  elements  are  reduced  by  a  rapid  fatty  degenera- 
tion, and  in  a  short  time  the  whole  organ  has  returned  to  its 
normal  condition. 


CHAPTER   V. 


THE  PHASES  OF  LIFE. 


The  child  has  at  birth  on  an  average,  rather  less  than  one- 
third  the  maximum  length,  and  about  one-twentieth  the 
maximum  weight,  to  which  in  future  years  it  will  attain. 

The  composition  of  the  body  of  the  nevv})orn  babe,  as 
compared  with  that  of  the  adult,  will  be  seen  from  the  ff)l- 
lowing  table,^  in  which  the  details  are  more  full  than  those 
given  on  p.  579 : 

Weiglit  of  organ  in  porcent-      Wfigbt  of  organ  in 
age  of  body-weight.  arlwll,   a.s   compared 


Newborn  babe. 

Adult. 

Avith    that    of    new- 
born babe  taken  as  1. 

Eye, 

.28 

.028 

1.7 

Brain, 

.     14.34 

2.37 

3.7 

Kidneys  J . 

.88 

.48 

12 

.Skin, 

1L3 

6.3 

12 

Liver, 

4.39 

2.77 

13.6 

Heart,      . 

.89 

.52 

15 

Stomach  and 
Intestine, 

} 

2.53 

2.34 

20 

Lungs,     . 

2.16 

2.01 

20 

Skeleton, 

16.7 

15.35 

26 

Muscles,  etc. 

5     • 

23.4 

43.1 

28 

Testicle,  . 

.037 

.8 

60 

'  Vierordt,  Grundriss  der  Physiologie,  5th  ed,  p.  605 


CHILDHOOD.  929 

It  will  he  observed  that  the  brain  and  eyes  are,  relatively 
to  the  whole  body-weight,  very  much  larger  in  the  babe  than 
in  the  adult,  as  is  also,  though  to  a  less  extent,  the  liver. 
This  disproportion  is  a  very  marked  embryonic  feature,  and 
as  far  as  the  brain  and  eye  are  concerned  at  least,  has  a 
mori)hological  or  phylogenic,  as  well  as  a  physiological  or 
teleological  significance.  Inasmuch  as  the  smaller  bod}^  has 
relatively  the  larger  surfi^ce,  the  skin  is  naturally  propor- 
tionately greater  in  the  babe.  It  is  chiefly  by  the  accumu- 
lation of  muscle  or  flesh,  |)roperly  so  called,  that  the  child 
acquires  the  bulk  and  weiglit  of  the  man,  the  skeletal  frame- 
work, in  spite  of  its  being  si)ecificall3'  lighter  in  its  earlier 
cartilaginous  condition,  maintaining  throughout  life  about 
the  same  relative  weight. 

The  increase  in  stature  is  very  rapid  in  early  infancy,  pro- 
ceeding however  by  decreasing  increments.  According  to 
Quetelet,^  there  is  a  gain  in  height  of  about  20  centimeters 
during  the  first  year,  the  50  cm.  babe  enlarging  to  the  70 
cm.  infant  of  one  year  old,  of  about  9  during  the  second,  of 
about  T  during  the  third,  of  about  6j  for  the  fourth,  and  so 
on,  decreasing  to  rather  below  (\  for  the  succeeding  ten  or 
twelve  3ears.  During  or  shortly  Isefore  puberty,  there 
is  again  a  somewhat  sudden  rise,  with  a  subsequent  more 
steady,  but  diminishing  increase  up  to  about  the  twenty- 
fifth  year.  From  thence  to  about  fifty  3eais  of  age  the 
height  remains  stationary,  after  which  there  may  be  a  de- 
crease, especially  in  extreme  old  age. 

The  increase  in  weight  is  also  very  rapid  at  first,  and  pro- 
ceeding, like  the  height,  with  diminishing  increments,  may 
continue  till  about  the  fortieth  year.  After  the  sixtieth  year 
a  decline  of  yariai)le  extent  is  generally  witnessed.  It  is  a 
remarkable  fact,  however,  that  in  the  first  i'ew  days  of  life, 
so  far  from  there  being  an  increase,  there  is  an  actual  de- 
crease of  weight,  so  tliat,  according  to  Quetelet,  even  on 
the  seventh  day  the  weight  still  continues  to  be  less  than  at 
birth. 

The  saliva  of  the  babe  is  active  on  starch,  and  its  gastric 
juice  has  good  peptic  powers,  from  which  we  may  infer  that 
its  digestive  processes  in  general  are  identical  with  that  of 
the  adult ;  but  the  feces  of  the  infant  contain,  besides  a  con- 
siderable quantity  of  undigested  food  (fat.  casein,  etc),  un- 
altered l>ile-pigment,  and  undecomposed  bile-salts. 

'  Physique  Sociale  (1869),  ii,  p.  13. 


930  THE    PHASES    OF    LIFE. 


According  to  Ilammarsten'  the  gastric  Juice  of  newborn  pup- 
pies, though  sufficiently  acid  to  curdle  milk,  does  not  contain 
pepsin,  or  the  lactic  acid  feniicnt ;  it  is  not  till  the  third  week 
that  peptic  digestion  is  set  up,  the  casein  previously  taken  being 
digested  by  the  pancreatic  .iuice;  in  young  rabbits  it  apix;ars  a 
week  earlier.  Like  Zweifel',''  Ilammarsten,  however,  found  pei>- 
sin  in  the  stomach  of  the  newborn  babe.  Zweifel  states  that  the 
pancreatic  juice  in  children,  while  active  on  fat  and  proteids 
from  the  first,  is  inert  toward  starch  for  the  first  two  months  ; 
and  that  the  amylolytic  ferment  is  for  the  same  period  absent 
from  the  submaxfilary,  though  present  in  the  parotid  saliva. 

The  heart  of  the  babe  (see  table,  p.  '.)28)  is,  relatively  to 
its  body-weigiit,  laiger  tlian  the  adult,  and  the  frequency  of 
the  heart-beat  much  greater,  viz.,  about  180  or  140  per 
minute,  falling  to  about  110  in  the  second  year,  and  about 
90  in  the  tenth  year.  Corresponding  to  the  smaller  bulk 
of  the  body,  the  whole  circuit  of  the  blood  system  is  trav- 
ersed in  a  shorter  time  than  in  ihe  adult  (12  seconds  as 
against  22j  ;^  and  consequently  the  renewal  of  the  blood 
in  the  tissues  is  exceedingly  rapid.  The  respiration  of  the 
babe  is  quicker  than  that  of  the  adult,  being  at  first  about 
35.  per  minute,  falling  to  28  in  the  second  year,  to  26  in  the 
fifth  year,  and  so  onwards.  The  respiratory  work,  while  it 
increases  absolutely  as  the  body  grows,  is,  relatively  to  the 
body-weiglit,  greatest  in  the  earlier  years.  It  is  worthy  of 
notice,  that  the  absorption  of  oxygen  is  said  to  be  relatively 
more  active  than  the  production  of  carbonic  acid  ;  that  is  to 
sa}',  there  is  a  continued  accumulation  of  capital  in  the  form 
of  a  store  of  oxygen- holding  explosive  compounds  (see  p. 
467).  This,  indeed,  is  the  striking  feature  of  infant  meta- 
bolism. It  is  a  metabolism  directed  laigely  to  constructive 
ends.  The  food  taken  represents,  undoubtedly,  so  much 
potential  energy  ;  but  before  that  energy  can  assume  a  vital 
mode,  the  food  must  be  converted  into  tissue  ;  and,  in  such 
a  conversion,  morphological  and  molecular,  a  large  amount 
of  energy  must  be  ex|jended.  The  metabolic  activities  of 
the  infant  are  more  pronounced  than  those  of  the  adult,  for 
the  sake,  not  so  mucli  of  energies  which  are  spent  on  the 
world  without,  as  of  energies  which  are  for  awhile  buried 
in  the  rapidly  increasing  mass  of  flesh.     Thus  the  infant  re- 

1  Ludwig's  Festgabe  (1874),  p.  116. 

2  Untersuch.  u.  d.  Verdauungsiipparat  d.  Xeugeborenen,  1874. 
^  Vierordt,  op.  cit. 


CHILDHOOD.  931 

quires  over  and  above  the  ^vants  of  the  man,  not  only  nn  in- 
come of  energy  corresponding  to  the  energy  of  the  flesh  nc- 
tnally  laid  on,  but  also  an  income  corresponding  1o  the 
energ}^  used  up  in  making  that  living  pcnl[)tured  flesh  out  of 
the  dead  amorphous  proteids,  fats,  carbohydrates,  and  salts 
which  serve  as  food.  Over  and  above  this,  the  infant  needs  a 
more  rapid  metabolism  to  keep  up  tlie  normal  l)odily  tempera- 
ture. This,  which  is  no  less,  indeed  slightly  (.3°)  higher,  than 
that  of  the  adult,  requires  a  greater  expenditure,  inasmuch 
as  the  infant  with  its  relatively  far  larger  surface,  and  its 
extremely  vascular  skin,  loses  heat  to  a  proportionately 
much  greater  degree  than  does  the  grown-up  man.  It  is  a 
matter  of  common  experience  that  children  are  more  affected 
by  cold  than  are  adults. 

This  rapid  metabolism  is  however  not  manifest  immediately 
upon  birth.  During  the  lirst  few  days,  corresponding  to  the  loss 
of  weight  mentioned  above,  the  respiratory  activities  of  the  tis- 
sues are  feeble  ;  the  embryonic  habits  seem  as  yet  not  to  have 
been  completely  thrown  off,  and,  as  was  stated  on  p.  492,  new- 
born animals  bear  with  impunity  a  deprivation  of  oxygen,  which 
w^ould  be  fatal  to  them  later  on  in  life. 

Tiie  quantity  of  urine  passed,  though  scanty  in  the  fiist 
two  days,  rises  ra])idly  at  tiie  end  of  the  first  week,  and  in 
youth  the  quantity  of  urine  passed  is,  relatively  to  the  l)ody- 
weight,  larger  than  in  adult  life.  Tliis  may  be,  at  least  in 
quite  early  life,  partly  due  to  the  more  liqui<l  nature  of  the 
food,  but  is  also  in  j^art  tiie  result  of  the  more  active  meta- 
bolism. For  not  only  is  the  quantity  of  urine  i)assed,  but 
also  tlie  amount  of  urea  and  some  other  urinary  constituents 
excreted,  relativeh'  to  the  body-weight,  greater  in  the  child 
than  in  the  adult.  Tlie  presence  of  uric,  of  oxalic,  and  ac- 
cording to  some,  of  hippuric  acids  in  unusual  quantities  is 
a  frequent  characteristic  of  the  urine  of  children.  It  is 
stated  that  calcic  phosphates,  and  indeed  the  phosphates 
generally,  are  deficient,  being  retained  in  the  body  lor  the 
building  up  of  the  osseous  skeleton. 

Associated  probably  with  these  constructive  labors  of  the 
growing  frame  is  the  prominence  of  the  lymphatic  system. 
Not  only  aie  the  lymphatic  glands  largely  developed  and 
more  active  (as  is  probably  shown  by  their  tendency  to  dis- 
ease in  youth),  but  the  quantity  of  lymph  circulation  is 
greater  tlian  in  later  years.  Characteristic  of  youth  is  the 
size  of  the  thymus  body,  which  increases  up  to  the  second 
year,  and  ma}'  then  remain   for  awhile  stationary  ;  but  gen- 


932  THE    PHASES    OF    LIFE. 

erallv  before  puberty,  has  suffered  a  retroojressive  metamor- 
phosis, and  fre(pientl3'  hardly  a  vestige  of  it  remains  behind. 
The  thyroid  body  is  also  relatively  greater  in  the  babe  than 
in  the  adult;  the  spleen,  on  the  other  hand,  which  grows 
rapidly  in  early  infancy,  is  not  only  absolutely,  but  also  rel- 
atively, greater  in  the  adult.  It  need  hardly  be  said  that 
the  recuperative  power  of  infancy  and  early  youth  is  ver}^ 
marked. 

It  would  be  beyond  the  scope  of  this  work  to  enter  into 
the  psyciiical  condition  of  the  babe  or  the  child,  and  our 
knowledge  of  the  details  of  the  working  of  the  nervous 
system  in  infancy  is  too  meagre  to  permit  of  any  profitable 
discussion.  It  is  hardly  of  use  to  say  that  in  the  young 
the  whole  nervous  system  is  more  irritable  or  more  excitable 
than  in  later  years  ;  by  which  we  probably  to  a  great  extent 
mean  that  it  is  less  rigid,  less  marked  out  into  what,  in  pre- 
ceding portions  of  this  work,  we  have  spoken  of  as  nervous 
mechanisms.  It  may  be  mentioned  that,  according  to  Solt- 
mann,'  stiuiulation  of  Hitzig's  cerebral  areas,  in  newborn 
animals,  does  not  give  rise  to  the  usual  localized  movements. 
The  sense  of  touch,  both  as  regards  pressure  and  tempera- 
ture, ap[>ears  well  developed  in  the  infant,  as  does  also  the 
sense  of  taste,  and  possibly,  though  this  is  disputed,  that  of 
smell.  The  pupil  (larger  in  the  infant  than  in  the  man)  acts 
fully,  and  Bonders'^  observed  normal  binocular  movements 
of  the  eyes  in  an  infant  less  than  an  hour  old.  The  eye  is 
(in  man)  from  the  outset  fully  sensitive  to  light,  though  of 
course  visual  perceptions  are  imperfect.  As  regards  hear- 
ing, on  the  other  hand,  very  little  reaction  follows  upon 
sounds,  i.  e.,  auditory  sensations  seem  to  be  dull  during  the 
first  few  days  of  life;  this  may  be  partly  at  least  due  to  ab- 
sence of  air  from  the  tympanum  and  a  tumid  condition  of 
the  tympanic  mucous  membrane.  As  the  child  grows  up 
his  senses  rapidly  culminate,  and  in  his  early  years  he  pos- 
sesses a  general  acuteness  of  sight,  heai'ing,  and  touch, 
which  fre(iuently  becomes  blunted  as  his  psychical  life  be- 
comes fuller.  Children  however  are  said  to  be  less  apt  at 
distinguishing  colors  than  in  sighting  objects  ;  but  it  does 
not  appear  whether  this  arises  from  a  want  of  perceptive 
discrimination  or  from  their  being  actually  less  sensitive  to 

1  Centrblt.  Med.  Wiss.,  1875,  p.  209.  Jahrb.  f.  Kinderheilkunde,ix 
(1875),  106. 

2  Pfliiger's  Arehiv,  xiii  (1876),  p.  384. 


PUBERTY.  •  933 

variations  in  line.  A  characteristic  of  the  nervous  system 
in  childhood,  the  result  probably  of  the  more  active  meta- 
bolism of  the  body,  is  the  necessitj'  for  long  or  frequent  and 
deep  slumber. 

Dentition  marks  the  first  epoch  of  the  new  life.  At  about 
seven  months  the  two  central  incisors  of  the  lower  jaw  make 
their  way  through  the  gum,  followed  immediately  by  the 
corresponding  teeth  in  the  upper  jaw.  The  lateral  incisors, 
first  of  the  lower  and  then  of  the  upper  jaw,  appear  at  about 
the  ninth  month,  the  first  molars  at  about  the  twelfth  month, 
the  canines  at  about  a  year  and  a  half,  and  the  temporary 
dentition  is  completed  by  the  appearance  of  the  second 
molars  usually  before  the  end  of  the  second  year. 

About  the  sixth  year  the  permanent  dentition  commences 
by  the  appearance  of  the  first  permanent  molar  beyond  the 
second  temporary  molar;  in  the  seventh  year  the  central 
permanent  incisors  replace  their  temporary  representatives, 
followed  in  the  next  year  by  the  lateral  incisors.  In  the 
ninth  j-ear  the  temporary  first  molars  are  replaced  by  the 
first  bicuspids,  and  in  the  tenth  3ear  the  second  temporary 
molars  are  similarly  replaced  by  the  second  bicuspids.  The 
canines  are  exchanged  about  the  eleventh  or  twelfth  year 
and  the  second  permanent  molars  are  cut  about  the  twelfth 
or  thirteenth  year.  There  is  then  a  long  pause,  the  third  or 
wisdom  tooth  not  making  its  appearance  till  the  seventeenth 
or  even  twenty-fifth  year,  or  in  some  cases  not  appearing 
at  all. 

Shortly  after  the  conclusion  of  the  permanent  dentition 
(the  wisdom  teeth  excepted),  the  occurrence  of  pul»erty 
marks  the  beginning  of  a  new  phase  of  life  ;  and  the  differ- 
ence between  the  sexes,  hitherto  merely  potential,  now  be- 
comes functional.  In  both  sexes  the  maturation  of  the 
generative  organs  is  accompanied  b\'  the  well-known  changes 
in  the  body  at  large  ;  but  the  events  are  much  more  charac- 
teristic in  the  typical  female  than  in  the  aberrant  male. 
Though  in  the  bo}',  the  breaking  of  the  voice  and  the  rapid 
growth  of  the  beard  which  accompany  the  appearance  of 
active  spermatozoa,  are  striking  features,  yet  they  are  after 
alb  superficial.  The  carves  of  his  increasing  weight  and 
height,  and  of  the  other  events  of  his  economy,  pursue  for 
awhile  longer  an  unchanged  course ;  the  boy  does  not  be- 
come a  man  till  some  years  after  puberty  ;  and  the  decline 
of  his  functional  manhood  is  so  gradual  that  frequentl}'  it 
ceases  only  when   disease  puts  an   end  to  a  ripe  old  age. 


934  •  THE    PHASES    OF    LIFE. 

With  the  occurrence  of  menstruation,  on  the  other  hand,  at 
from  thirteen  to  seventeen  years  of  age,  the  girl  almost  at 
once  becomes  a  woman,  and  her  functional  womanhood 
ceases  suddenly  at  the  climacteric  in  tlie  fifth  decennium. 
During  the  whole  of  the  childhearing  period  iier  organism 
is  in  a  comparatively  stationary  condition.  While  before 
tlie  age  of  pui)erty  up  to  about  the  eleventh  or  twelfth  year, 
tiie  girl  is  ligliter  and  shorter  than  the  boy  of  the  same  age, 
in  the  next  few  years  her  rate  of  growth  exceeds  his  ;^  but 
she  has  then  nearly  reached  her  maximum,  while  he  contin- 
ues to  grow.  Her  curve  of  weight  from  the  nineteenth  year 
onwanl  to  the  climacteric  remains  stationary,  being  followed 
subsequently  by  a  late  increase,  so  that  while  the  man  reaches 
his  maximum  of  weigiit  at  about  forty,  the  woman  is  at  her 
greatest  weight  about  fifty. '^ 

Of  the  statical  difierences  of  sex,  some,  such  as  the  for- 
mation of  the  pelvis,  and  the  costal  mechanism  of  respira- 
tion, are  directly  connected  with  the  act  of  childhearing, 
while  others  have  only  an  indirect  relation  to  that  duty; 
and  indications  at  least  of  nearl}'  all  the  characteristic  dif- 
ferences are  seen  at  birth.  The  bab}^  boy  is  heavier  and 
taller  than  the  baby  girl,  and  the  maiden  of  five  breathes 
with  her  ribs  in  the  same  wa}^  as  does  the  matron  of  forty. 
The  woman  is  lighter  and  shorter  than  the  man,  the  limits 
in  the  case  of  the  former  lieing  from  1.444  to  1.740  meters 
of  height  and  from  39.8  and  93.8  kilos  of  weight,  in  the  lat- 
ter from  1.467  to  1.890  of  height,  and  from  49.1  to  98.5  kilos 
of  w^eight.^  The  muscular  system  and  skeleton  are  both  ab- 
solutely and  relatively  less  in  woman,  and  her  brain  is 
lighter  and  smaller  than  that  of  man,  being  about  1272 
grams  to  1424.  Her  metabolism,  as  measured  by  the  re- 
spiratory and  urinary  excreta,  is  also  not  only  alisolutely 
but  relatively  to  the  body-weight  less,  and  her  blood  is  not 
only  less  in  quantity  but  also  of  lighter  specific  gravity  and 
contains  a  smaller  proportion  of  red  corpuscles.  Her 
strength  is  to  that  of  man  as  altout  5  to  9,  and  the  relative 
lei'gth  of  her  step  as  1000  to  1157. 

From  birth  onward  (and  indeed  from  early  intrauterine 
life)  the  increment  of  growth  progressively'  diminishes.     At 

^  Bowditch,  The  Growth  of  Children,  Annual  Keport  of  the  State 
Board  of  Health  of  Massachusetts,  1877.  Cf.  also  Pagliani,  Moleschott's 
Unteisuch.,  xii  (1878),  p.  89. 

2  Quetelet,  op.  cit.  .  ^  Quetelet,  op.  cit.,  ii,  p.  89. 


OLD    AGE.  935 

last  a  point  is  reached  at  wliicli  the  curve  cuts  the  abscissa 
luie.  and  the  increment  becomes  a  deciement.  After  the 
culmination  of  manhood  at  forty  and  of  womanhood  at  tlie 
climacteric,  the  prime  of  life  declines  into  old  age.  The 
metabolic  activity  of  the  body,  which  at  first  was  sufficient 
not  only  to  cover  tlie  daily  waste,  but  to  add  new  material, 
later  on  is  able  only  to  meet  the  daily  wants,  and  at  last  is 
too  imperfect  even  to  sustain  in  its  entirety  the  existing 
frame.  2seither  as  regards  vigor  and  functional  capacity, 
nor  as  regards  weight  and  bulk,  do  the  turning-points  of 
the  several  tissues  and  organs  coincide  either  with  each 
otlier  or  with  that  of  the  body  at  large.  We  have  already 
seen  that  the  life  of  such  an  organ  as  the  thymus  is  far 
shorter  tiian  that  of  its  possessor.  The  eye  is  in  its  dioptric 
prime  in  childliood,  when  its  media  are  clearest  and  its  mus- 
cular mechanisms  most  mobile,  and  then  it  for  tlie  most  part 
serves  as  a  toy  ;  in  later  years,  when  it  could  be  of  tlie 
greatest  service  to  a  still  active  brain,  it  has  alread}'  fallen 
into  a  clouded  and  rigid  old  age.  The  skeleton  reaches  its 
limit  verj'  nearly  at  the  same  time  as  the  wliole  frame 
reaches  its  maximum  of  lieight,  the  coalescence  of  the  va- 
rious epiphyses  being  prett}'  well  completed  b}'  about  the 
twenty-fifth  year.  Similarly  the  muscular  system  in  its  in- 
crease tallies  with  the  weight  of  the  whole  body.  The  brain, 
in  spite  of  the  increasing  complexity  of  structure  and  func- 
tion to  which  it  continues  to  attain  even  in  middle  life,  earl}'' 
reaches  its  limit  of  bulk  and  weight.  At  about  seven  years 
of  age  it  attains  what  may  be  considered  as  its  first  limit, 
for  though  it  may  increase  somewhat  up  to  twenty,  thirty, 
or  even  later  years,  its  progress  is  much  more  slow  after 
than  before  seven.  The  vascular  and  diyrestive  oro-ans  as  a 
whole  may  continue  to  incrense  even  to  a  ver}"  late  period. 
From  these  facts  it  is  obvious  that  though  the  phenomena 
of  old  age  are,  at  bottom,  the  result  of  the  individual  decline 
of  the  several  tissues,  they  owe  many  of  their  features  to  the 
disarrangement  of  the  whole  organism  produced  b}'  the 
premature  decay  or  disappearance  of  one  or  other  of  the 
constituent  bodily  factors.  Thus,  for  instance,  it  is  clear 
that  were  there  no  natural  intrinsic  limit  to  the  life  of  the 
muscular  and  nervous  systems  tliey  would  nevertheless  come 
to  an  end  in  consequence  of  the  nutritive  disturbances  caused 
bN'  the  loss  of  the  teeth.  And  what  is  true  of  the  teeth  is 
probaltly  true  of  many  other  organs,  with  the  addition  that 
these  cannot,  like  the  teeth,  be  replaced  b}'  mechanical  con- 


936  THE    PHASES    OF    LIFE. 

trivances.  Thus  the  term  of  life  wliich  is  allotted  to  a  mus- 
cle b}'  virtue  of  its  molecular  constitution,  and  which  it 
could  not  exceed  were  it  always  placed  under  the  most  favor- 
able nutritive  conditions  is,  in  the  organism,  determined  by 
the  similar  Hfe-terms  of  other  tissues ;  the  future  decline  of  the 
brain  is  probabl}'  involved  in  the  early  decay  of  the  thymus. 

Two  changes  characteristic  of  old  age  are  the  so-called 
calcareous  and  fatty  degenerations.  These  are  seen  in  a 
com[)letel3^  typical  form  in  cartilages,  as,  for  instance,  in  the 
ribs  ;  here  the  protoplasm  of  the  cartilage-corpuscle  becomes 
hardly  more  than  an  envelope  of  fat-globules,  and  the  supple 
matrix  is  rendered  rigid  with  araorplious  deposits  of  calcic 
phosphates  and  carbonates,  which  are  at  the  same  time  tiie 
signs  of  past  and  the  cause  of  future  nutritive  decline.  And 
what  is  obvious  in  the  case  of  cartilage  is  more  or  less  evi- 
dent in  other  tissues.  Everywhere  we  see  a  disposition  on 
the  part  of  protoplasm  to  fall  back  upon  the  easier  task  of 
forming  fat  rather  tiian  to  carry  on  the  more  arduous  duty 
of  manufacturing  new  material  like  itself;  everywhere  al- 
most we  see  a  tendency  to  the  replacement  of  a  structured 
matrix  by  a  deposit  of  amorphous  material.  In  no  part  of 
the  system  is  this  more  evident  than  in  the  arteries  ;  one 
common  feature  of  old  age  is  the  conversion  by  such  a 
change  of  the  supple  elastic  tubes  into  rigid  channels, 
whereby  the  supply  to  the  various  tissues  of  nutritive  ma- 
terial is  rendered  increasingly  more  difficult,  and  their  in- 
trinsic decay  proportionately  hurried. 

Of  the  various  tissues  of  the  body  the  muscular  and  ner- 
vous are,  however,  ihose  in  which  functional  decline,  if  not 
structural  deca}^  becomes  soonest  ai)parent.  The  dynamic 
coefiicient  of  the  skeletal  muscles  diminishes  rapidly  after 
thirty  or  forty  years  of  life,  and  a  similar  want  of  power 
comes  over  the  plain  muscular  fibres  also  ;  the  heart,  though 
it  may  not  diminish,  or  even  may  still  increase  in  weight, 
possesses  less  and  less  force,  and  the  movements  of  the  in- 
testine, bladder,  and  other  organs,  diminish  in  vigor.  In 
the  nervous  system,  the  lines  of  resistance,  which,  as  we 
have  seen,  help  to  map  out  tlie  central  organs  into  mechan- 
isms, and  so  to  produce  its  multifarious  actions,  become 
at  last  hindrances  to  the  passage  of  nervous  impulses  in 
an}'  direction,  while  at  the  same  time  the  molecular  energy 
of  tiie  impulses  themselves  becomes  less.  The  eye  becomes 
feeble,  not  only  from  cloudiness  of  the  media  and  presbyopic 
muscular  inability,  but  also  from  the  very  bluntness  of  the 


OLD    AGE.  937 

retina;  the  sensory  and  motor  impulses  pass  with  increas- 
ing slowness  to  and  from  the  central  nervous  system,  and 
the  brain  becomes  a  more  and  more  rigid  mass  of  proto- 
plasm, the  molecular  lines  of  which  rather  mark  the  history 
of  past  actions  than  serve  as  indications  of  present  potency'. 
The  epithelial  glandular  elements  seem  to  be  those  whose 
powers  are  the  longest  i)reserved  ;  and  hence  the  man  who 
in  the  prime  of  his  manhood  was  a  ''martyr  to  dyspepsia'' 
by  reason  of  the  sensitiveness  of  his  gastric  nerves  and  the 
reflex  inhibitory  and  otlier  results  of  their  irritation,  in  his 
later  years,  when  his  nerves  are  blunted,  and  nhen,  there- 
fore, his  pe[)tic  cells  are  able  to  pursue  their  cliemical  work 
undisturbed  by  exti'insic  nervous  worries,  eats  and  drinks 
with  the  courage  and  success  of  a  boy. 

Within  the  range  of  a  lifetime  are  comprised  many  periods 
of  a  more  or  less  frequent  recurrence.  In  spite  of  the  aids 
of  a  complex  civilization,  all  tending  to  render  the  condi- 
tions of  his  life  more  and  more  equable,  man  still  shows  in 
his  economy  the  eflTects  of  the  seasons.  Some  of  these  are 
the  direct  results  of  varying  temperature,  but  some  prob- 
ably', such  as  the  gain  of  weight  in  winter  and  the  loss  in 
summer,  are  habits  acquired  by  descent.  Within  the  year, 
an  approximately  monthly  period  is  manifested  in  the  female 
by  menstruation,  though  there  is  no  exact  evidence  of  even 
a  latent  similar  cycle  in  the  male.  The  phenomena  of  recur- 
rent diseases,  and  the  marked  critical  d;iys  of  many  other 
maladies,  may  be  regarded  as  pointing  to  cycles  of  smaller 
dui-ation  than  that  of  the  moon's  revolution,  unless  we  admit 
the  view  urged  by  some  authors  that  in  these  cases  the  re- 
currence is  to  be  attributed  rather  to  periodical  phases  in 
the  disease-producing  germ  itself,  than  to  variations  in  the 
medium  of  the  disease. 

Prominent  among  all  other  cyclical  evenis  is  the  fact  that 
all  animals  possessing  a  w^ell-developed  nervous  system, 
must,  night  after  night,  or  day  after  da^-,  or  at  least  time 
after  time,  la}' them  down  to  sleep.  The  salient  feature  of 
sleep  is  the  cessation  of  the  automatic  activity  of  the  brain  ; 
it  is  the  diastole  of  the  cerebral  iieat.  But  the  condition 
is  not  confined  to  the  cerebral  hemispheres  ;  all  parts  of  the 
body  either  directly  or  indirectly  take  share  in  it.  The 
phenomena  of  sleep  are  perhaps  seen  in  their  simplest  form 
in  the  winter-sleep  or  hibernation,  to  which  especially  cold- 
blooded animals,  but  also  to  some  extent  warm-blooded 
animals,   are  subject.     In  these  cases  the  cold  of  winter 


938  THE    PHASES    OF    LIFE. 

slackens  the  vibrations  and  lessens  the  explosions  of  the 
protoi)lasm,  not  only  of  nervous  but  also  of  muscular  and 
glandular  structures  ;  indeed  the  activity  of  the  whole  body 
is  lowered,  in  some  respects  almost  to  actual  arrest.  At 
the  same  time  that  the  labor  of  the  cerelual  molecules  be- 
comes insuflicient  to  develop  consciousness,  the  respiratory 
centre  is  either  wholly  quiescent  or  discharges  feeble  im- 
pulses at  rare  intervals,  and  the  heart  beats  with  a  slow  in- 
frequent stroke,  not  by  reason  of  any  inhibitory  restraint, 
but  because  its  very  substance  in  its  slow  molecular  ti'avail 
can  gather  head  for  explosions  only  after  long  j);iuses  of 
rest.  And  such  few  and  distant  beats  as  do  occur  are 
amply  sufficient  to  meet  the  needs  of  the  feeble  metal)olisin 
of  the  several  tissues.  The  sleep  of  every  day  differs  from 
the  sleep  of  winter-cold  chiefly  because  the  slackening  of 
molecidar  activities  is  due  in  the  former  not  to  extrinsic 
but  to  intrinsic  causes,  not  to  chancres  in  the  medium,  but 
to  exhaustion  of  tiie  subject,  and  because  the  phenomena 
are  largely  confined  to  the  cerebral  hemispheres.  It  is  true 
that  the  wdiole  body  shares  in  the  condition  ;  the  pulse  and 
breathing  are  slower,  the  intestine  and  other  internal  mus- 
cular mechanisms  are  more  or  less  at  rest,  the  secreting  or- 
gans are  less  active,  and  the  whole  metabolism  and  the  de- 
pendent temperature  of  the  body  are  lowered ;  but  we 
cannot  say  at  present  how  far  these  are  the  indirect  results 
of  the  condition  of  the  nervous  system,  or  how  far  they  in- 
dicate a  partial  slumbering  of  the  several  tissues. 

According  to  Mosso^  thoracic  respiration  becomes  more  promi- 
nent than  diaphragmatic  respiration  during  sleep,  and  the  Cheyne- 
Stokes  rhythm  of  respiration  (see  p.  479)  is  frequently  observed. 
During  sleep  the  pupil  is  contracted,  during  deep  sleep  exceed- 
ingly so  ;  and  dilation,  often  unaccompanied  by  any  visible 
movements  of  the  limbs  or  body,  takes  place  when  any  sensitive 
surface  is  stimulated  ;'  on  awaking  also  the  pupils  dilate.  The 
eyeballs  have  been  generally  described  as  being  during  sleep 
directed  upwards  and  converging,  or,  according  to  some  authors, 
diverging ;  but  Sander''  states  that  in  true  sleep  the  visual  axes 
are  parallel  and  directed  to  the  far  distance.  R;ihlmann  and 
Witkowski'  describe  the  eyes  of  children  as  continually  executing 
sleep  movements  often  irregular  and  unsymmetricai  and  unac- 
companied by  changes  in  the  pupils. 

^  Arch.  f.  Anat.  ii.  Phys.  (Phys.  Abth.),  1878,  p.  441. 

2  Rahlmann  nnd  Witkowski,"  Arch.  f.  Anat.  u.  Phvs.  (Phvs  Abth.), 
1878,  p.  109.  Sander,  Arch.  f.  Psych.,  ix  (1879),  p.  129.  Siemens,  ibid., 
p.  72. 

3  Op.  cit.  *  Op.  cit. 


SLEEP.  939 

We  are  not  at  present  in  a  position  to  trace  out  the  events 
■which  culminate  in  this  inactivity  of  the  cerebral  structures. 
It  has  been  uro;ed^  that  during  sleep  the  brain  is  anaemic; 
but  even  if  this  anaemia  is  a  constant  accompaniment  of 
sleep,  it  must,  like  the  vascular  condition  of  a  gland,  or 
any  other  active  organ,  be  regarded  as  an  effect,  or  at  least 
as  a  subsidiary  event,  ratlier  than  as  a  primary  cause.  The 
explanation  of  the  condition  is  rather  to  be  sought  in  purely 
molecular  changes  ;  and  tlie  analogy  between  the  systole 
and  diastole  of  the  heart,  and  the  w^aking  and  sleeping  of 
the  brain,  may  be  profitably  pushed  lo  a  very  considerable 
extent.  The  sleeping  brain  in  many  respects  closely  re- 
sembles a  quiescent  but  still  living  ventricle.  Both  are  as 
far  as  outward  manifestations  are  concerned  at  rest,  but  both 
may  be  awakened  to  activity  by  an  adequately  powerful 
stimulus.  Both,  though  quiescent,  are  irritable  ;  in  both  the 
quiescence  will  ultimatel}'  give  place  to  activity,  and  in  both 
an  appropriate  stimulus  applietl  at  the  right  time  will  deter- 
mine the  change  from  rest  to  action.  Just  as  a  single  prick 
will  under  certain  circumstances  awake  a  ventricle,  which 
for  some  seconds  has  been  motionless,  into  a  rhythmic  ac- 
tivity of  many  beats,  so  a  loud  noise  will  start  a  man  from 
sleep  into  a  long  day's  wakefulness.  And  just  as  in  the 
heart  the  cardiac  irritability  is  lowest  at  the  beginning  of 
the  diastole  and  increases  onwards  till  a  heat  bursts  out,  so 
is  sleep  deepest  at  its  commencement  after  the  day's  labor; 
thence  onward  slighter  and  slighter  stimuli  are  needed  to 
wake  the  sleeper. 

Kohlschutter,^  judijingof  the  depth  of  ordinary  nocturnal  sleep 
by  the  intensity  of  the  noise  required  to  wake  the  sleeper,  con- 
cludes that,  increasing  very  rapidly  at  first,  it  reaches  its  maxi- 
mum within  the  first'hour;  from"^thence  it  diminishes,  at  first 
rapidly,  but  afterwards  more  slowly.  At  the  end  of  an  hour  and 
a  half  it  falls  to  one-fourth,  at  the  end  of  two  hours  to  one-eighth 
of  its  maximal  intensity,  and  thence  onward  diminishes  with 
gradually  diminishing  decrements. 

We  cannot  at  pr.es^nt  make  any  definite  statements  con- 
cerning the  nature  of  the  molecular  changes  which  deter- 
mine this  rhythmic  rise  and  fall  of  cerel)ral  irritability. 
Preyer,^  leaning  towards  the  view  that  the  accumulation  of 

^  Durham,  Guv's  Hospital  Reports,  vol.  vi,  1860. 
2  Zeitschr.  f.  rat.  Med.,  xvii  (1862),  p.  209  ;  xxxiv  (18691  p.  42. 
^  Centralblatt  f.  Med.  Wiss.,  1875,  p.  577.     Ueber  die  Ursache  des 
Schlafes,  1877. 


940  THE    PHASES    OF    LIFE. 

the  products  of  protoplasmic  activity  rna^^  become  in  the 
end  an  obstruction  to  tliat  activit}',  has  been  led  to  think 
that  the  presence  of  lactic  acid,  one  of  the  products  certainly 
of  muscular  and  prol)ably  of  nervous  metabolism,  tends  to 
produce  sleep;  but  this  is  doubtful.  The  suggestion  of 
Pfliiger,^  that  the  diminution  of  irritability',  and  consequent 
suspension  of  automatism,  is  dependent  on  the  exhaustion 
of  the  store  of  intramolecular  oxygen  (p.  4G3),  is  more 
worthy  of  attention. 

As  was  previously  stated  (p.  599),  there  is  at  present  at  least 
no  satisfactory  evidence  that  tlie  assumption  of  oxygen  is  directly 
dependent  on  the  time  of  day,  the  striking  result  obtained  by 
Pettenkofer  and  Voit  there  quoted  not  being  corroborated  by 
subsequent  trials.^  The  hypothesis  of  Pflliger,  therefore,  unless 
subsequent  researches  reinstate  Pettenkofer  and  Voit's  first  view, 
needs  an  addition  to  explain  how  it  is  that  the  store  of  intra- 
molecular oxygen  becomes  exhausted  in  tlie  nervous  system. 
Henke^  had  previously  put  forward  a  not  wholly  unlike  hy- 
pothesis, as  had  also  Sommer.* 

The  phenomena  of  sleep  show  very  clearly  to  how  large 
an  extent  an  apparent  automatism  is  the  ultimate  outcome 
of  the  effects  of  antecedent  stimulation.^  When  we  wish  to 
go  to  sleep  we  withdraw  our  automatic  brain  as  much  as 
posihle  from  the  intiuence  of  all  extrinsic  stimuli;  and  an 
interesting  case  is  recorded^  of  a  lad  whose  connection  with 
the  external  world  was,  from  a  complicated  anaesthesia, 
limited  to  that  afforded  b}-  a  single  eye  and  a  single  ear, 
and  who  could  be  sent  to  sleep  at  will,  by  closing  the  e3e 
and  stopping  the  ear. 

The  cycle  of  the  day  is,  liowever,  manifested  in  many 
other  wa^ys  than  by  the  alternation  of  sleeping  and  waking, 
with  all  ihe  indirect  effects  of  tliese  two  conditions.  There 
is  a  diurnal  curve  of  temperature  (see  p.  614),  apparently 
independent  of  all  immediate  circumstances,  the  hereditary 
impress  of  a  long  and  ancient  sequence  of  days  and  nights. 
Even  tlie  pulse,  so  sensitive  to  all  bodily  changes,  shows, 
running  through  all  the  immediate  effects  of  the  changes  of 

'  Pfluger's  Archiv,  x  (1875),  p.  468. 

^  Sitzungsbericht.  Acad.  Wiss.  Miinohen,  1866-67. 

^  Zeitschr.  f.  rat.  Med.,  xiv  (1861),  p.  363. 

*  Zeitschr.  f.  rat.  Med.,  xxxiii  (1868). 

5  Cf.  Heubel,  Pfluger's  Archiv,  xiv  (1877),  p.  158. 

«  Pfluger's  Archiv,  xv  (1877),  p.  573. 


DEATH.  941 

the  minute  and  the  hour,  the  working  of  a  diurnal  influence 
which  cannot  be  accounted  for  by  waking  and  sleeping,  by 
working  and  resting,  by  meals  and  abstinence  between 
meals.  And  the  same  may  be  said  concerning  the  rhythm 
of  respiration,  and  the  products  of  pulmonary,  cutaneous, 
and  urinary  excretion.  There  seems  to  be  a  daily  curve  of 
bodih' metabolism,  which  is  not  the  product  of  the  day's 
events.  Within  ihe  day  we  have  the  narrower  rhythm  of 
the  respiratory  centre  witli  the  accompanying  rise  and  fall 
of  activity  in  the  vaso-raotor  centres.  And  lastly,  as  the 
fundamental  fact  of  all,  bodily  periodicity  is  that  alterna- 
tion of  the  heart's  systole  and  diastole  which  ceases  only  at 
death.  Though,  as  we  have  seen,  the  intermittent  flow  in 
the  arteries  is  toned  down  in  tlie  capillaries  to  an  appar- 
ently continuous  flow,  still  the  constantly  repeated  cycle  of 
the  cardiac  shuttle  must  leave  its  mark  throughout  the 
whole  web  of  the  body's  life.  Our  means  of  investigation 
are,  however,  still  too  gross  to  permit  us  to  track  out  its  in- 
fluence. Still  less  are  we  at  present  in  a  position  to  say 
how  far  the  fundamental  rhythm  of  the  heart  itself,  that 
rhythm  which  is  influenced,  but  not  created,  by  the  changes 
of  the  body  of  which  it  is  the  centre,  is  the  result  of  cos- 
mical  changes,  the  reflection  as  it  were  in  little  of  the  cycles 
of  the  universe,  or  how  far  it  is  the  outcome  of  the  inherent 
vibrations  of  the  molecules  which  make  up  its  substance. 


CHAPTER  VI. 
DEATH, 

When  the  animal  kingdom  is  surveyed  from  a  broad 
standpoint,  it  becomes  obvious  that  the  ovum,  or  its  correl- 
ative the  spermatozoon,  is  the  goal  of  an  individual  exist- 
ence: that  life  is  a  cvcle  beainnins  in  an  ovum  and  cominor 


942  DEATH. 

round  to  an  ovum  again.  The  greater  part  of  the  actions 
whicii,  looking  from  a  near  point  of  view  at  the  higher  ani- 
mals alone,  we  are  apt  to  consider  as  eminently  the  i)ur- 
posfes  for  which  animals  come  into  existence,  when  viewed 
from  tiie  distant  outlook  whence  the  whole  living  world  is 
surveyed,  fade  away  into  the  likeness  of  the  mere  byplay  of 
ovum-hearing  orgnnisms.  The  animal  bod}-  is  in  reality  a 
vehicle  for  ova;  and  after  the  life  of  the  parent  has  become 
potentially  renewed  in  the  offspring,  the  body  remains  as  a 
cast-off  envelope,  whose  future  is  but  to  die. 

Were  the  animal  fi-ame  not  tiie  complicated  machine  we 
have  seen  it  to  be,  death  might  come  as  a  simple  and  gradual 
dissolution,  the '^  sans  ever\  thing  "  being  the  last  stage  of 
the  successive  loss  of  fundamental  powers.  As  it  is,  how- 
ever, death  is  always  more  or  less  violent;  the  machine 
comes  to  an  end  by  reason  of  the  disorder  caused  by  the 
breaking  down  of  one  of  its  parts.  Life  ceases  not  because 
the  molecular  powers  of  the  whole  body  slacken  and  are 
lost,  but  because  a  weakness  in  one  or  other  part  of  the  ma- 
chinery tlirows  its  whole  working  out  of  gear. 

We  have  seen  that  the  central  factor  of  life  is  the  circula- 
tion of  the  blood,  but  we  have  also  seen  that  l)lood  is  not 
only  useless,  but  injurious,  unless  it  be  duly  oxygenated  ; 
and  we  have  further  seen  that  in  the  iiigher  animals  the 
oxygenation  of  the  blood  can  only  be  duly  effected  by  means 
of  the  respiratory  muscular  mechanism,  presided  over  by 
the  medulla  oblongata.  Thus  the  life  of  a  complex  animal 
is,  when  reduced  to  a  simple  form,  composed  of  three  factors: 
the  maintenance  of  the  circulation,  the  access  of  air  to  the 
haemoglobin  of  the  blood,  and  the  functional  activity  of  the 
respiratory  centre;  and  death  may  come  from  the  arrest  of 
either  of  these.  As  Bichat  put  it,  death  takes  place  by  the 
heart  or  by  the  lungs  or  by  the  brain.  In  reality,  however, 
when  we  push  the  analysis  further,  the  central  fact  of  death 
is  the  stoppage  of  the  heart,  and  the  consequent  arrest  of 
the  circulation  ;  the  tissues  then  all  die,  because  they  lose 
their  internal  medium.  The  failure  of  the  heart  may  arise 
in  itself,  on  account  of  some  failure  in  its  nervous  or  mus- 
cular elements,  or  by  reason  of  some  mischief  affecting  its 
mechanical  working.  Or  it  may  be  due  to  some  fault  in  its 
internal  me<linin,  such,  for  instance,  as  a  want  of  oxygena- 
tion of  the  blood,  which  in  turn  may  be  caused  by  either  a 
change  in  the  blood  itself,  as  in  carbonic  oxide  poisoning, 
or  by  a  failure  in  the  mechanical  conditions  of  respiration, 


DEATH.  943 

or  l)}^  a  cessation  of  the  action  of  the  respiratoiy  centre. 
The  failure  of  this  centre,  and  indeed  that  of  the  lieart 
itself,  may  be  caused  by  nervous  influences  proceeding  from 
the  brain,  or  brought  into  operation  by  means  of  the  cen- 
tral nervous  system  ;  it  may,  on  the  other  hand,  be  due  to 
an  imperfect  state  of  blood,  and  this  in  turn  ma^' arise  from 
the  imperfect  or  perverse  action  of  various  secretory  or 
other  tissues.  The  modes  of  death  are  in  reality  as  nu- 
merous as  are  the  possible  modifications  of  the  various  fac- 
tors of  life;  but  they  all  end  in  a  stoppage  of  the  circula- 
tion, and  the  withdrawal  from  the  tissues  of  their  internal 
medium.  Hence  we  come  to  consider  the  death  of  the 
bod\'  as  marked  by  the  cessation  of  the  heart's  beat,  a  ces- 
sation from  which  no  recovery  is  possible  ;  and  by  this  we. 
are  enabled  to  fix  an  exact  time  at  which  we  say  the  body  is 
dead.  We  can,  however,  fix  no  such  exact  time  to  the  death 
of  the  individual  tissues.  They  are  not  mechanisms,  and 
their  death  is  a  gradual  loss  of  power.  In  the  case  of  the 
contractile  tissues,  we  have  apparentlj'  in  rigor  mortis  a 
fixed  term,  b}'  which  we  can  mark  the  exact  time  of  their 
death.  If  we  admit  that  after  the  onset  of  rigor  mortis  re- 
covery of  irritabilit}'  is  impossible,  then  a  rigid  muscle  is 
one  permanently  dead.  In  the  case  of  the  other  tissues, 
we  have  no  such  objective  sign,  since  the  rigor  mortis  of 
simple  protoplasm  manifests  itself  chiefly  by  obscure  chemi- 
cal signs.  And  in  all  cases  it  is  obvious  that  the  possibility 
of  recovery,  depending  as  it  does  on  the  skill  and  knowl- 
edge of  the  experimenter,  is  a  wholly  artificial  sign  of  death. 
Yet  we  can  draw  no  other  sharp  line  between  the  seemingly 
dead  tissue  whose  life  has  flickered  down  into  a  smouldering 
ember  which  can  still  be  fanned  back  again  into  flame,  and 
the  aggregate  of  chemical  substances  into  which  the  decom- 
posing tissue  finally  crumbles. 

Moreover,  the  failure  of  the  heart  itself  is  at  bottom  loss 
of  irritability,  and  the  possibility  of  rccoveiy  here  also 
rests,  as  far  as  is  known  at  present,  on  the  skill  and  knowl- 
edge of  those  who  attempt  to  recover.  So  that  after  all 
the  signs  of  the  death  of  the  whole  body  are  as  artificial  as 
those  of  the  death  of  the  constituent  tissues. 


A  P  r  E  N  D  I  X. 


APPENDIX. 


ox  THE  CHEMICAL  BASIS  OF  THE  AXIMAL  BODY. 

Xative  protoplasm,  whenever  it  can  be  obtained  in  sufficient 
quantity  for  chemical  analysis,  is  found  to  contain  representatives 
of  three  large  classes  of  chemical  substances,  viz..  proteids.  carbo- 
hydrates, and  fats,  in  association  with  smaller  quantities  of  vari- 
ous saline  and  other  crystalline  bodies.  By  proteids  are  meant 
bodies  containing  carbon,  oxygen,  hydrogen,  and  nitrogen  in  a 
certain  proportion,  varying  within  narrow  limits,  and  having 
certain  general  features  ;  they  are  frequently  spoken  of  as  albu- 
minoids. By  carbohydrates  are  meant  starches  and  sugars  and 
their  allies.  Of  these  three  classes  of  bodies,  the  proteids  form 
the  chief  mass  of  ordinary  protoplasm,  but  fats  and  carbohy- 
drates are  never  wholly  absent.  To  obtain  evidence  of  the  pres- 
ence of  any  one  of  them  in  living  protoplasm  we  are  obliged  to 
submit  the  protoplasm  to  destructive  analysis.  We  do  not  at 
present  know  anything  detinite  about  the  molecular  composition 
of  active  living  protoplasm  ;  but  it  is  more  than  probable  that  its 
molectile  is  a  large  couiplex  one  in  which  a  proteid  substance  is 
pecuUarl}'  associated  with  a  complex  fat  and  with  some  repre- 
sentative of  the  carbohydrate  group,  i.  e.,  that  each  molecule  of 
protoplasm  contains  residues  of  each  of  these  three  great  classes. 

The  whole  animal  body  is  modi  tied  protoplasm.  Consequently 
when  we  examine  the  various  tissues  and  liuids  from  a  chemical 
point  of  view,  we  find  present  in  ditlerent  places,  or  at  diflerent 
times,  several  varieties  and  derivatives  of  the  three  chief  classes  ; 
we  find  many  forms  of  proteids  and  derivatives  of  proteids  in  the 
forms  of  gelatin,  chondrin.  etc.  ;  many  varieties  of  fats  :  and 
several  kinds  of  carbohydrates. 

AVe  find,  moreover,  many  other  bodies  which  we  may  regard 
as  stages  in  the  constructive  or  destructive  metabolism'^of  both 
native  and  ditierentiatecl  protoplasm,  and  which  are  important 
not  so  much  from  the  'quantity  in  which  they  occur  in  the  animal 
body  at  any  one  time  as  from  their  throwing  light  on  the  nature 
of  animal  metabolism  ;  these  are  such  bodies  as  urea,  lactic  acid, 
and  the  extractives  in  general. 

In  the  following  pages  the  chemical  features  of  the  more  im- 
portant of  these  various  substances  which  are  known  to  occtrrin 
the  animal  body  will  be  briefly  considered,  such  characters  only 
being  described  as  possess  or  promise  to  possess  physiological 


948        CHEMICAL    BASIS    OF    THE    ANIMAL    BODY. 


interest.  The  physiological  function  of  any  substance  must  de- 
pend ultimately  on  its  molecular  (including  its  chemical)  nature  ; 
and  though  at  present  our  chemical  knowledge  of  the  constitu- 
ents of  an  animal  body  gives  us  but  little  insight  into  their 
physiological  properties,  it  cannot  be  doubted  that  such  chemical 
information  as  is  attainable  is  a  necessary  preliminary  to  all 
physiological  study. 

PKOTEIDS. 

These  form  the  principal  solids  of  the  muscular,  nervous,  and 
glandular  tissues,  of  the  serum  of  blood,  of  serous  fluids,  and  of 
lymph.  In  a  healthy  condition,  sweat,  tears,  bile,  and  urine 
contain  mere  traces,  if  any,  of  proteids.  Their  general  percent- 
age composition  may  be  taken  as 


0. 

H. 

N. 

c.           s. 

From    20.9 

6.9 

15.2 

51.5              0.3 

to     28.5 

to  7.3 

to  17.0 

to  54.5         to  2.0 

(Hoppe-Seyler.' 

These  figures  are  obtained  from  a  consideration  of  numerous  analyses, 
slight  differences  in  the  various  results  l)eing  immaterial,  where  the 
purity  of  the  substance  operated  upon  cannot  be  definitely  determined. 

In  addition  to  the  above  constituents,  proteids  leave  on  ignition  a 
variable  quantity  of  ash.  In  the  case  of  egg-albnmin  the  principal  con- 
stituents of  the  ash  are  chlorides  of  sodium  and  potassium,  the  latter 
greatly  exceeding  the  former  in  amount.  The  remainder  consists  of 
sodium  and  potassium,  in  combination  with  phosphoric,  sulphuric,  and 
carbonic  acids,  and  very  small  quantities  of  calcium,  magnesium,  and 
iron,  in  union  with  the  same  acids.  There  is  also  a  trace  of  silica.^  The 
ash  of  serum-albumin  contains  an  excess  of  sodium  chloride,  but  the  ash 
of  the  proteids  of  muscle  contains  an  excess  of  potash  salts  and  phos- 
phates. The  nature  of  the  connection  of  the  ash  with  the  proteid  is 
still  a  matter  of  obscurity.     Globin  from  haemoglobin  is  free  from  ash. 

Proteids  are  all  amorphous  ;  some  are  soluble,  some  insoluble 
in  water,  and  all  are  for  the  most  part  insoluble  in  alcohol  and 
ether ;  they  are  all  soluble  in  strong  acids  and  alkalies,  but  in 
becoming  dissolved  mostly  undergo  decomposition.  Their  solu- 
tions possess  a  left-handed  rotatory  action  on  the  plane  of  polari- 
zation, the  amount  depending  on  various  circumstances,  and 
being,  with  one  exception,  viz.,  peptones,  changed  by  heating. 

Crystals  into  wdiose  composition  certain  proteid  (globulin)  elements 
enter  were  long  since  observed  in  the  seeds  of  many  plants ;  as  yet  they 
have  not  been  obtained  sufficiently  isolated  or  in  quantities  large  enough 

'  Hdb.  Phys.  Path.  Chem.  Anal.,  Ed.  iv,  (1875),  S.  223. 
2  See  Gmelin,  Hdb.  Org.  Chem.,  Bd.  viii,  S.  285. 


PROTEIDS.  949 


to  permit  of  any  accurate  analysis  to  be  made.  Quite  recently,  how- 
ever,' a  method  of  isolating  in  quantity  and  reerystallizing  the'^e  srb- 
stances  has  been  indicated,  and  it  seems  ])robable  that  analysis  of  the-e 
may  lead  to  interesting  information  on  the  subject  of  the  constitution 
and  combinations  of  proteids. 

Their  presence  may  be  detected  by  the  following  tests  : 

1.  Heated  with  strong  nitric  acid,  they  or  their  solutions  turn 
3'ellow^,  and  this  color  is.  on  the  addition  of  ammonia,  changed 
to  a  deep-orange  hue.     (Xanthoproteic  reaction.) 

2.  With  Millon's  reagent  they  give,  when  present  in  sufficient 
quantity,  a  precipitate,  which,  with  the  supernatant  lluid,  turns 
red  on  heating.  If  they  are  onh^  present  in  traces  no  precipitate 
is  obtained,  but  mereh'  the  red  coloration. 

3.  "With  caustic  soda  solution,  and  one  or  tw^o  drops  of  a  solu- 
tion of  cupric  sulphate,  a  violet  color  is  obtained,  which  deepens 
on  boiling. 

The  above  serve  to  detect  the  smallest  traces  of  all  proteids. 
The  two  following  tests  may  be  used  when  there  is  more  than  a 
trace  present,  but  do  not  hold  for  every  kind  of  proteid. 

4.  Eender  the  fluid  strongly  acid  with  acetic  acid,  and  add  a 
few  dr<)])s  of  a  solution  of  ferrocyanide  of  potassium  ;  a  precipi- 
tate shows  the  presence  of  proteids. 

5.  Eender  the  fluid,  as  before,  strongh'  acid  with  acetic  acid, 
add  an  equal  volume  of  a  concentrated  solution  of  sodium  sul- 
phate, and  boil.     A  precipitate  is  formed  if  proteids  are  present. 

This  last  reaction  is  useful,  not  only  on  account  of  its  exactness,  but 
also  because  the  reagents  used  produce  no  decomposition  of  other  bodies 
which  may  be  present ;  and  hence,  after  fihration,  the  same  fluid  may 
be  further  analyzed  for  other  substances.  Additional  methods  of  freeing 
a  sohition  from  proteids  are:  Acidulating  with  acetic  acid  and  boiling, 
avoiding  any  excess  of  the  acid  ;  precipitation  by  excess  of  alcohol ;  in 
the  latter  case  the  solution  n)ust  be  neutral  or  faintly  acid.  Hoppe- 
Seyler'^  recommends  tlie  employment  of  a  sat?nated  solution  of  fresidy 
jirecipitated  ferric  oxide  in  acetic  acid.  Rriicke's  metb.od  of  removing 
the  last  traces  of  proteids  from  glycogen  solutions  is  also  of  use  (see  p. 
977).  Precipitation  of  the  last  traces  (  f  proteids  by  means  of  hydrated 
oxide  of  lead  at  a  boiling  temperature^  may  be  also  employed. 

Proteids  may  be  very  conveniently  divided  into  classes. 

'  Drechsel,  Journ.  f.  prakt.  Chem.,  X.  F.  Bd.  xix  (1879),  S.  331. 

2  Op.  cit.,  S.  227. 

3  Hofmeister,  Zeitsch.  f.  Phvsiol.  Chem.,  Bd.  ii  (1878),  S.  288. 


950        CHEMICAL    BASIS    OF    THE    ANIMAL    BODY. 


Class  I. — Native  Albumins. 

Members  of  this  class,  as  their  name  implies,  occur  in  a  nat- 
ural condition  in  animal  tissues  and  fluids.  They  are  soluble  in 
water,  are  not  precipitated  by  very  dilute  acids,  by  carbonates  of 
the  alkalies,  or  by  sodium  chloride.  Tiiey  are  coaoulated  b}-  heat- 
ing to  a  temperature  of  about  70^.  If  dried  at  40^',  the  resulting 
mass  is  of  a  pale-yellow  color,  easily  friable,  tasteless,  and  in- 
odorous. 

1.  Eijg-alhumin. 

Forms  in  aqueous  solution  a  neutral,  transparent,  yellowish 
fluid.  From  this  it  is  precipitated  by  excess  of  stroni:;  alcohol. 
If  the  alcohol  be  ra[)idly  removed  the  precipitate  may  be  readily 
redissolved  in  water ;  if  subjected  to  lengthier  action  a  coagula- 
tion occurs,  and  the  albumin  is  then  no  longer  thus  soluble. 
Strong  acids,  especially  nitric  acid,  cause  a  coagulation  similar 
to  that  produced  by  heat  or  by  the  prolonged  action  of  alcohol ; 
the  albumin  becomes  profoundly  changed  by  the  action  of  the  acid 
and  does  not  dissolve  upon  removal  of  the  acid.  Mercuric  chloride, 
silver  nitrate,  and  lead  acetate  precipitate  the  albumin  without 
coagulation  ;  on  removal  of  the  precipitant  the  precipitate  may 
be  redissolved. 

Strong  acetic  acid  in  excess  gives  no  precipitate,  but  when  the 
solution  is  concentrated  the  albumin  is  transformed  into  a  trans- 
parent Jelh".  A  similar  jelly  is  produced  when  strong  caustic 
potash  is  added  to  a  concentrated  solution  of  egg-albumin.  In 
both  these  cases  the  substance  is  profoundly  altered. 

The  specific  rotatory  power  of  egg-albumin  in  aqueous  solution 
is,  for  yellow  light,  —  35.5°.  Hydrochloric  acid,  added  until  the 
reaction  is  strongly  acid,  increases  this  rotation  to — 37.7°.  The 
formation  of  the  gelatinous  compound  with  caustic  potash  is  at 
first  accompanied  with  an  increase,  but  this  is  followed  by  a 
decrease  of  rotation. 

Preparation. — White  of  hen's  egg  is  broken  up  with  scissors 
into  small  pieces,  diluted  with  an  equal  bulk  of  water,  and  the 
mixture  shaken  strongly  in  a  tlask  till  quite  frothy ;  on  standing, 
the  foam  rises  to  the  top,  and  carries  all  the  fibres  in  whose  mesh- 
work  the  albumin  was  contained.  The  fluid,  from  which  the 
foam  has  been  removed,  is  strained,  and  treated  carefully  with 
dilute  acetic  acid  as  long  as  any  precipitate  is  formed  ;  the  pre- 
cipitate is  then  filtered  oft",  and  the  filtrate  after  neutralization 
concentrated  at  40°  to  its  original  bulk. 

2.  Serum-alhinnin. 

This  form  of  albumin  resembles,  to  a  great  extent,  the  one 
previously  described.  The  following  may  suffice  as  distinguish- 
ing features  : 


PROTEIDS.  951 


1.  The  specific  rotation  of  serura-albumin  is  — 56°  ;  that  of 
egg-albumin  is  — 35.5^,  both  measured  for  yellow  light. 

2.  SeruQi-albumin  is  not  coagulated  by  ether,  egg-albumin  is. 

3.  Serum-alljumin  is  not  very  readily  precipitated  by  strong 
hydrochloric  acid,  and  such  precipitate  as  does  occur  is  readily 
redissolved  on  further  addition  of  the  acid ;  the  exact  reverse  of 
these  two  features  holds  good  for  egg-albumin. 

4.  Precipitated  or  coagulated  serum-albumin  is  readih' soluble, 
egg-albumin  is  with  difficulty  soluble,  in  strong  nitric  acid. 

Serum-albumin  is  found  not  only  in  blood-serum,  but  also  in 
lymph,  both  that  contained  in  the  proper  lymphatic  channels  and 
that  diffused  in  the  tissues ;  in  chyle,  milk,  transudations,  and 
many  pathological  tluids. 

It  is  this  form  in  which  albumin  generally  appears  in  the  urine. 

In  Piddition  to  the  above,  Scherer^  has  described  two  closely  related 
bodies,  to  which  he  gives  the  names  Paralbumin  and  Metalbumin  The 
tirst  he  obtained  from  ovarian  cysts;  its  alkaline  solutions  are  remarka- 
ble for  being  very  ropy.  It  seems  doubtful  whether  this  bodv  is  a  pro- 
teid;  it  differs  sensiblv  in  composition  from  these.  Ilaerlin-  gives  as 
its  composition,  O.  26.8;  H,  0.9;  N,  12.8  ;  C,  51.8  ;  S,  1.7  per  cent.  It 
seems  to  be  associated  with  some  body  like  glycogen,  capable  of  being 
converted  into  a  substance  giving  the  reactions  of  dextrose.  Metalbu- 
min, found  in  a  dro])sical  fluid,  resembles  the  preceding,  but  is  not  pre- 
cipitated by  hydrochloric  acid,  or  by  acetic  acid  and  ferrocyanide  of 
potassium  ;  it  is  precipitate  1.  but  not  coaguhitei,  by  alcohol  ;  its  solution 
is  scarcely  coagulated  on  boiling. 

Albumins  are  generally  found  associated  with  small  but  definite 
amoimts  of  saline  matter.  A.  Schmidt^  says  that  they  may  lie  freed 
from  these  by  dial3-sis.  and  that  they  are  then  not  coagulated  on 
boiling.  From  this  it  might  be  inferred  that  the  albumin  and 
the  saline  matters  were  peculiarly  related,  and  that  the  latter 
played  some  special  part  during  the  coagulation  of  the  former  by 
heat.  Schmidt's  observations,  however,  have  not  been  conclu- 
sively corroborated  b}'  subsequent  observers. 

Class  II. — Derived  Albumins  [Albuminates). 

1.   Acid-albumin.  .    . 

When  a  native  albumin  in  solution,  such  as  serum-albumin,  is 
treated  for  some  little  time  with  a  dilute  acid  such  as  hydro- 
chloric, its  properties  become  entirely  changed.  The  most 
marked  changes  are  (1)  that  the  solution  is  no  longer  coagulated 


^  Ann.  der  Chem.  und  Pliarm.,  Bd.  82,  S.  135. 
»  Chem.  Centralblatt,  18f)2.     No.  56. 
»  Pfluger's  Archiv,  xi  (1875),  S.  1. 


952        CHEMICAL    BASIS    OF    THE    ANIMAL    BODY, 


b}^  heat ;  (2)  that  when  the  solution  is  carefully  neutralized  the 
whole  of  the  proteid  is  thrown  down  as  a  precipitate  ;  in  other 
words,  the  seruin-alhumin  which  was  sohd)le  in  water,  or  at  least 
in  a  neutral  fluid  containinu:  only  a  small  quantity  of  neutral 
salts,  has  become  converted  into  a  substance  insoluble  in  water 
or  in  similar  neutral  tiuids.  The  body  into  which  serum-albumin 
thus  becomes  converted  by  the  action  of  an  acid  is  spoken  of  as 
add-alhwiii'in.  Its  characteristic  features  are  that  it  is  insoluble 
in  distilled  water,  and  in  neutral  saline  solutions,  such  as  those 
of  sodium  chloride,  that  it  is  readily  soluble  in  dilute  acids  or 
dilute  alkalies,  and  that  its  solutions  in  acids  or  alkalies  are  not 
coagulated  by  boiling.  When  suspended,  in  the  undissolved 
state,  in  water,  and  heated  to  TO*^,  it  becomes  coagulated,  and  is 
then  undistinguishable  from  coagulated  serum  albumin,  or,  in- 
deed, from  any  other  form  of  coagulated  proteid.  It  is  evident 
that  the  substance  when  in  solution  in  a  dikite  acid  is  in  a  dif- 
ferent condition  from  that  in  which  it  is  when  precipitated  ])y 
neutralization.  If  a  quantity  of  serum  or  egg-albumin  be  treated 
with  dilute  hydrochloric  acid,  it  will  be  found  that  the  conver- 
sion of  the  native  albumin  into  acid-albumin  is  gradual ;  a  speci- 
men heated  to  70^  immediately  after  the  addition  of  the  dilute 
acid,  will  coagulate  almost  as  usual ;  and  another  specimen  taken 
at  the  same  time  will  give  hardly  any  precipitate  or  neutraliza- 
tion. Some  time  later,  the  interval  depending  on  the  proportirm 
of  the  acid  to  the  albumin,  on  temperature,  and  on  other  circum- 
stances, the  coagulation  will  be  less,  and  the  neutralization  pre- 
cipitate will  be  considerable.  Still  later  the  coagulation  will  be 
absent,  and  the  whole  of  the  proteid  will  be  thrown  down  on 
neutralization. 

If  linely-chopped  muscle,  from  which  the  soluble  albumins 
have  been  removed  by  repeated  washing,  be  treated  for  some  time 
with  dilute  (.2  per  cent.)  hydrochloric  acid,  the  greater  part  of 
the  muscle  is  dissolved.  The  transparent  acid  tiltrate  contains  a 
large  quantity  of  proteid  material  in  a  form  which,  in  its  general 
characters  at  least,  agrees  with  acid-albumin.  The  acid  solution 
of  the  proteid  is  not  coagulated  by  boiling,  but  the  whole  of  the 
proteid  is  precipitated  on  neutralization  ;  and  the  precipitate,  in- 
soluble in  neutral  sodic  chloride  solutions,  is  readily  dissolved  by 
even  dilute  acids  or  alkalies.  The  proteid  thus  obtained  from 
muscle  has  been  called  syntonin,  but  we  have  at  present  no  satis- 
foctory  test  to  distinguish  the  acid-albumin  (or  syntonin)  prepared 
from  muscle  from  that  prepared  from  egg  or  serum  albumin. 
When  coagulated  albumin  or  other  coagulated  proteid  or  librin 
is  dissolved  in  strong  acids,  acid-albumin  is  formed  ;  and  when 
librin  or  any  other  proteid  is  acted  upon  by  gastric  juice,  acid- 
albumin  is  one  of  the  tirst  products  ;  and  these  acid-albumins 
cannot  be  distinguished  from  acid-albumin  prei)ared  from  muscle 
or  native  albuunn.  Though  hydrochloric  acid  is  perhaps  the 
most  convenient  acid  for  forming  acid-albumin,  other  acids  may 
also  be  used  for  the  purpose  of  preparing  it.     Acid-albumin  is 


PROTEIDS.  953 

soluble  not  only  in  dilute  alkalies,  but  also  in  dilute  solutions  of 
alkaline  carbonates  ;  its  solutions  in  these  are  not  coagulated  by 
boilino:. 

If  sodic  chloride  in  excess  is  added  to  an  acid  solution  of  acid- 
albumin,  the  acid-albumin  is  precii)itated  ;  this  also  occurs  on 
adding  sodium  acetate  or  phosphate. 

As  special  tests  of  acid-albumin  may  be  given  :  1.  Partial  coag- 
ulation of  its  solution  in  lime-water  on  boihug.  2.  Further  pre- 
cipitation of  the  same  solution  after  boiling,  on  the  addition  of 
calcic  chloride,  magnesic  sulphate,  or  sodic  chloride. 

Dissolved  in  very  dilute  hydrochloric  acid,  acid-albumin  (syn- 
tonin)  prepared  from  muscle  possesses  a  specific  la?vo-rotatory 
power  of  — 12-  for  light  3'ellow,  this  being  independent  of  the 
concentration.^  On  heating  the  solution  in  a  closed  vessel  in  a 
water-bath,  the  rotatory  power  rise's  to  — 84.80. 

2,   AJ kali-albumin. 

If  serum  or  eg<^  albumin  or  washed  muscle  be  treated  with 
dilute  alkali  instead  of  with  dilute  acid,  the  proteid  undergoes  a 
change  quite  similar  to  that  which  was  brought  about  by  the 
acid.  The  alkaline  solution,  when  the  change  has  become  com- 
plete, is  no  longer  coagulated  by  heat,  the  proteid  is  wholly  pre- 
cipitated on  neutralizati(m.  and  the  precipitate,  insoluble  in 
water  and  in  neutral  sodic  chloride  solutions,  is  readil}'  soluble 
in  dilute  acids  or  alkalies.  Indeed,  in  a  general  way,  it  may  be 
said  that  acid -albumin  and  alkali-albumin  are  nothing  more 
than  solutions  of  the  same  substance  in  dilute  acids  and  alkalies 
respectively.  When  the  precipitate  obtained  b}-  the  neutraliza- 
tion of  a  solution  of  acid-albumin  in  dilute  acid  is  dissolved  in  a 
dilute  alkali,  it  may  l3e  considered  to  become  alkali-albumin  :  and 
conversely  when  the  precipitate  obtained  from  an  alkali-albumin 
solution  is  dissolved  in  dilute  acid,  it  may  be  regarded  as  acid- 
albumin. 

It  is  stated  as  a  characteristic  reaction  of  this  modified  or  de- 
rived albumin  that  it  is  not  precipitated  when  its  alkaline  solu- 
tions are  neutralized  in  the  presence  of  alkaline  phosphates  ;  so- 
lutions of  acid-albumin,  on  the  contrary,  are  said  to  be  precipi- 
tated on  neutralizaiioii  in  the  presence  of  alkaline  phosphates, 
and  this  difference  is  considered  to  be  a  distinguishing  feature  of 
the  two  proteids. 

Alkali-albumin  may  be  prepared  by  the  action  not  only  of 
dilute  alkalies,  but  als^o  of  strong  caustic  alkalies  on  native  albu- 
mins as  well  as  on  coagulated  albumin  and  other  proteids.  The 
jelly  jiroduced  by  the  action  of  caustic  potash  on  white  of  egg, 
spoken  of  in  Class  I,  1.  is  alkali-albumin  ;  the  similar  jellv  pro- 
duced b}-  strong  acetic  acid  is  acid-albumin.  One  of  the  most 
productive  methods  of  obtaining  alkali-albumin  is  that  intro- 


Hoppe-Seyler,  Hdb.  Phys.  Path.  Chem.  Anal..  Ed.  iv  (1875),  S.  246. 


954        CHEMICAL    BASIS    OF    THE    ANIMAL    BODY. 


duced  by  Lieberkiihn,'  and  consists  in  adding  strong  solution  of 
caustic  potash  to  white  of  egg  until  the  above-mentioned  jelly  is 
obtained.  This  is  then  cut  into  small  pieces  and  dialyzed  until 
quite  white.  The  lumps  are  then  dissolved  in  the  water-bath, 
and  the  alkali-albumin  precipitated  by  the  careful  addition  of 
acetic  acid. 

Both  alkali  and  acid  albumin  are  Avith  difficulty  precipitated 
by  alcohol  from  their  alkaline  or  acid  solutions.  The  neutraliza- 
tion precipitate,  however,  becomes  coagulated  under  the  pro- 
longed action  of  alcohol. 

The  body  "  protein,"  for  whose  existence  Mulder  has  so  miicli  con- 
tended, appears,  if  it  exists  at  all,  to  be  closely  connected  with  this 
body.  All  subsequent  observers  have,  however,  failed  to  confirm  his 
views. 

The  rotatory  powder  of  alkali-albumin  varies  according  to  its 
source  ;  thus  when  prepared  by  strong  caustic  potash  from  serum- 
albumin,  the  rotation  rises  from  — 5(5^  (that  of  serum-albumin)  to 
— 80^,  for  yellow  light.  Similarly  prepared  fiom  egg-albumin,  it 
rises  from — 38.5^  to — 47'^,  and  if  from  coagulated  white  of  egg,  it 
rises  to  —  58.8^.  Hence  the  existence  of  various  forms  of  alkali- 
albumin  is  probable. 

In  addition  to  the  metbods  given  above,  alkali-alburnin  may  be  also 
readily  obtained  by  sliaking  milk  witlx  strong  caustic  soda  solution  and 
ether,  removing  the  etherial  solution,  precipitating  the  remaining  fluid 
with  acetic  acid,  and  washing  the  precipitate  with  water,  cold  alcohol, 
and  ether. 

The  most  satisfactory  method  of  regarding  acid  and  alkali 
albumin  is  to  consider  them  as  respectively  acid  and  alkali  com- 
pounds of  the  neutralization  precipitate.  We  have  reason  to 
think  that  Avhen  the  precipitate  is  dissolved  in  either  an  acid  or 
an  alkali,  it  does  enter  into  combination  with  them.  The 
neutralization  precipitate  is  in  itself  neither  acid  nor  alkali 
albumin,  but  may  become  either  upon  solution  in  the  respective 
reagent. 

It  is  probab'le  tliat  several  derived  albumins  exist,  differing  according 
to  the  proteid  from  which  tbey  are  formed  or  possil)lv  according  to  the 
mode  of  tlieir  {^reparation,  and  tliat  each  of  these  may  exist  in  its  co  - 
relative  forms  of  acid  and  alkali  albumin  ;  but  tbe  wbole  subject  requires 
further  investigation. 

Acid-albumin,  prepared  by  the  direct  action  of  dilute  acids  on 
native  albumins  or  on  muscle-substance,  contains  sulphur,  as 
shown  by  the  brow'u  coloration  which  appears  when  the  precipi- 
tate is  heated  with  caustic  potash  in  the  presence  of  basic  lead 
acetate.     Alkali-albumin,  at  all  events  as  prepared  by  the  action 

'  Poggendorff's  Annalen,  Bd.  Ixxxvi,  S.  118. 


PROTEIDS.  955 


of  strong  caustic  potash  or  soda,  does  not  contain  an}^  sulphur; 
and  the  acid-albumin,  prepared  by  the  solution  in  an  acid  of  the 
neutralization  precipitate  from  such  an  alkali-albumin  solution, 
is  similarly  free  from  sulphur. 

3.   Casein. 

This  is  the  well-known  proteid  existing  in  milk.  When  freed 
from  fat,  and  in  the  moist  condition,  it  is  a  white,  friable,  opaque 
body.  In  most  of  its  reactions  it  correspcmds  closely  with  alkali- 
albumin  ;  thus  it  is  readily  soluble  in  dilute  acids  and  alkalies, 
and  is  reprecipitated  on  neutralization  ;  if,  however,  potassium 
phosphate  is  present,  as  is  the  case  in  milk,  the  solution  must  be 
strongly  acid  before  any  precipitate  is  obtained. 

Yarions  reactions  have  at  different  times  been  assigned  to  casein  as 
characterizing  it  from  the  closely  allied  body  alkali-aibr.niin.  Later  le- 
searches  have,  liowever,  in  most  cases  cast  so  ni'.icii  douht  on  these  dif- 
ferences that  the  identity  or  non-identity  of  casein  and  alkali-albumin 
must  still  be  left  an  open  question. 

Casein,  as  occurring  in  miik,  has  had  several  reactions  ascribed  to  it, 
as  characteristic ;  but  these  lose  their  importance  on  considering  that 
milk  contains,  in  addition  to  casein,  other  substances,  sucli  as  potassium 
phosphate,  and  a  number  of  bodies  which  yield  acids  by  fermentation. 
The  presence  of  potassium  phosphate  has  an  especial  inliuence  on  the 
reaction  of  casein.  In  the  entire  absence  of  this  salt,  acetic  acid  in  the 
smallest  quantities,  as  also  carbonic  acid,  gives  a  precipitate  ;  but  if  this 
salt  is  present,  carbonic  acid  gives  no  precipitate,  and  acetic  acid  one 
only  when  the  solution  is  acid  from  the  presence  of  fiee  acid,  and  not 
from  that  of  acid  potassium  phosi)hate.' 

When  prepared  from  milk  b}^  magnesium  sulphate  (see  below) 
freed  by  ether  from  fats,  and  dissolved  in  water,  casein  possesses 
a  specitic  rotator}^  power  of — 80^  for  yellow  light ;  in  dilute  Jilka- 
line  sohitions  of —7(5^  ;  in  strong  alkaline  solutions  of — 91^  ;  in 
dilute  hydrociiloric  acid  of — 87"^. 

Casein  has  been  asserted  to  occur  in  muscle,  in  serous  fluids, 
and  in  blood-serum  (serum-casein).  In  many  cases  it  has  prob- 
ably been  confounded  with  globulin  (see  Class  III)  ;  but  blood- 
serum  and  muscle-plasma  undoubtedly  contain  an  alkali-albumin 
in  addition  to  whatever  globulin  may  be  present,  but  the  usual 
doubt  exists  as  to  the  identity  of  this  with  true  casein.  Its  pres- 
ence luay  be  shown  by  adding  dilute  acetic  acid  to  blood -serum 
which  has  been  freed  from  globulin  by  a  current  of  carbonic  acid 
gas  ;  a  distinct  precipitate  is  thrown  down.  A  substance  simi- 
lar to  casein  has  also  been  described  as  existing  in  uustriated 
muscle  and  in  the  protoplasm  of  nerve-cells. 

Frepandion. — liilute  miikwith  several  times  its  bulk  of  water, 
add  dilute  acetic  acid  till  a  precipitate  begins  to  appear,  then 
pass  a  current  of  carbonic  acid  gas,  tilter,  and  wash  the  precipi- 

1  See  Kiihne,  Lehrb.  d.  Physiol.  Chem.  1868,  S.  565. 


956         CHEMICAL    BASIS    OF    THE     ANIMAL     BODY. 


tate  with  water,  alcohol,  and  ether; -the  complete  removal  of  the 
fat  carried  down  with  the  casein  presents  some  difficulties.  Mag- 
nesium sulphate  added  to  saturation  also  precipitates  casein  from 
milk  ;  the  precipitate  thus  formed  is  readily  soluble  on  the  addi- 
tion of  water. 

Class  111.— Globulins. 

Besides  the  native  albumins  there  are  a  number  of  native  pro- 
teids  which  differ  from  the  albumins  in  not  being  soluble  in  dis- 
tilled water ;  they  need  for  their  solution  the  presence  of  an  ap- 
preciable, though  it  may  be  a  small  quantity  of  a  neutral  saline 
body  such  as  sodium  cbloride.  Thus  they  resemble  the  albu- 
minates in  not  being  soluble  in  distilled  water,  but  dilfer  from 
them  in  being  soluble  in  dilute  sodium  chloride  or  other  neutral 
saline  solutions.  Their  general  characters  may  be  stated  as  fol- 
lows : 

They  are  insoluble  in  water,  soluble  in  dilute  (one  per  cent.) 
solutions  of  sodium  chloride  ;  they  are  also  soluble  in  dilute  acids 
and  alkalies,  being  changed  on  solution  into  acid  and  alkali-albu- 
min respectively.  The  saturation  with  solid  sodium  chloride  of 
their  solutions  in  dilute  sodium  chloride  precipitates  most  mem- 
bers of  this  class. 

1.   Globulin  [Crystallin). 

If  the  crystalline  lens  be  rubbed  up  with  fme  sand,  extracted 
with  water  and  filtered,  the  filtrate  will  be  found  to  contain  at 
least  three  proteids.  On  passing  a  current  of  carbonic  acid  gas 
a  copious  precipitate  occurs  ;  this  is  globulin. 

The  addition  of  dilute  acetic  acid  to  the  filtrate  from  the  globulin, 
gives  a  precipitate  of  alkali-albnniin  ;  and  the  filtrate  from  this  if  heated 
gives  a  further  precipitate,  due  to  serum-albumin. 

In  its  general  reactions  globulin  corresponds  almost  exactly 
with  the  next  members  of  this  class  (pnraglobulin  and  fibrinogen), 
but  has  no  power  to  form  or  promote  the  formation  of  fibrin  in 
fluids  containing  the  above-mentioned  bodies,  and  possesses  the 
following  si)ecial  features  :  1.  According  to  Lehmann,  its  oxyge- 
nated, neutral  solutions  become  cloudy  on  heating  to  73^,  and 
are  coagulated  at  93^.  2.  It  is  readily  precipitated  on  the  addi- 
tion of  alcohol.  According  to  Hoppe-Seyler,  it  is  not  precipi- 
tated on  saturation  with  sodium  chloride,  resembling  vitellin  in 
this  respect. 

According  to  Kiihne^  and  Eichwald^  a  globulin  with  properties  iden- 
tical with  those  just  given  may  be  precipitated  from  dilute  serum  by 
the  cautious  addition  of  acetic  acid.     This  body  is  stated  by  WeyP  to 

'  Op.  cit.,  S.  175. 

2  Beitrage  zur  Chem.  d.  gewebebild.  Subst.,  Berlin,  1873.    Hf.  i. 

3  Zeitschr.  f.  Physiol.  Chem.,  Bd.  i  (1878),  S.  79. 


PROTEIDS.  957 

be  the  same  a=;  paraglobnlin  (fibrinoplastin),  the  latter  clifTering  from  it 
only  by  a  small  admixture  of  librin-ferment. 

2.  ParagJohulin  [FihrinopJastin). 

Preparation. — Blood-serum  is  diluted  tenfold  with  water,  and 
a  brisk  current  of  carbonic  acid  gas  is  passed  through  it.  The 
first-formed  cloudiness  soon  becomes  a  tlocculent  precipitate, 
which  is  finally  quite  granular,  and  nva}'  easily  be  separated  by 
decantation  and  fiUration  ;  it  should  be  washed  on  the  filter  with 
water  containing  carljonic  acid. 

It  has  usually  been  stated  that  paraglobnlin  may  be  separated 
from  serum  by  saturation  with  sodic  chloride.  According  to 
Hanunarsten,^  however,  this  is  only  in  part  true,  a  considerable 
portion  of  the  globulin  remaining  unprecipitated.  The  separa- 
tion may,  however,  be  comjiletely  efiected  by  saturation  with 
magnesic  sulphate.  When  determined  by  this  method  the  amount 
of  paraglobnlin  in  serum  is  very  considerable,  amounting-,  ac- 
cording to  Hammarsten,  to  as  much  as  4.5(35  per  cent,  (reckoned 
on  lOU  cc.  of  serum).  The  quantity  seems  to  vary  in  difterent 
animals,  the  precipitation  being  much  more  complete  in  serum 
from  ox-blood  than  in  that  from  the  blood  of  horses. 

From  its  solution  in  dilute  sodic  chloride,  paraglobnlin  maybe 
precipitated  by  a  current  of  carbonic  acid  gas,  or  the  addition  of 
cxceedinghj  dilute  (less  than  1  pro  mille)  acetic  acid.  If  the  acid 
is  strong  enouiih  to  dissolve  the  precipitated  proteid,  this  becomes 
immediately  changed  into  acid-albumin  (Class  II).  In  pure 
water,  free  from  oxygen,  paraglobnlin  is  insoluble,  but  on  shak- 
ing with  air  or  passing  a  current  of  oxygen,  solution  readily  takes 
place  ;  from  this  it  maybe  reprecipitated  by  a  current  of  carbonic 
acid  gas.  Very  dilute  alkalies  dissolve  this  bod}-  without  change  ; 
if,  however,  the  strength  of  the  alkali  be  raised  even  to  1  per  cent, 
the  paraglobnlin  is  changed  into  alkali-albumin  (Class  II). 

According  to  K  hue  and  A.  Schmidt,  the  solution  of  this  body 
in  water  containing  oxygen,  or  in  very  dilute  alkalies,  are  not 
coagulated  on  heating.  The  sodic  chloride  solutions  do,  how- 
ever, coagulate  when  heated  to  68^-70^  C..^  and  if  the  substance 
itself  be  suspended  in  water  and  heated  to  70^  it  is  coagulated. 
Although  insoluble  in  alcohol,  its  solutions  are  with  difiiculty 
precipitated  by  this  reagent. 

A  characteristic  test  f  )r  this  body  is  that  it  gives  rise  to  fibrin 
when  added  to  many  transudations,  e.  g.^  hydrocele,  pericardial, 
peritoneal,  and  pleural  fiuids. 

Paraglobulin  occurs  not  only  (and  chiefly)  in  blood-scrum,  but 
it  is  also  found  in  white  corpuscles,  in  the  stroma  of  red  cor- 
puscles (to  some  extent  at  least),  in  connective  tissue,  cornea, 
aqueous  humor,  lymph,  chyle,  and  serous  fluids. 

J  Pfliiger's  Archiv,  Bd.  xvii  (1878),  S.  446. 
"^  Hammarsten,  op.  eit. 


958        CHEMICAL    BASIS    OF    THE    ANIMAL    EODY 


For  the  occurrence  of  globulin  in  urine,  see  Eclefsen'  and  Senator.^ 

3.  Fibrinogen. 

The  general  reactiDns  of  this  body  are  identical  with  those  of 
paraglobulin.  The  most  marked  ditlerence  between  the  two  is 
the  point  at  which  coagulation  of  their  solutions  takes  place. 
Hannnarsten^  has  shown  that  librinogen  in  a  1-5  per  cent,  solu- 
tion of  sodic  chloride  coagulaics  at  from  5"2'^-^-55^  C,  whereas,  as 
stated  above,  paraglobulin  (fibrinoplastin)  coauulates  first  at  from 
68^-7tP  C.  The  characteristic  test  for  its  presence  is  the  forma- 
tion of  fibrin  when  its  solution  is  added  to  a  solution  known  to 
contain  paraglobulin  and  librin-fermeiit.  Minor  ditterences  be- 
tween the  two  may  be  thus  enumerated  :  In  the  preparation  of 
fibrinogen  the  containing  tluid  nuist  be  much  more  strongly 
diluted,  and  the  current  of  carbonic  acid  gas  must  pass  for  a 
much  longer  time.  The  precipitate  thus  obtained  ditfers  from 
that  of  paraglobulin  in  that  it  forms  a  viscous  deposit,  adhering 
more  closely  to  the  sides  and  bottom  of  the  containing  vessel ; 
there  is  also  no  Hocculent  stage  previous  to  the  viscous  precipi- 
tate. The  two  also  exhibit  slight  microscopical  ditferences. 
Alcohol  and  ether  both  precipitate  this  body  from  its  solution^ 
but  a  mixture  of  the  two  (8  parts  alcohol,  1  part  ether)  is  most 
eflectual. 

Fibrinogen  occurs  in  blood,  chyle,  serous  fluids,  and  in  various 
transudations. 

Preparation. — This  is  the  same  as  for  paraglobulin,  regard 
being  had  to  the  peculiarities  mentioned  above.* 

There  is  no  ])roof  that  the  icJiok  of  the  substance  thrown  down 
by  carbonic  acid  from  diluted  blood-serum  is  fibrinoplastic,  in- 
deed we  know  that  a  true  globulin  devoid  of  fibrinoplastic  ])rop- 
erties  may  be  prepared  from  serum. ^  WeyP  considers  that  there 
is  only  one  globulin  in  serum,  which  he  characterizes  by  the 
name  of  "serum-globulin,"  and  regards  fibrinoplastin  as  a  mix- 
ture of  this  body  with  a  portion  of  fil)rin-ferment.  We  know  for 
certain  (see  p.  34)  that  the  whole  of  the  fibrinf)plastic  precipitate, 
used  to  cause  the  coagulation  of  a  fibrinogenous  fluid,  does  not 
enter  into  the  composition  of  the  fibrin  produced  ;  we  also  know 
that  such  a  precipitate  may  lose  its  fibrinoplastic  powers  without 
any  marked  change  in  its  general  reactions.  It  would  seem  ad- 
visable, therefore,  to  speak  of  the  deposit  produced  by  carbonic 
acid  in  dilute  serum,  or  b}-  saturation  with  sodium  chloride  in 
undiluted  serum,  as  globulin,  and  to  distiuiiuish  it  as  fibrino- 


'  CentralLlatt  f.  d.  Med.  Wiss.,  1870,  S.  3G7.    Also  Arch.  f.  Klin.  Med. 
Bd.  7,  S.  69. 

■'  Virchow's  Archiv,  Bd.  60,  S.  476. 

^  Upsala  Liikarefoienings  Forhandlingar,  Bd.  xi,  1876. 

*  See  Hammarsten,  Pfl tiger's  Archiv,  Bd.  xix,  S,  563. 

^  Kiiline  and  Eichwald,  loc.  cit.  ^  Loc.  cit. 


PROTEIDS.  959 


plastic  globulin  when  it  is  able  to  give  rise  to  fibrin.  Fibrinogen 
similarly  might  be  spoken  of  as  librinogenous  globulin.  The 
name  crystullin,  rather  than  globulin,  might  then  be  given  to 
the  substance  obtained  from  the  crystalline  lens. 

4.  Myosin. 

This  is  the  substance  which  forms  tlie  chief  proteid  constituent 
of  dead,  rigid  muscle  ;  its  general  properties  and  mode  of  prepa- 
ration have  been  already  described  at  p.  95.  In  the  moist  condi- 
tion it  forms  a  gelatinous,  elastic,  clotted  mass  ;  dried,  it  is  very 
brittle,  slightlytransparent.  and  elastic.  From  its  solution  in  a 
sodium  chloride  solution  it  is  precipitated,  either  by  extreme  dilu- 
tion or  by  saturation  with  the  solid  salt.  When  precipitated  by 
dilution  and  submitted  to  the  prolonged  action  of  water  myosin 
loses  its  property  of  being  soluble  in  solutions  of  sodic  chloride.^ 
The  sodic  chloride  solution,  if  exposed  to  a  rising  temperature, 
becomes  milky  at  55^,  and  gives  a  tlocculent  precipitate  at  (50^. 
This  precipitate  is,  however,  no  longer  m3-osin,  for  it  is  insoltible 
in  a  10  per  cent,  sodium  chloride  solution,  and  does  not,  until 
after  many  days'  digestion,  yield  syntonin  on  treatment  with 
hydrochloric  acid  (.Iper  cent.).  It  is,  in  fact,  coagulated  proteid 
(see  Class  Y). 

Myosin  is  excessively  soluble  in  dilute  acids  and  alkalies,  but 
undergoes,  in  the  act  of  solution,  a  radical  change,  becoming  in 
the  one  case  acid-albtimin  or  syntonin,  in  the  other  alkali-albu- 
min (Class  II). 

Like  fibrin,  it  can  in  some  cases  decompose  hydrogen  dioxide,  and 
oxidize  guaiacum  with  formation  of  a  blue  color. 

5.  ViieUin. 

As  obtained  from  3-olk  of  egg,  of  which  it  is  the  chief  proteid 
constituent,  vitellin  is  a  white  granular  body,  insoluble  in  water, 
but  very  soluble  in  dilute  sodium  chloride  sohitions  ;  it  surpasses 
myosin  in  this  respect,  for  the  solution  may  be  easily  filtered. 
Its  coagulation-point  is  higher  than  that  of  myosin,  lying,  ac- 
cording to  Weyl,-'  between  70^  C.  and  80^  C.  Saturation  with 
solid  sodium  chloride  gives  no  precipitate  ;  in  this  respect  it  dif- 
fers from  most  other  members  of  this  class.  In  yolkof  egs;  vitel- 
lin is  always  associated  with,  and  probably  exists  in  combination 
with,  the  peculiar  complex  body  lecithin.     (See  p.  988.) 

Denis,  and  after  him  Hoppe-Seyler,  have  shown  that  vitellin  before 
the  treatment  requisite  to  free  it  from  lecithin,  possesses  properties  quite 
different  from  otbea-  proteids. 

1  Wevl,  Zeitsclir.  f.  Phvsiol.  Chem.,  Bd.  i  (1878),  S.  77. 
•''  Op.  cit. 


960         CHEMICAL    BASIS    OF    THE    ANIMAL    BODY. 


A  theory  has  been  advanced  that  vitellin  is  really  a  complex 
body  like  haemoglobin,  and  on  treatment  with  alcolu)l  splits  up 
into  coagulated  proteid  and  lecithin.  When  well  purified  it  con- 
tains .75  per  cent,  sulphur,  but  no  phosphorus.  Dilute  acids  or 
alkalies  readily  convert  it  in  its  uncoagulated  form  into  a  member 
of  Class  II. 

Fremy  and  Valenciennes^  have  described  a  series  of  proteids,  viz., 
ichthin,  ichtliidin,  etc.,  derived  from  fish  and  amphibia.  They  api)eir 
to  be  either  identical  with,  or  closely  related  to,  vitellin. 

Preparation. — Yolk  of  egg  is  treated  with  successive  quantities 
of  ether,  as  long  as  this  extracts  any  yellow  coloring  matter  ;  the 
residue  is  dissolved  in  moderately  strong  (10  per  cent.)  sodium 
chloride  solution,  and  filtered.  Tlie  filtrate  on  falling  into  a 
large  excess  of  water  is  precipitated.  In  this  state  it  is  mixed 
with  lecithin  and  nuclein,  and  in  order  to  free  it  from  these  it 
was  usually  treated  with  alcohol.  This,  as  above  stated,  entirely 
changes  the  vitellin  into  a  coagulate  1  form.  It  seems  probable 
that  the  separation  of  vitellin  from  the  other  bodies  with  which 
it  is  mixed  in  the  yolk  of  Qs^fr  may  be  effected  by  precipitating 
the  sodic  chloride  solution  by  the  addition  of  excess  of  water; 
the  precipitate  is  then  redissolved  in  10  per  cent,  solution  of 
sodic  chloride  and  the  process  repeated  as  rapidly  as  possible.^ 

6.   Glohin. 

Globin,  stated  by  Preyer''  to  be  the  proteid  residue  of  the  complex 
body  haemoglobin  (see  p.  454),  ought  probably  to  be  considered  as  an 
outlying  member  of  this  class.  It  is,  however,  not  readily  soluble  either 
in  dilute  acids  or  sodium  chloride  solutions.  It  is  remarkable  for  being 
absolutely  free  from  ash. 

Class  IV.     Fihrin. 

Insoluble  in  water  and  dilute  sodium  chloride  solutions  ;  soluble 
with  difficulty  in  dilute  acids  and  alkalies,  and  more  concentrated 
neutral  saline  solutions. 

Fibrin,  as  ordinarily  obtained,  exhibits  a  filamentous  structure, 
the  component  threads  possessing  an  elasticity  much  greater 
than  that  of  any  other  known  solid  proteid. 

If  allowed  to  form  gradually  in  large  masse-;,  the  filamentous  structure 
is  not  so  noticeable,  and  it  resembles  in  this  form  jiure  india-rubber. 
Such  Imnps  of  fibrin  are  capable  of  being  s|»lit  in  any  direction,  and  no 
definite  arrangement  of  parallel  bundles  of  fibres  can  be  made  out. 

At  ordinary  temperatures  fibrin  is  insoluble  in  water,  being 
dissolved  only  at  very  high  temperatures,  and  then  undergoing  a 

1  Compt.  Eend.,  T.  38,  pp.  4G9  and  525. 

^  Weyl,  op.  cit.,  S.  74.  ■'  Die  Blutkrystalle  (1871),  S.  16G. 


PROTEIDS.  961 


complete  elian2:e  in  its  characters.  In  hydrochloric  acid  soki- 
tions  of  1-5  per  cent,  fibrhi  swells  up  and  becomes  transparent, 
but  is  not  dissolved.'  In  this  condilion  the  mere  removal  of  the 
acid  b}-  an  excess  of  water,  neutralization,  or  the  addition  of 
some  salt,  causes  a  return  to  the  original  state.  U\  liowever, 
the  acid  be  allowed  to  act  for  many  days  at  ordinary  tempera- 
tures or  for  a  few  hours  at  40^-60^,  solution  takes  place,  and  the 
resulting  proteid  is  syntonin.  In  dilute  alkalies  and  ammonia, 
fibrin  is  much  more  readily  soluble,  though  in  this  case  also  the 
solution  is  greatly  aided  by  warming  ;  the  resulting  fluid  con- 
tains no  longer  tibrin,  but  alkali-albumin.  This  propert}'  is  not 
distinctly  characteristic  of  tibrin,  although  it  dissolves,  perhaps, 
more  readily  in  both  dilute  acids  and  alkalies  than  do  coagulated 
proteids.  Xone  of  these  solutions  can  be  coagulated  on  heating, 
■which  is  intelligible  when  it  is  remembered  that  they  no  longer 
contain  tibrin,  but  either  acid-  or  alkali-alljumin.  In  addition  to 
the  above  tibrin  is  soluble,  though  with  difficulty  and  only  after 
a  considerable  time,  in  10  per  cent,  solutions  of  sodium  chloride, 
potassium  nitrate,  or  sodium  sulphate.  These  solutions  may  be 
coagulated  by  a  temperature  of  (50°;  in  fact,  by  the  action  of  the 
neutral  saline  solutions  the  fibrin  has  become  converted  into  a 
body  exceedingly  like  myosin  or  globulin. 

On  ignition  of  librin  a  residue  of  inorganic  matter  is  always 
obtained  ;  it  is,  however,  considered  that  sulphur  is  the  only  one 
of  these  elements  which  enters  essentiall}'  into  its  composition. 
In  other  respects  tibrin  corresponds  entirely  in  general  compo- 
sition with  other  proteids. 

Suspended  in  water  and  heated  to  70°,  it  loses  its  elasticity, 
and  becomes  opaque  ;  it  is  then  indistinguishable  from  other 
coagulated  proteids. 

A  peculiar  property  of  this  body  remains  yet  to  be  mentioned,  viz., 
its  power  of  decomposino^  hydrogen  dioxide.  Pieces  of  fibrin  }ilaced  in 
this  fluid,  though  them^^elves  undergoing  no  change,  soon  become  covered 
with  bubl)les  of  oxygen  ;  and  guaiacura  is  turned  blue  by  fibrin  in  pres- 
ence of  hydrogen  dioxide  or  ozonized  turpentine.  In  the  language  of 
Schonbeins  theory  fibrin  is  an  ozone-bearer. 

Preparatioyi. — Either  by  washing  blood-clots,  or  whipping  blood 
with  a  bundle  of  twigs  and  then  washinir.  If  required  quite 
colorless  it  should  be  prepared  from  plasma  free  from  corpuscles. 
If  the  blood,  before  whipping,  be  diluted  with  an  equal  bulk  of 
water,  the  subsequent*  washing  of  the  fibrin  is  much  facilitated, 
and  it  may  readily  be  obtained  quite  white. 

When  globulin^  myosin,  and  tibrin  are  compared  with  each 
other,  it  will  be  seen  that  they  form  a  series  in  which  myosin  is 
intermediate  between  globulin  and  tibrin.    Globulin  is  excessively 

'  (_V)mpIete  solution  may,  however,  take  place  if  the  fibrin  contains 
pepsin.     See  note,  p.  oG7. 


962        CHEMICAL    BASIS    OF    THE    ANIMAL    BODY. 


soluble  in  eveu  the  most  dilute  acids  and  alkalies  ;  fibrin  is  almost 
insoluble  in  these  ;  while  myosin,  thoufrh  more  soluble  than  filirin, 
is  less  soluble  than  globulin.  Globulin  airain  dissolves  with  (he 
greatest  ease  in  a  ver}-  dikite  soluti(m  of  sodium  chloride.  Myosin, 
on  the  other  hand,  dissolves  with  difficulty  i  it  is  much  more  solu- 
ble in  a  10  per  cent,  than  in  a  1  per  cent,  solution  of  sodium 
chloride  ;  and  even  in  a  10  per  cent,  solution  the  myosin  can 
hardly  be  said  to  be  dissolved,  so  viscid  is  the  resulting  fluid  and 
with  such  difficulty  does  it  filter.  Fibrin  again  dissolves  with 
great  difficulty  and  ver\-  slowly  in  even  a  10  per  cent,  solution  of 
sodium  chloride,  and  in  a  1  per  cent,  solution  it  is  practically  in- 
soluble. "When  it  is  remembered  that  fibrin  and  myosin  are, 
both  of  them,  the  results  of  coagulation,  their  similarity  is  in- 
telligible. Myosin  is  in  fact  a  somewhat  more  soluble  form  of 
fibrin  deposited,  not  in  threads  or  filaments,  but  in  clumps  and 
masses. 

Class  Y .  —  Coagulated  Proteids. 

These  are  insoluble  in  water,  dilute  acids  and  alkalies,  and 
neutral  saline  solutions  of  all  strengths.  In  fact  they  are  really 
soluble  only  in  strong  acids  and  strong  alkalies,  though  prolonsred 
action  of  even  dilute  acids  and  alkalies  will  effect  some  solution, 
especially  at  high  temperatures.  During  solution  in  strong  acids 
and  alkalies  a  destructive  decomposition  takes  place,  but  some 
amount  of  acid  or  alkali-albumin  is  always  produced. 

Very  little  is  known  of  the  chemical  characteristics  of  this 
class.  They  are  produced  by  heating  to  70^,  solutions  of  eg^^r  or 
serum-albumin,  globulins  suspended  in  water  or  dissolved  in 
saline  solutions,  fibrin  suspended  in  water  or  dissolved  in  saline 
solutions,  or  precipitated  acid  and  alkali-albumin  suspended  in 
water.  They  are  readily  converted  at  the  temperature  of  the 
body  into  peptones,  by  the  action  of  gastric  juice  in  an  acid,  or 
of  pancreatic  juice  in  an  alkaline  medium. 

Class  YL—Feptones. 

Yer}'  soluble  in  water,  and  not  precipitated  from  their  aqueous 
solutions  by  the  addition  of  acids  or  alkahes,  or  by  boiling.  In- 
soluble in  alcohol,  they  are  precipitated  with  difliculty  by  this  re- 
agent, and  are  unchanged  in  the  process;  they  di tier  from  all 
other  proteids  in  not  being  coagulated  by  exposure  to  alcohol. 
They  are  not  precipitated  l3y  cupric  sulphate,  ferric  chloride,  or, 
except  in  the  instances  to  be  mentioned  presently,  by  potassium 
ferrocyanide,  and  acetic  acid.  In  these  points  the}^  difier  from 
most  other  proteids.  On  the  other  hand,  precipitation  is  caused 
b}' chlorine,  iodine,  tannin,  mercuric  chloride,  nitrates  of  mercury 
and  silver,  and  both  acetates  of  lead  ;  also  by  bile-acids  in  an 
acid  solution.  In  common  with  all  proteids.  these  bodies  possess 
a  specific  l?evo-rotatory  power  over  polarized  light ;  but  they  differ 


PROTEIDS.  9j3 


from  all  other  proteids  in  the  fact  that  boiUng  produces  no  change 
in  the  amount  of  rotation. 

A  sohition  of  peptones,  mixed  with  a  strong  sohition  of  caustic 
potash  gives,  on  the  addition  of  a  mere  trace  of  cupric  sulphate, 
a  red  color.  An  excess  of  the  cupric  salt  gives  a  violet  color, 
which  deepens  in  tint  on  boiling,  in  fact  the  ordinary  proteid  re- 
action. Other  proteids  simply  give  the  violet  color.  But  the 
most  characteristic  feature  of  peptones  is  their  extreme  diffusi- 
bility,  a  propert}'  whicli  they  alone,  of  all  the  proteids,  ma}-  be 
said  to  possess,  since  all  other  forms  of  proteids  pass  through 
membranes  with  the  greatest  difficulty,  if  at  all. 

Xotwitlistandino;  their  probable  formation  in  lame  quantities 
in  the  stomach  and  intestines,  to  Judije  from  the  result  of  artificial 
digestion,  a  very  small  quantity  only  can  be  found  in  the  contents 
of  these  organs,  or  in  tlie  chyle.  They  are  probabl}'  absorbed  as 
soon  as  formed.  Another  point  of  interest  is  their  reconversion 
into  other  forms  of  ))roteids,  since  this  must  occur  to  a  great  ex- 
tent in  the  body.  We  are,  however,  as  yet  ignorant  of  the  man- 
ner in  which  this  reverse  change  is  effected . 

Production. — All  proteids,  with  the  exception  of  lardacein, 
3'ield  peptones  (and  other  products)  on  treatment  with  acid  gas- 
tric or  alkaline  pancreatic  juice,  most  readily  at  the  temperature 
of  the  human  body.  Peptones  are  likewise  produced,  in  the  ab- 
sence of  pepsin  and  trypsin,  by  the  action  of  dilute  and  moder- 
ately strong  acids  at  medium  temperatures  ;  also  by  the  action  of 
distilled  water  at  very  high  temperatures  and  great  pressure.  For 
various  methods  of  preparing  peptones,  see  Adamkiewicz'  and 
Henninger.- 

Xo  exact  difference  in  percentage  composition  between  pep- 
tones and  the  proteids  from  which  they  are  formed  has,  at  pres- 
ent, been  established. 

AVe  have  used  the  phrase  '"])eptones"  in  the  plural  number 
because  we  have  reason  to  think  that  more  than  one  kind  of  pep- 
tone exists.  Meissner^  described  three  pepttmes,  naming  them 
respectively  A-B-  and  C-peptone.  He  distinguished  them  as  fol- 
lows :  A-peptone  is  precipitated  from  its  aqueous  solutions  by 
concentrated  nitric  acid,  and  also  by  potassium  ferrocyanide  in 
the  presence  of  even  weak  acetic  acid.  B-peptone  is  not  precipi- 
tated by  concentrated  nitric  acid,  nor  will  potassium  ferrocyanide 
give  a  precipitate  unless  a  considerable  quantit}'  of  strong  acetic 
acid  be  added  at  the  same  time.  C-peptone  is  precipitated  neither 
by  nitric  acid  nor  by*  potassium  ferrocyanide  and  acetic  acid, 
whatever  be  the  strength  of  the  acetic  acid.  In  place,  however, 
of  speaking  of  all  these  as  peptones,  it  is  better  to  consider 
C-peptone  as  the  only  real  peptone,  and  the  A-  and  B-peptones 


Die  Xiitur  u.  Xaiirv.erth  d.  Peptons  (1877),  S.  33. 

De  la  Xature  et  du  Role  physiologique  des  Peptones,  Paris,  1878. 

Zeitschr.  f.  rat.  Med.,  Bde.  vii,  viii,  x,  xii  nnd  xiv. 


964        CHEMICAL    BASIS    OF    THE    ANIMAL    BODY. 


as  not  peptones  at  all.  Nevertheless,  we  have  reason,  from  the 
researches  of  K'ihne,  to  speak  of  more  than  one  peptone,  viz.: 
of  a  hemipeptone  which  is  capahle  under  the  action  of  trypsin  of 
being  converted  into  leucin  and  tyrosin,  and  of  an  antipeptone 
which  resists  such  a  decomposition.  The  name  antipeptone  is 
given  to  the  latter  on  account  of  this  resistance  Avhich  it  offers 
towards  trypsin  ;  the  name  hemipeptone,  given  to  the  former, 
signifies  that  tliis  peptone  is  the  twin  or  correlative  half  of  anti- 
peptone. 

We  have  seen  (p.  317)  that  when  any  protcid  is  digested  with 
pepsin,  what  we  may  prehminarily  call  a  by-product  makes  its 
appearance.  This  by-product,  which  has  many  resemblances  to 
acid-albumin  or  syntonin,  appearinii;  as  a  neutralization  precipi- 
tate soluble  in  dilute  acids  and  alkali,  but  insoluble  in  distilled 
water,  is  generally  spoken  of  as  para  peptone.  According  to 
Tinkler'  this  neutralization  precipitate  is  es);ecially  abundant  if 
the  pepsin  be  previously  modified  b}'  exposure  to  a  temperature 
of  40^  to  60^  C.  The  pepsin  thus  modified  is  spoken  of  by  Finkler 
as  "isopepsin."  Many  authors  regard  parapeptone,  syntonin, 
and  acid-an)umin  as  being  the  same  thing.  Meissner,  however, 
gave  the  name  parapeptone  to  a  body,  which  need  not  and  prob- 
aijly  does  not  make  its  appearance  during  normal  natural  diges- 
tion, or  during  artificial  digestion  with  a  thoroughly  active  pepsin, 
but  which  is  formed  when  proteids  are  subjected  to  the  action  of 
weak  hydrochloric  acid,  either  alone  or  in  company  with  an  im- 
perfectly-acting pepsin,  and  which  in  certain  characters  is  quite 
distinct  from  ordinary  syntonin  or  acid-alljumin.  Its  distinguish- 
ing feature  is  that  it  cannot  be  changed  into  peptone  by  the  action 
of  even  the  most  energetic  pepsin,  though  it  is  readily  so  con- 
verted under  the  influence  of  trypsin  ;  otherwise  it  very  closely 
resembles  syntonin.  We  have  here  an  indication  that  the  simple 
characters  by  which  Ave  have  described  acid-albumin  may  be 
borne  by  bodies  having  marked  ditferences  from  each  other.  The 
researches  of  Klihne,  to  wiiich  we  have  briefly  referred  in  the 
text  (p.  338),  have  tiirown  an  important  light  on  these  differences. 
The  fundamental  notion  of  KUhne's  view  is  that  an  ordinary 
native  albumin  of  fibrin  contains  within  itself  two  residues,  which 
he  calls  respectively  an  anti-residtie  and  a  hemi-residue.  The 
result  of  either  peptic  or  tryptic  digestion  is  to  split  tip  the  albu- 
min or  fibrin,  and  to  produce  on  the  part  of  the  anti-residue  anti- 
peptone, and  on  the  part  of  the  hemi-residue  hemipeptone,  the 
latter  being  distinguished  from  the  fn-mer  by  its  being  snscep- 
tible  of  further  change  by  try])tic  digestion  into  leucin,  tyrosin, 
etc.  Antipei)tone  remains  as  antipeptone,  even  when  placed 
under  the  action  of  the  most  powerftil  tryjDsin,  provided  putre- 
factive changes  do  not  intervene. 

Before  the  stage  of  peptone  (whether  anti- or  hemi-)  is  reached, 

'  Pfliiger's  Archiv.  xiv  (1877),  S.  128. 


PROTEIDS.  96i 


there  is  an  intermediate  stage  corresponding  to  the  formation  of 
syntoniu.  In  both  normal  peplie  and  tryptic  digestion  antipep- 
tone  is  preceded  by  an  actialbumose.  and  hemipeptone  by  a 
hemialbumose.  Of  these  tlie  antialbumose  is  closely  related  to 
syntonin,  and  has  hitherto  been  regarded  as  syntonin.  The  hemi- 
albumose has  not  been  so  frequently  observed ;  it  was.  however, 
isolated  b\'  Meissner ;  it  is  apparent!}-  the  body  called  by  him 
A-peptone.  It  possesses  a  peculiar  feature  in  being  soluble  at 
about  7U-^  C. ,  and  beiug  reprecipitated  on  cooling  :  in  this  respect 
it  closely  resembles  a  proteid  body  observed  by  Bence-Jones  in 
the  urine  of  osteomalacia.  It  approaches  myosin  in  being  readily 
soluble  in  a  10  per  cent,  solution  of  sod ium"^  chloride. 

If,  however,  albumin  be  digested  with  insufficient  or  with  im- 
perfectly actiug  pepsin,  or  simply  with  dilute  hydrochloric  acid 
at  40-,  antialbumose  is  not  formed,  but  in  its  place  a  body  makes 
its  appearance  which  Kuhne  calls  antialbumate.'  Its  character- 
istic property  is  that  it  cannot  be  converted  by  peptic  digestion 
into  peptone,  though  it  can  be  so  changed  by  tryptic  digestion. 
It  is.  in  fact,  the  parapeptoiie  of  Meissner. 

It  may,  perhaps,  be  advisable,  now  that  Meissner's  parapep- 
tone  is  cleared  up,  to  reserve  the  name  parapei)tone  for  the  initial 
products  of  both  peptic  and  tryptic  digestion,  to  speak  of  anti- 
albumose and  hemialbumose  as  bting  both  parapeptones.  ]5ut 
in  this  sense  parapeptones  will  be  an  intermediate  and  not  a  col- 
lateral product  of  digestion. 

Meissner  also  described  a  particularly  insoluble  form  of  his 
para  peptone  as  dyspeptone,  and  another  intermediate  product  as 
metapeptone  :  but  further  investigation  of  both  these  bodies,  as 
well  as  of  his  B-peptone.  is  necessary.  Under  the  intluence  of 
dilute  hydrochloric  acid,  antialbumate  becomes  changed  into 
a  body  which  Iv'-.hne  calls  antialliumim,  and  whicli  seems  iden- 
tical with  the  very  insoluble  ]>roteid  descril^ed  by  Schlitzenberger 
as  "  hemiprotein,"'  and  probably  with  Meissner's  dyspeptone. 
The  same  body  is  produced  at  once  in  company  with  products 
belonging  to  the  hemi-group  by  the  action  of  3  to  5  per  cent, 
sulphuric  acid  on  native  albumin  or  tibrin.  The  following  table 
shows  the  relations  and  genesis  of  the  bodies  we  have  just  de- 
scribed. The  several  products  (antipeptone,  etc.)  are  given  in 
duplicate,  on  the  hypothesis  (which  though  not  proved  is  proba- 
ble) that  the  changes  of  digestion  are  essentially  hydrolytic 
changes,  accompanied  by  a  deduplication.  That  just  as  a  mole- 
cule of  starch  splits  up- into  at  least  two  molecules  of  dextrose, 
or  as  a  molecule  of  cane-sugar  splits  up  into  a  molecule  of  dex- 
trose and  a  molecule  of  levulcse.  so  a  molecule  of  antialbumose, 
for  instance,  splits  up  into  two  molecules  of  antipeptone.  and  so 
on.     But  the  whole  scheme  is,  of  course,  only  provisional. 

1  An  albumate  must  not  be  confounded  with  an  albuminate. 
81 


966        CHEMICAL    BASIS    OF    THE    ANIMAL    BODY 

DECOMrosiTioN  OF  Pkoteids  by  Digestion. 

Albumin, 


Antialbumose. 

Hemialbiimose.                       4- 

1 

1                 >' 

ipeptone.  Antipeptone. 

Ilemipeptone.  Hemipeptone.    1    -2 

1                  1       ij 

Leucin.  Tyrosin.  Leucin.  Tyrosin.   I     -^ 
etc.                        etc.                J    c^ 

Decomposition  by  Acids. 

1. 

By  .25  p.  c.  HCI  at  40^  C. 

Albumin. 

1 

Antiall)uinate. 

lieinialbumose. 

Antiali)umid. 

Hemipeptone.     Hemipeptone. 

2. 

By  3-5 

p.  c.  H2SO,  at  100^  C. 

Albumin. 

1 

Antialhumid. 

Hemialbnmose. 

Hemipeptone.     Hemipeptone. 

Leucin.  Tyrosin,  etc.  Leucin.  Tvrosin,  etc. 

Class  VIL — Lardacein^  or  the  so-called  amyloid  substance. 

The  substance  to  which  the  above  name  is  applied,  is  found  as 
a  deposit  in  the  spleen  and  liver,  also  in  numerous  other  organs, 
such  as  the  bloodvessels,  kidneys,  lungs,  etc. 

It  is  insoluble  in  water,  dilute  acids  and  alkalies,  and  neutral 
saline  solutions. 

In  centesimal  composition  it  is  almost  identical  with  other  pro- 
teids,^  viz.  : 

_  ^  C.  Schmidt,  Ann.  d.  Chem.  u.  Pharra.,  Bd.  110,  8.  250,  and  Fried- 
reich and  Kekule'   Virchow's  Archiv,  Ed.  16,  S.  50. 


PROTEIDS. 

O.  and  S. 

H.                        X. 

C. 

24.4 

7.0                      15.0 

53.6 

967 


The  sulphur  in  this  body  exists  in  the  oxidized  state,  for  boil- 
ing with  caustic  potash  gives  no  sulphide  of  the  alkali.  The 
above  results  of  analysis  would  lead  at  once  to  the  ranking  of 
lardacein  as  a  proteid.  and  this  is  borne  out  by  other  facts.  Strong 
hydrochloric  acid  converts  it  into  acid-albumin,  and  caustic  alka- 
lies into  alkali-albumin.  On  the  other  hand,  it  exhibits  the  fol- 
lowing marked  differences  from  other  proteids  :  It  wholly  resists 
the  action  of  ordinary  digestive  fluids:  it  is  colored  red.  not 
yellow,  b3'  iodine,  and  violet  or  pure  blue  by  the  joint  action  of 
iodine  and  sulphuric  acid.  From  these  last  reactions  it  has  de- 
rived one  of  its  names,  '•  am^ioid,''  though  this  is  evidently 
badly  chosen.  Xot  only  does  it  differ  from  the  starch  group  in 
composition,  but  by  no  means  can  it  be  converted  into  sugar  ; 
this  latter  is  one  of  the  crucial  tests  for  a  true  member  of  the 
amyloid  group.  According  to  Heschl'  and  CorniP  auilin-violet 
(methyl-anilin)  colors  lardaceous  tissue  rosy  red.  but  sound  tissue 
blue. 

The  colors  mentioned  above,  as  being  prtxluced  by  iodine  and  sul- 
phuric acid,  are  much  clearer  and  brighter  when  the  i-eagents  are  ap- 
plied to  the  purilied  lardacein.  AMien  the  reagents  are  applied  to  the 
crude  suLst  nice  in  its  normal  position  in  the  tissues,  the  c<jlors  oJjtained 
are  always  dark  and  dirty-looking. 

Purified  lardacein  is  readily  soluble  in  moderately  dilute  am- 
monia, and  can  by  evaporation  be  obtained  from  this  solution  in 
the  form  of  tough,  gelatinous  flakes  and  lumps  ;  in  this  form  it 
gives  feeble  reactions  onl}-  with  iodine.  If  the  excess  of  ammo- 
nia is  expelled,  the  solution  becomes  neutral,  and  is  precipitated 
b^'  dilute  acids. 

'^Preparation. — The  gland  or  other  tissue  containing  this  body, 
is  cut  up  into  small  pieces,  and  as  much  as  possible  of  the  sur- 
roundina:  tissue  removed.  The  pieces  are  then  extracted  several 
times  with  water  and  dilute  alcohol,  and  if  not  thus  rendered 
colorless  are  repeatedly  boiled  with  alcohol  containing  lu'dro- 
chloric  acid.  The  residue,  after  this  operation,  is  digested  at 
40^,  with  good  artificial  gastric  juice  in  excess.  Evervthing  ex- 
cept lardacein,  and  small  quantities  of  mucin,  nuclein,  keratin, 
together  with  some  portion  of  the  elastic  tissue,  will  thus  be  dis- 
solved and  removed:^  From  the  latter  impurities  it  may  be 
separated  by  decantation  of  the  finely-powdered  substance. 

The  chief  products  of  the  decomposition  of  proteids  are  ammo- 
nia, carbonic  acid,  leucin,  and  t3T0sin.     Several  other  bodies, 

*  Wien.  med.  Wochenschr.,  No.  32,  S.  714. 


Compt.  Rend.,  May  24,  1875. 


*  Kiihne,  Virchow's  Arch.,  Bd.  33, 


968         CHEMICAL    BASIS    OF    THE    ANIMAL    BODY, 


for  the  most  part,  like  leiicin,  amidated  acids,  such  as  aspartic 
acid,  ghitainic  acid,  etc.,  have  also  been  obtained.  But  urea  has 
never  yet  been  derived  by  direct  decomposition  from  protcid  ma- 
terial, the  statements  to  this  etlect  having  Ijeen  based  on  errors. 
In  spite  of  numerous  researches  we  cannot  at  present  state  defi- 
nitely what  is  the  real  constitution  of  a  proteid,  or  in  what  man- 
ner these  several  residues  are  contained  in  the  undecomposed 
substance.  It  is  unnecessary  to  give  here  any  of  the  formula} — 
nearly  all  empirical— wliich  have  been  made  to  represent  these 
bodies  ;  they  all  give  with  equal  exactitude  the  percentage  com- 
position, but  beyond  this  thuy  are  untrustworthy.  Of  the  va- 
rious attempts  which  have  been  made  to  assign  to  proteids  some 
detiiiite  molecular  structure,  none  appear  at  the  present  stage  of 
information  siithciently  reliable  for  general  acceptance. 

Among  the  inost  eluborate  l:i])()r.s  in  this  direction  may  be  mentioned 
those  of  liiasiwe'iZ  and  Habernian.  in  their  first  pul)l:cition,  starting 
from  the  general  similarity  of  the  products  of  decomposition  of  the  pro- 
teids and  carbohydrates,  they  tried  to  establish  a  delinite  relation  between 
the  two  classes  of  bodies.  In  this  they  were  not  successful,  and  from 
their  second  research'^  they  come  to  the  conclusion  that  the  carbohydrates 
take  no  pait  in  the  formation  of  the  proteids. 

Other  experiments  in  the  same  direction  are  due  to  Schu::zenberger.3 
He  shows  that  alljumin  can  be  decomposed  into  carbonic  anhydride  and 
ammonia,  and  that  the  ratio  of  these  two  is  the  same  as  thougli  urea  had 
been  the  body  on  which  he  o[)erated.  From  this  he  concludes  that  "the 
molecule  of  albumin  contains  the  gi-ouping  of  urea  and  represents  a  com- 
plex ureide."  In  his  second  pubii(;ation*  he  confirms  his  previous  re- 
sults, stating  that  the  ammonia,  carbonic  anhydride,  and  oxalic  acid, 
produced  by  the  decomposition  of  proteids,  are  so  connected  quantita- 
tively as  to  be  capable  of  derivation  from  varying  proportions  of  urea 
and  oxamide.  He  also  obtained  from  the  decomposition  of  proteids  a 
nitrogenous  residue  which  could  be  ibrnndated  as  giving  rise  to  all  the 
amidated  acids  and  other  bodies  spoken  of  above.  Thus,  according  to 
him,  albumin,  built  up  as  a  complex  iweide,  decomposes  into  ammonia, 
carbonic,  oxalic,  and  acetic  acids,  and  this  nitrogenous  body  :  this  last, 
then,  gives  rise  to  the  other  products  of  deconqjosition.^ 

It  will  be  noticed  that  in  the  general  description  of  the  various 
proteids,  distinctive  reactions  for  each  could  not  be  given,  but 
that  varying  solubilities  were  the  chief  means  at  our  disposal  for 
distinguishing  them.  They  may  be  arranged  according  to  their 
solubilities  in  the  following  tabular  form. 


'   Ann.  d.  Chem.  u.  Pharm.  Bd.  159,  S.  804. 

•^  Ibid,  Bd.  169,  S.  150.  ^  Comptes  Keiid-:s,  T.  80,  p.  232. 

*  Compt.  Rend.,  T.  81,  p.  1108. 

^  See  also  Schiitzenberger,  Ann.  de  Chem.  et  de  Phvs.,  T.  xvi  (1879), 
p.  280. 


PROTEIDS.  9(39 

Soluble  in  dlMiJkd  icater  : 

Aqueous  solution  not  coagulated  on  boiling,     Peptones. 
Aqueous  solution  coagulated  on  boiling,     .     Albumins. 

Insoluble  in  distilled  icatcr : 

Soluble  in  NaCl  solution  1  per  cent.,     .     .     Globulins. 
Insoluble,     "  "  ''         ... 

Soluble  in  HCl  .1  per  cent,  in  the  cold,  |      ^^'"f.    ;i''''  /'^' 
^  '  I        kah-albumin. 

Insoluble  in  HCl  .1  per  cent,  in  the  ]       i^.j    • 
cold,  but  soluble  at  60=,.     .     .     .•  j      ^''^'''"• 

Insoluble  in  HCl  .1  per  cent,  at  GO-  ;  soluble  in  strong 
acids. 


Soluble  in  gastric  iuice. 


Coagulated    al- 


buyni)i. 
Insoluble, Lardacein. 

Such  a  classification  is,  however,  obviously  a  wholly  artificial 
ORe.  useful  for  temporary  purposes,  but  in  no  way  illustrating 
the  natural  relations  of  the  several  members.  Xor  is  a  division 
into  ''  native  "''  and  ;■  derived  "  proteids  much  more  satislhctory. 
It  is  true  that  we  may  thus  put  together  serum- and  egg-albumin, 
with  vitellin.  myosin,  and  fibrin  on  the  one  iiand  ;  and  peptones, 
coagulated  proteids,  and  acid-  with  alkali-albumin,  on  the  other 
But  in  what  light  are  we  to  consider  casein,  seeing  that  though 
a  natural  product,  it  has  so  many  resemblances  to  alkali- 
albumin  V  Moreover,  the  S3'stem  of  classification  must  be  useless 
which  would  place  fibrinoplastic  globulin  and  fibrinogen  in  the 
same  class  as  fibrin,  and  yet  we  can  hardly  speak  of  either  of  the 
two  former  V)odies  as  derived  proteids.  If  the  vie\v  be  true  that 
when  fibrin  is  converted  into  peptone  the  large  molecule  of  the 
former  is  spUt  up,  with  assumi)tion  of  water,  into  two  smaller 
molecules  of  the  latter,  one  belonging  to  the  *'  anti  "  and  the 
other  to  the  "  hemi "  group,  we  might  speculate  on  a  ])ossible 
classification  of  all  proteids  into  hemi-proteids.  anti-proteids,  and 
holo-proteids.  Thus  serum-  and  egg-albumin,  myosin,  and  fibrin 
would  be  undoubtedh^  holo-proteids,  peptones  either  anti-  or 
hemi-proteids,  and  we  should  have  to  distinguish  probably  in 
the  heterogeneous  groups  of  derived  albumins  both  anti-.  hemi-, 
and  holo-proteid  members.  It  is  possible,  moreover,  that  fibrino- 
plastic and  fibrinogenous  globulin  and  casein  may  be  natural 
hemi-  or  anti-proteids,  and  not  holo-proteids.  But  we  have  at 
present  no  positive  knowledge  on  these  points. 

XlTROGEXOUS   XoX-CkYSTALLIXE   BODIES   ALLIED   TO 

Proteids. 

These  resemble  the  proteids  in  many  general  points,  but  ex- 
hibit among  themselves  much  greater  difierences  than  the  pro- 
teids do.     As  reirardis  their  molecular  structure  nothing  satistac- 


970        CHEMICAL    BASIS    OF    THE    ANIMAL    BODY. 


tory  is  known.  Their  percentaoje  composition  approaches  thnt 
of  the  proteids,  and  like  tliese  they  yield,  under  hydrolytic  treat- 
ment, large  quantities  of  leucin  and  in  some  cases  tyrosin.  They 
are  all  amorphous. 

Mucin.— {O,  35.75.     H,  6.81.     N,  8.50.    C,  48.94.)^ 

The  characteristic  component  of  mucus.  Its  exact  composi- 
tion is  not  yet  known,  the  figures  given  above  being  merely  an 
approximation. 

As  occurring  in  the  normal  condition  it  gives  to  the  fluids 
which  contain  it  the  well-known  ro])y  consistency,  and  can  be 
precipitated  from  these  by  acetic  acid,  alcohol,  alum,  and  min- 
eral acids  ;  the  latter,  if  in  excess,  redissolve  the  precipitate, 
but  this  is  not  the  case  with  acetic  acid.  In  its  precipitated  form 
it  is  insoluble  in  water,  but  swells  up  strongly  in  it,  and  this 
effect  is  increased  b}^  the  presence  of  man}-  alkali  salts.  Alkalies 
and  alkaline  earths  dissolve  it  readily.  Its  solutions  do  not 
dialyse  ;  the}^  give  the  proteid  reactions  with  Millon's  reagent 
and  nitric  acid,  but  not  that  with  sulphate  of  copper,  and  are 
precijHtated  by  basic  lead  acetate  only  when  neutral  or  faintly 
alkaline.  According  to  Eichwald,^  when  heated  with  dilute 
mineral  acids,  mucin  yields  acid-albumin,  and  another  body 
which  in  many  of  its  properties  closely  resembles  a  sugar  ;  it  re- 
duces solutions  of  cupric  suli)hate.  Prolonged  boiling  with  sul- 
phuric acid  gives  leucin  and  about  7  per  cent,  of  tyrosin. 

Preparation.  —From  ox-gall,  by  precipitation  with  alcohol,  re- 
dissolving  in  water  and  precipitating  with  acetic  acid.  It  may 
also  be  advantageously  obtained  from  snails''  or  the  submaxillary 
gland  of  the  ox.* 

C}w7idrin.—{0,  31.04.  H,  6.76.  :N',  13.87.  C,  47.74.  S,  60 
per  cent.  Y 

This  is  usually  regarded  as  forming  the  essential  part  of  the 
matrix  of  hyahne  cartilage,  and  is  contained  in  the  interstices  of 
the  fibres  in  elastic  cartilage.  A  similar  substance  can  be  pre- 
pared from  the  cornea.  Boiled  with  water,  it  dissolves  slowly, 
forming  an  opalescent  solution,  which  is  precipitated  by  acetic 
acid,  lead  acetate,  dilute  mineral  acids,  alum,  and  salts  of  silver 
and  copper  ;  an  excess  of  the  last  four  reagents  redissolves  the 
precipitate.  Solutions  of  this  body  gelatinize  on  standing,  even 
if  very  dilute  ;  the  solid  mass  is  insoluble  in  cold  water,  readily 
soluble  in  hot  water,  alkalies,  and  anmionia. 

1  Eichwald,  Ann.  d.  Chem.  u.  Pharm.,  Bd.  134,  S.  193. 

2  Op.  cit. 

3  Eich^vald,  op.  cit.  and  Chem.  Centralb.,  1866,  No.  14. 
*  Staedeler,  Ann.  d.  Chem.  u.  Pharm.,  Bd.  Ill,  S.  14. 

^  I.  V.  Mering,  Beitrag  zur  Chemie  des  Knorpels,  1873. 


CHONDRIN.  971 


The  aqueous  and  alkaline  solutions  of  chondrin  possess  a  left- 
handed  rotatory  power  on  polarized  light  of —  213. 5-^ ;  in  presence 
of  excess  of  alkali  this  becomes  —  552.0^,  both  measured  for  yellow 
light. 

It  seems,  according  to  the  observations  of  many,  that  chon- 
drin can,  b}'  heating  with  hydrochloric  acid,  be  converted  into  a 
body  whose  reactions  resemble  those  of  syntonin,  and  another 
substance,  which  like  the  similar  product  from  mucin,  so  far 
resembles  grape-sugar  that  it  reduces  cupric  salts  in  alkaline 
solution;^  it  appears,  however,  to  contain  nitrogen.  A  recent 
observer'  has  denied  the  existence  of  chondrin  as  a  distinct  sub- 
stance and  regards  it  as  in  all  cases  a  mere  mixture  of  other 
bodies.  Restates  that  a  substance  having  all  the  reactions  of 
the  so-called  chondrin,  may  at  any  time  be  produced  by  a  mix- 
ture of  mucin,  glutin,  and  inorganic  salts.  The  extreme  simi- 
larity in  the  reactions  of  chondrin  and  mucin  point  to  a  close 
relationship  between  the  two.  The  whole  subject,  however,  re- 
quires more  complete  investigation.  AVith  alkalies  or  dilute  sid- 
phuric  acid  chondrin  gives  leucin,  but  no  tyrosin  or  glycocoll. 
^Vhether  chondrin  exists  as  such  in  cartilage  is  uncertain  ;  it 
seems  probable  that  it  does  not,  since  its  extraction  from  carti- 
lage requires  an  amount  of  boiling  with  water  much  greater  than 
that  requisite  to  dissolve  dried  chondrin. 

Preparation. — From  cartilage  by  extracting  with  water,  and 
precipitating  with  acetic  acid. 

Glutin  or  GeUtin.—[0,  23.21.  H,  7.15.  X,  18.32.  C,  50.76. 
S,  .56  per  cent.) 

This  is  the  substance  which  is  yielded  Avhen  connective  tissue 
fibres  are  heated  for  several  days  with  very  dilute  acetic  acid,  at  a 
temperature  of  about  15^  C,  or  when  they  are  treated  with  water 
in  a  digester.  The  elastic  elements  of  connective  tissue  are  un- 
alfected  by  the  above  treatment. 

As  obtained  in  this  way  glutin  is  when  heated  a  thin  fluid, 
solidifying  on  cooling  to  the  well-known  gelatinous  form.  When 
dried  it  is  a  colorless,  transparent,  brittle  body,  swelling  up,  but 
remaining  undissolved  in  cold  water ;  heating,  or  the  addition  of 
traces  of  acids  or  alkalies,  readily  atfects  its  solutions.  When  dis- 
solved in  water  it  possesses  a  Isevorotatory  power  of— 13(P,  at 
30^  C.  ;  the  addition  of  strong  alkali  or  acetic  acid  reduces  this 
to  — 112°  or  — 114°;  both  measured  for  yellow  light.^  Its  solu- 
tions will  not  dialyse. 

Mercuric  chloride  and  tannic  acid  are  the  only  two  reagents 
which  yield  insoluble  precipitates  with  this  body.     Its  presence 

1  De  Barv,  Hoppe-Seyler's  Untersueh.,  Hft.  i,  S.  71. 
*  Morocliowetz,  Verhand.  natiirhist.  med.  Ver.  Heidelberg.,  Bd.   i 
(1876),  lift.  5. 
3  Hoppe-Seyler,  Hbdk.,  S.  222. 


972        CHEMICAL    BASIS    OF    THE    ANIMAL    BODY. 


prevents  the  action  of  Troinmer's  sugar  test,  since  it  readily 
dissolves  u\)  the  i)recipitated  cuprous  oxide.  The  proteid  reac- 
tions of  gkitin  are  so  feeble  that  tliey  are  probably  due  merely 
to  impurities.  Heated  with  sulphuric  acid  it  yields  ammonia, 
leucin  and  glycin,  but  no  tyrosin. 

It  appears  improbable  tli'at  glutin  exists  ready  formed  in  con- 
nective tissue  tibres,  since  these  do  not  swell  up  in  water,  and 
only  yield  glutin  after  prolonged  treatment  with  boiling  water  ; 
to  which  it  may  be  added  that  while  glutin  is  acted  upon  by 
trypsin,  the  connective  tissue  tibres  in  their  natural  condition 
resist  its  action  (see  p.  331);. 

Elastin.—{0,  20.5.     H,  7.4.    i^,  16.7.     C,  55.5  p.c.) 

This  characteristic  component  of  elastic  tibres  is  left  on  the 
removal  of  all  the  glutin,  mucin,  etc.,  from  such  tissues  as 
"  ligamentum  nuchre,"  advantage  being  taken  of  its  not  being 
altered  when  it  is  heated  with  w'ater,  even  under  pressure,  with 
strong  acetic  acid,  or  with  dilute  alkalies.  AVhen  moist  it  is  yel- 
low and  elastic,  but  on  drying  becomes  brittle.  It  is  soluble  in 
strong  alkalies  at  boiling  temperatures,  and  concentrated  sul- 
phuric and  nitric  acids  dissolve  it  even  in  the  cold.  It  is  pre- 
cipitated from  solutions  by  tannic  acid,  but  not  by  the  addition 
of  ordinary  acids.  Notwithstanding  that  it  closely  approaches 
the  proteids  in  its  percentage  composition,  and  gives  distinct 
although  feeble  proteid  reactions,  very  close  relationship  be- 
tween the  two  appears  improbable,  since  elastin  when  treated 
with  sulphuric  acid,  yields  leucin  (30-40  p.c.)  only,  and  no  tyro- 
sin. 

Hilirer^  has  obtained  a  similar  bodv  from  the  shell  membrane 


Keratin.— (O,  20.7—25.0.  H,  G.4— 7.0.  N,  16.2—17.7.  C, 
50.3—52  5.     S,  .7—5.0  p.c.) 

This  body,  though  somewhat  resembling  the  proteids  in  gen- 
eral composition,  (lifters  from  them  and  also  from  the  preceding 
bodies  so  widely  in  other  properties,  that  its  description  is  placed 
here  for  convenience  rather  than  anything  else.  Hair,  nails, 
feathers,  horn,  and  epidermic  scales  consist  for  the  most  part  of 
keratin.  Heated  with  water  in  a  digester  at  150^  keratin  is  par- 
tially dissolved  with  evolution  of  sulphuretted  hydrogen  ;  the 
solution  then  gives  with  acetic  acid  and  ferrocyanide  of  potas- 
sium a  precipitate  soluble  in  excess  of  the  acid.  Prolonged  boil- 
ing with  alkahes  and  acids,  even  acetic,  dissolves  keratin  ;  the 
alkaline  solutions  evolve  sulphuretted  hydrogen  on  treatment 
with  acids.  The  sulphur  in  keratin  is  evidently  very  loosely 
united  to  the  substance,  and  in  all  its  reactions  there  appears  to 
be  a  want  of  similarity  between  keratin  and  either  proteids,  mu- 

1  Ber.  d.  deutsch.  chem.  Gesellsch.,  1873,  S.  166. 


CARBOHYDRATES.  973 


cin  or  gelatin.  The  most  common  of  its  products  of  decompo- 
siiion  are  leiicin  (10  per  cent.),  and  tyrosin  (3.6  per  cent.),  and 
some  aspartic  acid  ;  no  glycin  is  formed.  What  is  generally 
known  as  keratin  is  probahfy  a  compound  body,  which"  has  not 
3'et  been  resolved  into  its  components. 

Ewald  and  Kuhne'  have  described  a  new  body  to  which,  since 
it  occurs  as  a  constituent  of  nervous  tissue  (both  of  nerves  and 
of  the  central  nervous  system),  and  is  yet  closely  identical  with 
ordinary-  horny  tissue,  they  give  the  name  of  neuro-keratin.  It' 
is  prepared  in  quantity  from  the  brain  by  extracting  this  tissue 
with  alcohol  and  ether,  and  subjecting  the  residue  to  the  actioa 
of  pepsin  and  trypsin.  The  final  residuum  is  neuro-keratin,  and 
amounts  to  15-20  per  cent,  of  the  original  tissue. 

Nudein.     C,,H,.,X,P,02,. 

Discovered  by  Miescher'-'  in  the  nuclei  of  pus-corpuscles  and  in 
the  yellow  corpuscles  of  yolk  of  egg.  Other  observei"8  have  sub- 
sequentl}'  obtained  it  from  yeast,  from  semen,  from  the  nuclei  of 
the  red  blood-corpuscles  of  birds  and  amphibia,  from  hepatic 
cells,  and  it  is  probably  present  in  all  nuclei. 

When  newh^  prepared  it  is  a  colorless  amorphous  body,  solu- 
ble to  a  slight' extent  in  water,  readily  soluble  in  many  alkaline 
solutions  ;  but  its  solubilities  alter  on  keeping.  If  added  gradu- 
ally in  sufficient  quantity  to  a  solution  of  caustic  alkali  it  first 
neutralizes  the  solution  and  then  renders  it  acid.  It  seems  to 
possess  an  indistinct  xanthoproteic  reaction,  but  gives  no  reac- 
tion with  Millon's  fluid.  It  yields  precipitates  with  several  salts, 
e.  y.,  zinc  chloride,  silver  nitrate,  and  cupric  sulphate. 

Preparation.  This  is  difficult,  since  nuclein  is  easily  decom- 
posed.^ The  most  remarkable  feature  of  this  body  is  its  large 
percentage  of  phosphorus.  9.59  per  cent.  This  phosphorus  is 
readily  separated  by  boiling  with  strong  hydrochloric  acid  or 
caustic  alkalies  ;  the  same  occurs  when  solutions  of  nuclein  are 
acidulated  and  allowed  to  stand. 


CARBOHYDEATES. 

Certain  members  only  of  this  class  occur  in  the  human  body ; 
of  these  the  most  important  and  widespread  is  that  known  as 
grape-sugar  or  dextrose  (glucose),  with  which  diabetic  sugar  seems 

'  Yerhand.  naturhist.  nied.  Yer.  Heidelberg.,  Bd.  i  (1876),  Heft  5. 
2  Med.  Cheiu.  Untersuch.,  Hoppe-Sevler,  Heft  4,  1872,  S.  441  und 
502. 

^  Miescher,  op.  cit. 

82 


974        CHEMICAL    BASIS    OF    THE    ANIMAL    BODY. 


to  be  identical.^  Xext  to  this  comes  milk-su2jar.  Inosit  is  an- 
other body  of  this  class,  aUhouudi  it  differs  in  many  important 
points  from  the  preceding  two.  Glycogen  belongs  properly  to  the 
sub-class  of  carbohydrates  known  as  starches. 

These  bodies  are  often  con-iidered  to  be  polyatomic  alcohols.  Several 
of  them  stand  in  peculiar  relation  to  mannit,  and  may  be  converted  into 
that  substance  by  the  action  of  sodium  amalgam,^ 

1.   Dextrose  (Grape-sugar).     CgHi.^Oe  +  H^^O. 

Occurs  in  the  contents  of  the  alimentary  canal  to  a  variable 
extent,  dependent  on  the  nature  of  the  food  taken.  It  is  also  a 
normal  constituent  of  blood,  chyle,  and  lymph.  Concerning  its 
presence  in  the  liver,  see  p.  54().  The  amniotic  fluid  also  contains 
this  body.  Bile  in  the  normal  condition  is  free  from  sugar,  so 
also  is  urine,  though  this  point  has  given  rise  to  great  dispute.^ 
The  disease  diabetes  is  characterized  by  an  excess  of  dextrose  in 
the  fluids  and  tissues  of  tlie  body  (see  p.  551). 

When  pure,  dextrose  is  colorless  and  crystallizes  in  four-sided 
prisms,  often  agglomerated  into  warty  lumps.  The  crystals  will 
dissolve  in  their  own  weight  of  cold  water,  requiring,  however, 
some  time  for  the  process  ;  they  are  very  readily  soluble  in  hot 
water.     Dextrose  is  soluble  in  alcohol,  but  insoluble  in  ether. 

The  freshly  prepared  cold  aqueous  solution  of  the  crystals  possesses  a 
dextro-rotatory  power  of  -f-  104°  for  yellow  liglit.  This,  quickly  on 
heating,  more  slowly  on  standing,  falls  to  -j-  56°;  at  which  point  it  re- 
mains constant. 

Dextrose  readily  forms  compounds  with  acids  and  bases  ;  the  latter 
are  very  unstable,  decomposition  rapidly  ensuing  on  heating  them. 
When  its  metallic  compounds  are  decomposed  the  decomposition  is  in 
many  cases  accompanied  by  the  precipitation  of  the  metals,  e.g.,  silver, 
gold,  mercury,  bismuth.  Caustic  alkalies  readily  decompose  it,  as  also 
does  ammonia. 

Dextrose  is  readily  and  completely  precipitated  by  lead  acetate 
and  ammonia. 

An  important  property  of  this  body  is  its  power  of  undergoing 
fermentations.  Of  these  the  two  principal  are  :  (1.)  Alcoholic. 
This  is  produced  in  aqueous  solutions  of  dextrose,  under  the  in- 
fluence of  yeast.  The  decomposition  is  the  following  :  C,;H,.,0;  = 
2C,H,jO  +  2C0  ,  yielding  (ethyl)  alcohol  and  carbonic  anhydride. 
Other  alcohols  of  the  acetic  series  are  found  in  traces,  as  also  are 
glycerin,  succinic  acid,  and  probably  many  other  bodies.     The 

^  The  question,  however,  whether  several  varieties  of  sugar  occurring 
in  the  animal  body  have  not  been  confounded  together  under  the  com- 
mon name  of  dextrose  or  gkicose  may  be  considered  at  present  an  open 
one. 

2  Linnemann,  Ann.  d.  Chem.  u.  Pharm.,  Bd.  128,  8. 136. 

*  See  Seegen,  Der  Diabetes  Mellitus,  2(1  ed.,  S.  196. 


CARBOHYDRATES.  975 


fermentation  is  most  active  at  about  2o^  C.  Below  5^  or  above 
45^'  it  almost  entirely  ceases.  If  the  saccharine  solution  contains 
more  than  15  per  cent,  of  sugar  it  will  not  all  be  decomposed,  as 
excess  of  alcohol  stops  the  reaction.  (2.)  Lactic.  This  occurs  in 
the  presence  of  decomposing  nitrogenous  matter,  especially  of 
casein,  and  is  probably  the  result  of  the  action  of  a  specific  fer- 
ment. '  The  first  stage  is  the  production  of  lactic  acid,  0^11,.  O^  = 
2C;HhO;..  In  the  second  butyric  acid  is  formed  with  evolution  of 
h3drogen  and  carbonic  anhydride  :  2C;;Hj;0i  =  C^H.O;  +  2CO_,+ 
2H.,.  The  above  changes,  the  first  of  which  is  probabl}-  under- 
gone by  sugar  to  a  considerable  extent  in  the  intestine,  are  most 
active  at  35^  ;  the  presence  of  alkaline  carbonates  is  also  favor- 
able. It  is,  moreover,  essential  that  the  lactic  acid  should  be 
neutralized  as  fast  as  it  is  formed,  otherwise  the  presence  of  the 
free  acid  stops  the  process. 

The  detection  and  estimation  of  dextrose  are  so  fully  given  in 
various  books  that  they  need  not  be  detailed  here. 

2.  Maltose.     C,,H,20„  +  H.O. 

This  form  of  sugar  was  first  described  by  Dubrunfaut  as  a 
product  of  the  action  of  malt  on  starch.  Its  existence  was  for  a 
long  time  doubted  until  Sullivan  repeated  and  confirmed  the  pre- 
vious experiments.  According  to  him  it  crystaUizes  in  fine  acicu- 
lar  crystals,  possesses  a  specific  rotator}^  power  of  +  150"  and  a 
reducing  power  which  is  only  one-third  as  great  as  that  of  dex- 
trose. Musculus  and  Gruber-  have  recently  shown  that  it  may 
also  be  formed  by  the  action  of  sulphuric  acid  on  starch,  and  that 
it  is  capable  of  undergoing  alcoholic  fermentation. 

3.  Jfilk-sugar.     C,,H,,Oa  +  H,0. 

Also  known  as  lactose.  It  is  found  in  milk,  and  is  the  only 
sugar  which  enters  into  the  composition  of  this  secretion. 

it  yields,  when  pure,  hard  colorless  cr3-stals,  belonging  to  the 
rhombic  system  (four  or  eight-sided  prisms).  It  is  less  soluble  in 
water  than  dextrose,  requiring  for  solution  six  times  its  weight 
of  cold,  but  only  two  parts  of  boiling,  water;  it  is  entirely  in- 
soluble in  alcohol  and  ether.  It  is  fulh'  precipitated  from  its 
solutions  by  the  addition  of  lead  acetate  and  ammonia. 

When  fre<ldy  di-;-;olved  its  aqnoous  solution  possesses  a  specific  dextro- 
rotatorv  power  of  -|--*3.1°  for  yellow  liglit;  this  diminislies,  slowly  on 
standing,  rapidly  oa  boilihir.  until  it  finally  remains  constant  at  -|-59.3°. 
The  amount  of  rotation  is  independent  of  the  concentration  of  the  solu- 
tion. 

Lactose  unites  readily  with  bases,  forming  unstable  compounds;  from 

-  Lister,  Path.  Soc.  Trans.,  vol.  for  1878,  p.  425;  also  Quart.  Jour,  of 
Micros.  Science,  vol.  xviii  (1878),  p.  177. 

^  Zeitschr.  f.  Physiol.  Chem.,  Bd.  ii  (1878),  S.  177. 


976        CHEMICAL    BASIS    OF    THE    ANIMAL    BODY, 


its  metallic  compounds  the  metal  is  precipitated  in  the  reduced  state  on 
boiling  ;  it  reduces  copper  salts  as  readily  as  dextrose. 

Lactose  is  orenerally  stated  to  admit  of  no  direct  alcoholic  fer- 
mentation ;  this  may  however  sometimes  be  induced  by  a  lengthy 
action  of  yeast.  By  boilini;;  with  dilute  mineral  acids  lactose  is 
converted  into  galactose,  which  readily  undergoes  alcoholic  fer- 
mentation. 

Galactose  is  very  readily  soluble  in  water,  though  insoluble  in  alcohol. 
It  possesses  a  higher  rotatory  power  than  lactose,  viz.,  +  83.2°  ;  in  a 
freshly  prepared  solution  the  rotation  is  +  139.6°.  It  may  be  remarked 
here  that  though  isolated  lactose  is  incapable  of  direct  alcoholic  fermen- 
tation, milk  itself  may  be  fermented  ;  Berthelot  was  unable  in  this  direct 
alcoholic  fermentation  to  detect  any  intermediate  change  of  the  lactose 
into  another  fermentable  sugar. 

Lactose  is  however  directly  capable  of  undergoing  the  lactic 
fermentation  ;  the  circumstances  and  products  are  the  same  as 
in  the  case  of  dextrose  (see  above).  The  action  is  generally  pro- 
ductive of  a  collateral  small  quantity  of  alcojiol. 

The  tests  for  the  presence  of  this  body  are  the  same  as  for  dex- 
trose, with  the  exception  of  the  alcoholic  fermentation. 

Prepcnrition.— After  the  removal  of  the  casein  and  other  pro- 
teids  of  the  milk,  the  mother  liquor  is  evaporated  to  the  crystal- 
lizing point ;  the  crystals  are  purified  by  repeated  crystallization 
from  warm  water. 

4.  Inosit.     C«H,.,06+2ILO. 

This  substance  occurs  but  sparingly  in  the  human  body ;  it 
was  found  originally  by  Scherer'  in  the  muscles  of  the  heart. 
Cloetta  showed  its  presence  in  the  lungs,  kidneys,  spleen,  and 
liver,-  and  M'/dler  in  the  brain. "*  It  occurs  also  in  diabetic  urine, 
and  in  that  of  ^  Bright's  disease,"  and  is  found  in  abundance  in 
the  vegetable  kingdom. 

Pure  inosit  forms  large  efflorescent  crystals  (rhombic  tables) ; 
in  microscopic  preparations  it  is  usually  obtained  in  tufted  lumps 
of  fine  crystals.  Easily  soluble  in  water,  it  is  insoluble  in  alco- 
hol and  ether.  It  possesses  no  action  on  polarized  light,  and 
does  not  reduce  solutions  of  metallic  salts. 

It  admits  of  no  direct  alcoholic,  but  is  capable  of  undergoing 
the  lactic  fermentation  ;  according  to  Hilger'  the  acid  formed  is 
sarcolactic.     It  is  unaltered  by  heating  with  dilute  mineral  acids. 

Preparation. — It  may  be  precipitated  from  its  solutions  by  the 
action  of  basic  lead  acetate  and  ammonia. 


1  Ann.  d.  Chem.  u.  Pharm.,  Bd.  73,  S.  322.     ''  Ibid.,  Bd.  99,  S.  289. 
3  Ibid.,  Bd.  103,  S.  140.  *  Ibid.,  Bd.  160,  S.  333. 


CARBOHYDRATES,  977 


As  a  special  test  may  be  mentioned  the  production  of  a  bright- 
violet  color  by  careful  evaporation  to  dryness  on  platinum  foil, 
with  a  little  ammonia  and  calcium  chloride. 


B}^  boiling  starch-paste  with  dilute  acids,  or  by  the  action  of 
ferments,  the  starch  is  converted  into  an  isomeric  body,  to  which, 
from  its  action  on  polarized  light,  the  name  dextrin  has  been 
given.  It  is  soluble  in  water,  but  is  precipitated  by  alcohol.  It 
does  not  undergo  alcoholic  fermentation  until  after  it  has  been 
changed  into  dextrose,  nor  can  it  reduce  metallic  salts.  It  yields 
a  reddish  port-wine  color  with  iodine,  which  disappears  on  warm- 
ing and  does  not  return  on  cooling.  Further  action  of  acids  or 
of  ferments  converts  dextrin  into  dextrose.  Dextrin  is  present 
in  the  contents  of  the  alimentary  canal  after  a  meal  containing 
starch,  and  has  also  been  found  in  the  blood.  Concerning  achro- 
odextrin  and  other  varieties  of  dextrin  see  p.  3U7. 

6.   Glycogen.     C,H,oO,. 

Belongs  to  the  starch  division  of  carbohydrates.  Discovered 
by  Bernard  in  the  liver  and  other  organs  (see  p.  54:2). 

Glycogen  is,  when  pure,  an  amorphous  powder,  colorless,  and 
tasteless,  readily  soluble  in  water,  insoluble  in  alcohol  and  ether. 
Its  aqueous  solution  is  generally  though  not  always  strongly 
opalescent,  but  contains  no  particles  visible  microscopically  ;  the 
opalescence  is  much  reduced  by  the  presence  of  free  alkalies.  The 
same  solution  possesses,  according  to  Hoppe-Seyler,  a  very  strong 
dextro-rotatory  power  ;  it  dissolves  hydrated  cupric  oxide  ;  but 
this  is  not  reduced  on  boiling. 

By  the  action  of  dilute  mineral  acids  (except  nitric)  it  is  par- 
tially converted  into  a  form  of  sugar  very  closely  resembling, 
though  probably  dilFering  somewhat  from  true  dextrose,  and  the 
same  conversion  is  also  readily  effected  by  the  action  of  amy- 
lolytic  ferments.  The  sugar  into  which  the  glycogen  of  the  liver 
is  converted  after  death  (see  p.  546),  appears  to  be  true  dextrose ; 
so  also  the  sugar  of  diabetes.  Musculus  and  v.  Mering'  however 
state  that  the" result  of  the  action  of  diastase,  or  salivary  or  pan- 
creatic ferment,  upon  glycogen  is  a  mixture  of  achroodextrin 
and  maltose;  tlie  quantity  of  dextrose  making  its  appearance  at 
tlie  same  time  being  very  small. 

Opalescent  solutions  of  glycogen  usually  become  clear  on  the 
addition  of  caustic  alkali ;  Vintschgau  and  Dietl-  have  shown 
that  this  is  accompanied  by  a  change  which  converts  a  portion 
of  the  gl3'cogen  into  a  substance  to  which  they  give  the  name  of 
3.-glycogen-dextrin.     (K  Uine'  had  previously  described  a  body 

'  Zeitschr.  f.  phvsiol.  Cliem..  Bd.  ii  (1878),  S.  403. 
2  Pfiuger's  Arch.,  Bd.  xvii  (1S78),  S.  154. 
'^  Lehrb.  d.  phvsiol.  Chem.  (1868),  S.  63. 


978         CHExMICAL    BASIS    OF    THE    ANIMAL    BODY. 


to  which  he  gave  the  nameglycouen-dextrin.  That  described  by 
Yintschgau  and  Dietl  differs  slightly  from  Kiihue's  body,  hence 
the  name.)  xVccording  to  these  authors  one-tifth  of  the  glycogen 
is  at  the  same  time  changed  into  some  other,  at  present  undeter- 
mined, substance.  Normal  lead  acetate  gives  a  cloudiness,  the 
basic  salt  a  precipitate,  in  its  solutions. 

As  tests  for  this  body  may  be  used  the  formation  of  a  port- 
wine  color  with  iodine  ;  this  disappears  on  warming,  but  in  this 
respect  differing  from  dextrin,  returns  on  cooling."  (The  same 
color  is  produced  by  dextrin,  but  this  does  not  reappear  on  cool- 
ing after  its  disappearance  (  n  warming.) 

Preparation  of  Glycogen. — The  following  is  Brlicke's'  methods. 
The  filtered  or  simply  strained  decoction  of  perfectly  frtsh  liver 
or  other  glycogenic  tissue  is,  when  cold,  treated  alternately  with 
dilute  h3'drochlo]-ic  acid,  and  a  solution  of  the  double  iodide  of 
potassium  and  mercur}-,^  as  long  as  any  precipitate  occurs.  In 
the  presence  of  free  hydrochloric  acid,  the  double  iodide  precipi- 
tates proteid  matters  so  completely  as  to  render  their  separation 
by  filtration  easy.  The  proteids  being  thus  got  rid  of,  the  gly- 
cogen is  precipitated  from  the  filtrate  by  adding  alcohol  to  "the 
extent  of  between  60  and  70  per  cent.  Too  much  alcohol  is  to 
be  avoided,  since  other  substances  as  well  are  thereby  precipitated. 
The  glycogen  is  now  washed  with  alcohol,  first  of  (30  and  then  of 
95  per  cent.,  afterwards  with  ether,  and  finally  with  absolute 
alcohol.     It  is  then  dried  over  sulphuric  acid. 

FATS,  THEIR  DERIYATIYES  AXD  ALLIES. 
The  Acetic  Acid  Series. 
General  formula  C„II.^,.0.^  (monobasic). 

This,  which  is  one  of  the  most  complete  homologous  series  of 
organic  chemistry,  runs  parallel  to  the  series  of  monatomic  alco- 
hols. Thus  formic  acid  corresponds  to  meth}^  alcohol,  acetic 
acid  to  ethyl  (ordinary)  alcohol,  and  so  on.  The  several  acids 
may  be  regartied  as  being  derived  from  their  respective  alcohols 
by  simple  oxidation  :  thus  ethyl  alcohol  yields  by  oxidation  acetic 
acid:  C2H„0  +  0_  =C_H^O_,-fH  O.  The  various  members  differ 
in  composition  by  CH ,,  and  the  boiling-points  rise  successively  by 
about  19^  C.  Similar  relations  hold  good  with  regard  to  their 
melting-points  and  specific  gravities.     The  acid  properties  are 

»  Sitznngsber.  d.  Wiener  Akad.,  Bd.  63  (1871),  ii  Abth. 

^  This  may  be  prepared  by  precipitating  potassium  iodide  with  mer- 
curic chloride  and  dissolving  the  washed  precipitate  in  a  hot  solution  of 
potassium  iodide  as  long  as  it  continues  to  be  taken  up.  On  cooling, 
some  amount  of  precipitate  occui-s,  which  must  be  hkeredoff;  the  filtrate 
is  then  readv  for  use. 


FATS,    ETC.  979 


strongest  in  those  where  n  has  the  least  vahie.  The  lowest  mem- 
bers of  the  series  are  volatile  liquids,  acting  as  powerful  acids ; 
these  successively  become  less  and  less  fluid,  and  the  highest  mem- 
bers are  colorless  solids,  closely  resembling  the  neutral  fats  in 
outward  appearance.  Consecutive  acids  of  the  series  present  but 
very  small  ditferences  of  chemical  and  physical  properties,  hence 
the  difhculty  of  separating  them  ;  this  is  further  increased  in  the 
animal  body  by  the  fact  that  exactly  those  acids  which  pf^sent 
the  greatest  similarities  usually  occur  together. 

The  free  acids  are  found  only  in  small  and  ver}^  variable  quan- 
tities in  various  parts  of  the  body  ;  their  derivatives,  on  the  other 
hand,  form  most  important  constituents  of  the  human  frame,  and 
will  be  considered  further  on. 

Formic  acid.     CHO  .  OH. 

When  pure  is  a  strongly  corrosive,  fuming  fluid,  with  powerful 
irritating  odor,  solidifying  at  0^  C,  boiling  at  100^  C,  and  capa- 
ble of  being  mixed  in  all  proportions  with  water  and  alcohol.  It 
has  been  found  in  various  parts  of  the  body,  such  as  the  spleen, 
thymus,  pancreas,  muscles,  brain,  and  blood  ;  from  the  latter  it 
may  be  obtained  by  the  action  of  acids  on  the  haemoglobin.  Ac- 
cording to  some  authors'  it  occurs  also  in  urine. 

Heated  with  sulphuric  acid  it  yields  carbonic  oxide  and  water  ; 
with  caustic  potash  it  gives  hydrogen  and  oxalic  acid. 

Acetic  acid.     CiHnO  .  OH. 

Is  distinguished  by  its  characteristic  odor  ;  its  boiling-point  is 
117^  C.  ;  it  solidities  at  5^\  and  is  fluid  at  all  temperatures  above 
15°  C.     It  is  soluble  in  all  proportions  in  alcohol  and  water. 

It  occurs  in  the  stomach  as  the  result  of  fei-mentative  changes 
in  the  food,  and  is  frequently  present  in  diabetic  urine.  In  other 
organs  and  fluids  it  exists  only  in  minute  traces. 

AVith  ferric  chloride  it  yields  a  blood-red  solution,  decolorized  by  hy- 
drochloric acid.  (It  differs  in  this  last  reaction  from  sulphocyanide  of 
iron.)  Heated  with  alcohol  and  sulphuric  acid,  the  characteristic  odor 
of  acetic  ether  is  obtained.     It  does  not  reduce  silver  nitrate. 

Propionic  acid.     C^H^O  .  OH. 

This  acid  closely  resembles  the  preceding  one.  It  possesses  a 
very  sour  taste  and  .pungent  odor ;  is  soluble  in  water,  boils  at 
141°  C,  and  may  be  separated  from  its  aqueous  solution  by  ex- 
cess of  calcium  chloride. 

It  occurs  in  small  quantities  in  sweat,  m  the  contents  of  the 
stomach,  and  in  diabetic  urine  when  undergoing  fermentation. 
It  is  similarly  produced,  mixed,  however,  with  other  products, 

'  Buliginsky,  Hoppe-Seyler's  Med.  chem.  Mittheihing.,  Heft  2,  S.  240. 
Thudichum,  Journ.  of  the  Chem.  Soc,  vol.  viii,  p.  400. 


980        CHEMICAL    BASIS    OF    THE    ANIxMAL    BODY. 


during  alcoholic  fermentation,  or  by  the  decomposition  of  glyc- 
erin.    It  partially  reduces  silver  nitrate  solution  on  boiling. 

Butyric  add.     CiH-O  .  OH. 

An  oily  colorless  liquid,  with  an  odor  of  rancid  butter,  soluble 
in  water,  alcohol,  and  ether,  boiling  at  1G"2^  C.  Calcium  chlo- 
ride separates  it  from  its  aqueous  solution. 

Found  in  sweat,  the  contents  of  the  large  intestine,  faeces,  and 
in  urine.  It  occurs  in  traces  in  many  other  fluids,  and  is  plenti- 
fully obtained  when  diabetic  urine  is  mixed  with  powdered  chalk 
and  kept  at  a  temperature  of  So-*  C.  It  exists,  as  a  neutral  fat, 
in  small  quantities  in  milk. 

This  is  the  principal  product  of  the  second  stage  of  lactic  fer- 
mentation.    (See  Dextrose.) 

Valerianic  acid.     C.iHyO  .  OH. 

An  oily  liquid,  of  penetrating  odor  and  burning  taste  ;  soluble 
in  30  parts  of  water  at  12^0.,  readily  soluble  in  alcohol  and 
ether.  Boils  at  175^  C.  Possesses,  in  free  and  combined  form, 
a  feeble  right-handed  rotation  of  the  plane  of  polarization. 

It  is  found  in  the  solid  excrements,  and  is  formed  readily  by 
the  decomposition,  through  putrefaction,  of  impure  leucin,  am- 
monia being  at  the  same  time  evolved  ;  hence  its  occurrence  in 
urine  when  that  fluid  contains  leucin,  as  in  cases  of  acute  atrophy 
of  the  liver 

Ca}jroic  acid.  C,;H,,0  .  OH. 
Caprijlic  ''  C,H„0  .  OH. 
Caijric     "         C,oH„0  .  OH. 

These  three  occur  together  (as  fats)  in  butter,  and  are  con- 
tained in  varying  proportions  in  the  fseces  from  a  meat  diet. 
The  flrst  is  an  oily  fluid,  slightly  soluble  in  water  ;  the  others  are 
solids  and  scarcely  soluble  in  water  ;  they  are  soluble  in  all  pro- 
portions in  alcohol  and  ether.  They  may  be  prepared  from 
butter,  and  separated  by  the  varying  solubilities  of  their  barium 
salts. 

Laurostearic  acid.     Ci.,H,.0  .  OH. 
Myristic  "        C,]lll,0  .  OH. 

These  occur  as  neutral  fats,  in  spermaceti,  in  butter,  and  other 
fats.     They  present  no  points  of  interest. 

Palmitic  acid.     C,«H„0  .  OH. 
Stearic       ''         C,«H,,0  .  OH. 

These  are  solid,  colorless  when  pure^  tasteless,  odorless,  crys- 
talline bodies,  the  former  melting  at  02^0.,  the  latter  at  69.2^  C. 
In  water  they  are  quite  insoluble  ;  palmitic  acid  is  more  readily 
soluble  in  cold  alcohol  than  stearic.     Both  are  readily  dissolved 


PATS,    ETC.  981 


b}^  hot  alcohol,  ether,  or  chloroform.  Glacial  acetic  acid  dis- 
solves them  ill  large  quantity,  the  solution  being  assisted  by- 
warming.  They  readily  form  soaps  with  the  alkalies,  also  with 
many  other  metals.  The  varying  solubilities  of  their  barium 
salts  afllbrd  the  means  of  separating  them  when  mixed. ^  This 
may  also  be  applied  to  many  others  of  the  higher  members  of  this 
series. 

These  acids  in  combination  with  gh'cerin  (see  below),  together 
with  the  analogous  compound  of  oleic  acid,  form  the  principal 
constituents  of  human  flit.  As  salts  of  calcium  they  occur  in 
the  fscces  and  in  ''adipocere,"  and  probably  in  chyle,  blood,  and 
serous  fluids,  as  salts  of  sodium.  They  are  found  in  the  free 
state  in  decomposing  pus,  and  in  the  caseous  deposits  of  tuber- 
culosis. 

The  existence  of  margaric  acid,  intermediate  to  the  above  two,  is  not 
now  admitted,  since  Heintz-  has  sliow'n  that  it  is  really  a  mixture  of 
palmitic  and  stearic  acid.  Margaric  acid  possesses  the  anomalous  melt- 
ing-point of  59.9°  C.  A  mixture  of  60  parts  stearic  and  40  of  palmitic 
acids,  melts  at  60.3°. 

Acids  of  the  Oleic  (Acrylic)  Series.    H(C  H2,_3)02. 

(Monobasic.) 

Many  acids  of  this  series  occur  as  glycerin  compounds  in  va- 
rious fixed  fats.  They  are  very  unstable,  and  readily  absorb 
oxygen  when  exposed  to  the  air.  The  higher  members  are 
decomposed  on  attempting  to  distil  them.  Their  most  peculiar 
property  is  that  of  being  converted  by  traces  of  isO,  into  solid, 
stable  metameric  acids,  capable  of  being  distilled.  They  bear  an 
interesting  relation  to  the  acids  of  the  acetic  series,  breaking  u}) 
when  heated  with  caustic  potash  into  acetic  acid  and  some  other 
member  of  the  same  series.     Thus, 

Oleic  aciil  Potassium  acetate.  Potassium  palinitate. 

HC,sH3,0.-}-2KHO  =  KC,H^O,   +    KC„H,.0,     +  PL. 

Oleic  acid.     C.,H,,0  .  OH. 

This  is  the  only  acid  of  the  series  which  is  physiologically  im- 
portant. It  IS  lound  united  with  glycerin  in  all  the  fats  of  the 
human  body.  In  the  small  intestine  and  chyle  it  exists  also 
either  as  a,  salt  of  po.tassium,  or  sodium,  or,  it  may  be,  in  the  free 
state. 

When  pure  it  is,  at  ordinary  temperatures,  a  colorless,  odorless, 
tasteless,  oily  liquid,  solidifying  at  4^  C.  to  a  cr3'Stalline  mass. 
Insoluble  in  water,  it  is  soluble  in  alcohol  and  etlier.  It  cannot 
be  distilled  without  decomposition.  It  readily  forms  with  potas- 
sium and  sodium  soaps,  which  are  soluble  in  water.     Its  coiii- 

1   Heintz.  Annal.  d.  Phys.  u.  Chem.,  Bd.  92,  S.  588.  '^  Op.  ch. 


982        CHEMICAL    BASIS    OF    THE    ANIMAL    BODY. 


pounds  with  most  other  bases  are  insoluble.  It  may  be  distin- 
f^nished  from  the  acids  of  the  acetic  series  by  its  reaction  with 
1^0.,  and  by  the  changes  it  undergoes  when  exposed  to  the  air. 

The  Neutral  Fats. 

These  may  be  considered  as  ethers  formed  by  replacing  the 
exchangeable  atoms  of  hydrogen  in  the  triatomic  alcohol  glycerin 
(see  below),  by  the  acid  radicles  of  the  acetic  and  oleic  series. 
Since  there  are  three  such  exchangeable  atoms  of  hydrogen  in 
glycerin,  it  is  possible  to  form  three  classes  of  these  ethers  ;  only 
those,  however,  which  belong  to  the  third  class  occur  as  natural 
constituents  of  the  human  body ;  those  of  the  first  and  second 
are  only  of  theoretical  importance. 

They  possess  certain  general  characteristics  Insoluble  in  water 
and  cold  alcohol,  they  are  readily  soluble  in  hot  alcohol,  ether, 
chloroform,  etc.  ;  they  also  dissolve  one  another.  They  are  neu- 
tral bodies,  colorless  and  tasteless  when  pure  ;  are  not  capable 
of  being  distilled  without  undergoing  decom])osition,  and,  as  a 
result  of  this  decomposition,  yield  solid  and  liquid  hydrocarbons, 
water,  fatty  acids,  and  a  peculiar  body,  acrolein.  (Glycerin  con- 
tains the  elements  of  one  molecule  of  acrolein,  and  two  molecules 
of  water. ) 

They  possess  no  action  on  polarized  light. 

They  may  readily  be  decomposed  into  glycerin  and  their  re- 
spective fatty  acids  by  the  action  of  caustic  alkalies  or  of  super- 
heated steam. 

Palmitin  (Tri-palmitin).     ^/,^tP'Xx   |  O,. 

The  following  reaction  for  the  formation  of  this  fat  is  typical 
for  all  the  others  : 

Glycerin.  I'alinitic  Acid.  Palmitin. 

Palmitin  is  slightly  soluble  in  cold  alcohol,  readily  so  in  liot 
alcohol  or  in  ether  ;  when  pure  it  crystallizes  in  fine  needles  ;  if 
mixed  with  stearin  it  generally  forms  shapeless  lumps,  although 
the  mixture  may  at  times  assume  a  crystalline  form,  and  was 
then  regarded  as  a  distinct  body,  namely,  margarin.  It  possesses 
three  different  melting-points,  according  to  the  previous  tem- 
peratures to  which  it  has  been  subjected.  It  solidifies  in  all  cases 
at  450  C. 

Preparation. — From  palm  oil,  by  removing  the  free  palmitic 
acid  with  alcohol,  and  crystallizing  repeatedly  from  ether. 


C II        ) 

Stearin  (Tri-stearin).      ,q  4t  '^qn    \  O3. 


FATS,    ETC.  983 


This  is  the  hardest  and  least  fusible  of  the  ordinar}^  fats  of  the 
body  ;  is  also  the  least  soluble,  and  hence  is  the  first  to  crystal- 
lize out  from  solutions  of  the  mixed  fats.  It  crystallizes  usuallj^ 
in  square  tables.  It  presents  peculiarities  in  its  fusing-points 
similar  to  those  of  palmitin. 

Preparation. — From  mutton  suet,  its  separation  from  palmitin 
and  olein  being  eftected  by  repeated  crystallization  from  ether, 
stearin  being  the  least  soluble. 

Oleim  (Tri-olein).      (^  A.O),  |  q^_ 

Is  obtained  with  difficulty  in  the  pure  state,  and  is  then  fluid 
at  ordinary  temperatures.  It  is  more  soluble  than  the  two  pre- 
ceding ones.  It  readily  undergoes  oxidation  when  exposed  to  the 
air,  and  is  converted  by  mere  traces  of  NO^  into  a  solid  isomeric 
fat.  Olein  yields,  on  dry  distillation,  a  characteristic  acid,  the 
sebacic,  and"^is  saponified  with  much  greater  difiiculty  than  are 
palmitin  and  stearin. 

Preparation. — From  olive  oil,  either  by  cooling  to  0^  and  press- 
ing out  the  olein  tliat  remains  fluid,  or  by  dissolving  in  alcohol 
and  cooling,  when  the  olein  remains  in  solution  while  the  other 
fats  crystatiize  out. 

Glycerin.    ^j^^4  O3. 

This  principal  constituent  of  the  neutral  fats  ma}^,  as  above 
stated,  be  looked  upon  as  a  triatomic  alcohol. 

When  pure,  glycerin  is  a  viscid,  colorless  liquid,  of  a  well- 
known  sweet  taste.  It  is  soluble  in  water  and  alcohol  in  all  pro- 
portions, insoluble  in  ether.  Exposed  to  very  low  temperatures 
it  becomes  almost  solid  ;  it  may  be  distilled  in  close  vessels  with- 
out decomposition  between  275^-280^  C. 

It  dissolves  the  alkalies  and  alkaline  earths,  also  many  oxides, 
such  as  those  of  lead  and  copper ;  many  of  the  fatty  acids  are 
also  soluble  in  glycerin. 

It  possesses  no  rotatory  power  on  polarized  light. 

It  is  easily  recognized  by  its  ready  solubility  in  water  and  alco- 
hol, its  insolubilit}^  in  ether,  its  sweet  taste,  and  its  reaction  with 
bases.  The  production  of  acrolein  is  also  characteristic  of  glyc- 
erin. 

CJIA  +  211  O  =  C3H,0  (Acrolein). 

Preparation.^ — By  saponification  of  the  various  oils  and  fats. 
It  is  also  formed  in  small  quantities  during  the  alcoholic  fermen- 
tation of  sugar.  ^ 

1  Pasteur,  Ann.  d.  Chem.  u.  Pharm.,  Bd.  106,  S.  338. 


984 


CHEMICAL    BASIS    OF    THE    ANIMAL    BODY. 


Soaps. — These  may  be  formed  by  the  action  of  caustic  alkalies 
on  fats.  The  process  consists  in  a  substitution  of  the  alkali  for 
the  radicle  of  glycerin,  the  latter  combining  with  the  elements 
of  water  to  form  glycerin.     Thus  : 


Tri-ste-rin. 


P()t:i.s.si^  Sfaraff 


0  =  3 


C,JI.,0 


Gly-erin. 

CJL 


OH 


H3 


O. 


Pancreatic  juice  can  split  up  fats  into  glycerin  and  the  free  fatty  acid 
(see  p.  339),  and  the  bile  is  known  to  be  capable  of  saponifying  these 
fatty  acids.  The  amount  of  soaps  formed  in  the  alimentary  canal  is,  how- 
ever, small  and  unimportant. 

Acids  of  the  Glycolic  Series. 

Running  parallel  to  the  monatomic  alcohols  (CEf^^  +  .O)  is  the 
series  of  diatomic  alcohols  or  glycols  (CH^,,  +  ,0  ).  Thus  corre- 
sponding to  ethyl  alcohol  is  the  diatomic  alcohol,  ethyl-glycol. 
As  from  the  monatomic  alcohols,  so  from  the  glycols,  acids  may 
be  derived  by  oxidation  ;  from  the  latter  (glycols)  however  two 
series  of  acids  can  be  obtained,  known  respectively  as  the  glycolic 
and  oxalic  series.  The  first  stage  of  oxidation  of  the  glycol  gives 
a  member  of  the  glycolic  series  ;  thus, 

Efhyl-glj'crl.  Glj'r-olic  acid.  ^ 

C,HA  +  0,=  C  H,0..  +  H  O,  or  more  generally 

c  h;^  .  ,0,  +0.= G,  H, p,  h  h:o. 

By  further  oxidation  a  member  of  the  glycolic  series  can  be 
converted  into  a  member  of  the  oxalic  series  ;  thus, 

Glycolic  acid.  Oxalic  acid. 

C,H,0,  +  O,  =  C.,H,0,  +  H,0,  or  more  generally 
0,  II,„  O .  +  0  =  C,  H ,_,0,  +  up. 

The  acids  of  the  gl3^colic  series  are  diatomic  but  monobasic ; 
those  of  the  oxalic  series  are  diatomic  and  diabasic. 

The  following  table  miy  ba  given  to  show  the  general  relation- 
ships of  alcohols  and  acid  : 


Radical. 

Alcohol. 

Acid. 

Glycols. 

Acid  L 

Acid  ir. 

Fonnic. 

Carbonic. 

Methyl  (CH3 

CII3OH) 

lICHOo 

" 

H,C03 

" 

Acetic 

EtIivl-iilv<-ol. 

Glvcolic. 

Oxalic. 

Ethyl  (C2H5) 

CaHs'OH) 

HC0H3M, 

Coii4  0ino 

HC^HjOa 

H.,ro04 

Proi. ionic. 

Proi.vl-.^lvcul. 

Lactic. 

Malonic 

Propyl  (CsHt 

TaTVOH) 

HC3H,')o 

(a'fsOino 

HrsH, O3 

n,'3iiy>4 

Hilt  V  lie. 

Butvi-.ivcol 

Ox  lull  Vi  ic. 

SiH  ciuic 

Butyl  (C4H9) 

CJIs'OII) 

Hr«H,'^5 

C."«<)Il2 

HC,U,'), 

IW\\U'\ 

GLYCOLIC    ACID    SERIES.  985 


Glycolic  Acid  Series. 
Lactic  acid.     C,;H„0.i. 

jS'ext  to  carbonic  acid,  the  most  important  member  of  this  se- 
ries, as  far  as  physiology  is  concerned,  is  lactic  acid. 

Lactic  acid  exists  in  fonr  isomeric  moditications,  but  of  these 
only  three  have  been  found  in  the  human  body.  These  three  all 
form  syrupy,  colorless  fluids,  soluble  in  all  ])roportions  in  water, 
alcohol,  and  ether.  They  possess  an  intensely  sour  taste,  and  a 
strong  acid  reaction.  When  heated  in  solution  they  are  partially 
distilled  over  in  the  escaping  vapor.  They  form  salts  with 
metals,  of  which  those  with  the  alkalies  are  very  soluble  and  crys- 
tallize with  ditticult}'.  The  calcium  and  zinc  salts  are  of  the 
greatest  importance,  as  will  be  seen  later  on. 

1.  Ethi/Udene-Jactic  arid.  This  is  the  ordinary  form  of  the 
acid,  obtained  as  the  characteristic  ])roduct  of  the  well-known 
''lactic  fermentation."  It  occurs  in  the  contents  of  the  stomach 
and  intestines.  According  to  Heintz  it  is  found  also  in  muscles, 
and  according  to  Gscheidlen^  in  the  ganglionic  cells  of  the  gray 
substance  of  the  brain.  In  many  diseases  it  is  found  in  urine, 
and  exists  to  a  large  amount  in  tliis  excretion  after  poisoning  by 
phosphorus.  3 

It  maybe  prepare  1  by  tlie  general  methods  of  slowly  oxidizing  the 
corresponding  givcol  or  by  acting  on  the  monochlorinated  propionic 
acid  and  with  moist  silver  oxide.  In  obtaining  it  from  the  products  of 
lactic  fermentation,  the  crusts  of  zinc  lat-tate  are  })uritied  by  several  crys- 
tallizations, and  the  acid  liberated  from  the  compound  by  the  action  of 
sulphuretted  hydrogen. 

2.  Eihylene-lactic  acid.  This  acid  is  found  accompanying  the  one 
next  to  be  described,  in  the  watery  extract  of  muscles.  From 
this  it  is  separated  by  taking  advantage  of  the  different  solubili- 
ties of  the  zinc  salts  of  the  two  acids  in  alcohol.  It  seems  prob- 
able, however,  that  it  has  not  yet  been  prepared  in  the  pure  state 
by  this  method. 

Wislicenus  first  obtained  this  acid  by  heating  hydroxycyanide  of 
ethylene  with  aqueous  solutions  of  the  alkalies.* 

The  same  observer  found  it  also  in  many  pathological  fluids. 

3.  SarcoJactic  acid.  This  acid  has  not  yet  been  procured  synthet- 
ically. As  its  name  inijilies,  it  is  that  form  of  the  acid  which  oc- 
curs in  muscles,  and  hence  exists  in  large  quantities  in  Liebig's 
''  extract  of  meat."     It  is  often  found  also  in  pathological  fluids. 

'  Ann.  d.  Chem.  u.  Pharm.,  Bd.  157,  S.  320. 

2  Fflii.uer's  Archiv,  Bd.  viii  (1873-74),  S.  171. 

•''  Schultzen  and  Riess,  Ueber  acute  Phosphorvergiftung. 

*  Ann.  d.  Cliem.  u.  Pharm.,  Bd.  128,  S.  6. 


986        CHEMICAL    BASIS    OF    THE    ANIMAL    BODY, 


This  is  the  only  acid  of  this  series  which  possesses  any  power  of 
rotating?  the  plane  of  polarized  ligjht.  It  is  otherwise  indistin- 
guishable from  the  preceding  ethylidene-lactic  acid,  and  is  gener- 
ally represented  by  the  same  formula.  The  free  acid  has  dextro- 
the  anhydride  Isevo-rotatory  action.  The  specfic  rotation  for 
zinc  salt  in  solution  is  —7.65°  for  yellow  light. 

The  zinc  and  calcium  salts  of  sarcolactic  acid  are  more  soluble 
both  in  water  and  alcohol  than  those  of  ethylidene-lactic  acid,  but 
less  so  than  those  of  ethylene  lactic  acid  ;  and  the  same  salts  of 
ethylene-lactic  acid  contain  more  water  of  crystallization  than 
those  of  the  other  two. 

Heintz'  has  compared  the  above  acids  to  the  modifications  capable  of 
existing  in  tartaric  acid.'^ 

Hydracrylic  acid,  the  fourth  in  this  series  of  lactic  acids,  is  distin- 
guished by  the  nature  of  its  decomposition  on  heating.  It  is  never 
found  as  a  constituent  of  animal  bodies. 

Oxalic  Acid  Series. 
Oxalic  acid.    H.C^O^. 

In  the  free  state  this  acid  does  not  occur  in  the  human  body. 
Calcium  oxalate,  however,  is  a  not  unfrequent  constituent  of 
urine,  and  enters  into  the  composition  of  many  urinary  calculi, 
the  so-called  mulberry  calculus  consisting  almost  entirely  of  it. 
It  may  also  occur  in  faeces,  and  in  the  gall-bladder,  though  this 
is  rarely  observed. 

As  ordinarily  precipitated  from  solutions  of  calcium  salts  by 
ammonium  oxalate,  calcium  oxalate  is  quite  amorphous,  but  in 
urinary  deposits  it  assumes  a  strongly  characteristic  crystalline 
form,  viz.,  that  of  rectangular  octohedra.  In  some  cases  it  pre- 
sents the  anomalous  forms  of  rounded  lum|)s,  dumb-bells,  or 
square  columns  with  pyramidal  ends.  It  is  insoluble  in  Avater, 
alcohol,  and  ether,  also  in  ammonia  and  acetic  acid.  Mineral 
acids  dissolve  this  salt  readily,  as  also  to  a  smaller  extent  do 
solutions  of  sodium  phosphate  or  urate.  All  the  above  char- 
acteristics serve  to  detect  this  salt ;  its  microscopical  appearance, 
however,  is  generally  of  most  use  for  this  purpose. 

The  pure  acid  is  prepared  either  by  oxidizing  sugar  with  nitric 
acid,  or  decomposing  ligneous  tissue  with  caustic  alkalies. 

Succinic  acid.     'HL,CJI^O^. 

This  is  the  third  acid  of  the  oxalic  series,  being  separated  from 
oxalic  acid  by  the  intermediate  malonic  acid,  H.CjH.^O^.     It  oc- 

'  Op.  cit. 

^  See  further,  Wislicenus,  op.  cit.  Also  Ann.  d.  Chem.  u.  Pharm.,  Bd. 
166,  S.  3,  Bd.  167,  S.  802,  and  Zeitschr.  f  Chem.,  Bd.  xiii,  S.  159. 


CHOLESTERIN.  987 


curs  in  the  spleen,  the  thymus,  and  thyroid  bodies,  hydrocephalic 
and  hydrocele  fluids. 

According  to  Meissner  and  Shepard,^  it  is  found  as  a  normal  constitu- 
ent of  urine.  This  is  contested  by  Salkowski,"^  and  also  by  von  Speyer. 
It  seems  probalde,  however,  that  since  wines  and  fermented  liquors  con- 
tain succinic  acid,  and  this  latter  passes  unchanged  into  the  urine,  that 
it  may  thus  be  occasionally  present  in  this  excretion. 

Succinic  acid  crystallizes  in  large  rhombic  tables,  also  at  times 
in  the  form  of  large  prisms  ;  they  are  soluble  in  5  parts  of  cold 
water,  and  2.2  of  boiling,  slightly  soluble  in  alcohol,  and  almost 
insoluble  in  ether.  The  crystals  melt  at  18fP  C,  and  boil  at  235^ 
C,  being  at  the  same  time  decomjiosed  into  the  anhydride  and 
water.  The  alkali  salts  of  this  acid  are  soluble  in  waiter,  insolu- 
ble in  alcohol  and  ether. 

Preparation. — Apart  from  the  synthetic  methods,  it  may  readily 
be  obtained  by  the  fermentation  of  calcic  malate,  acetic  acid  be- 
ing produced  simultaneously. 

Its  presence  is  recognized  by  the  microscopic  examination  of 
its  crystals,  and  its  characteristic  reaction  with  normal  lead  ace- 
tate. With  this  it  gives  a  precipitate,  easily  soluble  in  excess  of 
the  precipitant,  but  coming  down  again  on  warming  and  shaking.^ 

CHOLESTERIN.       (C^gH^/).) 

This  is  the  only  alcohol  which  occurs  in  the  human  bod}^  in  the 
free  state.  (The  triatomic  alcohol  glycerin  is  almost  alwaj'S 
found  combined  as  in  the  fats  ;  and  cetyl-alcohol,  or  ethal,  is  ob- 
tained only  from  spermaceti.)  It  is  a  white  crystalline  body  crys- 
tallizing in  fine  needles  from  its  solution  in  ether,  chloroform,,  or 
benzol ;  from  its  hot  alcoholic  solutions  it  is  deposited  on  cooling 
in  rhombic  tables.  (Fig.  259.)  AVhen  dried  it  melts  at  145°,  and 
distils  in  closed  vessels  at  36CP.  It  is  quite  insoluble  in  water 
and  cold  alcohol ;  soluble  in  solutions  of  bile  salts. 

Solutions  of  cholesterin  possess  a  left-handed  rotatory  action 
on  polarized  light,  of  —32°  for  yellow  light,  this  being  indepen- 
dent of  concentration  and  of  the  nature  of  the  solvent. 

Heated  with  strong  sulphuric  acid  it  yields  a  hydrocarbon  ; 
with  concentrated  nitric  it  gives  cholesteric  acid  and  other  prod- 
ucts. It  is  capabler  of  uniting  with  acids  and  forming  com- 
pound ethers. 

Cholesterin  occurs  in  small  quantities  in  the  blood  and  many 

^  Untersuch.  iiber  d.  Entsteh.  d.  Hippursiiure.     Hannover,  1866. 
2  Pfliiger's  Archiv,  Bd.  ii  (1869),  S.  367,  and  Bd.  iv  (1871),  S.  95. 
"  For  further  particulars  see  Meissner,  op.  cit.,  and  Meissner  and  Solly, 
Zeitschr.  f.  rat.  Med.  (3),  Bd.  xxiv,  S.  97. 


988 


CHEMICAL    BASIS    OF    THE    ANIMAL    BODY. 


tissues,  and  is  present  in  abundance  in  the  white  matter  of  the 
cerebro-spinal  axis  and  in  nerves.  It  is  a  constant  constituent 
of  bile,  forming  frequently  nearly  the  whole  mass  of  gallstones. 


Rhombic  Tables  of  Cliolesterin.] 


It  is  found  in  many  pathological  fluids,  hydrocele,  the  Huid  of 
ovarial  cysts,  etc. 

Preparation. — From  gallstones  by  simple  extraction  with  boil- 
ing alcohol,  and  treatment  with  alcoholic  potash  to  free  from  ex- 
traneous matter. 

As  tests  for  this  substance  maybe  given  :  With  concentrated  sul- 
phuric acid  and  a  little  iodine  a  violet  color  is  obtained,  changing 
through  green  to  red.  This  is  applicable  to  the  microscopic  crys- 
tals "After  dissolving  in  sulphuric  acid  a  blood-red  solution  is 
formed  on  the  addition  of  chloroform,  changing  to  purple,  and 
finally  becoming  colorless  ;  the  sulphuric  acid  under  the  chloro- 
form has  a  green  fluorescence.  After  evaporation  to  dryness  with 
nitric  acid,  the  residue  turns  red  on  treating  with  ammonia. 

This  body  is  described  here  rather  for  the  sake  of  convenience  than 
from  its  possessing  any  close  relationship  to  the  substances  immediately 
preceding. 

Complex  Xitrogexous  Fats. 

Leciihin.     C^.H,,NP09. 

Occurs  widely  spread  throughout  the  body.  Blood,  bile,  and 
serous  fluids  contain  it  in  small  quantities,  while  it  is  a  conspicu- 
ous component  of  the  brain,  nerves,  yolk  of  egg,  semen,  pus, 
white  blood-corpuscles,  and  the  electrical  organs  of  the  ray. 


COMPLEX    FATS.  989 


When  pure,  it  is  a  colorless,  slightly  crystalline  substance, 
which  can  be  kneaded,  but  often  crumbles  during  the  process. 
It  is  readily  soluble  in  cold,  exceedingly  so  in  hot  alcohol ;  ether 
dissolves  it  freely  though  in  less  quantities,  so  also  do  chloroform, 
fats,  benzol,  carbon  disulphide,  etc.  It  is  often  obtained  from 
its  alcoholic  solution,  by  evaporation,  in  the  form  of  oily  drops. 
It  swells  up  in  water,  and  in  this  state  yields  a  flocculent  precip- 
itate with  sodium  chloride. 

Lecithin  is  easily  decomposed  ;  not  only  does  this  decomposi- 
tion set  in  at  70-  0.,  but  the  solutions,  if  merely  allowed  to  stand 
at  the  ordinary'  temperature,  acquire  an  acid  reaction,  and  the 
substance  is  decomposed.  Acids  and  alkalies,  of  course,  effect 
this  much  more  rapidly.  If  heated  with  baryta-water  it  is  com- 
pletely decomposed,  tlie  products  being  neurin,  glycerinphos- 
phoric  acid,  and  barium  stearate.  This  may  be  thus  repre- 
sented : 

Glyceri  II  phosphoric 
Lecithin.  Stearic  Acid.  Acid  Neuriii. 

C,,H^XPO,  +  3H,0  =  2C,sH3.0,  +    C3H,P0«     +  C,H,,XO,. 

When  treated  in  an  ethereal  solution  with  dilute  sulphuric 
acid,  it  is  merely  spht  up  into  neurin  and  distearyl-glycerinphos- 
phoric  acid.  Hence  Diakonow'  regards  lecithin  as  the  distearyl- 
glycerinphosphate  of  neurin,  two  atoms  of  hydrogen  in  the 
glycerinphosi)horic  acid  being  replaced  '  b}' the  radicle  of  stearic 
acid.  It  appears  also  that  there  probablj-  exist  other  analogous 
compounds  in  which  the  radicles  of  oleic  and  palmitic  acids  take 
part. 

Preparation. — Usually  from  the  yolk  of  egg,  where  it  occurs 
in  union  with  vitellin.  Its  isolation  is  complicated,  and  the 
reader  is  referred  to  Hoppe-Seyler.^ 

Glycerinpliosxjliork  acid.     C.HyPO^. 

Occurs  as  a  product  of  the  decomposition  of  lecithin,  and  hence 
is  found  in  those  tissues  and  tluids  in  which  this  latter  is  pres- 
ent ;  in  leuch?emia  the  urine  is  said  to  contain  this  substance. 
It  has  not  been  obtained  in  the  solid  form.  It  has  been  pro- 
duced synthetically  by  heating  glycerin  and  glacial  phosphoric 
acid  ;  it  may  be  regarded  as  formed  by  the  union  of  one  mole- 
cule of  glycerin  with  one  of  phosphoric'^acid,  with  elimination  of 
one  molecule  of  water.  It  is  a  dibasic  acid  ;  its  salts  with  baryta 
and  calcium  are  insoluble  in  alcohol,  soluble  in  cold  water.  So- 
lutions of  its  salts  are  precipitated  by  lead  acetate. 

Protagon..     (C.coHsogN.PO.s  ?) 

A  crystalline  body,  containing  nitrogen  and  phosphorus,  ob- 

'  Hoppe-Sevler's  Med.  chera.  Untersiich.,  Heft  ii  (1867),  S.  221,  Heft 
iii  (1868),  S.  405.     Centralb.  f.  d.  med.  Wiss.  (1868),  Nr.  1,  7,  u.  28. 
-  Med.  chem.  Untersuch.,  Heft  ii  (1867),  S.  215. 

83 


990        CHEMICAL    BASIS    OF    THE    ANIMAL    BODY. 


tained  by  Liebreich'  from  the  brain  substance  and  regarded  by 
him  as  its  principal  constituent.  The  researclies  of  Hoppe-Sey- 
ler  and  Diakonovv  tended  to  show  that  protagon  was  merely  a 
mixture  of  lecithin  and  cerebrin.  A  repetition  of  Liebreich's 
experiments  has  led  Gamgee  and  Blankenhorn'  to  confirm  the 
truth  of  his  results.  Protagon  appears  to  separate  out  in  the 
form  of  very  small  needles,  often  arranged  in  groups,  from  warm 
alcohol  by  gradual  cooling  ;  it  is  slightly  soluble  in  cold,  more 
soluble  in  hot  alcohol  and  ether.  It  is  insoluble  in  water,  but 
swells  up  and  forms  a  gelatinous  mass.  It  melts  at  200°  C.  and 
forms  a  brown  syrupy  tiuid. 

Preparation. — Finely  divided  brain  substance,  freed  from 
blood  and  connective  tissue,  is  digested  at  45^  C.  with  alcohol 
(85  per  cent.)  as  long  as  the  alcohol  extracts  anything  from  it. 
The  protagon  which  separates  out  from  the  filtrate  is  well 
washed  with  ether  to  get  rid  of  all  cholesterin  and  other  bodies 
soluble  in  ether,  and  finally  purified  by  repeated  cystallization 
from  warm  alcohol. 

murin.  (Cholin).     C.H.^NO,. 

Discovered  by  Strecker^  in  pig's-gall,  then  in  ox-gall.  It  does 
not  occur  either  in  the  free  state  or  apart  from  lecithin.  It  is  a 
colorless  fluid,  of  oil}'  consistence,  possesses  a  strong  alkaline  re- 
action, and  forms  with  acids  very  deliquescent  salts.  The  salts 
with  hydrochloric  acid  and  the  chlorides  of  platinum  and  gold 
are  the  most  important. 

JSTeurin  is  a  most  unstable  bod}^  mere  heating  of  its  aqueous 
solution  sufficing  to  split  it  up  into  glycol,  trimethylamin  and 
ethylene  oxide. 

Preparation. — From  yolk  of  egg.     For  this  see  Diakonow.* 

Wurtz^  has  obtained  it  synthetically,  first  by  the  action  of  glycol  hy- 
drochloride on  trimethylamin,  and  tlien  by  that  of  ethylene  oxide  and 
water  on  the  same  substance.  The  above,  together  with  the  mode  of  its 
decomposition,  point  to  the  idea  that  neurin  may  be  regarded  as  tri- 
methyl-oxyethyl-ammonium  hydrate,  N (CH3)3(C2H50)OH. 

Cerehrin.    (CnHg^NO,  ?) 

Is  found  in  the  axis  cylinder  of  nerves,  in  pus-corpuscles,  and 
largely  in  the  brain.  In  former  times  many  names  were  given 
to  the  substance  when  in  an  impure  state,  ex.  gr..  cerebric  acid, 
cerebrote,  etc.     W.  Mailer'^  first  prepared  it  in  the  pure  form, 

1  Ann.  d.  Chem.  u.  Pharm.,  Bd.  134,  S.  29. 

"^  Zeitschr.  f.  phvsiol.  Chem.,  Bd.  iii  (1879),  S.  260,  and  Jl.  of  Physiol., 
vol.  ii  (18741,  p.  113. 

3  Ann.  d.  Chem.  u.  Pharm.,  Bd.  123,  S.  353;  Bd.  148,  S.  76. 
*  Op.  cit.  (sub  Lecithin). 

5  Ann.  d.  Chem.  u.  Pharm.,  Sup.  Bd.  6,  S.  116,  u.  197. 

6  Ann.  d.  Chem.  u.  Pharm.,  Bd.  105,  S.  361. 


UREA.  991 


and  constructed  the  above  formula  from  his  analyses  ;  the  mean 
of  these  is  O,  15.85  ;  H,  11.2  ;  N,  4.5  ;  C,  68.45.  Great  doubts 
are  however  thrown  upon  its  purity  by  the  researches  of  later 
observers.  According  to  Liebreich'  and  Diakonow,^  it  is  a  glu- 
coside. 

Cerebrin  is  a  light,  colorless,  exceedinglv  hygroscopic  powder, 
which  swells  up  strongly  in  water,  slowly  in  the  cold,  rapidly  on 
heating.  When  heated  to  80^'  it  turns  brown,  and  at  a  some- 
what higher  temperature  molts,  bubbles  up,  and  finally  burns 
away.  It  is  insoluble  in  cold  alcohol  or  ether;  warm "^ alcohol 
dissolves  it  easily.  Heated  with  diUite  mineral  acids,  cerebrin 
yields  a  sugar-like  body,  possessing  left-handed  rotation,  but  in- 
capable of  Fermentation. 


Preparation.— Fov  this  see  W.  Mailer. 


NITROGENOUS  METABOLITES. 

THE  UREA  &ROUP,  AMIDES,  AND  SIMILAR   BODIES. 

Urea.     (NHJ.CO. 

The  chief  constituent  of  normal  urine  in  mammalia,  and  some 
other  animals  ;  the  urine  of  birds  also  contains  a  small  amount. 
Normal  blood,  serous  liuids,  lymph,  and  the  liver,  all  contain  the 
same  body  in  traces.  It  is  not  found  in  the  muscles  as  a  normal 
constituent,  but  may  make  its  appearance  there  under  certain 
patholouical  conditions. 

When  pure  it  crystallizes  from  a  concentrated  solution  in  the 
from  of  long,  thin,  glittering  needles.  If  deposited  slowly  from 
dilute  solutions,  the  form  is  that  of  four-sided  prisms  with  pyram- 
idal ends ;  these  are  always  anhydrous.  It  possesses  a  some- 
what bitter  cooling  taste,  likc^  saltpetre.  It  is  readily  soluble  in 
water  and  alcohol,  the  solutions  being  neutral.  In  anhydrous 
ether  it  is  insoluble.  The  crystals  may  be  heated  to  120-  C. 
without  being  decomposed  ;  at  a  higher  temperature  the}^  are 
first  liquefied'and  then  burn,  leaving  no  residue.  Heated  with 
strong  acids  or  alkalies,  decomposition  ensues,  the  final  products 
beingcarbonic  anhydride  and  ammonia.  The  same  decomposi- 
tion may  also  occur -as  the  result  of  the  action  of  a  specific  fer- 
ment on  urea  in  an  aqueous  solution.'  Nitrous  acid  at  once 
decomposes  it  into  carbonic  anhydride  and  free  nitrogen.  It 
readily  forms  compounds  with  acids  and  bases  ;  of  these  the  fol- 
lowing are  of  importance  : 

'  Arch.  f.  pathol.  Anat.,  Bd.  39  (1867). 

2  Centrall).  f.  d.  raed.  Wiss.,  1868,  No.  7. 

=*  Op.  ch,  '  Musculus,  Pfliiger's  Archiv,  Bd.  xii  (1876),  S.  214. 


992        CHEMICAL    BASIS    OF    THE    ANIMAL    BODY, 


Nitrate  of  urea.     (NH,),CO  .  HKO3. 

Crystallizes  in  six-sided  or  rhombic  tables.  Insoluble  in 
ether  and  nitric  acid,  soluble  in  water,  slightly  soluble  in  al- 
cohol. 

Oxalate  of  urea.     (H  (XX,),  CO),  .  H2C.O,  +  H,0. 

Often  crystallizes  in  long  thin  prisms,  but  under  the  micro- 
scope is  obtained  in  a  form  closely  resembling  the  nitrate  ;  it  is 
slightly  soluble  in  Avater,  less  so  in  alcohol. 

With  mercuric  nitrate  urea  yields  three  salts,  containing  re- 
spectively, 4,  3,  and  2  equivalents  of  mercuiy  to  one  of  urea. 
The  first  is  the  precipitate  formed  in  Liebig's  quantitative  deter- 
mination of  urea.  The  exact  constitution  of  these  salts  has  not 
yet  been  determined. 

Preparation.— Ammomc  sulphate  and  potnssic  cyanate  are 
mixed  together  in  aqueous  solution,  and  the  mixture  is  evapo- 
rated to  dryness.  The  residue  when  extracted  with  absolute 
alcohol  yields  urea.  From  urine,  either  by  evaporating  to  dry- 
ness, and  then  extracting  with  alcohol,  or  concentrating  only  to 
a  syrup,  and  then  forming  the  nitrate  of  urea  ;  this  is  washed 
wath  pure  nitric  acid  and  decomposed  with  barium  carbonate. 

Detection  in  Solutions. — In  addition  to  the  microscopic  appear- 
ances of  the  crystals  obtained  on  evaporation,  the  nitrate  and 
oxalate  should  be  formed  and  examined.  Another  part  should 
give  a  precipitate  with  mercuric  nitrate,  in  the  absence  of  sodic 
chloride,  but  not  in  the  presence  of  this  last  salt  in  excess.  A 
third  portion  is  treated  with  nitric  acid  containing  nitrous  fumes  ; 
if  urea  is  present,  nitrogen  and  carbonic  anhydride  will  be  ob- 
tained. To  a  fourth  part  nitric  acid  in  excess  and  a  little  mer- 
cur}'  are  added,  and  the  mixture  is  warmed.  In  presence  of 
urea  a  colorless  mixture  of  gases  (N  and  CO_,)  is  given  off.  A 
fifth  portion  is  kept  melted  for  some  time,  dissolved  in  water,  and 
cupric  sulphate  and  caustic  soda  are  added  ;  a  red  or  violet  color, 
due  to  biuret,  is  developed. 

Urea  is  generally  considered  as  being  an  amide  of  carbonic 
acid.  The  amide  of  an  aeid  is  formed  when  water  is  removed 
from  the  ammonium  salt  of  the  acid  ;  if  the  acid  be  dibasic  and 
two  molecules  of  water  be  removed,  the  result  is  often  spoken  of 
as  a  diamide.  Thus  if  from  ammonic  carbonate,  (X1I,),C0;^, 
two  molecules  of  water,  "2H,0,  be  removed,  carbonic  acid  being 
a  dibasic  acid,  the  result  is  urea  ;  thus  : 

(NH4)  CO,  +  2H2O  =  (NH,),CO, 

which  may  be  written  either  according  to  the  ammonia  type  as 

CO  ]  ,  ^„ 

H2  1^  X,  or  as  CO  ]  ^g^ 


H 


UREA.  993 


two  atoms  of  amidogen  (XH.)  beins:  substituted  for  two  atoms 
of  hydroxyl  (HO). 

The  connection  between  carbonic  acid  and  urea  is  shown  by 
the  foct  that  not  only  may  urea  be  formed  out  of  ammonium 
carbcunate  by  dehydration,  but  also  ammonium  carbonate  may 
be  formed  out  of  urea  by  hydration,  as  when  urea  is  subjected  to 
the  specific  ferment  mentioned  above.  Reirarded  then  as  a  dia- 
mide  of  carbonic  acid,  urea  may  1>e  spoken  of  as  carbamide. 
Kolbe  however  is  inclined  to  regard  it,  not  as  the  diamide  of  car- 
bonic acid,  but  as  tlie  amide  of  carbamic  acid.  Ammonium  car- 
bamate. COjXjH,-  minus  HO,  gives  urea.  CO,  X.-,  H^ — which,  if 
carbamic  acid  be  written  as  ('O,  OH,  XH-,  may  be  written  as 
CO,  XHj,  XH:,  one  atom  of  amidogen  being  substituted  for  one 
atom  of  hydroxyl,  and  not  two,  as  when  the  substance  is  re- 
garded as  Gerived  from  carbonic  acid.  For  the  bearing  of  this 
dilference  of  derivation  see  p.  575. 

Wanklyn  and  Gamgee,'  however,  since  urea  when  lieated  with 
a  large  excess  of  potassium  permanganate  gives  off  all  its  nitro- 
gen in  a  free  state  and  not  in  the  oxidized  form  of  nitric  acid,  as 
do  all  other  amides,  conclude  that  it  is  not  an  amide  at  all,  that 
it  is  isomeric  only  and  not  identical  with  carbamide. 

It  is  important  to  remember  that  urea  is  also  isomeric  with 

ammonium  cyanate.  C  -  q>-tt  fiud  indeed  was  first  formed  ar- 
tificially by  Wiihlerfrom  this  body.  AVe  thus  have  three  isomeric 
compounds,  ammonium  cyanate.  urea,  and  carljamide,  related  to 
each  other  in  such  a  way  that  urea  may  be  obtained  readily  either 
from  ammonium  cyanate  or  from  ammonium  carbamate,  and 
may  with  the  greatest  ease  be  converted  into  ammonium  carbon- 
ate. Xow  urea  is  a  much  more  stable  body  than  ammonium 
cyanate,  and  in  the  transformation  of  the  latter  into  the  former 
energy  is  set  free  ;  and  it  is  worthy  of  notice  that  though  the 
presence  of  suljihocyanides  in  the  saliva  probabh*  indicates  the 
existence  of  cyanic  residues  in  the  bodv,  the  nitrogenous  products 
of  the  decomposition  of  prott-ids  belong  cliierly  to  the  class  of 
aniides,  cyanogen  compounds  being  rare  among  them.  PtiUger^ 
has  called  attenticm  to  the  great  molecular  energy  of  the  cyano- 
gen compounds,  and  has  suggested  that  the  functional  metabo- 
lism of  protoplasm  by  Avhich  energy  is  set  free,  may  be  compared 
to  the  conversion  of  the  energetic  unstable  CTanogen  compounds 
into  the  less  energetic  and  more  stable  amides.  In  other  words, 
ammonium  cyanate  is  a  type  of  living,  and  urea  of  dead  nitrogen, 
and  the  conversion  of  the  former  into  the  latter  is  an  image  of 
the  essential  change  which  takes  place  when  a  living  proteid 
dies. 

Compound  Ureas. — The  hydrogen  atoms  of  nrea  can  be  replaced  by 
alcohol  and  acid  radicles.     The  results  are  compound  ureas.     Many  of 


Journ.  Chem.  Soc.  2,  vol.  vi,  p.  25. 
Pflujer's  Archiv,  Bd.  x  (1875j,  S.  337 


994        CHEMICAL    BASIS    OF    THE    ANIMAL    BODY. 


them  are  called  acids,  since  the  hydrogen  from  the  amide  group,  if  not 
all  replaced  as  above,  can  be  replaced  by  a  metal.  Thus  the  substitution 
of  oxalyl  (oxalic  acid)  gives  parabanic  acid, 

rco 

N2  \  H2  or  CO,  NHj,  N  .  CA  I 
tCA 

of  tartronyl  (tartronic  acid),  dialuric  acid,  CO,  NH2,  N.C^HA;  of 
mesoxalyl  (mesoxalic  acid),  alloxan,  CO,  NH2,  N  .  C3O3.  These  bodies 
are  interesting  as  being  also  obtained  by  the  artificial  oxidation  of  uric 
acid. 

Uric  add.  C.H.NA- 

The  chief  constituent  of  the  urine  in  birds  and  reptiles  ;  it 
occurs  only  sparingly  in  this  excretion  in  man  and  most  mam- 
malia. Itis  normally  present  in  the  spleen,  and  traces  of  it  have 
been  found  in  the  lungs,  muscles  of  the  heart,  pancreas,  brain, 
and  liver.  Urinary  and  renal  calculi  often  consist  largely  of  this 
body,  or  its  salts.  In  gout,  accumulations  of  uric  acid  salts  may 
occur  in  various  parts  of  the  body,  forming  the  so-c  illed  gouty 
concretions. 

It  is  when  pure  a  colorless,  crystalline  powder,  tasteless,  and 
without  odor.  The  crystalline  form  is  very  variable,  but  usually 
tends  towards  that  of  rhombic  tables.'  When  impure  it  crystal- 
lizes readily,  but  then  possesses  a  yellowish  or  brownish  color. 
In  water  it  is  very  insoluble  (1  in  14,000  or  15,000  of  cold  water)  ; 
ether  and  alcohol  do  not  dissolve  it  appreciably.  On  the  other 
hand,  sulphuric  acid  takes  it  up  without  decomposition,  and  it  is 
also  readily  soluble  in  many  salts  of  the  alkalies,  as  in  the  alka- 
lies themselves.     Ammonia,  however,  scarcely  dissolves  it. 

Salts  of  Uric  Acid. — Of  these  the  most  important  are  the  acid 
urates  of  sodium,  potassium,  and  ammonium.  The  sodium  salt 
crystallizes  in  many  different  forms,  these  not  being  character- 
istic, since  they  are  almost  the  same  for  the  corresponding  com- 
pounds of  the  other  two  bases.  It  is  very  insoluble  in  cold  water 
(1  in  1100  or  1200),  more  soluble  in  hot  (1  in  125).  It  is  the  prin- 
cipal constituent  of  several  forms  of  urinary  sediment,  and  com- 
poses a  large  part  of  uiany  calculi  ;  the  excrement  of  snakes  con- 
tains it  largely.  The  potassium  resembles  the  sodium  salt  very 
closely,  as  also  does  the  compound  with  ammonium  ;  the  latter 
occurs  generally  in  the  sediment  from  alkaline  urine. 

Preparation. — Usually  from  guano  or  snake's  excrement. 
From  guano  by  boiling  with  caustic  potash  (1  part  alkali  to  20 
of  water)  as  long  as  ammonia  is  evolved.  In  the  filtrate  a  pre- 
cipitate of  acid  urate  of  potassium  is  formed  by  passing  a  current 

^  See  Ultzmann  and  K.  B.  Hoffman,  Atlas  der  Harnsediraente,  Wien, 

1872. 


URIC    ACID.  995 


of  carbonic  anhydride,  and  this  salt  is  then  decomposed  by  excess 
of  hydrochloric  acid. 

The  presence  of  uric  acid  is  recognized  by  the  following  tests. 
The  substance  having  been  examined  microscopically,  a  portion 
is  evaporated  rarefulh/  to  dryness  with  one  or  two  drops  of  nitric 
acid.  The  residue  will,  if  uric  acid  is  present,  be  of  a  red  color, 
which  on  the  addition  of  ammonia  turns  to  purple.  This  is  the 
murexide  test,  and  depends  on  the  presence  of  alloxan  andallox- 
antin  in  the  residue.  Schiff '  has  given  a  delicate  reaction  for 
uric  acid.  The  substance  is  dissolved  in  sodic  carbonate,  and 
dropped  on  paper  moistened  with  a  silver  salt.  If  uric  acid  be 
present  a  brown  stain  is  formed,  due  to  the  reduction  of  the  silver 
carbonate.  An  alkaline  solution  of  uric  acid  can,  like  dextrose, 
reduce  cupric  sulphate,  with  precipitation  of  the  cuprous  oxide. 

Unlike  urea,  uric  acid  cannot  be  formed  artificially  ;  and  un- 
like urea  and  the  urea  compounds,  it  resists  very  largely  the 
action  of  even  strong  acids  and  alkalies.  This  last  fact  would 
seem  to  indicate  that  urea  residues  do  not  pre-exist  in  uric  acid  ; 
nevertheless  by  oxidation  uric  acid  does  give  rise,  not  only  to 
ordinary  urea,  but  also,  and  at  the  same  time,  to  the  compound 
ureas  spoken  of  above.     Thus  b}'  oxidation  with  acids. 

Uric  acid.  Alloxan.  Urea. 

c^H.N.o.,  +  H,o  +  o = c,x.ii,o,  +  c:n^,h,o. 

Now  alloxan,  as  was  stated  above,  is  a  compound  urea,  viz., 
mesoxalyl-urea,  and  by  h^'dration  can  be  converted  into  mesox- 
alic  acid  and  urea,  thus  : 

Alloxan.  Mesoxalic  acid.  Urea. 

and  by  the  action  of  chlorine  uric  acid  can  be  split  up  directly 
into  a  molecule  of  mesoxalic  acid  and  two  molecules  of  urea  : 

Uric  acid.  Mesoxalic  acid.  Urea. 

C5H,:N^A  +  Cl,  +  4H,0  =  C,HA  +  2CX,H,0  +  2HC1. 

By  oxidation  with  alkalies,  uric  acid  is  converted  into  allantoiu 
and  carbonic  acid  : 

Uric  acid.  Allantoin. 

C5H,:N^,03.+  h.o  +  O  =  C  JI,X,0,  +  CO, ; 

and  allantoin.  by  hydration,  becomes  allanturic  or  lantanuric  acid 
and  urea  : 

Allantoin.  Urea.  Allanturic  acid. 

CJIeN.Og  +  H,,0  =CH,N20  +  C^H.N.O. 
Kow  allanturic  acid  is  a  compound  urea,  with  a  residue  of  gl}^- 

.     1  Ann.  d.  Ghem.  u.  Pharm.,  Bd.  109,  S.  65. 


996        CHEMICAL    BASIS    OF    THE    ANIMAL    BODY 


oxylic  acid.  By  other  oxidations  of  uric  acid,  parabanic  acid 
(oxalyl-urea),  oxaluric  acid  (whicli  is  hydrated  parabanic  acid), 
and  dialiiric  acid  (tartronyl-urea)  are  obtained.  In  fact  all  these 
decompositions  of  a  molecule  of  uric  acid  lead  to  two  molecules 
of  urea  and  a  carbon  acid  of  some  kind  or  other. 

There  are,  however,  reasons  for  thinking  that  before  the  urea 
can  be  obtained  from  the  uric  acid  a  molecular  change  takes  place  ; 
that  part  of  the  nitrogen  of  uric  acid  exists  as  a  cyanogen  resi- 
due, which  on  the  splitting  up  of  the  uric  acid  is  converted  into 
the  same  condition  as  the  rest  of  the  nitrogen,  viz  ,  into  the  amide 
condition.  It  has  been  supposed,  indeed,  that  uric  acid  is  tar- 
tronyl  cyanamide,in  which  two  molecules  of  amidogen  have  been 
replaced  by  the  radical  of  tartronic  acid,  and  two  others  by  two 
atoms  of  cyanogen,  thus  : 

(:N'H),(CN)2C,H..0,  or  nJ  (CN)2 

[h, 

If  this  be  so,  since  the  metabolism  of  the  animals  in  which  uric 
acid  replaces  urea  cannot  be  supposed  to  be  fundamental!}"  dif- 
ferent from  that  of  the  urea- producing  animals,  we  may  infer  that 
the  antecedent  of  both  uric  acid  and  urea  in  the  regressive  meta- 
bolism of  proteids  is,  as  we  suggested  above,  a  body  containing 
some  at  least  of  its  nitrogen  in  the  form  of  cyanogen. 

Kreatin.     C.H.N.O,. 

Occurs  as  a  constant  constituent  of  the  juices  of  muscles, 
though  possibly  it  may  be  formed  during  the  process  of  extraction 
by  the  hydration  of  kreatinin.  Kreatin  is  not  a  normal  constitu- 
ent of  urine,  but  it  is  said  to  occur  in  traces  in  several  fluids  of 
the  body.  When  found  in  urine  its  presence  is  probably  due  to 
the  conversion  of  kreatinin,  a  constant  constituent  of  urine,  into 
kreatin  during  its  extraction,  since  Dessaignes'  has  shown  that 
the  more  rapidly  the  separation  is  effected,  the  less  is  the  quantity 
of  kreatin  obtained,  and  the  greater  the  amount  of  kreatinin. 

In  the  anhydrous  form  it  is  white  and  opaque,  but  crystallizes 
with  one  molecule  of  water  in  colorless  transparent  rhombic 
prisms.  It  possesses  a  somewhat  bitter  taste,  is  soluble  in  cold, 
extremely  soluble  in  hot  water,  is  less  soluble  in  absolute  than 
in  dilute  alcohol,  and  is  insoluble  in  ether. 

It  is  a  very  weak  base,  scarcely  neutralizing  the  weakest  acids. 
It  forms  crystalline  compounds  with  sulphuric,  hydrochloric,  and 
nitric  i.cids. 

Preparation. —From  extract  of  muscle  by  precipitating  com- 
pletely with  basic  lead  acetate,  and  crystallizing  out  the  kreatin, 
mixed  with  kreatinin.  From  this  latter  it  is  separated  by  the 
formation  of  the  zinc-salt  of  kreatinin,  kreatin  not  readily  yield- 
ing a  similar  compound. 

1  J.  Pharm.  (3),  Bd.  xxxii,  S  41. 


THE    UREA    GROUP.  997 


Kreatin  may  be  converted  into  kreatinin  under  the  influence  of  acids, 
the  transformation  being  one  of  simple  dehydration. 

Kreatin  may  be  decomposed  into  sarcosin  (methyl-gljcin)  and 
urea : 

C,H,X,0,  +  H,0  =  C;H,XO,  +  CH,]S\0  ; 

it  may  be  formed  syiitbetically'  by  the  action  of  sarcosin  and 
cyanamide  : 

C,H,NO,  +  CH.X2  =  C,H„N,0. 

Sarcosin  is  glycin  in  which  one  atom  of  hydrogen  has  been  re- 
placed by  the  alcohol  radical  methyl,  thus  : 

C  H  O  I  C.H2(CH3)0  ]  ^ 

Glycin     XH,  j  O  becomes    "    XH,        |^' 

like  glycin,  sarcosin  has  not  been  found  in  a  free  state  in  the  body. 
Kreatinin.     C^H-N.O. 

This,  which  is  simply  a  dehydrated  form  of  kreatin,  occurs 
normally  as  a  constant  constituent  of  urine  and  of  muscle  ex- 
tract. It  crystallizes  in  colorless  shining  prisms,  possessing  a 
strong  alkaline  taste  and  reaction.  It  is  readily  soluble  in  cold 
water  (1  in  11.5),  also  in  alcohol,  but  is  scarcely  soluble  in  ether. 
It  acts  as  a  powerful  alkali,  forming  with  acids  and  salts  com- 
pounds which  crystallize  well.  Of  these  the  most  important  is 
the  salt  with  zinc  chloride  (C,II;X.O)  Zn  CI,.  It  is  formed  when 
a  concentrated  solution  of  the  chloride  is  added  to  a  not  t  >o  dilute 
solution  of  kreatinin.  Since  the  comp(nmd  is  ver}-^  little  soluble 
in  alcohol,  it  is  better  to  use  alcoholic  rather  than  aqueous  solu- 
tions. It  crystallizes  in  warty  lumps  composed  of  aggregated 
masses  of  prisms  or  fine  needles. 

Prejjaration. — Either  by  the  action  of  acids  on  kreatin,  or  from 
human  urine  by  concentrating  and  precipitating  with  lead  ace- 
tate ;  in  the  filtrate  from  this  a  second  precipitate  is  caused  by 
the  addition  of  mercuric  chloride,  and  consists  of  a  compound  of 
this  salt  with  kreatinin.  The  mercury  is  removed  by  sulphur- 
etted hydrogen,  and  the  kreatinin  purified  by  the  formation  of  the 
zinc  salt  and  washing  with  alcohol. 

Kreatinin-zinc  chloride  may  be  converted  into  kreatin  by  the  action 
of  hydrated  oxide  of  lead  on  its  boiling  aqueous  solution. 

Allantoin.     CiHsX.Os. 

The  characteristic  constituent  of  the  allantoic  fluid  of  the 
foetus  ;  it  occurs  also  in  the  urine  of  animals  for  a  short  period 

1  Sitzungsber.  d.  bayersch.  Akad.,  1868,  Hft.  3,  S.  472. 
84 


998        CHEMICAL    BASIS    OF    THE    ANIMAL    BODY, 


after  their  birth.  Traces  of  it  are  sometimes  detected  in  this 
excretion  at  a  later  date. 

It  crystallizes  in  small,  shining,  colorless  prisms,  which  are 
tasteless  and  odorless.  They  are  soluble  in  1(30  parts  of  cold, 
more  soluble  in  hot  water,  insoluble  in  c(^ld  alcohol  and  ether, 
soluble  in  hot  alcohol.  Carbonates  of  the  alkalies  dissolve  them, 
and  compounds  may  be  formed  of  allantoin  with  metals,  but  not 
with  acids. 

Allantoin,  as  already  stated,  p.  995,  is  one  of  the  products  of 
the  oxidation  of  uric  acid,  and  by  further  oxidation  gives  rise  to 
urea. 

Preparation. — This  is  best  done  b}^  the  careful  oxidation  of  uric 
acid  either  by  means  of  potassium  permanganate  or  ferrocyanide, 
or  by  plumbic  oxide. 

Hi/poxanthin  or  Sarl'in.     0511^^40. 

Is  a  normal  constituent  of  muscles,  occurring  also  in  the 
spleen,  liver,  and  medulla  of  bones.  In  leuci^emia  it  appears  in 
the  blood  and  urine.  It  crystallizes  in  fine  needles,  which  are 
soluble  in  300  parts  of  cold,  more  soluble  in  hot  water,  insoluble 
in  alcohol,  soluble  in  acids  and  alkalies.  It  forms  crystalline 
compounds  with  acids  and  bases.  It  is  precipitated  by  basic  ace- 
tate of  lead,  the  precipitate  being  soluble  in  a  solution  of  the 
normal  acetate.  Its  preparation  from  muscle -extract  depends 
on  its  precipitation  first  by  basic  acetate  of  lead,  and  then  by  an 
ammoniacal  solution  of  silver  nitrate  after  the  removal  of  kreatin. 

Both  hypoxantliin  and  the  next  body,  xanthin,  can  also  be  obtained  from 
proteids  by  the  action  of  putrefactive  changes,  of  water  at  boiling  tem- 
perature, of  dilute  hydrochloric  acid  (.2  per  cent.)  at  40°  C,  and  by  the 
action  of  gastric  and  pancreatic  ferments.^  Chittenden  has  noticed  a 
peculiar  difierence  between  fibrin  and  egg-albumin  when  submitted  to 
the  above  processes  ;  he  finds  that  the  latter  does  not  yield  hypoxanthin 
when  treated  with  boiling  water,  with  dilute  hydrochloric  acid,  or  gas- 
tric ferment,  while  the  former  does.  Egg-albumin,  on  the  other  hand, 
yields  hypoxanthin  by  the  action  of  pancreatic  ferment  in  alkaline  solu- 
tion, but  not  so  readily  as  fibrin  does. 

Xanthin.     C5H4K4O,. 

First  discovered  in  a  urinary  calculus,  and  called  xanthic  oxide. 
More  recently  it  has  been  found  as  a  normal,  though  scanty,  con- 
stituent of  urine,  muscles,  and  several  organs,  such  as  the  liver, 
spleen,  thymus,  etc. 

When  precipitated  by  cooling  from  its  hot,  saturated,  aqueous 
solution,  it  falls  in  white  flocks,  but  if  the  solution  be  allowed  to 


'  Salomon,  Zeitschr.  f.  Physiol.  Chem.,  Bd.  ii  (1878-1879),  S.  90. 
Kranze,  Inaug.  Diss.,  Berlin,  1878.    Chittenden,  Journ.  of  Physiol.,  vol. 

ii  (1879),  p.  28. 


THE    UREA    GROUP.  999 


evaporate  slowly  it  is  obtained  in  small  scales.  When  i)nre  it  is 
a  colorless  powder,  very  insoluble  in  water,  requiring  1500  times 
its  bulk  for  solution  at  100^  C.  Insoluble  in  alcohol  and  ether, 
it  readily  dissolves  in  dilute  acids  and  alkalies,  forming  crystal- 
lizable  compounds. 

Hypoxanthin  by  oxidation  becomes  xanthin.  Both  these 
bodies,  as  well  as  the  following,  guanin  and  carnin,  are  evidently 
closely  allied  to  uric  acid  ;  indeed,  uric  acid  by  the  action  of  so- 
dium-amalgam may  be  converted  into  a  mixture  of  xanthin  and 
hj^poxanthin. 

Preparation. — It  is  obtained  from  urine  and  the  aqueous  ex- 
tract of  muscle  by  a  process  similar  to  that  for  hypoxanthin,  and 
is  then  separated  from  the  latter  by  the  action  of  dilute  hydro- 
chloric acid ;  this  separation  depends  on  the  different  solubilities 
of  the  hydrochlorates  of  the  two  bodies.  For  further  informa- 
tion see  Neubauer.^ 

Carnin.     CjHsX.O^. 

Discovered  by  Weidel-  in  extract  of  meat,  of  which  it  consti- 
tutes about  one  per  cent. 

It  crystallizes  in  white  masses  composed  of  ver}-  small  irregu- 
lar crystals  ;  it  is  soluble  with  dirtieulty  in  cold,  more  easily  sol- 
uble in  hot  water,  insoluble  in  alcohol  and  ether.  Its  aqueous 
solution  is  not  precipitated  b}'  normal  lead  acetate,  but  is  by  the 
basic  acetate  of  this  metal.  It  unites  with  acids  and  salts,  form- 
ing crystalline  compounds. 

Preparation. — Is  found  in  the  precipitate  caused  in  extract  of 
meat  by  basic  acetate  of  lead.* 

This  body  possesses  an  interesting  relation  to  hypoxanthin,  into  which 
it  may  be  converted  by  the  action  either  of  nitric  acid,  or,  still  better,  of 
bromine. 

Guanin.     C^H.X.O. 

First  obtained  from  guano,  but  recently  observed  as  occurring 
in  small  quantities  in  the  pancreas,  liver,  and  muscle  extract. 

It  is  a  white  amorphous  powder,  insoluble  in  water,  alcohol, 
ether,  and  ammonia.  It  unites  with  acids,  alkalies,  and  salts  to 
form  crystallizable  compounds. 

Preparation. — From  guano  by  boiling  successively  with  milk 
of  lime  and  caustic  soda,  precipitating  with  acetic  acid,  and 
purifying  by  solution  in  hydrochloric  acid  and  precipitation  by 
ammonia. 


^  Harn- Analyze,  ed.  vii  (1876),  S.  24. 

»  Ann.  d.  Chem.  u.  Pliarm.,  Bd.  158,  S.  365. 

^  See  Weidel,  op.  cit. 


1000      CHEMICAL    BASIS    OF    THE    ANIMAL    BODY. 


Guanin  may,  by  the  action  of  nitrous  acid,  be  converted  into 
xanthin.  By  oxidation  it  can  be  made  to  yield  principally  guan- 
idine  and  parabanic  acid,  accompanied  however  by  small  quan- 
tities of  urea,  xanthin,  and  oxalic  acid. 

Its  separation  from  hypoxanthin  and  xanthin  depends  on  its 
insolubility  in  water  and  behavior  with  hydrochloric  acid. 

Kynurenic  acid.     C,,^Il]iNJD^-{-2I{0. 

Found  in  the  urine  of  dogs,  and  first  described  by  Liebig.^ 
When  pure  it  crystallizes  in  brilliant  white  needles,  insoluble  in 
cold,  soluble  in  hot  alcohol.  The  only  salt  of  this  body  wliich 
cr3\stallizes  well  is  that  formed  with  barium.  For  preparation 
and  other  particulars  see  Liebig-  and  Schultzen  and  Schmiede- 
berg.^ 

Glycin.  C,H./:N"HJ0(0H).  Also  called  Glycocoll  and  Gly- 
cocine. 

Does  not  occur  in  a  free  state  in  the  human  bod}^  but  enters 
into  the  com])ositi(m  of  many  important  substances,  ex.  gr.^  hip- 
puric  and  bile  acids.  It  crystallizes  in  large,  colorless,  hard 
rhombohedra,  which  are  easily  soluble  in  water,  insoluble  in 
cold,  slightly  soluble  in  hot  alcohol,  insoluble  in  ether.  It  pos- 
sesses an  acid  reaction,  but  a  sweet  taste.  It  has  also  the  prop- 
erty of  uniting  with  both  acids  and  bases,  to  form  crystallizable 
compounds.  In  this  it  exhibits  its  amide  nature,  and  that  it  is 
an  amide  is  rendered  evident  from  the  methods  of  its  synthetic 
preparation;  thusmono-chlor-acetic  acid  and  ammonia  give  gly- 
cin and  ammonium  chloride:  O.HaClO.+i^NH.,  =C..II.j(NH.;)0 
(0H)+]SrH4Cl.  It  is  amido-acetic  acid.  Heated  with  caustic 
baryta  it  yields  ammonia  and  methylamine. 

Preparation. — From  glutin  by  the  action  of  acids  or  alkalies  ; 
from  hippuric  acid  by  decomposing  this  with  hydrochloric  acid 
at  a  boiling  temperature  and  removing  by  precipitation  the  si- 
multaneously formed  benzoic  acid. 

Taurin.    C.HjNO.S. 

In  addition  to  entering  into  the  composition  of  taurocholic 
acid  (see  p.  1006),  taurin  is  found  in  traces  in  the  juices  of  muscle 
and  of  the  lungs. 

It  crystallizes  in  colorless,  regular,  six-sided  prisms ;  these  are 
readily  soluble  in  water,  less  so  in  alcohol.  The  solutions  are 
neutral.  It  is  a  very  stable  compound,  resisting  temperatures 
of  less  than  240^  C.  ;  it  is  not  acted  on  by  dikite  alkalies  and 
acids,  even  when  boiled  with  them.  It  is  not  precipitated  by 
metallic  salts. 

'  Ann.  d.  Chem.  u.  Pliarm.,  Brl.  86,  S.  125,  and  Bd.  108,  S.  354. 

''  Op.  cit.  3  Ann.  d.  Chem.  u.  Pliarm.,  Bd.  164,  S.  155. 


1001 


Taurin  is  amiflo-isethionic  acid  ;  and  may  be  synthetically  pre- 
pared from  isethionic  (ethyl-sulphuric)  acid  by  the  action  of  am- 
monia ;  thus  : 

Isethionic  acid.     Ammonia.    Tiiurin. 

^'r'  ]  SO^+^^H,  =  ^  I  SO+H,0. 

Preparation. — As  a  product  of  the  decomposition  of  bile,  and 
is  purified  b}"  removing  any  traces  of  bile  acid  s  by  means  of  lead 
acetate,  and  then  successfully  crystallizing  from  water. 

Leiicin.     C.Hi.XO,. 

Is  one  of  the  principal  products  of  the  decomposition  of  nitro- 
genous matter,  either  under  the  influence  of  putrefaction  or  of 
strong  acids  and  alkalies.  It  occurs  however  normally  in  the 
pancreas,  spleen,  th3'!nus,  thyroid,  salivary  glands,  liver,  etc., 
and  is  one  of  the  products  of  the  tryptic  (pancreatic)  digestion 
of  proteids  ;  in  acute  atrophy  of  the  liver  it  is  present  in  the 
urine  in  large  quantity,  in  company  with  tyrosin. 

As  usually  obtained  in  an  impure  form  it  crystallizes  in  rounded 
lumps  which  are  often  collected  together,  and  sometimes  exhibit 
radiating  striation.  When  pure,  it  forms  very  thin,  white,  glit- 
tering flat  crystals.  These  are  easily  soluble  in  hot  water,  less 
so  in  cold  water  and  alcohol,  insoluble  in  ether.  They  feel  oily 
to  the  touch,  and  are  without  smell  and  taste.  Acids  and  alka- 
lies dissolve  them  readily,  and  crystallizable  compounds  are 
formed. 

Carefnlly  heated  to  170^  it  sublimes,  but  at  a  higher  temperature  is 
decomposed,  yieldinor  amylamin,  carbonic  anhydride,  and  ammonia.  In 
the  presence  of  putrefying  animal  matter  it  splits  up  into  valeric  acid 
and  ammonia  ;  in  this  it  exhibits  its  amide  nature. 

Lcucin  is  amido-caproic  acid,  and  may  be  written  thus  : 

Preparation. — From  horn  shavings  by  bailing  with  sulphuric 
acid,  neutralizing  with  baryta  and  separating  from  tyrosin  by 
successive  crystallization.  See  also  Kuhne,' who  prepares  it  by 
the  action  of  pancreatic  ferments  on  proteids. 

Scherer  has  given  the  following  test  forleucin.  The  suspected 
substance  is  evaporated  carefully  to  dryness  with  nitric  acid  ;  the 
residue,  if  it  is  leucin,  will  be  almost  transparent  and  turn  yellow 
or  brown  on  the  addition  of  caustic  soda.  If  heated  again  with 
the  alkali  an  oilj^  drop  is  obtained,  which  is  quite  characteristic 

'  Virchow's  Arehiv,  Bd.  39,  S.  130. 


1002      CHEMICAL    BASIS    OF    THE    ANIMAL    BODY. 


of  this  substance.  Leiiein,  if  not  too  impure,  may  be  easily 
recognized  by  its  subliming  on  l)eing  heated  ;  a  characteristic 
odor  of  amylamin  is  at  the  same  time  evolved. 

Cystin.     C,H,NSO,. 

Is  the  chief  constituent  of  a  rarely  occurring  urinary  calculus 
in  men  and  dogs.  It  may  also  occur  in  renal  concretions,  and  in 
gravel. 

From  calculi  it  is  obtained  by  extraction  with  ammonia,  as 
colorless  six-sided  tables  or  rhombohedra,  which  are  neutral  and 
tasteless.  It  is  insoluble  in  water,  alcohol,  and  ether  ;  soluble  in 
ammonia  and  the  other  alkalies,  and  also  in  mineral  acids.  The 
fact  that  this  body  is  one  of  the  few  crystalline  substances,  occur- 
ring physiologically,  which  contain  sulphur,  renders  its  detection 
very  easy.  Apart  from  its  insolubility  in  water,  etc.,  it  yields 
with  caustic  potash  and  salts  of  either  silver  or  lead  a  brown 
coloration,  due  to  the  presence  of  the  sulphides  of  these  metals. 

According  to  Dewar  and  Gamgee^  cystin  is  amido-snlpho-pyrnvic 
acid,  and  its  forninla  is  C3H5NSO2 — pyruvic  being  lactic  acid  minus 
two  atoms  of  hydrogen. 

The  Aromatic  Series. 

Benzoic  acid.     IIC;H-,0,. 

This  is  not  found  as  a  normal  constituent  of  the  body,  but  owes 
its  presence  in  urine  to  the  decomposition  of  hippuric  acid, 
whereby  glycin  and  benzoic  acid  are  formed  : 

Hippuric  acid.  Glyoin.         Benzoic  acid. 

C.,H,(C,H50)N02  +  H,0  =  C2H5NO.  4-  C,H,02. 

The  sublimed  acid  is  generally  crystallized  in  fine  needles, 
which  are  light  and  glistening  ;  any  odor  they  possess  is  not  due 
to  the  acid,  but  to  an  essential  oil  with  which  they  are  mixed. 
AVhen  precipitated  from  solution  the  crystalline  form  is  always 
indistinct.  This  acid  is  soluble  in  200  parts  cold  or  25  parts  of 
boiling  water,  but  is  easily  soluble  in  alcohol  or  ether.  It 
sublimes  readily  at  145°  C.  It  also  passes  off  in  the  vapors 
arising  from  its  heated  solutions. 

Preparation. — Either  as  above  from  hippuric  acid  b}-  fermen- 
tation, or  the  action  of  hydrochloric  acid,  or  by  sublimation 
from  gum- benzoin. 

Tyrosin.     CyH,,NO;.. 

Generally  accompanies  leucin,  and  is,  perhaps,  found  normally 
in  small  quantities  in  the  pancreas  and  spleen.    It  is  also  usually 


Journ.  of  Anat.  and  Physiol.,  Nov.  1870,  p.  148. 


THE    AROMATIC    SERIES.  1003 


obtained  in  large  quantities  b}^  tbe  decomposition  of  proteid  mat- 
ter, either  by  putrefaction  or  the  action  of  acids. 

The  researches  of  Radziejewskyi  render  it  probable  that  tyrosin  does 
not  occur  normally  in  any  part  of  the  human  organism,  except  as  a  prod- 
uct of  pancreatic  digestion. 

It  crj'Stallizes  in  exceedingly  fine  needles,  which  are  usually 
collected  into  feathery  masses.  The  crystals  are  snow-white, 
tasteless,  and  odorless,  almost  insoluble  in  cold  water  ;  readily 
soluble  in  hot  water,  acids,  and  alkalies  ;  insoluble  in  alcohol  and 
ether.  If  crystallized  from  an  alkaline  solution  tyrosin  often 
assumes  the  form  of  rosettes  composed  of  fine  needles  arranged 
radiately. 

Tyrosin  does  not  sublime  by  heating,  but  is  decomposed  with 
an  odor  of  phenol  and  nitrobenzol.  On  boiling  with  Milhm's 
reagent  it  gives  a  reaction  almost  identical  with  that  for  proteids 
(Hoffmann's  test) .  Treated  with  strong  sulphuric  acid  and  gently 
warmed,  it  yields,  on  the  addition  of  chloride  of  iron,  a  velvet 
color  (Piria's  test). 

Tyrosin  is  an  ammonia  compound,  belonging  to  the  aromatic 
(benzoic)  series. 

Preparation. — By  means  similar  to  those  employed  for  leucin, 
the  separation  of  the  two  depending  on  their  solubilities.  Ac- 
cording to  Kuhne's  method-  large  quantities  are  easily  obtained 
as  the  result  of  pancreatic  digestion.  It  has  not  yet  been  formed 
synthetically. 

mpimricadcl.  CJl.^0,.  OrBenzoyl-glycin.  C.H,(CjH,0):NO,. 

Is  found  in  considerable  quantities  in  the  urine  of  herbivora, 
and  also,  though  to  a  smaller  amount,  in  the  urine  of  man.  It  is 
formed  in  the  body  by  the  union  with  dehydration  of  glycin  and 
benzoic  acid.   (Seep.  577.) 

Crystallized  from  a  saturated  aqueous  solution,  it  assumes  the 
form  of  tine  needles  ;  if  from  a  more  dilute  solution,  white,  semi- 
transparent  four-sided  prisms  are  obtained.  These,  when  pure, 
are  odf)rless,  with  a  somewhat  bitter  taste.  They  are  soluble  in 
600  parts  of  cold  water ;  readil}-  soluble  in  alcohol  ;  less  so  in 
ether.     All  the  solutions  redden  litmus. 

Ilippuric  acid  is  monobasic,  and  forms  salts  which  are  readily 
soluble  in  water  (except  the  iron  salts) ;  from  these,  if  in  sulli- 
ciently  concentrated  solutions,  excess  of  hydrochloric  acid  pre- 
cipitates the  acid  in  fine  needles.  When'^heated  with  concen- 
trated mineral  acids  it  is  resolved  into  benzoic  acid  and  glycin. 

1  Archiv  f.  path.  Anat.,  Bd.  36,  S.  1.  Zeitsch.  f.  anal.  Chem.,  Bd.  5,  S. 
466. 

2  Op.  citi  (sub  Leucin). 


1004      CHEMICAL    BASIS    OF    THE    ANIMAL    BODY. 


The  same  decomposition  occurs  in  presence  of  putrefying  bodies. 
Strong  nitric  acid  produces  an  odor  of  nitrobenzol. 

Preparation. — FreHh  urine  of  horses  or  cows  is  boiled  with 
milk  of  lime,  filtered,  and  the  filtrate  evaporated  to  a  small  bulk  ; 
the  hippuric  acid  is  then  precipitated  by  adding  an  excess  of  hy- 
drochloric acid. 

When  heated  in  a  small  tube,  hippuric  acid  gives  a  sublimate 
of  benzoic  acid  and  amnionium  benzoate,  accompanied  by  an 
odor  like  that  of  new  hay,  while  oily,  red  drops  are  observed  in 
the  tube.  This  is  very  characteristic,  and  distinguishes  it  from 
benzoic  acid. 

Plienylic  [Carholic]  arJd.     CgH,;0. 

This  acid  occurs  only  as  a  urinary  constituent.  According  to 
the  older  view  it  was  a  normal  constituent  of  this  excretion  ;  it 
seems,  however,  more  probable  that  it  is  due  to  some  decomposi- 
tion occurring  in  the  urine,  by  the  processes  requisite  for  its  iso- 
lation. 

Biiliginsky'  says  the  urine  of  many  animals,  of  cows  and  horses  al- 
ways, contains  a  substance  insoluble  in  alcohol,  and  not  precipitated  by- 
lead  acetate  and  ammonia,  which  by  the  action  of  dilute  mineral  acids 
gives  carbolic  acid.  The  same  acid  applied  to  the  body  externally  or 
internally  also  passes  into  the  urine."'^  Similarly  benzol  (Cglie)  when 
taken  into  the  stomach  appears  as  carbolic  acid  in  the  urine.^ 

The  pure  acid  crystallizes  in  long,  colorless,  prismatic  needles  ; 
they  melt  at  .35'^  C,  and  boil  at  ISO^  C.  It  is  readily  soluble  in 
alcohol  and  ether,  slightly  soluble  in  water  (1  part  in  20).  In 
most  cases  it  acts  as  a  weak  acid,  forming  crystalline  salts  with 
the  alkalies.  With  nitric  acid  it  yields  picric  acid.  Its  solutions 
reduce  silver  and  mercury  salts. 

Preparation. — By  the  dry  distillation  of  salicylic  acid,  also 
from  the  acid  products  of  the  distillation  of  coal. 


The  Bile  Series. 

Cholic  {or  Cholalic)  add.     II.C,jH,,,0,-|-H.O. 

Occurs  in  traces  in  the  small  intestine,  in  larger  quantities  in 
the  contents  of  the  large  intestine,  and  the  excrements  of  men, 
cows,  and  dogs.     In  icterus,  the  urine  often  contains  traces  of 

1  Hoppe-Seyler,  Med.  chem.  Untersuch.,  Heft  2  (1867),  S.  234. 

2  Almen,  Nenes  Jahrb.  d.  Pharni.,  Bd.  34,  S.  111.  Salkowski,  Pflu- 
ger's  Archiv,  Bd.  v  (1871-72),  S.  335. 

3  Schultzen  and  Naunvn,  Reichert  u,  Du-Bois  Revmond's  Archiv, 
1867,  Heft  3,  S.  349. 


THE    BILE    SERIES.  1005 


this  acid.  But  its  principal  interest  lies  in  its  being  the  starting- 
point  for  the  various  bile  acids  (see  below).  The  pure  acid  may 
be  amorphous,  or  crystalline,  in  the  latter  case  crystallizing  from 
hot  alcoholic  solutions  in  tetrahedra.  These  crystals  are'insol- 
iible  in  water  and  ether.  In  the  amorphous  form,  it  is  some- 
what sokible  in  water  and  ether.  Heated  to  200^  C,  it  is  con- 
verted into  water  and  dyslysin  (C:.iH,.0:,). 

This  acid  possesses,  in  the  anhydrous  condition,  a  specific  ro- 
tatory- powder  of  +  50^  for  yellow  light  ;  when  it  crystallizes  with 
H._0,  the  rotation  is +  35-.  The  rotatory  power  of  the  alkali 
salts  are  always  less  than  the  above,  and  when  in  solution  in  al- 
cohol the  rotation  is  independent  of  the  concentration.  For  the 
alcoholic  solution  of  the  sodium  salt  the  rotation  is  +  31.4^. 

Pveparotion. — Bv  the  decompositions  of  bile-acids  by  means  of 
acids,  alkalies,  or  fermentative  changes. 

Bayer'  has  recently  examined  the  bile-acids  obtained  from  liuman 
bile,  and  has  prepared  from  them  cholalic  acid.  To  this  he  assigns  the 
formuhi  C,8H2804.  If  tliis  be  so,then  cholalic  acid  of  human  bile  would 
seem  to  be  a  body  entirely  different  from  that  obtained  from  ox-bile,  and 
analyzed  bv  Strecker.  Bayer's  results  however  require  further  confir- 
mation. 

Peitenl'ofer''s  test. 

This  well-known  test  for  bile-acids  depends  on  the  reaction  of 
cholalic  acid  in  presence  of  sugar  and  sulphuric  acid.  If  to  a 
solution  of  the  acid  a  little  sugar  be  added,  and  then  sulphuric 
acid,  keeping  the  temperature  below  but  not  much  below  7(PC., 
a  beautiful  reddish  purple  is  obtained.  This  gives  a  character- 
istic spectrum  with  two  absorption  bands,  one  between  D  and  E, 
nearest  to  E,  the  other  close  to  F  on  the  red  side  of  F. 

Proteids,  and  other  bodies  easily  decomposed  b}'  sulphuric  acid, 
such  as  amyl-alcohol,  gives  a  similar  coloration,  and  the  reaction 
is  much  impeded  by  the  presence  of  coloring  matters.' 

Glycocholic  acid.     C.^eH+aXO^. 

This  is  the  principal  bile-acid  of  ox-gall ;  it  is  also  present  in 
the  bile  of  man,  but  has  so  flir  not  been  observed  in  that  of  car- 
nivora.     In  icterus  the  urine  may  contain  traces  of  this  acid. 

It  crystallizes  in  tine,  glistening  needles.  These  are  slightly 
soluble  in  cold  water  ;  readily  so  in  hot  water  and  alcohol ;  in- 
soluble in  ether.  They  possess  a  bitter  and  yet  sweet  taste,  and 
a  strong  acid  reaction. '^ 

^  Zeitschr.  f.  physiol.  Chem.,  Bd.  ii  (1878-79),  S.  358. 

^  For  further  information  on  this  subject  see  :  Bischofl',  Zeitsch.  f  rat. 
]\Ied.,  Ser.  3.  Bd.  21,  S.  126.  Schenk,  Anatom.  phvsiol.  Untersuch., 
Wien,  1872,  S.  47. 


1006      CHEMICAL    BASIS    OF    THE    ANIMAL    BOLY. 


The  salts  of  this  acid  are  readily  soluble  in  water  and  crystal- 
lize well.  The  salts,  as  well  as  the  free  acid,  exert  risht-handed 
polarization  amounting  to  +  29.0^  for  the  acid,  and  +  25.7^  for 
the  soduim  salt,  both  measured  for  yellow  light. 

Glycocholic  acid  is  a  compound  of  glycin  and  cholalic  acid  ; 
thus  : 

Cholalic  acid.        Glycin.  Glycocholic  acid. 

C,4H,oO,4-  C,XHA-H,0=  C,6FI,3NOe. 

Prolonged  boiling  with  dilute  mineral  acids  or  caustic  alkalies  decom- 
poses this  body  into  glycin  and  cholic  acid  ;  if  dissolved  in  concentrated 
sulphuric  acid  and  then  warmed,  one  molecule  of  water  is  removed,  and 
cholonic  acid  obtained,  C26H41NO5.  The  barium  salt  of  this  last  acid  is 
insoluble  in  water,  which  fact  is  of  importance,  since  cholonic  acid  pos- 
sesses nearly  the  same  specific  rotatory  power  as  glycocholic. 

Preijaration. — From  ox-gall,  by  evaporating  to  a  syrup,  de- 
colorizing with  animal  charcoal,  extracting  with  strong  alcohol, 
and  precipitating  by  a  large  excess  of  etlier.  Its  separation  from 
taurocholic  acid  depends  on  the  precipitation  of  its  solution  by 
normal  lead  acetate. 

Taurocholic  acid.     C26H4.5NSOr. 

Occurs  also  in  ox -gall,  but  is  found  especially  plentiful  in 
human  bile  and  that  of  carnivora. 

It  has  not  yet  been  obtained  in  the  crystalline  form,'  although 
its  salts  crystallize  readily.  When  dried  it  is  an  amorphous 
powder,  with  pure  bitter  taste,  easily  soluble  in  water  and  alco- 
hol, insoluble  in  ether.  All  its  salts  are  soluble  in  water,  and  are 
precipitated  by  basic  lead  acetate  only  in  the  presence  of  free 
ammonia!  The  sodium  salt  dissolved  in  alcohol  has  a  specitic 
rotatory  power  of -r  24.5^  ;  if  dissolved  in  water  this  rotation  is 
less,  and  in  this  respect  it  resembles  glycocholic  acid. 

This  acid  is  far  more  unstable  than  the  preceding  one,  being 
decomposed  if  boiled  with  water.  The  products  of  decomposi- 
tion are  taurin  and  cholalic  acid. 

Taurocholic  acid  is  a  compound  of  taurin  and  cholalic  acid  ; 
thus  : 

Cliolalic  acid.  Taurin.  Taurocholic  acid. 

C^^H^.A  +  CiH7N0;S  —  HO  =  C26H45XO;S. 

Preparation. — From  the  gall  of  dogs  by  a  process  similar  to 
that  for  glycocholic  acid.  It  is  separated  from  traces  of  this 
latter  and  from  cholic  acid  by  preparation  with  basic  lead  acetate 
and  ammonia. 


^  Xenbauer  u.  Yogel,  Harn-Analyse,  Ed.  vii  (187G),  S.  97. 


THE    INDIGO    SERIES.  1007 


The  Indigo  Series. 
Indican. 

There  often  occurs'  in  the  urine  and  sweat  of  men  and  animals 
a  certain  substance  which  has  not  yet  been  satisfactorily  isolated, 
but  which  yields  by  the  action  of  acids  the  blue  coloring  matter 
indigo  as  one  product  of  the  decomposition.  A  similar  substance 
is  found  in  several  plants  (Indigofera,  Isatis),  and  the  two  were 
considered  by  Schunck  to  be  identical.  Hoppe-Seyler,^  on  the 
other  hand,  having  regard  to  the  greater  ease  with  which  the 
indican  from  plants  undergoes  decomposition,  regards  them  as 
most  probably  different  substances.  Banmann  showed^  that  the 
two  were  really  different,  and  has  confirmed  his  previous  results 
in  a  recent  publication.*  According  to  him,  the  indican  obtained 
from  urine  is  not  a  glucoside  (so  also  Hoppe-Seyler),  and  yields 
sulphuric  acid  bv  the  action  of  hydrochloric  acid.  He  assigns  to 
it  the  formula  KC\H,XSO,. 

Indican  appears  in  urine,  according  to  JatFe  and  other  ob- 
servers, as  the  result  of  the  presence  of  indol  in  the  alimentary 
canal. 

It  is  always  estimated  by  conversion  into  indigo. 

Indigo.     C,H>^,0. 

It  is  formed,  as  stated  above,  from  indican,  and  gives  rise  to 
the  bluish  color  sometimes  observed  in  sweat  and  urine. 

It  ma}',  by  slow  formation  from  indican,  be  obtained  in  fine 
crystals  ;  these  are  insoluble  in  water,  slightly  soluble  with  a 
faint  violet  color  in  alcohol  and  ether.  Chloroform  also  dissolves 
them  to  a  slight  extent.  Indigo  is  soluble  in  strong  sulphuric 
acid,  forming  at  the  same  time  two  compounds  with  this  acid  ; 
these  are  soluble  in  water.  It  possesses  a  pure  blue  color  ;  when 
pressed  with  a  hard  body  a  reddish  cop]ier- colored  mark  is  left, 
and  the  crystals  exhibit  the  same  color  if  seen  in  redected  light. 

The  sohible  compounds  with  sulphuric  acid  give  an  absorption 
band  in  the  spectrum  which  lies  close  to  the  D  line  and  to  the  red 
side  of  it.     This  may  be  used  to  detect  indigo. 

Treated  with  reducing  agents,  indigo  is  decolorized,  being  re- 
duced to  indigo- white.  "The  latter  contains  two  atoms  more  hy- 
drogen than  indigo. 


'  Schunck,  Phil.  Mag.,  vol.  x,p.  73  ;  xiv,  p.  228;  xv,  pp.  29,  117, 1S3. 
Chem.  Centralb.,  1856,  S.  50;  1857,  S.  957;  1858,  S.  225.  Hoppe- 
Sevler,  Arch.  f. -path.  Anat.,  BJ.  xxvii,  S.  3S8.  Jaffe,  Pfliiger's  Arch., 
Bd.  hi  (1870),  S.  448. 

2  Handb.  d.  path.  chem.  Anal.,  Ed.  iv  (1875),  S.  191. 

^  Pfliiger's  Arch.,  Bd.  xiii  (1876),  S.  301.  Zeitschr.  f.  phvsiol.  Chem., 
Bd.  i  (1877-78),  S.  60. 

*  Zeitschr.  f.  phvsiol.  Chem.,  Bd.  iii  (1879),  S.  254. 


1008      CHEMICAL    BASIS    OF    THE    ANIMAL    BODY. 


Inclol     C«H,K. 

To  this  body  the  specific  odor  of  the  faeces  is  partly  due.  It  is 
obtained  as  the  final  product  of  the  reduction  of  indigo  ;  and 
also  by  the  distillation  of  proteid  matter  with  caustic  alkalies. 

It  often  occurs  among  the  products  of  the  action  of  pancreatic 
ferment  on  proteids  ;  its  presence  in  such  cases  appears,  however, 
to  be  due,  not  to  the  action  of  the  trypsin,  but  to  a  simultaneous 
putrefaction  under  the  influence  of  bacteria,  etc'  If  the  pan- 
creatic digestion  be  carried  on  in  the  presence  of  salic3'lic  acid, 
indol  does  not  make  its  appearance  ;  see  p.  337.  Indol  gives  a 
characteristic  red  color  with  nitrous  acid. 

Skatol. — Noticed  by  Brieger^  as  one  of  the  products  of  the  ac- 
tion of  putrefactive  changes  in  the  small  intestine.  Secretan^ 
had  previously  described  a  similar  substance  as  arising  from  the 
putrefaction  of  albumin. 

Skatol  is  crystalline  and  contains  nitrogen  ;  it  is  more  soluble 
in  water  than  indol,  and  does  not  give  rise  to  any  red  coloration 
■with  nitrous  acid.     Xo  formula  has  as  yet  been  assigned  to  it. 

Skatol  readily  passes  into  the  urine  when  it  occurs  in  the  ali- 
mentary canal,  and  then  gives  a  violet-red  reaction  with  strong 
hydrochloric  acid. 

V.  Xencki*  prepares  this  substance  by  the  putrefaction  of  a 
mixture  of  finely  divided  pancreas  and  muscle-substance.  After 
the  addition  of  acetic  acid  the  mass  is  distilled,  when  the  skatol 
readily  passes  over.  From  the  distillate  it  is  precipitated  by 
picric  acid,  and  the  precipitate  when  again  distilled  with  ammonia 
gives  off  pure  skatol,  which  may  be  finally  purified  by  crystalliza- 
tion. 

^  Kiihne,  Verhand.  d.  Heidlb.  natnrhist.  med.  Ver.  N.  S.,  Bd.  i,  Hft.  3. 
Bericht  d.  Deiitsclien  cheni.  Gesellschaft,  1875,  S.  206. 

•'  Ber.  d.  Deutseh.  ciiera.  GeselL,  Jahrg.  x  (1877),  S.  1027. 
3  Recherche^  sur  putrefaction  de  ralbimiine,  Geneva,  187(3. 
*  Centralb.  f.  d.  med.  Wiss.,  1878,  S.  849. 


INDEX. 


Aberration,  spherical,  of  the  eye,  673 

Absorption  by  the  skin,  518 

Absorption  off.it,  proteids,  and  prod 
ucts  of  digestion,  401,  415 

Absorption  of  food  by  diffusion,  413, 
415 

Accelerating  fibres,  vaso-motor,  167 

Accelerator  nerves,  251,  259,  295 

Accommodation,  power  of,  in  tbe  eye, 
657  ;    mechanism  of.  663 

Acetic  acid,  978  ;  action  on  red  blood- 
corpuscles,  49 

Acbroodextrin,  307,  555, 

Acid-albumin,  318,  951,  969 

Acidity  of  urine,  526 

Acids,  decomposition  of  proteids  by, 
965 

Acids  in  perspiration,  512 

Aconite,  action  on  heart,  242;  on  the 
respiratory  centres,  478 

Acoustic  apparatus  of  the  ear,  736 

Adamuk  on  the  brain.  849,  850,  854 

Adipose  tissue.    {Sfe  ¥at.) 

Afferent  impulses,  162,  163,  250.787,- 
of  vaso-motor  action,  268,  269,  270, 
271  ;  of  deglutition,  379;  in  respi- 
ration, 471  ;  in  micturition,  539 ; 
nerves  conveying,  634 

After-images  of  vision,  700 

Air-cells.  418;  tidal,  stationary,  and 
residual,  in  respiration,  .421  ;  its 
changes  in  respiration,  435,  489  ; 
chambers  or  passages.  747 

Al.idoff  on  diabetes,  553 

Albertoni,  on  the  brain,  837 

Albumin,  action  of  gastric  juice  on, 
318 

Albumins,  950,  966,  968 

Albuminates,  951 

Alcohol,  action  on  vaso-motor  cen- 
tres, 285  ;  on  the  he.irt,  242  ;  on  ac- 
celerator nerves,  254 


Alimentary    canal,   303  ;    changes     of 
food  in  the,  392 

Alimentary  mechanism,  21 

Alkali-albumin,  953,  969 

Alkaline  urine  of  herbivora.  526 

Allantoic  vessels,  911,  916 

Allantoin,  997 

Allantois,  910 
i  Alveolar  passages.  417 
'[  Alveoli,  pulmonary,  418 

Amido  caproic  acid,  337 
j  Ammonia  in  expired   air,  438  ;   action 
on  accelerator  nerves,  254  ;  on  respi- 
ratory centres;   478 

Amniotic  cavity,  910 

Amnion,  910 

Amoebae,  properties  of,  13,  61,  376,  405 

Amoeboid   movements,  14,  51,  61 

Ainyl  nitrite,  action  on    vagi  nerves, 
248  ;    on    vasomotor   centres,   285  ; 
j       on   the    arterioles,    285  ;   action    on 
j       muscles,  153 

I  Amylolvtic  action  of  pancreatic  juice, 
334,  335  ;   of  saliva.  307,  309,  368 

Amylolytic  ferment,  309,  310 

Analyses,  of  perspiration,  512;  of 
j  the  composition  of  the  animal  body, 
I       579,  580,  928 

Anelectrotonus,  109 
;  Aneurism.  38 

Animal   body,  chemical  basis    of  the, 
947 

Anode.  107 

Antiarin,  action  on  spinal  vaso-motor 
centres,  284 

Antipeptone.  338,  966 

Antiperistaltic  action,  382 

Anus,  387 

Aorta,  pressure  in,  213 

Aortic  valves,  201,  216,  219 

ApertursescalsB  vestibuli  cochleae,  730, 
732 


1010 


INDEX. 


Apnoea,  477.  495  ;  action  of  on  intesti- 
nal peristalsis,  HSl 

Apmnorphia,  action  on  accelerator 
fibres  of  vagi  nerves,  254  ;  on  respi- 
ratory nerves  and  centres,  478  ;  ac- 
tion on  muscles,  153 

Appendages  of  skin,  506 

Appreciation  of  apparent  size,  708 

Aqueduct  of  Sylvius,  808 

Aqueous  humor,  653,  654 

Arbor  vitas  uterinus,  896 

Arch  of  Corti,  733 

Area  germinativa,  908  ;  pellucida, 
908  ;  vasculosa,  908 

Areola,  cutaneous,  501 

Arteria  centralis  retina,  646 

Arterial  blood,  439,  450,  456,  459, 
465,  475,  482 

Arterial  pulse.      {See  Pulse.) 

Arteries.  170.  179.  183,  189,  193,  196. 
204  ;  contractility  and  dilation  of, 
259,  260,  349,  357;  renal,  52S ; 
walls  of,  170.  171 

Artificial  diabetes,  551 

Ar,ytenoid  cartilages,  875 

Ascending  aorta,  pulse-wave  in.  233 

Asphyxia,  381,  426,  470,  476,  489, 
496 

Aspirates  (voice),  881 

Astigmatism,   673 

Atropin,  its  effects,  247,  354 

Aubert  on  cutaneous  respiration,  513 

Auditory  sensations,  740 

Aaerbach,  nervous  plexus  in  the  in- 
testines, 162;  peristaltic  move- 
ments in  digestion,  380 

Augmenting  fibres,  167 

Auricles,  198  ;   blood  pressure  in,  211 

Auriculo-ventricular  valves.  198,  199, 
214 

Automatic  action,  14,  157,  160,  162, 
250;  of  the  heart,  161;  of  peri- 
staltic movements,  380  ;  of  the  re- 
spiratorj'  centre,  470  ;  the  spinal 
cord  as  a  centre  of  this  action,  784 

Automatic  tissues,  19 

Axillary  artery  of  the  tortoise,  its 
contractility.  260 

Axis  cylinders  of  nerves,  631 


Bacillary  layer  of  retina,  652 
Bacteria,  398.  401 
Balogh.  cerebral  convolutions,  833 
Bantings  dietetic  system.  619 
Basillary  membrane,  733 
Bat.  movement  of   veins  in  its  wing, 
261 


Bauer,  absorption  of  products  of  di- 
gestion, 402 

Baxt,  cardiac  accelerator  nerves,  251  ; 
velocity  of  nervous  impluses,  638 

Beat  of  the  heart.      {See.  Heart-beat.) 

Beaumont,  Dr.,  researches  on  diges- 
tion. 393,  415 

Becher,  on  respiration,  437,  461 

Becker,  salivary  secretion,  371 

Bed-sores,  617 

Bees,  temperature  of,  605 

Behavior  of  brainless  animals,  776, 
810 

Bell,  Sir  Charles,  roots  of  spinal 
nerves.  634  ;  motor  and  sensory 
fibres.  872 

Belladonna,  action  on  accelerator 
nerves  and  centres,  254  ;  action  on 
vagi  nerves, 248  ;  on  vaso-motor  cen- 
tres, 285;  on  muscles  of  the  arteri- 
oles, 285  ;  on  the  respiratory  cen- 
tres. 478 

Benzoic  acid,  578 

Bernard,  Claude,  on  the  "  internal 
inediuui,"  2  t ;  section  of  the  cervical 
sympathetic,  284,  297  ;  pancreatic 
juice,  334  ;  secretion  of  saliva,  347  ; 
mechanism  of  digestive  secretion, 
349,  350,  355  ;  digestion.  399,  415  ; 
haemoglobin,  453  ;  cutaneous  secre- 
tion, 515;  glycogen,  542;  ther- 
mogenic and  frigorific  nerves,  613; 
olfactory  organs,  751 

Bernoulli's  model  of  respiratory  move- 
ments, 431 

Bernstein,  muscul.ar  contraction-wave, 
82  ;  muscular  contraction  ;  his  diffe- 
rential rheotome  (diagram),   135 

Bernstein,    N.    0.,    pancreatic  juice, 
j       333,  340,  359 

Berzelius,    researches     on    digestion, 
415 
I  Bichat  on  death,  942 
'  Bidder  and  Schmidt  on  digestion,  397, 
I      415;   on    nutrition    and  starvation, 
I       579.  581,  584,  624 
;  Bidder,    nerves    of    the   submaxillary 
ganglion,  350 

Bile,  303,  328-332  ;  its  color,  329  ; 
constituents,  pizments,  329,  330  ; 
bile  salts,  330,  1004;  action  on  food, 
332  ;  secretion  of,  358,  374  ;  its  ef- 
feet  on  fat,  396  ;   in  the  foetus,  919 

Biliary  ducts.  327,  328 

Bilirubin,  58,  329 

Biliverdin,  330 

Binz,  on  the  action  of  quinine,  52 

Binocular  vision,  709 


INDEX. 


1011 


Birds,  brainless,  their  behavior,  813, 
850 

Birds,  uric  acid  in,  576 

Bischoff.  on  nutrition  and  starvation, 
579.  585,   624 

Black's  discovery  of  carbonic  acid  in 
air,  500 

Bladder,  537 

Blagden,  Dr.,  effects  of  heat,  608 

Blastoderm,  908,  916 

Blind  spot,  652,  677 

Blood.  19,  23-60;  its  chemical  com- 
position, 43  ;  coagulation,  24  ;  cor- 
puscles, 46,  50  ;  action  of  differ- 
ent substances  on,  49  ;  fibrin,  25  ; 
fibrino-plastin  and  fibrinogen,  30; 
fibrin  ferment,  33;  gases  of,  439; 
influence  of  the  living  bloodvessels, 
35  ;  sources  of  the  fibrin-factors, 
33  ;  hi.story  of  the  corpuscles,  53  ; 
quantity  and  distribution  of  blood 
in  animals  and  man,  59  ;  velocity 
of  flow  ;  Volkmann's  hfemadroino- 
meter,  184  ;  Ludwig's  stromuhr 
(diagram),  186  ;  Vierordt's  haema- 
tachouieter,  186;   sugar  in,  412  ' 

Blood,  changes  in  quantity  and  qual-  i 
ity,  290-297  ;  effect  of  its  condition  ' 
on   peristaltic    movements,  381  ;  re- 
spiratory changes  in  it,  438  ;  rela- 
tions of  oxygen  in  the   blood,  441  ; 
color    of  arterial   and  venous,  450  ;  I 
effect    of  respiration,    475-478;  re-] 
lations  of  carbonic  acid  and  nitro-  1 
gen  in  blood,  456,  458 

Blood,  circulation  of  the,  170,  297 

Blood,  in  men.«truation,  902 

Blood  of  the  fcetus,  916 

Blood-plasma,  96,  97 

Blood-pressure,  170-297  ;  apparatus 
for  investigating  (diagram),  178; 
endocardiac  pressure  ;  Pick's  ma- 
nometer, 182 ;  curves  of  presrure 
in  cavities  of  heart,  left  ventricle, 
and  aorta  (diagrams),  207,  213  ;  its 
relation  to  heartbeat,  255,  256  ;  ef- 
fect of  bleeding  and  injection  of 
blood,  291  ;  in  asphyxia.  493  ;  in 
secretion  of  urine,  528 

Blood-supply,  its  influence  on  muscu- 
lar contraction,  125 

Blushing.  266 

Bofhefontaine,  cerebral  convolutions, 
833  .  j 

Boll,  visual  purple  of  the  retina,  684 

Bone,  19,  21 

Bowman,  on  renal  secretion,  528  ' 

Boyle,  on  respiration,  499  - 


Brachia,  804 

Brachial  plexus,  section  of,  262 

Brain,  the,  and  automatic  reflex  ac- 
tion in.  167,  168  ;  pulsation  of  the, 
479;  its  functions,  810,  858;  cere- 
bral convolutions  in  the  dog  and 
man  (diagrams),  829,  830,  831;  ef- 
fects of  stimulation  of,  829  ;  growth 
of  the,  935 

Brainless  animals,  behavior  of,  810, 
816 

Bread.     (See  Dietetics.  Nutrition.) 

Breathing.      (See  Respiration.) 

Breuer.  respiratory  action  of  vagus, 
472 

"  Bright  "  colors,  695 

Brodie,  bodily  heat,  nutrition,   609 

Bronchi,   417 

BiOwn-Seqiiard,  vascular  mechanism, 
297  ;  on  the  si>inal  cord,  790  ;  cere- 
bral convolutions,    833 

Briicke,  on  blood-clotting,  36  ;  semi- 
lunar valves  of  the  heart,  214,  215, 
216  ;  digestion  of  starch,  3il6  ;  pep- 
tone and  pepsin,  321,  322,  337, 
338,  366,  367  ;  absorption  of  pro- 
teids,  410 

"  Buffy  coat"  in  blood,  26 

Bulbs  of  Krause,  504 

Bunge,  hippuric  acid,  578 

Busch,  movements  of  the  stomach, 
•  386,  393  ;  digestion,  393 

Butyric  acid,  980 


Ccecum,  399,  400 

Caffein,  action  on  respiration  centres, 
478 

Calabar  bean,  action  on  vagi  centres 
and  nerves,  248 

Calcareous  degeneration,  936 

Calamus  scriptorius,  802 

Caiiees  of  kidney,  519 

Canal  of  Schlemm,  646 

Capillary  circulation,  173,  190,  191, 
192,  193,  195,  196,  296;  changes 
in  peripheral  resistance,  287-290  ; 
blood  pressure  in  renal  secretion, 
528;  plexuses,  172;  structure  of, 
172 

Caproic  acid,  980 

Capsule  of  Giisson,325;  Malpighian, 
522  ;  of  cerebrum,  internal,  ex- 
ternal, 804 

Carbohydrate  food,  effects  of,  590 

Carbohydrates  in  the  human  body, 622 

Carbolic  acid,  1004 

Carbonic  acid,  in  expired  air,  421,436, 


1012 


INDEX. 


437,  43S;  in  the  blood,  4.39;  exit 
from  blood,  459  ;  in  the  tissues, 
462  ;  effects  of  excess  of,  477.  478, 
496 

Cardiac  impulse,  205,  221 

Cardiac  inhibition,  245 

Cardiac  muscles,  153 

Cardiac  sound,  for  measuring  blood- 
pressure  (diaji^ram),  208 

Cardiograph,  208 

Cardio-inhibitory  centre,  250,  256.  293 

Carnin,  999 

Carnivorous  animals,  nutrition  of, 
592 

Carotid  artery,  blood-pressure  in,  180, 
183 

Cartilage,  19.  21 

Cartilages  of  the  ribs,  their  action  in 
respiration,  429 

Cartilages,  nasal,  432 

Carville,  on  the  brain,  846 

Casein,  323,  563,  955 

Cat,  saliva  of,  311;  blood  crystals, 
445  ;  perspiration,  515,  517  ;  com- 
position of  body,  580 

Cauda  equina,  769 

Caudate  nucleus,  804 

Cells,  migrating.  155  ;  ectoderraic  and 
endodermic,  156  ;  epithelium,  of  al- 
imentary canal,  303  ;  epithelium, 
299  ;  demilune,  305  ;  nerve,  627 

Cellulose,  307 

Central  nervous  mechanism,  22,  159 

Central  space,  733;  canal,  771  ;  lobe 
of  brain,  806 

Centres  of  organic  functions  in  me- 
dulla oblongata,  857 

Ceradina,  on  valves  of  the  heart,  218 

Cerebellum,  805,  853 

Cerebral  actions,  rapidity  of,  858 

Cerebral  convolutions  of  the  dog  and 
man  (diagrams),   829,  830,  831 

Cerebrin.  990 

Cerebral   lobes,  806 

Cerebro-spinal  axis,  625 

Cerebrum,  806,  808 

Cervical  sympathetic,  section  of,  272 

Chaperon,  spinal  cord,  778 

Chauveau,  instrument  for  measuring 
blood-pressuie.  178,  184;  move- 
ments of  the  oe-^ophagus,  384 

Chemical  action,  tissue  of,  299,  499  ; 
digesti(m,  299,  415;  respiration, 
416,  500 

Chemical  aspects  of  respiration,  462, 
468 

Chemical  basis  of  the  animal  body, 
947 


Chemical  changes  in  muscular  con- 
traction, 94,    101 

Chemical  changes  in  tissues,   18 

Chemical  composition  of  blood,  43 

Chemical  substances  in  muscles,  94, 
101 

Children,  temperature  of,  614 

Chloral,  its  effects  on  cerebral  func- 
tions, 269;  action  on  vaso-motor 
centres,  285  ;  on  respiratory  centres, 
478 

Chloroform,  action  on  heart,  242  ;  on 
vagi  centres,  248;  on  vaso-motor 
centres,  285 

Cholesterin.      (SeeBWe.) 

Choletelin,    330 

Cholic  acid,  1004 

Chondrin,  970 

Chorda  and  symnathetic  saliva,  352, 
354 

Chorda  tympani,  stimulation  of  the  : 
vascular  effects,  276,  282  ;  secreting 
effects,  352,  368  ;  thermic  effects, 
603,  614 

Chordge  vocales,  875,  877 

Chordas  tendinese.  201,  215 

Chorda  dorsales,  908 

Chorion,  911 

Choroid  coat  of  eye,  647 

Chromatic  aberration  of  the  eye,  674 

Chyle.  402,  404 

Chyme,  393,  394,  397,   398 

Cifiary  ganglia,  668 

Ciliary  movement,  154 

Ciliary  muscle,  617,  665  ;  processes, 
647 

Ciliated  cells.  154,  301,  900 

Circulation  of  the  blood,  19,  169.  297; 
effects  of  respiration  on,  438  ;  in 
asphyxia,  492  ;   in  the  foetus,  920 

Cleavage  nucleus,  907 

Cleavage  of  the  yolk,  907 

Coagulation  of  the  blood,  24,  28 

Coagulated  proteids,  962,  969 

Cochlea,  731  ;  functions  of,  740 

Colai-aoti,  effects  of  cold  on  guinea- 
pigs,  611,  613 

Cold,  effect  of,  on  temperature  of  the 
body,  611,  615  ;  on  rabbits  and 
guinea-pigs,  611,  613,  614 

Colon,  386 

Colorblindness,  699 

Color  sensations,  694 

Color,  "pale."  "rich,"  "deep," 
"bright,"  695 

Color  of  the  retina,  684 

Color  of  venous  and  arterial  blood, 
450,  456 


INDEX. 


1013 


Color  vision,  694-700  | 

Coluinnje  curnese,  201  ! 

Columns  of  the  spinal  cord,  770  | 

Commissure  of  the  spinal   cord,  7fi9. 

771 
Compensating    action    for   local    dis- 
turbance, 292-297 
Composition  of  the  animal  body,  579, 

580 
Cones  of  retina,  652 
Conjunctival  epithelium,646  ;» mucous 

membrane,   655 
Consonants,  884 

Constriction    of   arteries.      {See    Con- 
traction.) 
Contractile  tissues,  61-155  ;   phenom- 
ena  of  muscle   and  nerve,  64;    un 
striated  muscular  tissue,  149  ;    car- 
diac muscles,  153  ;  cilia,    154  ;   mi- 
grating cells,  155 
Contractile  tissues,  illustrated  by  the 
pendulum   myograph,  7!  ;  the  mag- 
netic interruptor,  78,  79 
Contractility  of  the  amoeba,  13 
Contraction,     law    of    muscular,   61  ; 
contractility    of  bloodvessels,    259-  i 
297  j 

Contraction  of  the  walls  of  the  stom- 
ach,  385 
Contractiun.     {See  Muscular  Contrac- 
tion.) 
Contrast,  visual  sensations  of,  705 
Convulsions  in  asphyxia,  490,  491  i 

Convulsive  centre,  490,  857  ; 

Co-ordination    of   visual    movements, 

715 
Corium,  501.  752  ; 

Cornea,  645 

Coronary  arteries,    201,  216,  256,  294 
Corpora' Arantii,  201,  216  | 

Corpora  quadrigeinina,  804,  849  | 

Corpora  striata.  804,  844-849  ;    quad-  i 
rigemina,  804  ;  geniculata.  805  ' 

Corpuscles  of  the  blood,  23,  24,  176,  ; 
177,   443,  451,   457,  463,   465,  467; 
their  history,  53 
Corpuscles,  in  inSammation,  288,  289  , 
Corpuscles,  inorganic  salts  in,  50 
Corpuscles,   salivary,    306,   311,   354; 
of  Krause,  504  ;  tactile,  504  ;  axile, 
504;    Pacinian,    505;      Malpighian 
(renal)  522;    (splenic),  567 
Corpuscles,  starch,  307 
Corpus  luteum,   902;   dentatum,  801, 

806  ;  callosum,  808 
Corti,  rods  of,  7;i3,  740  I 

Cortical  substance  of  kidney,  519         I 
Corvisart,  researches  on  digestion,  415  ' 


Coughing,  498 

Cowper's  glands,  898 

Cranial  nerves,  637,  860 

Crassamentum,  or  blood-clot.25 

Cricoid  cartilages,  875 

Cristse  acousticae,    735 

Crura  cerebri,  802.  856  ;  section  of, 
852 

Crusta,  802,  804 

Crying,  499 

Crystalline  lens,  653 

Currents.  (See  Electric  Currents, 
Nerve  Currents.) 

Curves,  pulse  (with  tracings),  226- 
238 

Curves,  respiratory  (with  tracings), 
423 

Cutaneous  respiration,  513 

Cyon,  diabetes,  553  :  urea  in  the  liver, 
574 

Czermak,  efifects  of  chorda  stimula- 
tion, 371 


Danilewsky,  on  pancreatic  juice,  340 

Deahna,  on  urari  stimulation,  269  ; 
blood-pressure,  295 

Death,  941  ;  death  agony,  perspira- 
tion in,  515 

Decidua,  913 

Decomposition  of  proteids,  966-969 

Deen,   Van.  on  the   spinal  cord,  798 

"  Deep  '■  colors,  695 

Defecation.  387 

Deglutition,  377 

Deratschenko,  secretion  of  tears,  724 

Denis,  on  coagulation  of  the  blood,  29 

Dentition.  933 

Depressor  nerve,  267 

Derived  proteids,  969 

Derma,  501 

Detrusor  urinae,  538  - 

Dextrin,  307,  308,  977 

Dextrose.  308,  974 

Diabetes,  557 

Diabetic  centre,  551,  857 

Diagrams  :  apparatus  for  experiments 
with  muscle  and  nerve,  68,  69  ;  pen- 
dulum myograph,  71  ;  muscle- 
curves,  70,  76,  77,  78  ;  nervous 
impulses,  73  ;  the  magnetic  inter- 
ruptor, 78  ;  muscular  fibre  under- 
going contraction.  84  ;  non-polar- 
izable  electrodes,  87 ;  muscle- 
nerve  preparations,  J07,  109;  il- 
lustrating electrotonus,  107  ;  sim- 
plest forms  of  a  nervous  system, 
156 ;   Du    Bois-Reymond's    electro- 


85 


1014 


INDEX. 


motive  molecules,  130;  in  their  bi- 
polar condition,  1  M  1  ;  the  fall-rheo- 
toine,  i;-!o  :  Bernstein's  differential 
rheotome,  1H5,  137  ;  electrotonic 
currents,  142  ;  kymograph,  184  j 
Ladwig's  stromuhr,  for  mensuring 
velocity  of  flow  of  blood,  186  ;  Ma- 
rey's  tambour,  with  cardiac  sound, 
208,-  blood-pressure,  178,  180; 
Pick's  spring  manometer,  182  ; 
curves  of  pressure  in  cavities  of 
heart,  207;  curves  of  pressure  in 
aorta  and  heart,  213  ;  sounds  of  the 
heart,  220  ;  pulse  curves,  228,  233, 
234  ;  cardiac  inhibition,  246,  257, 
258  ;  cervical  and  thoracic  ganglia 
of  rabbit,  2  )2  ;  of  dog,  253  ;  sub- 
maxillary gland  of  dog,  348;  secre- 
tion of  p.increatic  juice,  360;  pan- 
creas of  the  rabbit,  363  :  sections 
of  mucous  glands,  368;  of  a  serous 
gland,  370  ;  of  the  parotid  of  the 
rabbit,  370;  respiratory  movements. 
423;  apparatus  for  taking  tracings 
of  movetnents  of  air  in  respiration, 
424  ;  Ludwig's  mercurial  ga>-pump, 
440  ;  blood-pressure  curves  and  in- 
trathoracic pressure,  483  ;  Purkin- 
je's  figures,  680;  muscles  of  the  eye- 
balls, 714;  the  horopter,  718;  areas 
of  spinal  nerves,  788,  789;  cerebral 
convolutions  of  the  dog,  829;  of 
man,  831    832;  the  larynx,  878 

Diaphragm,  its  action,  205,  427,  433, 
468,  469 

Diastole  of  heart,  length  of.  220 

Dicrotic  pulse-wave,  233,  234 

Dietetics.  619 

Diet  of  an  animal,  normal,  582 

Digestion,  tissues  and  mechanisms  of, 
21,  303,  415;  saliva,  306;  gastric 
juice,  314;  bile,  328;  pancreatic 
juice,  333  ;  succus  entericus,  348  ; 
secretion  of  digo.«tive  juices,  345, 
vi76  ;  mucous  and  serous  glands. 
368;  muscular  mechanism,  376-392; 
changes  of  food  in  the  alimentary 
c-inal,  392  ;  absorption  of  products, 
401  ;  decomposition  of  proteids, 
966 

Digestive  secretion,  mechanism  of, 
345 

Digitalis,  action  on  vagi  nerves  and 
centres,  248;  on  intracardiac  inhi- 
bition ganglia,  248  ;  on  vasomotor 
centres,  285 

Dilation  of  bloodvessels.  260,293,  352, 
358 


Dioptric  mechanisms  of  sight,  655 

Distribution  of  blood  in  the   body,  60 

Divers.  re.«|jiration  of,  492 

Dock,  on  glycogen,  544  ;  on  sugar  in 
urine,  554 

Dog,  quantity  and  distribution  of 
blood  in  the,  60  ;  arterial  pressure, 
183,  258,  483  ;  velocity  of  the  cir- 
culation, 195  ;  section  of  vagi,  259; 
cervical  and  thoracic  ganglia  of 
(diagram),  253;  saliva,  311  ;  bile, 
330  ;  pancreatic  juice,  333  ;  sub- 
maxillary gland  (diagram),  348  ; 
blood-crystals,  445,  459  ;  perspira- 
tion, 515;  cerebral  convulutions 
(diagrams),  829,   830 

Dogiel,  on  blood  circulation,  188  ; 
sounds  of  the  heart,  221 

Donders,  length  of  the  cardiac  systole, 
210;  pulse-waves,  230;  inhibition 
of  heart-beat,  246  ;  movements  of 
the  eyeballs,  711;  the  rapidity  of 
mental  operations,  859,  860 

Drowning.  492 

Du  Bois-Reymond,  perdulum  myo- 
graph, 71  ;  on  muscle-currents,  89; 
electromotive  molecules,  130,  131  ; 
muscle  and  nerve,   144,    145,  146 

Duct,  hepatic.  325  ;  lactiferous  or  ga- 
lactooherous,  561  ;  pancreatic,  334; 
Wharton's,  311  ;  Steno's,  310  ;  vitel- 
line, 908 

Ductus  communis  choledochus,  328  ; 
cochlearis,  733.  734;  reunions,  733, 
734 

Duodenum,  385,  390,  395 

Durham,  sleep,  939 

Dyspepsia.  937 

Dyspeptone,  338 

Dyspnoea,  426,  470,  476,  477,  478,  490, 
495 

Ear,  the,  725 
Ebstein,  on  pepsin,  366 
Eckhard,  action  of  submaxillary  gan- 
glion, 349  ;  on    secretion  of  saliva, 
356;    diabetes,   551,553;    morphia 
diabetes,    554  ;     spinal    cord,     785  ; 
!      cerebral  convolutions,  833  ;  the  cer- 
ebellum, 854 
Ectodermic  cells,  156 
Eetosarc,  14 
I  Endosarc,  14 

;  E<lgren,  movements  of  the  pupil,  667 
[  Edwards,      W.,    respiratory    changes, 

436,  466,  500 
j  Eel,  caudal  vein,  261  ;  iris,  867  ;  con- 
I      traction  of  the  pupil,  667 


INDEX. 


1015 


Efferent  impulses  in  secretion  of  saliva, 
351  ;  vomiting,  391;  in  reflex  ac- 
tion. 777 

Ei<g  albumin,  950 

Eichhorst,  nutrition,  trophic  nerves, 
618 

Elaslin,  972 

Electric  currents  of  nerve  and  muscle, 
87.  107,  130  ;  the  fall-rheotome,  132, 
133  ;  Bernstein's  differential  rheo 
tome.  134,  135 

Electrodes,  non-polariznb'e,  illustrat- 
ing nerve-currents  (diagram),  87 

Elfctrotonic  currents,  142 

Electrotonus.  107,  142 

Emetics,  effect  of,  391 

Emminghaus,  movements  of  chyle, 
407 

Emotions  causing  micturition,  539 

Eiidocardiac  pressure,  206-209  ;  Pick's 
spring  manometer,  182 

Endocardium,  201 

Endodermic  cells,  157 

Endnlympb.  736 

End-plate  of  motor  nerve,  83 

Energy  of  the  body  (income  and  ex- 
penditure), 394  ;   muscular,  596 

Engelmann  on  muscle-currents,  90  ; 
autoQiatic  action  of  ureter,  162  ; 
ciliary  movement  in  the  frog,  155; 
peristaltic  movements,  383 

Entoptic  phenomena  of  sight,  675 

Epidermis,  500 

Epiglottis,  277,  874 

Epithelium  cells,  299,  346,  362,  404, 
405,  532 

Erect  posture,  889 

Ergot,  action  on  muscles,  153  ;  on 
vagi  nerves,  248;  on  vasomotor 
centres,  285 

Erismann,  on  cutaneous  secretion, 
514 

Eructation,  395 

Erythrogranulose,  307 

Estor.  seat  of  oxidation  in  respiration, 
462 

Ether,  action  on  respiratory  centres. 
478;  action  on  blood-cfupuscles.  49 

Eustachian  tube,  727.  739 

Excretion  of  urine,  523  ;  of  milk,  561; 
of  nitrogen  in  muscular  exercise, 
597,  598.  (See  Defecation,  Micturi- 
tion.) 

Excretory  tissues,  17,  19 

Exhaustion,  muscular,  121 

Exner,  on  visual  sensations.  683  ;  re- 
flex actions,  783;  on  the  rapidity 
of  mental  apsrations,  858 


Expiration,    421,  426  ;  movements  in, 

433,  482,  490 
Explosives  (voice),  886 
Eye,    the    (s^e     Sight),    physiological 

anatomy  of,  644 
Eyeballs,  movements  of  the,  711,  822, 

850 


Facial  respiration,  434 
Fasciculi  teretes,  801,  802 
Fa?ces,  388.  400 
Fainting.  250 

Fallopian  tubes,  896.  901,  906 
Fall-rheotcnie  (diagram),  133 
Falsetto  voice.  882 
Fat.  history  of,  556,  621 
Fat  of  milk.  563 

Fats,  their  derivatives  and  allies,  978 
Fats  in  serum,  44;   action  of  bile  on, 
332  ;  of  pancreatic  juice,  339  ;   di- 
gestion of.  393,  396,  397,  413 
Fatty  degeneration.  936 
Fatty  food,  effects  of,  590.  592.  621 
,  Fauces,  377,  378,  390 
Fechner's  formula  of  visual  sensations, 

691 
Feeling  and  touch.  758 
Female  pronucleus,  907 
Fenestrated  membrane,  170 
!  Fenestra  ovalis,  727  ;  rotunda,  727 
I  Ferment,  amylolytic,  310 
Ferments,  organized  and  unorganized, 
310;     saliva.    310;     gastric     juice, 
321;   of  pancreatic  juice,  335,  364; 
in  the  small  intestine,  398 
:  Fernet,  on  respiration,  500 
;  Ferrier,  on   the    brain.  829,  836,  839. 
846,  852;   cerebral    convolutions  of 
!       the  dog    and    man  (diagrams),  829, 
!       830,  831 
Fibrse  arciforraes,  801 
Fibres,  muscle,    63,  149;   nerve,  629; 
medullated  nerve,  631  ;  non-medul- 
i       lated,    631  ;   efferent    and    afferent, 
!       633;   terminations  of  nerve,  633 
I  Fibrilise.  muscular,  63  ;  nerve.  63) 


Fibrin.    25-35, 

969 
Fibrin-ferment, 
Fibrinogen,  31, 
Fibrinoplastin, 


148,   317,     320,    958, 


33 
958 

30,  31,  957 
Fick,  on  blood-circulation,  212,  214; 
spring  manometer  (diagram),  182; 
nutrition,  animal  heat,  601  ;  urea 
and  muscular  exercise,  598  ;  mus- 
cles of  the  eyeballs  (diagram),  714  ; 
spinal  cord,  597 


1016 


INDEX. 


Filum  terminale,  R25,  769  | 

Flatulency,  ^^95 

Fleischl.  nervous  irritability,  118 
Flexures,  cephalic,  caudal,  908 
Flourens,  on    the    rei^piratory  centre,  ; 
470  ;   on  the  brain,  851  | 

Foetus.  {Sf'ft  Embryo.) 
Food,    action  of  bile  and    pancreatic 

juice  on,  IV^2 
Food,    fattening    diet,  590  ;    potential  : 
energy  of  food,  ;^94  J 

Food,    glycogen    produced    by,     544- 

551 
Food,  its  effect  on    the  stomach,  H85  ; 
absorption  by  diffusion,  418;  effects 
of  carbohydrate,  590 
Food,  its   changes  in  the    alimentary 

canal,  392 
Food,  tissues    and    mechanisms  of  di- 
gestion,  :^03-4l5  ;  changes  of  food 
in  the    alimentary    canal,  392  ;  ab- 
sorption of  products   of   digestion, 
401 
Force  of  heart-beat,  225 
Fordyce.  Dr.,  effect  of  heat,  608 
Formic  acid,  979 
Fourth  ventricle,  801 
Fovea  centralis,    652  ;    hemispherica, 

730;   hemielliptica,  730 
Fossas,  nasal,  747 
Frankland,  on  the  potential  energy  of 

food,  595 
Frequency  of  heart-beat,  225 
Frerichs,  on  digestion,  415 
Frigorific  nerves,  613 
Fritsch,  cerebral    convolutions  of  the 

dog  (diagram),  829 
Frog,  experiments  on  the  :  nerves,  64, 
65  ;  i-kelelal  muscles,  64  ;  the  rheo- 
scopic  frog,  92  ;  muscle-current-=, 
86,  93,  102  ;  lymphatic  heart,  161, 
162;  heart,  90,  166,  210.  242,  245, 
249  ;  cuntiactility  of  arteries,  259  ; 
bloodvessels,  288  ;  capillary  circu- 
lation. 296  ;  cutaneous  respiration, 
513  ;  contraction  of  the  pupil,  667  ; 
visual  purple  in,  684  ;  spinal  cord, 
773.  798;  lymph-heart,  784,  785 
Frog,  brainless,  its  behavior,  164,  774, 

777,  812 
Frontal  lobes  of  cerebrum.  806 
Functional   activity,   its   influence  on 

muscular  irritability,  127 
Funiculi  of  nerves,  629 
Funke,     on    succus    entericus,     349  ; 
sugar  in  blood  and  urine,  413  ;   res- 
piration, 388;  quaniity  of  perspira- 
tion, 511 


Galabin,  Dr.,  diagrams  of  pulse- 
curves,  233.   234 

Gall-bladder.  328 

Ganglia,  161,  165,  166,  243.  244,  380, 
384,  635  ;  cervical  and  thoracic,  of 
rabbit  and  dog  (diagrams),  252, 
253 

Ganglion  layer  of  retina,  650 

Garrod,  on  pulse- waves,  230  ;  heart- 
beat, 294  ;  quantity  and  flow  of 
blood,  294 

Gases,  in  eructation,  395  ;  in  the  large 
intestine.  398;   in  the  blood,  438 

Gases  in  urine,  525 

Gases,  poisonous,  respiration  of,  496 

Gas-pump,  mercurial,  Ludwig's  (dia- 
gram), 440 

Ga.-^kell,  W.  H.,  contraction  and  dila- 
tion of  arteries,  283 

Gastric  juice,  306.  314,  356,  393  ;  arti- 
ficial, 317;   glands,  313 

Gastric  compared  with  pancreatic 
digestion,  234 

Gaule  and  Goltz,  their  maximum 
manometer,  212,  213 

Gelatin,  971  ;   as  food.  593 

Gerlach,  on  cutaneous  respiration,  513 

Gestation,  924 

Giddiness,  822 

Gilbert  and  Liwes,  on  the  formation 
of  fat,  590.  592,  624 

Glands,  submaxillary,  secretion  of 
saliva,  347;  submaxillary  of  dog 
(diagram).  348 ;  gastric,  314;  sail- 
vary,  303;  of  rabbit,  369;  secret- 
ing  sweat,  509,  514;  mammary, 
561  ;   lachrym  il.  Meibomian,  724 

Glandular  epithelium.  306 

Glisson,  on  muscular  contraction,  66 

Glisson's  capsule,  325 

Globin,  454 

Globulin,  50,  306,  454.  956,  969 

Globus  major,  minor,  899 

tJlomeruli,  renal,  528 

Glottis,  its  action  in  respiration,  435, 
877,  879;  contractions  of  the  (dia- 
gram). 878 

Gluiin,  971 

Glycerin,  983 

Glycerin  phosphoric  acid,  989 

Glycocholic  acid,  1005 
'  Glycin,  1000 

Glycogen.  543,  977 

Gme'in,  researches  on  digestion.  415 

Goltz,  his  maximum  manometer,  2  12, 
213;  on  vaso-motor  actions,  282; 
movements  of  the  oesophagus.  384, 
386  ;    defecation,  387,   388 ;    move- 


INDEX, 


1017 


ments  of  lymph,  407  ;  micturition, 
539  ;  reflex  actions,  779  ;  lympb- 
hearls.  785  ;  the  cerebral  convolu- 
tions, 837.  838  ;  menstruation,  901  ; 
impregnation,  905 

Goose,  bile  of,  331  ;  blood-crystals, 
445 

Graafian  follicle,  901  | 

Granular  layer  of  retina,  652 

Gianulose,  307 

Grebant,  on  urea,  573 

Gray  matter  of  the  spinal  cord,  771, 
7S9 

Growth,  phases  of  life,  928 

Grutzner,  on  pepsin.  3t)(i  ;  afferent  and 
efferent  nerve-fibres,  63M 

G.*cheidlen,  on  the  origin  of  urea,  573, 
574 

Guanin,  999 

Guinea-pig.  saliva  of  the,  311  ;  blood- 
crystals,  445:   effect  of  cold  on.  609 

Gustatory  buds,  754,  756 

Gyergyai,  absorption  of  proteids  in 
digestion,  412 

Gyrus  fornicatus,  807,  808 

Hiiberman,  on  proteids,  968 

Haomadromometer  of  Volkmanu,  for 
measuring  blood-pressure,   18  + 

Hasmatachometer,  for  measuring  blood- 
pressure,  186 

Haematin.  454,  455 

Hsematohlast,  56 

Haematoidin.  58 

Hsemoglobin,  49.  58,  444,  456 

Hgemorrhage,  effects  of,  on  vascular 
mechanism,  291 

Haerlin,  on   paralbumin,  951 

Hair-cells,  733 

Hairs,  506 

Hales,  Dr.  Stephen,  circulation  of 
blood,  179,  296 

Halford,  sounds  of  the  heart.  22' 

H.ilier.  on  muscular  contraction.  66  ; 
on  physiology  of  muscle  and  nerve, 
149  ;   respiratory  movements,  431 

Hiillsten,  contractile  tissues,  118 

Hambergers  model  of.  respiratory 
movememis,  431 

Hammarsten,  coagulation  of  blood, 
34  ;  gastric  juice  in  newborn  ani- 
mals. 929,  930 

Hayem,  red  blood-corpuscles,  56 

Hearing,  736 

Heart,  the,  197,  226  ;  phenomena  of 
the  normal  beat,  203  ;  curves  of 
pressure  in  cavities  of  heart,  206, 
207  ;  mechanism  of  the  valves,  214- 


218  ;  sounds  of  the  heart,  220-222  ; 
its  failure  before  death,  942 
Heart-beat,    161;     normal,    170,    179, 
192,   231,   238;    variations  in,  224, 
255,  493,  528 
Heart-murmurs,  221 
Heart  of  the  babe,  930 
Heart  of  the  frog,  166 
Heat,  loss  of  energy  from,  596 
Heat,  sources  and  distribution  of,  600 
Heat,  varying  production   of,  607 
Hedgehog,  blood-cryst  ils  of  the,  445 
Heidenhain,  on  pancreatic  digestion, 
335  ;    mechanism  of  digestive  secre- 
tion,  349,  355,   357,   367  ;     mucous 
and  serous   glands,   370,   373,    394  ; 
researches    on    digestion,    415;     on 
renal  secretion,  533  ;   on  nutrition, 
590,    610  ;    bodily  heat,    602,    603, 
606,  610,  614;  lymph-hearts,  785 
Helicotrema,  732 
Hellebore,  action  on  heart,  242 
Heller,  movements  of  chyle,  406 
Helmhollz,  on  muscular  contraction, 
101  ;   velocity  of  nervous  impulses, 
149  ;   loss  of  energy  from  heat,  606  ; 
dioptric     mechanisms,     676  ;     color 
sensations.  695  ;   the  horopter,  718  j 
musical  sounds,  745 
Helmont,  Van,  on  carbonic  acid  gas, 

499 
Hemipeptone,  338 
Hensen,  on  auditory  hairs,  743 
Heiisen     and    Yolkers,     sight,     move- 
ments of  the  pupil,  671 
Hepatic  artery,    327  .;    and   the  secre- 
tion of  bile,  374  ;    hepatic  cells,  17, 
325,  374,  542,  551  ;  duct,  325,  327, 
328;    lobules,  325  ;   vein,  327 
Herbivoious  animals,  nutrition  of,  419 
Hering.    respiratory  action   of  vagus, 
}       472  ;    nervous  mechanism  cf  respi- 
j       ration,  474  ;   color  sensations,  698  ; 
!       sensations  of  temperature.  762,  763 
I  Hermann,   on    muscular    contraction, 
I       82  ;    rigor    mortis,     and     electrical 
I       theory   of   muscle.    100,    138,     146, 
'       149  ;  respiration  of  muscle,  149 
Herzen,   inhibition    of   reflex    action, 

788 
Herzenstein,  secretion  of  tears,  724 
Hiatus,  732 
Hiccough,  498 
Hippocampus  major,  809 
Hippuric  acid,  577 

Hirschmann.  on  visual  sensations,  692 

Hitzig,    on  the  cerebral    convolutions 

I      of  the   dog    (diagram),    828;    829, 


1018 


INDEX, 


838,  836;  cerebellum,  853;  ver- 
tigo. 854 

Hiasiwitz,  on  proteid.*,  968 

Holmgren,  movements  of  the  pupil. 
667,  671  ;  electric  currents  of  the 
optic  nerve,  687 

Hook,  on  artificial  respiration,  499 

Hoppe-Seyler,  on  the  composition  of 
blood,  43,  49.  52  ;  on  bile,  332  ; 
haemoglobin,  456  ;  respiration,  500  ; 
nutrition,  589  ;  analysis  of  proteids, 
948 

Horopter,  the,  717 

Horse,  blood-circulation  in  the,  36,  40, 
41,  179,  187,  195.  207;  saliva,  311, 
392;  blood  crystals,  445;  locomo- 
tion, 892 

Horvath,  death  from  extreme  heat, 
615 

Houckgeest.  Van  B  aam,  peristaltic 
action,  382 

Hufner,  on  influence  of  bacteria  in 
digestion,  337 

Hutchinson,  vital  capacity  of  the 
lungs,  422 

Huxley,  blood-corpuscles,  56 

Hyaloid  membrane,  650,  654 

Hydra,  157 

Hydraulic  principles  of  blood-circula- 
tion, 190 

Hydrobilirubin.  59 

Hydrocyanic  acid. action  on  the  heart, 
242 ;  on  the  vagi  nerves,  248  ;  on 
the  respiratory  centres,  478  ;  on  the 
muscles,  153 

Hydrozoa,  ciliary  movement  in,  157 

Hydruria,  or  excessive  renal  secre- 
tion, 530 

Hymen,  894 

Hyperpnoe.i,  490 

Hypoglossal,  vaso-motor  action  of  the, 
262 

Hypoxanthin,  525,  570,  998 

Ileo-csecal  valve,  383,  386,  400 

Impregnation,  905 

Impulses,    nervous,  157,  158;  efferent 

and    afferent,     162;    afferent,    634; 

conduction  of  by  the  spinal   cord, 

787;   nervous,   in  respiration,  469; 

sensory  and  motor,  168 
Income  and  outcome  of  diet,  394 
Income  of  enersy,  394 
Incontinence  of  urine,  540 
Incus,  728 

Indican  in  urine,  525,  1007 
Indigo,  1007 
Indigo-carmine,  excretion  of,  533 


Indol.  337 

Induction  -  machine,  68;  induction- 
shock,  effects  of,  67,  103,  109,  110, 
245 

Inert  layer  in  capillary  circulation, 
177 

Infants,  temperature  of,  614 

Inflammation,  its  effects,  288 

Infundibulum,  pulmonary,  418;  of 
cochlea,  731 

Infusoria,  ciliary  movement  in,  154 

Inhibition,  166;  of  heart-beat.  245, 
249;  of  peristaltic  action,  38!  ;  of 
saliva.  355  ;  of  refl-'X  action,  777  ; 
parturition,  925 

Inogen,  1-18 

Inosit,  976 

Insensible  perspiration,  511 

Inspiration,  mechanics  of,  420.  421, 
427-434 ;  nervous  mechanism  of, 
468;  effects  on  ciiculation,  481  ; 
asphyxia.  489 

Integration  of  fundamental  tissues,  19 

Intercostal  mu-^cles,  their  action  in 
respiration,  430 

Internal  ear,  729 

Internal  auditory  meatus,  731 

Internal  granule-layer  of  retina,  652 

Intestine,' large,  386,  :-i99 

Intestine,  small,  379,  395 

Iris,  648 

Irradiation  of  visual  sensations,  705 

Irritable  tissues,  19 

Irritability  of  nerve  and  muscle.  64— 
67,  89,  109,  110.  120 

Island  of  Reil,  806 

Isthmus  fducium,  377 

J.iborandi,  its  effect  on  heart-beat,  248 
Jacob's  membrane,  652 
Jacobson,  on  blood-pressure,  189 
Jaffe.  urobilin  in  urine,  59  ;   pigments 

of  bile,  330 
Jaundice,  375 
Jervia,  action  on  the  heart,  242  ;   on 

vasomotor  centres,  285 
Jones,  Wharton,  blood-corpuscles,    56 
Judell,  composition  of  red  corpuscles, 

49 
Judgments,     visual,     709  ;    auditory, 

746  ;   tactile,  764 
Juices,  digestive,  303,  376 
Jumping,  891 

Katelectrotonus,    108,    109,    110,    111, 

112,  113.  121 
Kathode.  107 


INDEX. 


iOL9 


Kemmerieh,  on  the  secretion  of  milk, 
5rt4 

Kendal,  on  cutaneous  secretion.  514 

Kendall,  v.iso  motor  action,  281,  282 

Keratin.  972 

Kidneys,  anatomy  of,  519 

Kidneys,  secretion  by  the,  523-537, 
570 

Klein,  origin  of  white  blood-cor- 
pusc'es,  57 

Knock,  bodily  heat,  614 

Knoll,  on  the  corpora  quadrigemina, 
850,  852 

Kohlschiitter,  sleep,  939 

Kciniker.  red  corpuscles,  57;  succus 
entericus,  349 

Korner,  on  uterine  contractions,  926 

Kreatin.  kreatinin,  100,  525,  570, 
571,  572,  573 

Kronecker,  on  muscular  contraction, 
116,  130  ;  functional  activity  of 
muscles,  129 

Kiihne.  on  the  chemistry  of  muscle, 
96,  169  ;  gastric  juice,  323  ;  pan- 
creatic juice,  334;  proteids,  338, 
339  ;  mechanism  of  salivary  secre- 
tion, 571  ;  secretion  in  the  pan- 
creas, 362;  visual  purple  of  the 
retina,  685 

Kupffer,  on  endings  of  nerves  in  sali- 
vary glands,  353 

Kiirschner,  on  heart-beat.  204 

Kymogr;iph  for  recording  arterial  pres- 
sure (diagram),  184 


Labia  majora.  minora,  894 

L;tbor,  loss  of  energy  by,  595,  596 

Libor-pains,  925 

Labored  respiration.  421,  427,  432, 
434 

Labyrinth,  osseous,  729  ;  membra- 
nous, 734 

Lachrymal  glands,  724 

Lacteals,  402.  404 

Lactic  acid.  985;   in  muscle,  100 

Lactose.  975 

Lagrange,  on  respiration,  500 

Lamina fusca,  647  ;  spiralis,  731;  den- 
ticulata,  732  ;   dorsales.  908 

Landois,  on  blood  circulation,  210; 
cerebral  convolutions.  832 

Langendorf,  nervous  mechanism  in 
respiration,  475  ;  inhibition  of  re- 
flex action,  778 

Langley.  salivary  secretion,  354 

Lardaceia,  966 


Laryngeal  nerve,  superior,  in  respira- 
j       tion,   472;    in  voice,  869  ;   inferior, 
in  respiration,  474 

Laryngeal  respiration,  401 

Laryngoscope,  432 

Larvnx.  277,  874;  diagrams  of  the, 
876,  878 

Lateral  tracts,  801 

Latschenberger,  on  urari  stimulation, 
269  ;  blood-pressure,  295  ;  respira- 
tion, 488 

Laughing,  499 

Laurostearic  acid,  980 

Lavoisier,  on  respiration,  499 

Lawes  and  Gilbert,  on  the  formation 
of  fat.  592 

Layer  of  rods  and  cones,  652 
■  Lea  and  Kiihne,  secretion  in  the  pan- 
'       creas,  362 

Lecithin.  49.  394.  989 

Legg,  Wickham,  on  diabetes.  555 

Lens  crystalline.  653 

Lenticular  nucleus.  814 

Leucin,   336,  337,  338.  398.  576.  1001 

Leuwenhoek,  capillary  circulation, 
296 

Levatores  costaruni,  432 

Liebermann,  pigments  of  bile,  329 
,  Liebig.  on  formation  of  fat,  596  ;   nu- 
I       trition,  584,  596.  597,  624 
I  Life,  the  phases  of,  928 

Ligaments,  hepatic,    325 

Ligamentum  iridis  pectinatum,  648 
j  Lingual  nerve,  262.  347 

Lister,  J.,   coagulation  of  the  blood, 
1       37.  39 

Listing,   movements   of  the   eyeballs, 
712 
,  Liver,   324;    secretion   of    bile,   358; 
I      a  source  of  sugar,  542  ;    a  source  of 
I       heat,  600 

Lobes  of  cerebrum,  806 

Lobule,  pulmonary.  418 

Locomotor  ataxy.  768 

Locomotor  mechanisms,  888 

Loculi  of  spleen.  567 

Locus  niger.  802 

Loop.^  of  Henle,  521,  533 

Lor'et,  instrument  for  measuring 
blood-pressure,  187 

Loven,  constriction  and  dilation  of 
arteries,  269,  275 

Lower,  on  respiration,  499 

Luchsinger,    vaso-motor   action.    280, 

281  ;  cutaneous  secretion,  517;  per- 

I       spiration  in  the  cat,  517 

I  Ludwig,    ou    blood-circulation,    185; 

1      his  stromuhr,   185  ;    sounds   of  the 


1020 


INDEX. 


heart,  221  ;  vascul.ar  mechanism, 
297;  peristaltic  action,  382  ;  mer- 
curial gas-pump  (diagram),  440; 
respiration,  500;  renal  secretion, 
6H2  ;  temperature  of  submaxillary 
gland,  354 

Lumbar  cord,  782,  924 

Lungs,  the,  4lfi;  circulation  through, 
419;  mechanics  of  pulmonary  res- 
piration. 420  ;  elastic  force  of,  421, 
480;  respiratory  changes  in,  458; 
loss  of  heat  from,  606 

Lunulae  of  heart  valves,  216 

Lutein,  58 

Lymph,  lymph-vessels,  lymphatic 
glands,  66,  403,  404 

Lymph-hearts  of  the  frog,  161.  784 

Lymphatic  system  in  infancy  and 
youth,  931 


Maculge  acoustioEe,  735 

Macula  lutea,  652 

Magendie,  on  vomiting,  390  ;  sensory 
nerves.  635;    olfactory  nerve,  755 

Magnetic  interruptor  (diagram),  78 

Magnus,  on  respiration,  500 

Male  pronucleus,  907 

Malleus,  727 

M;ilpighi,  capillary  circulation,  296 

MaJpighian  bodies  of  the  kidney,  519, 
522,  523,  527  ;  capsules,  glomeruli, 
522;   layer  of  skin,  501 

Maltose,    308 

Mammary  gland,  561 

Manometer  applied  to  blood-circula- 
tion, 180.  257,  258;  to  heart-beat, 
212,  213,  257,  258.    {See  Diagrams.) 

Marching,  891 

Marey,  on  blood-circulation,  194; 
blood  pressure,  206  ;  pulse-waves, 
228  ;  heart-beat,  228  ;  Marey's  tim- 
bour  (diagram),  208,  424  ;  pneu- 
mograph 423  ;  locomotion  of  the 
horse,  892 

Mastication,  376 

Mayer,  respiration,  488 

Mayow,  on  changes  of  air  in  respira- 
tion, 488  ;   on  oxygen,  499 

Maxwell,  on  color  sensations,  695 

Meat.    (.Sc«  Dietetics,  Nutrition.) 

Meatus  auditorius  externus,  726 

Meatus  urinarius,  894 

Mechanical  tissues,  19 

Mechanism  of  digestive  secretion.  345 

Mechanisms  of  respiration,  419-500 

Mechanisms  of  reproduction,  893 

Meconium,  919 


Medulla  oblongata,  798,  857  ;  cardio- 
inhibitory  centre,  250  ;   respiratory 
centre,     470  ;     vaso-motor    centre, 
278  ;   centre  for  secretion  of  saliva, 
347;   for  deglutition.  379  ;  for  move- 
ments of  oesophagus  and  stomach, 
379  ;   for  vomiting,  391  ;  convulsive 
centre,  490  ;    as  a   centre  of  co-or- 
dination in  the   frog,   812,  813  ;   in 
the  mammal,  798,  857 
Medullary  substance  of  kidney,  519; 
medullary   substance   of    Schwann, 
629 
Medullated  nerve-fibres,  631 
Meibomian  glands.  723 
Meissner,  plexus  of  the  intestines,  162  ; 
peptic    digestion,    338;     peristaltic 
action  in  digestion.  380  ;    urea  and 
urates  in  the   liver,  574  ;    hippuric 
acid,  578  ;   peptones,  962 
Merabrana  limitans  interna,  650  ;  ex- 
terna, 662;  tectoria,  731  ;  basilaris, 
732  ;    granulosa,  897 
Membrane  of  Demours,  646  ;    of  Reis- 

ner,  732 
Membranous  l.ibyrinth,  734 
;  Menstruation,  901 

Mental  emotions  producing  perspira- 
I      tion,  615 

I  Mercurial     gas  pump,    Ludwig     (dia- 
I       gram),  440 
Mercury  manometer  applied  to  blood- 
circulation,  178,  180,  257,  258.    (See 
Diagrams.) 
Metabolic  tissues,  17,  19 
Metabolic  products  in  urine,  637,  670, 
1       678 

'  Metabolic   phenomena    of    the    body, 
I       541-625 
Met;ibolism  of  the  embryo,  918,  919 
Met.ibolites,  nitrogenous    991 
Meta peptone,  338 
Meyer.  Lothar,  on  respiration,  500 
Michieli,    the    cerebral   convolutions, 

835,  837 
Micturition,  537.  541 
Mie.«cher,    on     blood-oorpuscles,    52  ; 

nuclein,  973  ;  spinal  cord,  793 
Migrating  ceils,  155 
!  Milk,  662-566  ;   action  of  gastric  juice 
I      on,  323 
I  Milk-sugar,  975 
Modiolus,  731 

Molecular  layers  of  retina,  652 
Moleschott,  norm.il  diet  of  man,  582 
i  Monkey,  cerebral  convolutions,  830 
j  Morphia  diabetes,  564 
1  Mosso,   changes    in    the    circulation, 


INDEX. 


1021 


290  ;  movements  of  the  oesophagus, 
383  ;    sleep.  938 

Motor  fibres.  633,  634.  fi35.  63fi 

Motor  nerves,  158,  168.  637.  861 

Mouth,  its  action  in  digestion,  392 

Mucin.  970 

Muciparous  cells.  369 

Mucous  glands,  368,  314 

Mucous  membrane  of  stomach,  312  ; 
of  intestine,  340 

Miiller,  J.  J.,  researches  on  respira- 
tion, 461 

Mulier,  Worm,  effects  of  bleeding, 
291 

Mu'ler,  W.,  changes  of  air  in  re.-^pira- 
tion,  436 

Mulier,  J.,  on  the  senses.  769 

Munk.  on  cc'-ebral  localiz.ttinn.  839 

Muscarin,  its  effects  on  heart-beat, 
248 

Muscle  and  nerve.  62,   113.  120,  130 

Muscle  and  nerve,  electrical  phe- 
nomena of,  130;  energy  of,  146; 
chemical  changes  in.  146 

Muscle-nerve  preparation  as  a  ma- 
chine, 113 

Mu.-cle-currents,  86 

Muscle-curves,  diagrams  of,  67,  74, 
75,  77 

Muscle-plasma,  96 

Muscles,  61,  155;  chemical  changes  in 
muscle,  94  ;  energy  of  muscle,  146; 
glycogen  in,  549;  kreatinin,  57(1; 
respiratory  changes  in,  462  ;  phe- 
nomena of  muscle  and  nerve,  62  ; 
irritability  of,  120  ;  unstriated  mus- 
cular tissue,  149;  cardiac  muscles, 
153;  cilia,  154;  migratory  cells, 
155  ;   action  of  poisons  on,   153 

Muscles  of  defecation,  387 

Muscles  of  mastication  and  degluti- 
tion, 376,  377 

Muscles  of  micturition,  537-541 

Muscles  of  respiratiim,  427-435,  468 

Muscles  of  the  eyeballs,  713 

Muscles  of  the  foetus,  918 

Muscles  of  the  larynx,  880^ 

Muscular  contraction,  shown  by  the 
pendulum  myograph,  67,  74.  75, 
77  ;  changes  in  a  muscle  during 
contraction.  8'  ;  change  of  form, 
81  ;  electrical  ch.anges.  36;  physi- 
cal changes.  81  ;  chemical  changes, 
94;  law  of  contraction,  111  :  cir- 
cumstances affecting  its  amount 
and  character,  il4 

Muscular  energy,  sources  of.  146,  022 

Muscular  fibre-cells,  61,  63.  149 


Muscular  fibres  in  arteries,  170,  171, 
259 

Muscular  mechanisms,  21 

Muscular  mechanisuis  cf  digestion, 
376-392;  of  respiration.  419-500; 
mastication,  376;  deglutition.  377; 
peristaltic  action,  153,  379;  move- 
ments of  the  ce-ophagus,  383  ;  of 
the  stomach,  385  ;  of  the  large  in- 
testine. 386:  vomiting,  389 

Muscular  mechanisms,  special,  874 

Muscular  irritability,  64,  66,  110,  HI 

Muscular  sense.  766 

Muscular  sound,  80.  153 

Muscular  tissues.   19 

Muscularis  muco.-aj.  313 

Musculi  papillares.  20  1 

Musculus,  action  of  saliva  on  starch, 
308;    maltose,  975 

Musical  sounds,  nature  of.  740 

Myograph,  pendulum  (diagram),  67, 
71 

Myosin  in  muscular  tissues,  96,  101, 
959 

Myristic  acid,  980 

Nails,  506 

Nares,  747,  748 

Naicotics,  action  on  muscles,  153 

Narrow  tubes  of  Henle,  521 

Nasal  fo^sse,  747 

Nates.  81)4 

Native  albumins,  950 

Nawrocki,  cutaneous  secretion,  517 

Nausea.  389 

Negative  variation,  in  nerve  currents, 
91.  92  ;   of  muscle-currents,  91 

Nerve  and   muscle,  phenomena  of,  64 

Nerve-cells,  627  ;   nerve-fibres.  629 

Nerve-currents,  natural,  86  ;  illus- 
trated by  non  polarizable  electrodes 
(diagram) ,  87  ;  negative  variation. 
91 

Nerve-roots.   159 

Nerves,  irritability  of,  120;  accel- 
erator, 251,  295;  experiments  with 
pendulum  myograph,  67  ;  irrita- 
bility of,  120,*  121  ;  cardiac,  of  the 
dog,  253;  thermogenic,  613  ;  frigo- 
rific.  613 

Nerves,  chemical  changes  in.  148 

Nerves,  cranial.  625,  637,  861 

Nerves,  energy  of.  146 

Nerves,  their  effect  on  constriction 
and  dilation  of  arteries.  261 

Nerves  employed  in  defecation,  387 

Nerves  in  connection  with  striated 
muscles,  64 


86 


1022 


INDEX. 


Nerves,  their  influence  on  the  secre- 
tion and  ejection  of  tnilk,  565 

Nerves  of  mnstication  and  deglutition, 
376,  377,  379 

Nerves  of  sight,  650,  681,  861 

Nerves  of  touch,   503,  761,  768 

Nerves,  renal,  530 

Nerves,  sensory,  633 

Nerves,  spinal,  625,  634 

Nerves,  splenic,  569 

Nerves,  vaso-motor,   261 

Nervi  erigentes,  274 

Nervi  mesenteric!,  249 

Nervous  action  in  the  oesophagus,  383, 
384 

Nervous  action  in  vomiting,  391 

Nervous  influences  on  peristaltic  ac- 
tion, 380.  381 

Nervous  impulses  curves  illustrating 
their  velocity,  74  ;  changes  in  the 
nerve  during  their  passage,  75,  76, 
77,  114,  130 

Nervous  irritability,  109,  110 

Nervous  mechani.*in  for  secreting  di- 
gestive juices,  345,  356,  359 

Nervous  mechanism  of  the  gastric 
movements,  385 

Nervous  mechanism  of  perspiration, 
515 

Nervous  mechanism  of  respiration, 
469,  470 

Nervous  system,  20,21,  22;  general 
arrangement  of,  625  ;  elementary 
structure  of,  627  ;  cerebro-spinai, 
625  ;  ganglionic  or  sympathetic, 
627  ;  simplest  forms  of  (diagram), 
156  ;  its  influence  on  heart-beat, 
minute  arteries,  and  capillaries, 
238  ;  its  influence  on  nutrition,  616  ; 
in  infancy  and  youth,  932,  933 

Nervous  tisr^ues,  properties  of,  17,156- 
169;   metabolism  of,  596,  604 

Nervous  tissues,  general  properties  of, 
158. 

Neurilemma,  630 

Neurin,  989 

Neuroglia.  806 

Neutral  fats,  982 

Neutral  salts,  35 

Nicol^ki,  vasomotor  nerves,  275 

Nicotin,  its  efi'ect  on  heart  beat,  248  ; 
peristaltic  action,  383 

Nitrogen  of  inspired  and  expired  air, 
436 

Nitrogen,  quantity  in  arterial  and  ve- 
nous blood,  441 

Nitrogen,  its  relations  in  the  blood, 
458 


Nitrogenous     crystalline     bodies     in 

urine,  524 
Nitrogenous  food,  619 
Nitrogenous  metabolism,  587 
Nitrogenous  metabolites,  991 
Nitrous  oxide  gas,  action  in  producing 

anaesthesia,  496 
Nee  I  id  vital,  470 

Non-nitrogenous  metabolism,  619 
Non-polarizable  electrodes  (diagram), 

87 
Normal  blood  plasma.  31 
Normal  diet,  582,  619 
Nostrils,    their  action   in  respiration, 

434 
Nothnagel,    on    the    brain,   833,    847. 

848,  854. 
Nuclein,  973 

Nucleus,  lenticular,  caudate,  804 
Nussbaum,  renal  secretion,  535,  536 
Nutrition,  541  ;  production  of  glyco- 
gen, 544  ;  of  the  embryo,  915 

Occipital  lobe,  806 

Ocular  spectra,  707 

Odor  of  the  breath,  438 

Oehl,  movements  of  the  pupil,  670 

ffisophagu.s,  movements  of,  383,  389 

Old  age,  935,  966 

Oleic  acid,  981 

Olein,  983 

Olfactory  organs,  748  ;  cells,  749 

Olivary  body,  801 

Omphalomesenteric  vessels,  909 

Opium,  action  on  vagi  nerves  and  cen- 
tres, 248  ;  on  respiratory  centres, 
478 

Oppler  on  renal  secretion.  572 

Optic  nerve,  650,  861 

Optic  nerve-fibre  layer  of  retina,  650 

Ora  serrata,  650,  654 

Organ   of  Corti,  733 

Organs  of  generation,  894,  901 

Os  orbiculare,  728 

Osseous  labyrinth,  729 

O.-sicles  of  the  ear,  727,  737 

Optic  thalami,  804,  844 

Otoliths,  734 

Otic  ganglia,  166 

Ovoid  peptic  cells,  314 

Ovaries,  896,  901,  903,  905 

Ovule,  897,  900,  901,  903.  906.  907 

Ovum,  893.  894,  906,  912,  913,  914, 
916,  942 

Owsjanniliow,  vaso-motor  centre,  278; 
on  reflex  actions,  782 

Ox,  saliva  <.f  the,  311;  bile,  329; 
blood  crystals,  446 


INDEX. 


1023 


Oxalic  acid.  98fi 

Oxidation,  seat  of,  in  respirntion,  462 

Oxygen  inhnled  in  respiration,  419, 
421,  48P,  487,  438;  quantity  and 
condition  in  arterial  and  venous 
biood.  4.S9.  441.  456,  476.  477;  its 
entrance  into  the  lungs  in  respira- 
tion, 458  467  ;  the  cause  of  dysp- 
noea, asphyxia,  and  apnoea,  475, 
476,  477.  478,  489,  495. 

Oxygen,  action  on  the  muscles,  15."} 

Oxygen  tension.  458.  467 

Oxyhaetnoglobin,   449.  450,  451,  452 

Palate  in  deglutition,  377.  378 

"  Pale"  colors.  695 

Palmitic  acid.  980 

Palmitin.  982 

Pancreatic  digestion,  396-399 

Pancreatic  juice.  303,    333,   359,  361, 

395.  396,  398,  399 
Papillae,  simple  and  compound.   502, 

752;  eircumvallate,    752;   filiform, 

753  ;  fungiform,  753 
Papillary  layer  of  skin.  502;  of  tongue, 

752 
Paraglobulin.  31,   34.  41,  42,  957 
Paralvtic  saliva,   354,  371 
Parapeptone,  319,  332,  336,  337,  338, 

397 
Parenchyma  of  lunes.  416 
Parietal  lobe  of  cerebrum,  806 
Parinaud,  on  bodily  heat,  610 
Parkes.   on   urea  and  muscular  exer- 
cise,  597 
Parotid  saliva.  310,   356 
Parturition,  924 
P.nschutin,   on    the    action    of  saliva, 

319;     movements    of   lymph,    407; 

inhibition  of  reflex  action,  778 
Passages,  alveolar,  417;  intercellular, 

418 
Pavy,  on  nutrition,  glycogen. 546, 547 
Peduncles  of  cerebellum.  805,  806 
Pendulum   myograph   (diagram).   71  ; 

diagrams  obtained  by  it,  70,  73,  76 
Penicilliura,  593 
Penis.   897  ;   mechanism*  of  erection, 

276,  906  ' 
Peptic  digestion,  317,  324,  393 
Peptic  glands,  314;   cells,  314 
Pepsin,  the  ferment  of  gastric  juice, 

321,  332.  338,  357 
Peptone,   319 

Peptones,  319,  338,  332,  962,  969 
Peptones  in  gastric  juice,  317 
Perceptions,  tactile.  764-766  ;   visual, 

719-723 


Periodicity  in  the  phenomena  of  the 
body,  658 

Perilymph,  734 

Perimysium,  62 

Perineurium.  629 

Peripheral  resistance  in  blood-circu- 
lation, 194,  239.  288,  289,  295 

Peri.-taltic  contractions,  161  ;  in  de- 
fecation. 387,  388  ;  in  digestion, 
379,  380  ;  in  the  oesophagus,  383  ; 
in  the  stomach,  385 

Perspiration,  nature  and  amount  of, 
511-514;  secretion  of,  514;  ner- 
vous mechanism  of,  515  ;  average 
loss  by,  511-513 

Pettenkofer,  on  changes  of  air  in  res- 
piration, 437  :  on  nutrition,  585, 
587,  590,  624  ;  sleep,  940 

Pettenkofer's  test,  332 

Peyer's  patches,  341 

Pfliiger,  blood.  31,  34;  nervous  irri- 
tability during  electrotonus.  102, 
115,  149  ;  endings  of  nerves  in  sal- 
ivary glands,  305,  353,  inhibition 
of  peristaltic  action.  381  ;  pump  for 
extracting g.is  from  blood,  440,  441  ; 
hsemoglobin.  454  ;  seat  of  oxidation 
in  respiration,  462  :  respiratory 
changes  in  tissues,  464.  466,  467, 
500;   spinal  cord,  776;  sleep,  940 

Pharynx  in  deglutition,  377;  vomit 
ing,  389-392 

Phases  of  life,  928 

Philipeaux,  on  union  of  sensory  and 
motor  nerves,  641 

Phosphorus  as  an  element  of  food, 
623 

Photochemistry  of  the  retina,  681 

Phrenic  nerve,  its  eflFeet  on  respira- 
tion, 469 

Phthisis,  cold  sweats  in.  515 

Phvsostigmin,  its  effects  on  the  pupil, 
670 

Pig.  saliva  of  the,  311;  bile,  330; 
blood  crystals,  445 

Pigments  in  bile,  329;   in  urine,  525, 
528,  533.  534 
,  Pinna,   726 

Pituitary  mucous  membrane,  747 
;  Placenta,  914,  921 
!  Planer,  on  gases  of  intestine,  398 

Planum  semilunare,  731 

Plasma  of  the  blood,  31,   40,  41.  43, 
!       96,  97 

Plasmine,  29,  31,  33 

Plateau,  on  after-images,  702 

Plethysmograph,  for  measuring 
changes  in  the  circulation,  290 


1024 


INDEX. 


Plosz.  absorption  of  proteids  in  diges- 
tion, 412 
Pneumogastric  nerve,  its  influence  in 

respiration,  472-475 
Pneumographs.    Marey's   and  Tick's, 

424,  425,  426 
Poiseuille,  application  of  the  mercury 

manometer  to  blood-circulation,  178 
Poison,  effect  of   urari,  65  ;    carbonic 

oxide,  496 
Polyuria,  or  excessive  renal  secretion. 

530,  531  ;  point  of  puncture  of  the 

medulla  to  produce,  551 
Polar  ve.^icle,  907 
Pons  Varolii,  802,  856,  857 
Portal  canal,    326;   circulation,   408; 

(renal)  circulation,  522 
Potassium    nitrite,    action    on    heart, 

242 
Potassium  bromide,   action  on  heart, 

242 
Potential  energy  of  food,  394 
Pre-existenoe    theory  of   muscle    and 

nerve.  130 
Predicrotic  pul.«ewave,  233,  234,  236 
Pregnancy.  924 
Pressure,     blood,     180-297,    479-489. 

(See  Blood-pressure.) 
Pressure  of  air  in  respiration,  496 
Pressure,  sensations  of,  764 
Preyer,  on    blood-corpuscles,  58;     on 

haemoglobin  and  baematin.  454,456  ; 

sleep,  939 
Priestley,  on  respiration,  combustion, 

and  oxygen,  499 
Primitive  trace,  908 
Processus    gracilis,    728  ;     e  cerebello 

ad    testes,  801  ;  vocales,  875  ;  mus- 

cularis,  875 
Pronucleus,  907 
Proprionic  acid,  979 
Prostate  gland,  898 

Protagon,  989  i 

Protective  mechanisms  of  the  eye,  723 
Proteid  food,  metabolic  effects  of,  587, 

590 
Proteids,  947,  948  ;    action  of  gastric 

juice  on,  3J 7-324;  action   of  pan- 
creatic juice    on,  334  ;    changes    in 

stomach,  393  ;  in  the  intestine,  395  ; 

absorption  of  in  digestion,  410  ;    as 

sources  of  fat,  591 
.Proteolysis,  digestive,  theory  of.  337 
Protopla.«m,   properties    of,     13,    156; 

free,  51  ;  fixed,  51  ;   in   adipose  tis- 
sue, 560  ;  spinal,    775,  780 
Protoplasm  of  embryonic  tissues,  918 
Prout,  on  digestion,  415 


Ptyalin  of  saliva,  310,  322 

Puberty,  901,  934 

Pulmonary  respiration,  mechanics  of, 

420;    valves,    201 
Pulsation  of  the  brain,  479 
Pulse,   the,    183,   226-238;   sphygmo- 

graph  tracings  of  pulse-waves.  228, 

233,   234  ;   predicrotic  and    dicrotic 

waves.  233,  234 
Pulsus  venosus.  480 
Pump  action  of  the  heart,    202,    228, 

229,    230,  231 
Pupil  of  the  eye,  its  movements,  666- 

672,  861 
Purgative  action  of  salts,  414 
Purkinje's  figures,   678,   6S1  ;   on  the 

effects  of  galvanic  currents  on  the 

brain,  854 
Purple,  visual,  684 
Purpurin  in  urine,  525 
Pylorus.  382,  385,  390,  393.  394,  398 
Pyramids  of  Ferrein,  520  ;  renal,  519  ; 

anterior,  799  ;   posterior,  801 
Pyrexia,  611 
Pyrosis  '^^^^ 
Python,  temperature  of,  605 


Quetelet,  phases  of  life,  929 
Quinine,    action    of  on    reflex   action, 

778  ;  action  on  heart,    242  ;  action 

on  white  corpuscles.  52 


Rabbit,  quantity  and  distribution  of 
blood  in  the,  60;  arterial  pressure, 
183;  velocity  of  blood-current,  188; 
circulation,  195;  heart-beat.  251  ; 
cervical  and  thoracic  ganglia  (dia- 
gram), 252  ;  inhibition  of  heart- 
beat, 256,  257  ;  contractility  of  the 
arteries  of  the  ear,  260  ;  stimula- 
tion of  depressor  nerve,  267;  saliva, 
311  ;  submaxillary  gland,  369,  370  ; 
blood-crystals,  445  ;  blood-pressure 
in  respiration,  482  ;  eff'ect  of  cold 
on,  611.  612,  613;  movements  of 
the  pupil,  670  ;   spinal  cord,  797 

Ranke,  on  distribution  of  blood  in  the 
body,  59  ;  perspiration,  512  ;  nu- 
trition, 595,  597 

Ransome,  Dr.  A.,  power  of  gastric 
juice,  331  ;  movement  of  ribsin  res- 
piration, 430 

Rat,  saliva  of  the,  311;  bloodcrys- 
tals,  445 

Reaction  period,  858 

Rectum,  in  defecation,  387 


INDEX. 


1025 


Red  corpuscles  of  blood,  their  chemical 
composition,  50,  443  ;  their  fate,  57 

Eeflex  actions,  1^2 

Reflex  actions,  the  spinal  cord  as  a 
centre  of,  773  ;   characters  of,  773 

Reflex  actions,  inhibition  of.  777 

Reflex  actions,  parturition,  924 

Reflex  centres,  777 

Reflex  inhibition  of  heart-beat,  249 

Reflex  micturition,  539 

Regeneration  of  tissues,  893 

Regio  olfactoria,  719 

Regnault  and  Reiset  on  cutaneous 
respiration,  513  ;   on  nutrition,  584 

Reich,  secretion  of  tears,  724 

Renal,  secretion, 523  ;  vena  portal  sys- 
tem. 522 

Rennet,  323 

Reproduction  of  the  amoeba,  16 

Reproduction,  tissues  and  mechanisms 
of,   19,  893 

Resonants  (voice),  887 

Respiration  of  the  amoeba,  Ifi,  17 

Respiration, tissues  and  mechanism  of. 
419-500,-  mechanics  of  pulmonary 
respiration,  420  ;  apparatus  for  tak- 
ing tracings  of  movements  of  air 
(diagram).  424,  425  ;  changes  of  air 
in,  435;  changes  in  blood,  438; 
in  the  lungs.  458;  in  the  tissues, 
462  ;  nervous  mechanism,  468  ;  ef- 
fects on  the  circulation,  479  ;  eff'ects 
of  changes  in  the  air  breathed,  489; 
modified  respiratory  movements, 
496 

Respiration,  cutaneous,  513 

Respiration  as  a  regulator  of  temper- 
ature, 605.  606.  607 

Respiration  of  the  foetus,  916 

Respiration,  failure  of  before  death, 
942 

Respiratory  centre,  470,  478 

Respiratory  curves,  tracings  of,  180, 
423 

Respiratory  mechanisms,  21 

Respiratory  muscles.  427-134 

Rest,  muscular  exhaustion  restored 
by. 128 

Restifurm  bodies,  801 

Rete,  mucosum,  501  ;    testes,  899 

Reticular,  membrane,  734 

Retina,  649 

Retching,  189 

Rheometer  of  Ludwig,  for  measuring 
blood-pressure,   185 

"Rheoscoj.ic  Frog.'"  92,  93 

Rbeotomes.  Fall-rheotome,  133  ;  Bern- 
stein's differential  rheotome.  135 


Rhythm  of  heart-beat,  225  ;  of  respi- 
ration, 423,  437,  469.  472,  475, 
487  ;  in  asphyxia,  489,  490 

Ribs,  movement  in  respiration,  427, 
429,  430,  431,  432,  433,  434 

"  Rich  ''  colors.  695 

Rigor  mortis,  81,  94,  125,  149,  493, 
943 

Rima  glottidis,  877 

Ringer,  daily  variation  in  the  temper- 
ature of  the  body.  615 

Ritter's  tetanus,  l'l2 

Ritter-Valli,  law  of  irritability  of 
nerves.  122 

Rods  and  cones  of  retina,  652 

Rods  of  Corti.  133 

Rohris,  on  perspiration.  514;  effect  of 
cold  on  rabbits,  611  ;  urari  poison- 
ing, 611 

Romanes,  on  contractile  tissues,  113 

Rosenthal,  respiratory  function  of 
vagus,  and  theory  of  nervous  mech- 
anism of  respiration,  474  ;  on  re- 
flex actions,  784 

Ruge.  gases  in  the  large  intestine,  400 

Running.  891 

Rutherford,  vaso-motor  nerves  of 
stomach,  358 


Saccule,  734 

Sacculus  laryngis,  876,  877 

Salicylic  acid,  action    on    respiratory 
j       centres,  478 

Schneiderian  membrane,  744 

Scrotum.  898 

St.  Pierre  and  Estor,  seat  of  oxidation 

!       in  respiration,  462 

j  Saliva,  ;')06-312  :  its  action  on  starch, 

306;  quantity  of.  346;  action  of.346, 

392;  in  vomiting,  389;  relation  to 

taste,  758  ;    temperature  of,  353 

Saliva  of  infants,  929 

Salivary  corpuscles,  306,  311,  354 

Salts,  as  food,  393 

Salts,  in  bile,  330  ;  in  blood.  50  ;  in 
urine.  523  ;  absorption  into  blood 
and  urine,  4  14 

Samuel,  eflfeet  of  cold  on  rabbits.  612 

Sanderson,  Burdon,  dicrotic  pulse- 
veave,  236  ;  recording  stethometer, 
425  ;  cerebral  convolutions,  835 

Saphena  artery  of  the  rabbit,  its  con- 
tractility, 260 

Sarcolactic  acid,  985 

Sarcolemiua.  63 

Sarcous  elements,  63 


1026 


INDEX 


Sarkin,  998 

Senlse.  vestibuli,  782  ;  tympani,  732 

Scaleni  muscles,  480 

Sclerotic  coat  of  eye,  646 

Schjifer,  red  corpuycles,  54 

Schsirling,  on  cutaneous  respiration, 
513 

Schech,  on  the  Inrynx,  882 

Scheiner's  experiment  on  sight,  659 

Schememefjewski,  changes  in  the  tis- 
sues in  respiration,  659 

Scherer,  paralbumin  and  metalbumin, 
951 

Schiff,  mechanism  of  digestive  secre- 
tion, 349  ;  on  secretion  of  bile,  375  ; 
movements  of  the  oe-sophagus,  384; 
vomiting,  390;  spinal  cord,  791, 
792 

Schmidt,  A.,  fibrinoplastin  and  fibrin- 
ogen. 31,  33,  35  ;  red  corpuscles,  55  ; 
relation?  of  neutral  salines  and  of 
gastric  juice,  320;   albumins,  951 

Schmidt  and  Bidder,  absorption  of  fat 
in  digestion,  397  ;  researches  on  di- 
gestion, 415 

Schmidt  and  Mulheim,  on  absorption, 
412 

Schmidt,  C,  composition  of  blood, 
50  ;  on  lardacein,  966 

Schmiedeberg,  cardiac  accelerator 
nerves,  251  ;   hippurie  acid,  578 

Schultze,  M;ix.  the  visual  purple, 
684  ;   olfactory  cells,  749 

Schultzen,  on  urea,  575 

Schiitzenberger,  on  proteids,  968 

Schwann,  researches  on  digestion, 
415 

Sciatic  nerve,  vaso -motor  action  of, 
262,  268 

Secretion  by  the  skin,  510-518 

Secretion  by  the  kidneys,  523-537 

Secretion  by  the  renal  epithelium, 
532 

Secretion  of  milk,  564 

Secretions,  digestive.  {Se^  Saliva, 
Bile,  Pancreatic  Juice.) 

Secreting  tissues.  17,    19 

Segtnentation  of  the  yolk,  907 

Semen,  905 

Semicircular  canals,  730 

Semilunar  valves  of  the  heart,  198, 
201,  216-219 

Seminal  fluid,  898,  899 

Sensations,  auditory,  740 

Sensations,  tactile.  764 

Sensations,  visual,  676 

Sense,  muscul.ir,  765 

Sense  organs,  642 


Sensible  perspiration,  511 

Sensitive  cells,  158 

St-nsory  fibres,  633 

Sensory  nerves,  158.  168,  633,  860 

S-'quin,  on  perspiration,  511 

Serum,   its  chemical  composition,  44, 

46 
Serum-albumin,  950 
Setschenow,   inhibition  of  reflex   ac- 
tion, 778 
Sexual  generation,  893 
Sharpey,  sounds  of  the  heart,  720 
Sheep's  blood,   36,   189,   445  ;    saliva, 

311 
Shepard,  hippurie  acid,  578 
Sighing.  498 
Sight,  655 
Sight,    protective  mechanisms  of  the 

eye,  723 
Singing.  881,  882,  883 
Sinitzen,  on  trophic  nerves,  618 
Sinus,  venosus    242,  915;  of  Valsalva, 

201,  217;   circularis  iridis,  646 
Size,  appreciation  of.  719 
Size  of  the  body  ;    phases  of  life.  928 
Skatol,  1008 

Skeletal  muscles,  62,  64,  786,  888 
Skeleton,  growth  of  the,  935 
Skin,  18;  anatomy  of,  500  ;  absorption 

by  the,  518  ;   secretion  by  the,    510- 

5"l8 
Skin,  loss  of  heat  from  th«,  604 
Skin,    terminal    organs   of   the,    503, 

761 
Sleep,  937 
Smell.  749 
Sneezing,  499 
Soaps,  984 
Sobbing,  498 

Solidity,  judgment  of,  721 
Soltmann,  cerebral  areas   in  the  newly 

born,  932 
Sound,  the  voice,  877 
Sounds,  musical,  740 
Spallanzani,   researches  on  digestion, 

415  ;     respiratory    changes    in    the 

tissues,  466 
Special  muscular  mechanisms,  874 
Spectra    of     haemoglobin,    444,    445  ; 

hferaatin,  454,  455 
Speech,  883 

Spermatozoon,  62,  899,  900 
Sphenoparietil   lobe.  806 
Spherical  aberration  in  the  eye,  673, 

894,  899 
Sphincter  vesicae.  538 
Sphygmograph,  226 
Sphygmograph  tracings,  233,  234 


INDEX. 


1027 


Spies?,  temperature  of  the  submaxil- 
lary gland.    603 

Spinal  cord,  769-773  ;  section  of.  ef- 
fect on  blood-pressure.  278  ;  its  ac- 
tion on  respiration,  469  ;  of  rabbit, 
section  of,  610  ;  as  a  centre  of  auto- 
matic action.  784  ;  as  a  conductor 
of  impulses,  787;   parturition,  924 

Spinal  nerves,  162,163,  634;  roots  of, 
634 

Spirometer,  422 

Splanchnic  nerve,  vaso  motor  action, 
262  ;  relation  to  gastric  secretion, 
358  ;  relation  to  peristaltic  move- 
ments, 381,  386;  and  lenal  secre- 
tion. 530 

Spleen  the,  566 

Sporadic  glanglia,  161 

Sprengel's  pump  for  extricating  gas 
from  blood.  4o9 

Stannius,  experiments  on  heart-beat, 
249 

Stapes,  729 

Starch,  action  of  saliva  on,  306,  392, 
395  ;  action  of  gastric  juice  on, 
316  ;  action  of  pancreatic  juice  on, 
334  ;  as  food,  590,  593 

Starvation,  efiFects  of.  580-582 

Statistics  of  nutrition,  579 

Stearic  acid,  989 

Stearin,  982 

Stereoscope,  716 

Stimulation,  impulses  in  nerves  pro 
duced  by,  157 

Stimulation  of  afferent  nerves,  effect 
on  vaso-motor  centre,  267,  268,  269 

Stimulation  of  the  chorda  tympani, 
349,  350,  351,  352.  353.  369 

Stimuli,  character  of  reflfX  actions  de- 
pending on  the  nature.  778 

Stimuli  in  aid  of  parturition,  925, 
928 

Stimulus,  as  affecting  muscular  con- 
traction, 114,  123;  in  unstriated 
muscles,  151 

Stirling,  the  muscle-nerve  machine, 
116  ,     . 

Stokes,  on  the  spectra  of  haemoglobin, 
449,  454 

Stomach,  secretion  by,  356  ;  its 
movements  in  digestion,  385  ;  its 
action  in  vomiting.  389  ;  its  action 
on  food,  392  ;  digestion  in  the,  392- 
395.      (.S*^e  Digestion.) 

Stra.ssburg's  researchts  on  respira- 
tion, 459,  460 

Stroganow,  oxygen  in  the  lungs  in 
respiration,  459 


Stromuhr,  or  rheoraeter  for  measuring 
blood- pressure,    185 

Strvchnia,  action  of,  254,  285,  774, 
777 

Subbotin,  fat  of  man  and  the  dog, 
559  ;   the  secretion  of  milk,  564 

Sublingual  saliva,  311 

Submaxillarv  gland,  secretion  of  sali- 
va, 347-356,  368.  369  ;  of  dog  (dia- 
gram).  348;   of  dog,  368 

Submaxillary  saliva,  311 

Subiculum  cornu  Ammonis,  808 

Substantia  gelatinosn,  771 

Succinic  acid,  986 

Succus  entericus,  306,  348,  361 

Sugar,  conversion  of  starch  into,  by 
the  saliva,  306-311  ;  action  of  gas- 
tric juice  on.  316  ;  digestion  of, 
392;  in  small  intestine,  396 

Sugar  in  urine,  551  ;  in  the  hepatic 
blood,  542,  545  ;  in  the  blood  and 
urine.  413,  466,  545.  546 

Sugar,  milk-sugar,  563,  564 

Sugar  as  food,  592.  593 

Sulci,  806 

Suppression  of  urine,  537 

Suslowa,  lymph-hearts  of  the  frog, 
785 

Suspensory  ligament,  647,  654 

Swallowing.  384,  395 

Sweat.      (See  Perspiration,) 

Sympathetic  action,  vaso-motor.  270 

Syntonin.  338 

Systole  of  heart,  duration  of,  210 

Tactile  judgments,  764 

Tactile  perceptions,  764.  766 

Tactile  sensations.  761.  791,  838 

Tambour.  Marey's,  for  measuring 
blood-pressure  (diagram),  206,  208, 
424 

Tannic  acid,  action  on  blood-corpus- 
cles, 49 

Tarchanoff.  on  the  f^pleen,  569 

Tartar  emetic,  effects  of,  391  ;  action 
on  heart.  242 

Taste.  751,  7..5  ;   buds,  755 

Tnurin,  1000 

Taurocholic  acid,  1006 

Tears,  724 

T^eth.  action  in  raasticition,  376 

Tegmentum,  804 

Temperature,  its  influence  on  muscu- 
lar irritability.  123;  on  ciliary  ac- 
tion. 154  ;  on  the  ,«aliva,  308  ;  on 
the  gastric  juice,  321 

Temperature  of  man  and  other  ani- 
mals, 605,  614,  615 


1028 


INDEX. 


Temperature,  its  effects  on  animals, 
607.  608,   615 

Temperature,  sensations  of   762 

Tt-mperature.      {S  e  Cod,  Heat.) 

Tension  of  the  gases  of  blood  and  pul- 
monary air,  458-462,  467.  468 

Terminal  organs  of  the  skin,  503,  764 

Testes,  804 

Testicles,  898 

Tests  for  proteids,  949 

Tetanic  contractions.  75 

Tetanus.  75.  77,  79.  80,  99,  115.  128; 
sound  in,  221 

Tetanus,  Ritter's,  112 

Thermogenic  nerves,  610 

Thiry,  on  succus  entericus,  348 

Thoracic  duct.  403 

Thoracic  respir.itory  movements,  427  ; 
effect  of  on  circulation.  479 

Thudichum.  on  pigments  in  urine,  525 

Thymus,  570,  931 

Thyroid  cartilage,  875 

Tiedemann,  researches  on  digestion, 
415 

Time  required  for  reflex  actions,  782 

Tissues,  fundamental,  19 

Tissues,  contractile,  61-155 

Tissues,  embryonic,   918 

Tissues,  metabolic,  542 

Tissues,  nervous,  properties  of.  156- 
169 

Tissues  of  chemical  action  and  their 
mechanisms,  299-415  ;  digestion, 
303-415;   respiration,  416-500 

Tissues  of  reproduction,  893 

Tis.^ues.  respiratory,  changes  in  the. 
462 

Tissues,  the  death  of,  943 

"  Tone"  of  arteries,  263 

Tongue.  751  ;  its  action  in  mastication 
and  deglutition.   376.  379 

Torricellian  vacuum  for  extracting 
gas  from  blood,  439 

Touch,  761 

Trabeculse  of  spleen,  566 

Trachea,   416 

Tracings  of  respiratory  movements. 
423  ;  blood-pressure  curves  and  in- 
trathoracic pressure,  483.  {See  Dia- 
grams.) 

Traube's  curves  of  blood  pressure  in 
respiration,  486,  488,  493 

Tricuspid  v.ilves  uf  the  heart,  199, 
214,  218,  219 

Trophic  nerves,  616,  619 

Trypsin,  335,  338,  340 

Tschesohichin.  bodily  heat,  610 

Tuberculo  cinereo,  802 


Tubulfs  of  Bsllini,  520  ;  spcretingr, 
521  ;  intermediary,  intercahited, 
52!  ;   nerve,  629;  seminiferous,  899 

Tubuli  uriniferi,   520,  523 

Tuft,  ren.l.   Malpighian,  522 

Tunica  alhuginea,  899 

Turtle's  heart-beat.  36,  242 

Tympanic,  membrane,  727  ;  bone,  727 

Tympanum,  727 

T>rosin,  336,  337,  338,  398,  574 

Undulations  of  blood-pressure  in  res- 
piration, 479-489 

Unstriated  muscular  tissue,  149 

Urasmic  poi.'Joning,   572 

Urari  poison,  its  effects  on  contractile 
tissues.  65,  113;  iis  effect  on  heart- 
beat, 247,  248  ;  its  effect  on  cere- 
bral fu  ictions,  268  ;  on  chorda 
tympani.  355  ;  on  vomiting.  390  ; 
on  re.*piration,  484  ;  in  producing 
diabetes.    554 

Urea,  525,  574,  575  :  presence  in  per- 
spiration, 512  ;  effect  on  secretion 
of  urine.  535;  secretion  of,  534; 
and  its  allies,  the  history  of,  570- 
578  ;  relation  to  muscular  exercise, 
597,  598 

Ureter,  perist.iltic  contraction  of  the, 
162.  166;   in  micturition,  537 

Urethra,  538,  898 

Uric  acid.  524  ;  source  of,  577  ;  in 
the  spleen.  570 

Urine,  composition  of,  523-527;  se- 
cretion of,  527  ;  act  of  micturition, 
537  ;  kreatin  in,  570,  571,  672; 
hippuric  acid,  577,  578 

Urine  of  infancy,  9  U 

Urine,  sugar  in,  413,  551.  554 

Uriniferous  tubules,  519-522,  527, 
533 

Urobilin  in  urine,  59,  525,  330 

Urochrome,  525 

Urnerythrin  in  urine.  525 

"Uterine  milk."  918 

Uterus.  894  ;  in  menstruation,  902, 
904;   in  parturition,  924-928 

Utricle,  734 

Vagina,  894 

Vagus,  cardio-inhibitory  action  of,  its 

effect.  245  ;  relation  to  movements 

of  stomach,  385  ;   to  vomiting,  391  ; 

respiratory  function  of  the.  471 
Vagus  and  the  secretion  of  urine,    531 
Valerianic  acid,  980 
V.ilves    of   the    heart,    198,  201,214- 

218 


INDEX. 


1029 


Viilvulas  conniventes,  340 

Vnlve  of  Vieussens,  802 

Varnishing  of  animals,  its  effects,  513 

Vas  deferens,  899 

Vasa,  vasorutu,  175  ;  recta,  899;  ef- 
ferentia.  899 

Vascular  area,  909 

Vascular  mechanism.  20,  169;  physi- 
cal phenomena  of  the  circulation, 
170  ;  the  heart,  197,  203  ;  the  pulse, 
22fi  :  vita!  phenomena  of  the  circu- 
lation. 238  ;  changes  in  the  heart 
beat,  240;  in  the  calibre  of  the 
minute  arteries,  vaso-raotor  actions, 
259  ;  conc-triction  and  dilation,  285  ; 
changes  in  the  capillary  districts, 
287  ;   in  the  quantity  of  blood,  290 

Vaso-constrictor  and  vasodilator 
nerves,  280 

Vaso-motor  actions,  259 

Vaso-motor  action.  reialii<g  to  secret- 
ing activity.  252 

Vaso  motor  centre.  278  ;  relation  to 
afferent  nerves,  2fi8  ;  relation  to 
respiratory  centre,  484  ;  relation  to 
renal  secretion.  529 

Vaso  motor  mechanisms,  local,  273, 
275 

Vaso-motor  nerves,  2fil,  285 

Veins.  173,  189;  effect  of  respiratory 
movements  on  the,  481  ;  valves  of, 
175;  interlobular.  32ti  ;  intralob- 
ular, 32fi  ;  sublobular,  327  ;  splenic. 
567 

Velocity  of  the  flow  of  blood,  183,  190. 
195;  of  the  pulse  wave,  226;  of 
sensory  impulses.  638 

Venous  'blood.  439,  450,  456,  459, 
467,  475 

Venous  pulse,  238 

Ventricle  of  the  heart,  198,  204 

Veratiia,  action  on  vagi  centres  and 
nerves,  248  ;  on  vaso-motor  cen- 
tres, 285;  on  ve.-^piratory  centres, 
478 

Veratroidia,  action  on  vagi  nerves, 
248 

Vesicuiae  seminales.  899 

Vertigo,  822,  855 

Vierordt,  numeration  of  blood- cor- 
puscles, 53  ;  hsematachometer  for 
measuring  blood-pressur-".  186 

Villi,  343  ;  action  of  the,  in  absorp- 
tion, 404 

Villi  of  chorion,  911 

Vision,  region  of  di-tinct,  704  ;  the 
reaction  period,  858.      (S-^e  Sight.) 

Visual  impulses,  origin  of,  677 


Visual  judgments,  719 

Visual  perceptions,  702 

Visual  purple,   684 

Vi>ual  sensations    676-694 

"  Vital  capacity  "  of  the  lun^s,  422 

Vital  phenomena  of  the  circulation, 
238 

Vitellin,  859 

Vitreous  body.  654 

Vitelline  duet.  908 

Vocal  cords,  277,  875,  876,  877,  879, 
880.  881,  882.883 

Voice,  the,  877-883 

Voit,  changes  of  air  in  respiration, 
435;  effects  of  starvation,  582;  nu- 
trition, 582,  584.  585.  687,  589, 
590.  597,  599  ;   sleep,    939 

Volkmann,  researches  on  blood-circu- 
lation, 184,  187,  296;  lymph- 
hearts,  784 

Vomiting,  389 

Vowel  rounds.  883 

Vulpian,  vaso-motor  action,  284  ;  on 
union  of  motor  and  sensory  nerves, 
64  1,  642;  on  conduction  of  im- 
pulses in  the  spinal  cord,  791 


Waldeyer,  lymph-hearts,  785 
Walking,  890 

Waller,  A.,  vascular  mechanism.  297 
Wasmann,  'researches    on    digestion, 

416 
Weber,    pulse-waves,   230  ;    muscular 

contraction,   149  ;  on  visual  sensa- 
tions. 692  ;  on    tactile    perceptions, 

763.  764,  769 
Weight  of   the   body  ;   phases  of  life, 

928 
Weiske  and  Wildt,  on  nutrition,  691 
Wharton's  duct,  351 
Whispering,  888 
White  corpuscles,   32,  41,    60,  52,  56, 

57.  61 
While  substance  of  Schwann,  630 
Williams,  on  menstruation,  904 
Winogradoff,  diabetes,  654 
Winking,  724 
Wif^licenus,    on    urea    and    muscular 

exercise.  698,  699 
Wittich,  diabetes  and  digestion,  415, 

655 
Wolferz,  secretion  of  tears,  724 
Wolff  berg,  researches  on  re.-^piration, 

460 
Woroschiloff   on    reflex   actions,    783, 

793 
Wundt,  spinal  ganglia,  637 


1030 


INDEX. 


Xanthin,  100,  525,  570,  571,  998 

Yawning,  498 
Yellow  spot,  652,  693,  700 
Young-Helmholtz,     theory    of     color 
sensations,  698 

Zalesky,  on  renal  secretion,  572 


Zawilski,  digestion  of  fats,  409 

Zona  pellucida.  908 

Zone  of  Zinn,  654 

Zuntz,  alkalescence  of  shed  blood,  44 

effect  of  cold  on  rabbits,  611  ;   urar 

poisoning,  611 
Zymogen,  364 


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DISEASES  OF  SPECIAL  ORGANS. 

Morris's  Manual  of  Skin  Diseases.    One  volume  12mo.  of  320  pages.    Cloth,  S1.75. 
Burnett  on  the  Ear.    Its  Auatomv,  Physiology,  and  Diseases.     In  one  volume  8vo. 

of  61.')  pages,  with  87  illustrations.     Cloth,  §4.50;  leather,  $.5.50. 
Carter's  Practical  Treatise  on  Diseases  of  the  Eye.     In  one  volume  8vo.  of  ahout 

500  pages  and  124  illustrations.    Cloth,  $3.75. 
Browne  on  the  Throat  and  its  Diseases.     In  one  imperial  8vo.  volume  of  350  pages, 

■with  100  illustrations  in  colors,  and  50  wood  engravings.    Cloth,  $5. 
Flint  on  Piithisi-.     In  one  8vo.  vi.hiuie.    Cloth,  $3.50. 
Flint  on  Percussion  and  Auscultation.    Secoud  edition.     In  one  12mo.  volume. 

Cloth,  $1.63. 
Flint's  Practical  Treatise  on  the  Physical  Exploration  of  the  Chest  and  the  Diag- 
nosis of  Diseases  Atfecting  the  Respiratory  Organs.   In  one8vo.  vol.   Cloth,  $4.50. 
Flint's  Practical  Treatise  on  Diseases  of  the  Heart.     In  one  8v(i.  volume.    Cloth,  $4. 
Habersuun  on  Disea.ses  of  the  Alimentary  Canal.    In  one  volume  8vo.  of  over  500 

pages.     Cloth.  $3.50. 
Bu.MSTKAD  on  Venereal  Diseases.    New  edition.    In  one  volume  8vo.  of  835  pages, 

with  138  illustrations.     Cloth,  $4.75;  leather,  $5.75. 
Fox's  Epitome  of  Skin  Diseases,  with  Formulae.     In  one  volume  12mo.  of  about  250 

pages.     Cloth,  $1.38. 
Gross's   Practical  Treati.se  on   the  Diseases,   Injuries,  and   Malformations  of  the 
Urinary  Bladder,  the  Prostate  Gland,  and  the  Urethia.    Third  edition.    In  one 
volume  8vo.  of  574  pages,  with  170  illustratiiMis.    Cloth,  $4.50. 
ROBKRTS  on  Urinary  and  Renal  Diseases,  Including  Urinary  Deposits.    In  one  vol- 
ume 8vo.  of  616  pages.     Cloth,  $4. 
Hamilton  on  Nervous  Disease.s,  their  Description  and  Treatment.     In  one  volume 

Svo.  of  512  pages,  with  53  illustrations.     Cloth,  $3..50. 
Blandford  on  Iu^anity  and  its  Treatment      I  n  one  vol.  Svo.  of  471  pp.    Cloth,  $3.25. 

CYN/ECOLOCY. 
Emmet's  Principles  and  Practice  of  Gvmecohigv.    Second  edition.    In  one  volume 

Svo.  of  875  pages,  with  133  illustrations.     Cloth,  $5;  leather,  $ti. 
Thomas's  Practical  Treatise  on  tlie  Diseases  of  Women.    In  one  volume  8vo.  of  400 

pages,  with  191  illustrations.    Cloth,  $5;  leather,  $6. 
Barnes's  Clinical  Exposition  of  the  Medical  and  Surgical  Diseases  of  Women.  Second 
edition.    In  one  vol.  Svo.  of  781  i)p.,  with  ISl  ilhist.     Cloth,  $4..'i0;  leather,  $5.50. 
OBSTETR  CS. 
Playfair's  Midwifery.    Third  edition.     In  one  volume  Svo.  of  654  pages,  with  183 

illustrations.     Cloth,  $4;  leather,  $.5. 
Leishman's  System  of  Midwifery.    Third  edition.    In  one  volume  Svo.  of  733  pages, 
with  over  200  illustrations.     Cloth,  $4.50  ;  leather,  $5..50. 
DISEASES  OF  CHILDREN. 
Smith's  Practical  Treatise  on  the  Diseases  of  Iiilancy  and  Childhood.     In  one  vol- 
ume Svo.  of  over  750  pages,  with  illustrations.     Cloth,  $4.50;  leather,  $5.50. 
SURGERY. 
Gross's  System  of  Surgery,  Pathological,  Diagnostic,  Therapeutic,  and  Operative. 
Fifth  edition.    In  two  volumes  imperial  Svo.  of  2;W0  pages,  with   1400  illustra- 
tions.    Leather,  $15. 
Ashhukst's  Principl.s  and  Practice  of  Surgerv.    In  one  volume  Svo.,  of  over  1000 

pages,  with  542  illustrations.     Cloth,  $6 ;  leather,  $7. 
Bryant's  Practice  of  Surgery.     In  one  volume  imperial  Svo.  of  over  1000  pages,  with 

672  illustrations.     Cloih,"$);  leather,  $7. 
Erichsen's  Science  and  Art  of  Surgery  ;  heing  a  Treatise  on  Surgical  Injuries,  Dis- 
eases, and  Operations.    In  two  volumes  Svo.  of  2000  pages,  with  862  illustrations. 
Cloth,  $8.-50;  leather,  $10.50. 
Stimson's  Manual  of  Operative  Surgery.    In  one  volume  12mo.  of  about  500  pages, 

with  332  illustrations.    Cloth,  $2.-50. 
Holmes's  Surgery,  its  Principles  and  Practice.    In  one  volume  Svo.  of  nearly  1000 

pages,  with  411  illustrations,     t  loth,  $6;  leather,  $7. 
HAMiLTitN's  Practical  Treatise  on  Fractures  and  Dishjcations.     In  one  volume  Svo. 
of  831  pages,  with  344  illustraiious.    Cloth.  $5.75;  1  at  her,  $6.75. 
MEDICAL  JURISPRUDbNCE. 
Taylor's  Medical  Juri.-prudcnce.     lu  one  volume  Svo.  of  nearly  900  pages.    Cloth, 

$5;  leather,  $6. 
Taylor  ou    Poisons  in  relation   to  Medical  Jurisprudence  and  Medicine.     In  cue 
volume  Svo.  of  7SS  pages,  with  104  illus.  rations.     Cloth,  $5.-50  ;  leather,  $6.50. 


HENRY  C.  LEA'S  SON  &  CO.,  PHILADELPHIA. 


CATALOGUE  OF  BOOKS 

PUBLISHED  BY 

HENRY  C.  LEA'S  SON  &  00. 

(LATE  HENRY  C.   LEA.) 


The  books  in  the  annexed  list  will  be  sent  by  mail,  post-paid,  to  any 
Post  OflBce  in  the  United  States,  on  receipt  of  the  printed  prices.  No 
risks  of  the  mail,  however,  are  assumed,  either  on  money  or  books.  Gen- 
tlemen will  therefore,  in  most  cases,  find  it  more  convenient  to  deal  with 
the  nearest  bookseller. 

Detailed  catalogues  furnished  or  sent  free  by  mail  on  application.  An 
illustrated  catalogue  of  64  octavo  pages,  handsomely  printed,  mailed  on 
receipt  of  10  cents.     Address, 

HENRY  C.  LEA'S  SON  &  CO., 
Nos.  706  and  708  Sansom  Street,  Philadelphia. 


Free  of  Postage. 


AMERICAN  JOURNAL  OF  THE  MEDICAL  SCIENCES. ")     ,.      . 
Edited  by  I.  Minis  Hays,  M.D.,  published  quarterly,    |  ^^^f^  °^® 
1150  large  8vo.  pages  per  annum,  j^  L»ollars  per 

MEDICAL    NEWS     AND    ABSTRACT,    monthly,    768  I  .    annum, 
large  Svo.  pages  per  annum,  J  '"^  advance. 

Separate  s7ibscription  to 

AMERICAN  JOURNAL  OF  THE  MEDICAL  SCIENCES,  when  not 
paid  for  in  advance,  Five  Dollars. 

THE  MEDICAL  NEWS  AND  ABSTRACT,  free  of  postage,  in  ad- 
vance, Two  Dollars  and  a  half. 

OBSTETRICAL  JOURNAL  OF  GREAT  BRITAIN  AND  IRELAND. 
$3  00  per  annum,  in  advance.  Single  Numbers,  25  cents.  Is  pub- 
lished monthly,  each  number  containing  sixty- four  octavo  pages. 


ALLEN  (HARRISON).  A  SYSTEM  OF  HUMAN  ANATOMY. 
WITH  AN  INTRODUCTORY  CHAPTER  ON  HISTOLOGY,  by 
E.  0.  Shakespeare,  M.D.  In  one  large  and  handsome  quarto  vol., 
with  numerous  wood-cuts,  and  several  hundred  original  illustrations 
on  lithographic  plates.     {Prepariiig.) 

A  SHTON  (T.  J.)     ON  THE  DISEASES,  INJURIES,  AND  MALFOR- 

ci    MATIONS  OF  THE  RECTUM   AND    ANUS.     With   remarks    on 

Habitual  Constipation.     Second  American  from  the  fourth  London 

edition,  with  illustrations.    1  vol.  8vo.  of  about  300  pp.     Cloth,  $3  25. 


2  HENRY  C.  LEA'S  SON  &  CO.'S  PUBLICATIONS. 

ASHHURST  (JOHN,  Jr.)  THE  PRINCIPLES  AND  PRACTICE  OF 
SURGERY.  FOR  THE  USE  OF  STUDENTS  AND  PRACTI- 
TIONERS. Second  and  revised  edidon.  In  1  large  8vo.  vol.  of 
over  1000  pages,  containing  642  wood-cuts.  Cloth,  $6  00;  leather, 
$7  00.      {Now  ready.) 

ATTFIELD  (JOHN).  CHEMISTRY;  GENERAL,  MEDICAL,  AND 
PHARMACEUTICAL.  Eighth  edition,  revised  by  the  author.  In 
1vol.  12mo.  ofTOOpages,  with  87  illustrations.  Cloth,  $2.60;  leather, 
$3.00.     {Noiv  ready.) 

ASHWELL  (SAMUEL).  A  PRACTICAL  TREATISE  ON  THE  DIS- 
EASES OF  WOMEN.  Third  American  from  the  third  London  edi- 
tion. In  one  8vo.  vol.  of  528  pages.  Cloth,  $3  50. 
BROWNE  (LENNOX).  THE  THROAT  AND  ITS  DISEASES.  With 
one  hundred  illustrations  in  color  and  fifty  wood-cuts.  In  one  hand- 
some imp.  8vo.  vol.,  cloth,  $5.00.  {Just  issued.) 
BROWNE  (EDGAR  A.)  HOW  TO  USE  THE  OPHTHALMOSCOPE. 
Elementary  instruction  in  Ophthalmoscopy  for  the  Use  of  Students. 
In  one  small  12mo.  vol  ,  many  illust.     Cloth,  $1.      {Just  issued.) 

BLOXAM  (C.  L.)  CHEMISTRY,  INORGANIC  AND  ORGANIC. 
With  Experiments.  In  one  handsome  octavo  volume  of  700  pages, 
with  300  illustrations.    Cloth,  $4  00  ;  leather,  $5  00. 

BRINTON  (WILLIAM).    LECTURES  ON  THE  DISEASES  OF  THE 
STOMACH.    From  the  second  London  ed.    1  vol.  8vo.    Cloth,  $3  25. 
BASHAM   (W.  R.)     RENAL  DISEASES;  A  CLINICAL  GUIDE  TO 
THEIR   DIAGNOSIS   AND   TREATMENT.       With   illustrations. 
1  vol.  12mo.     Cloth,  $2  00. 

BUMSTEAD  (F.  J.)  THE  PATHOLOGY  AND  TREATMENT  OF 
VENEREAL  DISEASES.  Fourth  edition,  revised  and  enlarged, 
with  the  co-operation  of  R.  W.  Taylor,  M.D.  1  vol.  8vo.,  of  835 
pages,  with  138  illustrations.  Cloth,  $4  75;  leather,  $5  75.  {Just 
ready.) 
AND  CTJLLERIER'S  ATLAS  OF  VENEREAL.  See"CuLT.ERiER." 

BARLOW  (GEORGE  H.)  A  MANUAL  OF  THE  PRACTICE  OF 
MEDICINE.  1  vol.  8vo.,  of  over  60  pages.  Cloth,  $2  50. 
BRISTOWE  (JOHN  SYER).  A  TREATISE  OF  THE  PRACTICE  OF 
MEDICINE.  Second  American  edition,  revised  by  the  author. 
Edited  with  additions  by  James  H.  Hutchinson,  M.D.  In  one 
handsome  8vo.  volume  of  nearly  1200  pages.  Cloth,  $5  GO;  lea- 
ther, $6  00.  {Just  ready.) 
BOWMAN  (JOHN  E.;  INTRODUCTION  TO  PRACTICAL  CHEM- 
ISTRY, INCLUDING  ANALYSIS.  Sixth  American,  from  the  sixth 
London  edition,  with  numerous  illustrations.  1  vol.  12mo.  of  350 
pages.     Cloth,  $2  25. 

BELLAMY'S  MANUAL  OF  SURGICAL  ANATOMY.  With  numerous 
illustrations.  In  one  royal  12mo.  vol.  Cloth,  $2  25.  {Lately  issued.) 
BAIRD  (ROBERT).  IMPRESSIONS  AND  EXPERIENCES  OF  THE 
WEST  INDIES.  1  vol.  royal  12mo.  Cloth,  75  cents. 
BRYANT  (THOMAS).  THE  PRACTICE  OF  SURGERY.  Second  Am. 
from  Second  English  Edition.  In  one  handsome  8vo.  vol.  of  over 
1000pp., with672illust.    Cloth,  $6.00;  leather,  $7.00.     {Now  ready.) 

BARNES  (ROBERT).  A  PRACTICAL  TREATISE  ON  THE  DIS- 
EASES OF  WOMEN.  Second  American,  from  Second  English  Edn. 
In  one  handsome  8vo.  vol.  of  about  784  pages,  with  181  illustrations, 
cloth,  $4  50  ;   leather,  $5  60.     {Just  issued.) 


HENRY  C.   LEA'S  SON  c^-  CO.'S  PUBLICATIONS.  3 

BARNES  (FANCOTJST).  A  MANUAL  OF  MIDWIFERY  FOR  MID- 
WIVES.  In  one  neat  royal  12mo.  vol.,  with  numerous  illustra- 
tions.    Cloth,  $125.      {Nou>  Ready.) 

BURNETT  (CHARLES  H.)  THE  EAR:  ITS  ANATOMY.  PHYSI- 
OLOGY, AND  DISEASES.  A  Practical  Treatise  for  the  Use  of 
Students  and  Practiticners.  In  one  handscme  8vo  vol.  of  615  pp., 
•with  ST  illustrations.      Cloth    $4  50  ;  leather,  $5  50. 

BLANDFORD  (5.  FIELDING).  INSANITY  AND  ITS  TREATMENT. 
With  an  Appendix  of  the  laws  in  force  in  the  United  States  on  "^he 
Confinement  of  the  Insane,  by  Dr.  Isaac  Ray.  In  one  handsome  8vo. 
vol.,  of  471  pages.     Cloth,  $3  25. 

CHARCOT  (J.  M.)  LECTURES  ON  THE  NERVOUS  SYSTEM.  1  vol. 
Svo.  of  288  pages,  with  illustrations.     Cloth,  §1  75.     {Now  ready.) 

CLASSEN'S  QUANTITATIVE  ANALYSIS.  Translated  by  Edgar  F. 
Smith,  Ph.D.  In  one  handsome  12mo.  vol.  cloth.  $2.  (Jnst  issued.) 
CARTER  (R  BRUDENFLL).  A  PRACTICAL  TREATISE  ON  DIS- 
EASES OF  THE  EYE.  With  additions  and  test-types,  by  John 
Green,  M.D.  In  one  handsome  Svo.  vol.  of  about  500  pages,  with 
124  illustrations.     Cloth,  $3  75. 

CHAMBERS  (T.  K.)  A  MANUAL  OF  DIET  IN  HEALTH  AND 
DISEASE.  In  one  handsome  octavo  volume  of  310  pages.  Cloth, 
$2  75. 

COOPER  (B.B.)  LECTURES  ON  THE  PRINCIPLES  AND  PRACTICE 
OF  SURGERY.     In  one  large  Svo.  vol.  of  750  pages.     Cloth,  $2  00. 

CARPENTER  (WM.  B.)  PRINCIPLES  OF  HUMAN  PHYSIOLOGY. 
A  new  American,  from  the  Eighth  English  Edition.  In  one  large 
vol.  8vo.,  of  1083  pages.  With  373  illustrations.  Cloth,  $5  50; 
leather,  raised  bands.  $6  50.      {Lately  issued.) 

PRIZE  ESSAY  ON  THE  USE  OF  ALCOHOLIC  LIQUORS  IN 

HEALTH  AND  DISEASE.     New  Edition,  with  a  Preface  by  D.  F. 
Condie,  M.D.     1  vol.  l2mo.  of  178  pages.     Cloth,  60  cents. 

CLELAND  (JOHN).  A  DIRECTORY  FOR  THE  DISSECTION  OF 
THE  HUMAN  BODY.     In  one  small  royal  12mo.  vol.    Cloth,  $1  25. 

CENTURY  OF  A^IVIERICAN  MEDICINE  —A  History  of  Medicine  in 
America,  1776-1876.  In  one  royal  12mo.  vol.  of  366  pages.  Cloth 
$2  25. 

CHURCHILL  (FLEETWOOP).  ON  THE  THEORY  AND  PRACTICE 
OF  MIDWIFERY.  With  notes  and  additions  by  D.  Francis  Condie, 
M.D.  With  about  200  illustrations.  In  one  handsome  Svo.  vol.  of 
nearly  700  pages.     Cloth,  $4;  leather,  $5. 

ESSA.YS  ON  THE  PUERPERAL  FEVER,  AND  OTHER  DIS- 
EASES PECULIAR  TO  WOMEN.  In  one  neat  octavo  vol.  of 
about  450  pages.  *  Cloth,  $2  50. 

CHADWICK  (JAMES  R.)  A  MANUAL  OF  THE  DISEASES  PECU- 
LIAR TO  WOMEN.  In  one  neat  royal  12mo.  vol.  With  illustra- 
tions.     {Preparing.) 

CDRNIL  (V,).  AND  RANVIER  (L.).  MANUAL  OF  PATHOLOGICAL 
HISTOLOGY.  Translated,  with  Notes  and  Additions,  by  E.  0. 
Shakespeare  and  Henry  C.  Simes,  M  D.  In  one  vol.  Svo  of  784  pp. , 
with  360  illus.     Cloth,  $5  50  ;  leather,  $6  50.      {Just  ready.) 

03NDIE  (D.  FRANCIS).  A  PRACTICAL  TREATISE  ON  THE  DIS- 
EASES OF  CHILDREN.  Sixth  edition,  revised  and  enlarged.  In 
one  large  Svo.  vol.  of  800  pages.     Cloth,  $5  25  ;  leather,  S6  25. 


4  HENRY  C.  LEA'S  SON  &  CO.'S  PUBLICATIONS. 

CLOWES   (VR'^NK).     AN    ELEMENTARY    TREATISE    ON  PRAC- 
TICAL CHEMISTRY  AND  QUALITATIVE  INORGANIC  ANA- 
LYSIS.  From  the  Second  Eng.  Ed.  In  one  12mo.  vol.    Cloth,  $2  50. 
OTJLLERIER  (A.)     AN  ATLAS  OF  VENEREAL  DISEASES.     Transs- 
lated  and  edited  by  Freeman  J.  Bumstead,  M.D.     A  large  imperial 
quarto  volume,  with  26  plates  containing  about  150  figures,  beauti- 
fully colored,  many  of  them  the  size  of  life.     In  one  vol.,  strongly 
bound  in  cloth,  $17. 
■  Same  work,  in  five  parts,  paper  covers,  for  mailing,  $3  per  part. 
nYCLOPEDIA  OF  PRACTICAL  MEDICINE.     By  Dunglison,  Forbes, 
^     Tvveedie,  and  Conolly.     In  four  large  super-royal  octavo  volumes,  of 
3254  double-columned  pages,  leather,  raised  bands,  $15.    Cloth,  $11. 
nHRISTISON  &  GRIFFITH'S  DISPENSATORY.     1  vol.,  cloth,  $4. 

CAMPBELL'S  LIVES  OF  LORDS  KENYON,  ELLENBOROUGH,  AND 
TENTERDEN.  Being  the  third  volume  of  "  Campbell's  Lives  of 
the'Chief  Justices  of  England."  In  one  crown  octavo  vol.  Cloth,  $2. 
|ALTON(J.  C.)  A  TREATISE  ON  HUMAN  PHYSIOLOGY.  Sixth 
edition,  thoroughly  revised,  and  greatly  enlarged  and  improved,  with 
316  illustrations.  In  one  very  handsome  8vo.  vol.  of  830  pp. 
Cloth,  $5  50;  leather,  $6  50. 

DUNCAN  (J  MATTHEWS)      CLINICAL  LECTURES  ON  THE  DIS- 
EASES OF   WOMEN.     Delivered  in  St.  Bartholomew's  Hospital. 
In  one  neat  Svo.  volume.     Cloth,  $1  50.     {Just  ready.) 
AVIS  (F.  H.)     LECTURES  ON    CLINICAL   MEDICINE.     Second 
edition,  revised  and  enlarged.     In  one  12mo.  vol.       Cloth,  $1  75. 
lON  QUIXOTE  DE  LA  MANCHA.   Illustrated  edition.    In  two  hand- 
some vols,  crown  Svo.     Cloth,  $2  60  ;  half  morocco,  $3  70. 
DfiWEES  (W.  P.)     A  TREATISE  ON  THE  DISEASES  OF  FEMALES. 
With  illustrations.     In  one  Svo.  vol.  of  536  pages.     Cloth,  $3. 

DRUITT  (ROBERT).  THE  PRINCIPLES  AND  PRACTICE  OF  MO- 
DERN SURGERY.  A  revised  American,  from  the  eighth  London 
edition.  Illustrated  with  432  wood  engravings.  In  one  Svo.  vol. 
of  nearly  700  pages.     Cloth,  $4;  leather,  $5. 

DUNGLISON  (ROBLEY).  MEDICAL  LEXICON;  a  Dictionary  of 
Medical  Science.  Containing  a  concise  explanation  of  the  various 
subjects  and  terms  of  Anatomy,  Physiology,  Pathology,  Hygiene, 
Therapeutics,  Pharmacology,  Pharmacy,  Surgery,  Obstetrics,  Medical 
Jurisprudence,  and  Dentistry.  Notices  of  Climate  and  of  Mineral 
Waters  ;  Formulae  for  OfiBcinal,  Empirical,  and  Dietetic  Preparations, 
with  the  accentuation  and  Etymology  of  the  Terms,  and  the  French 
and  other  Synonymes.  In  one  very  large  royal  Svo.  vol.  New  edi- 
tion. Cloth,  $6  50;  leather,  $7  50. 
DE  LA  BECHE'S  GEOLOGICAL  OBSERVER.  In  one  large  Svo.  vol. 
of  700  pages,  with  300  illustrations.  Cloth,  $4. 
DANA  (JAMES  D.)  THE  STRUCTURE  AND  CLASSIFICATION  OF 
ZOOPHYTES.  Withillust.  onwood.  Inoneimp.4to.  vol.  Cloth,  $4. 
ELLIS  (GEORGE  VINER).  DEMONSTRATIONS  IN  ANATOMY. 
Being  a  Guide  to  the  Knowledge  of  the  Human  Body  by  Dissection. 
From  the  eighth  and  revised  English  edition.  Illustrated  by  248 
engravings  on  wood.  In  one  very  handsome  Svo.  vol.  of  over  700  pp. 
Cloth,  $4  25  ;  leather,  $5  25.      {Now  Ready.) 

EMMET  (THOMAS  ADDIS).  THE  PRINCIPLES  AND  PRACTICE 
OF  GYNECOLOGY,  for  the  use  of  Students  and  Practitioners.  Sec- 
ond edition,  enlarged  and  revised.  In  one  large  Svo.  vol.  of  875 
pp. ,  with  135  original  illustrations.  Cloth,  $6;  leather,  $6,  {Just 
ready.) 


D 


HENRY  C.   LEA'S  SON  &  CO.'S  PUBLICATIONS.  5 

EaiCHSEN  (JOHN  E.)  THE  SCIENCE  _AjSrp  ART  OF  SURGERY. 
A  new  and  improved  American,  from~the  Seventh  enlarged  and 
revised  London  edition.  Revised  by  the  Author.  Illustrated  with 
863  engravings  on  wood.  In  two  large  8vo.  vols.  Cloth,  $8  50  ; 
leather,  raised  bands,  $10  50.      {Just  issued.) 

ENC1^CL0P5;DIA  of  geography,  in  three  large  8vo.  vols.  Illus- 
trated with  S3  maps  and  about  1100  wood-cuts.     Cloth,  $5. 

FOSTER  (MICHAEL).  TEXT-BOOK  OF  PHYSIOLOGY.  A  new 
American,  from  the  third  English  edition.  Edited,  with  notes  and 
additions,  by  Edward  T.  Reichart,  M.D.  In  one  handsome  12mo. 
vol.  of  over  1000  pp.,  with  259  illus.  Cloth,  S2  50;  leather,  $3  25. 
(Just  ready.) 

FINLAYSON    (JAMES).     CLINICAL    MANUAL   FOR   THE    STUDY 
OF  MEDICAL  CASES.     In  one  handsomp  ^^vo.  vol.  with  numerous 
illustrations.      Cloth,  $2  63.      {Just  ready .) 
■pOTHERGILL'S  PRACTITIONERS  HANDBOOK  OF  TREATMENT. 
■»-      In  one  handsome  8vo.  vol.  of  about  550  pp.   Cloth.  $4.    (Just  i  ssu.ed] 

ON  THE  ANTAGONISxM  OF  THERAPEUTIC  AGENTS.     In 

one  neat  12mo.  vol.  of  about  200  pages.     Cloth,  81.      (Just  issued  ) 

FARQUHARSON  (ROBERT).  A  GUIDE  TO  THERAPEUTICS. 
Second  American  edition,  revised  by  the  author  Edited,  with  ad- 
ditions, embracing  the  U.  S.  Pharmacopoeia,  by  Frank  Woodbury, 
M.D.   In  one  neat  royal  ]2mo.  volume.   Cloth,  $2  25.     (Nou-  Ready.) 

FENWICK    (SAMUEL).     THE    STUDENTS'    GUIDE    TO  MEDICAL 
DIAGNOSIS.     From  the  Third  Revised  and  Enlarged  London  Edi- 
tion.    In  one  vol.  royal  12mo.     Cloth,  $2  25. 
■pox   (TILBURY).     EPITOME  OF  SKIN  DISEASES,  with   Formulae 
-*-      for  Students  and  Practitioners.     Second  Am.  Edition,  revised  by  the 
author.     In  one  small  12mo.  vol.     Cloth,  $1.38.     (Now  ready.) 

FLINT  (AUSTIN).  A  TREATISE  ON  THE  PRINCIPLES  AND 
PRACTICE  OF  MEDICINE.  Fourth  edition,  thoroughly  revised 
and  enlarged.  In  one  large  8vo.  volume  of  1070  pages.  Cloth,  $6  ; 
leather,  raised  bands,  $7.      (Lately  issued.) 

CLKnICAL    MEDICINE.     A    SYSTEMATIC    TREATISE    ON 

THE  DIAGNOSIS  ANJL»  TREATMENT  OF  DISEASE.  Designed 
for  Students  a-. d  Practitioners  of  Medicine.  In  one  handsome  8vo. 
vol.  of  about  900  pages.     Cloth,  $4  50;  leather,  $5  50.   (Just  Ready.) 

A  MANUAL  OF  PERCUSSION  AND  AUSCULTATION;  of  the 

Physical  Diagnosis  of  Diseases  of  the  Lungs  and  Heart,  arad  of  Tho- 
racic Aneurism.  Second  edition,  revised  and  enlarged.  In  one 
handsome  royal  12mo.  volume.     Cloth,  $1  63. 

MEDICAL  ESSAYS.     In  one  neat  12mo.  volume.     Cloth,  $1  38. 

A  PRACTICAL  TREATISE  ON  THE  PHYSICAL  EXPLORA- 
TION OF  THE  CHEST,  AND  THE  DIAGNOSIS  OF  DISEASES 
AFFECTING  THE  RESPIRATORY  ORGANS.  Second  and  revised 
edition.     One  8vo.  vol.  of  595  pages.     Cloth,  $4  50. 

^ A  PRACTICAL  TREATISE  ON  THE  DIAGNOSIS  AND  TREAT. 

MENT  OF  DISEASES  OF  THE  HEART.  Second  edition,  enlarged. 
In  one  neat  Svo.  vol.  of  over  500  pages,  $4  00. 

ON  PHTHISIS  :  ITS  MORBID  ANATOMY,  ETIOLOGY,  etc.. 


in  a  series  of  Clinical  Lectures.    A  new  work.    In  one  handsome  8vo. 
volume.     Cloth,  $3  50. 

FOWNES  (GEORGE).  A  MANUAL  OF  ELEMENTARY  CHEMISTRY. 
A  new  American,  from  the  enlarged  English  edition.  In  one  royal 
12mo.  vol.  of  over  1000  pages,  with  177  illustrations,  and  one  col- 
ored plate.     Cloth,  $2  75  ;  leather,  $3  25.      (Just  issued.) 


HENRY  C.  LEA'S  SON  &  CO.'S  PUBLICATIONS. 


FULLER  (HENRY).  ON  DISEASES  OF  THE  LUNGS  AND  AIR 
PASSAGES.  Their  Pathology,  Physical  Diagnosis,  Symptoms,  and 
Treatment.  From  the  second  English  edition.  In  one  8vo  vol. 
of  about  500  pages.     Cloth,  $.3  50. 

GALLOWAY  (ROBERT).  A  MANUAL  OF  QUALITATIVE  ANAL- 
YSIS. In  one  12mo.  vol.,  cloth,  $2  75. 
a  LUGE  (GOTTLIEB).  ATLAS  OF  PATHOLOGICAL  HISTOLOGY. 
Translated  by  Joseph  Leidy,  M.D.,  Professor  of  Anatomy  in  the 
University  of  Pennsylvania,  &c.  In  one  vol.  imperial  quarto,  with 
320  copperplate  figures,  plain  and  colored.     Cloth,  $4. 

GREEN  (T.  HENRY).  AN  INTRODUCTION  TO  PATHOLOGY  AND 
MORBID  ANATOMY.  Third  Amer.,  from  the  fourth  Lond.  Ed. 
In  one  handsome  8vo.  vol.,  with  numerous  illust.  Cloth,  $2  25. 
{No to  ready.) 

GRAY  (HENRY).  ANATOMY,  DESCRIPTIVE  AND  SURGICAL. 
A  new  American,  from  the  eighth  and  enlarged  London  edition.  To 
which  is  added  Holden's  "Landmarks,  Medical  and  Surgical."  In  one 
large  imperial  8vo.  vol.  of  nearly  1000  pages,  with  522  large  and  elabo- 
rate engravings  on  wood.  Cloth,  $6;  leather,  $7.  {Just  issued.) 
GREENE'S  (WILLIAM  H).  A  MANUAL  OF  MEDICAL  CHEMIS- 
TRY. For  the  Use  of  Students.  Based  upon  Bowman's  Medical 
Chemistry.  In  one  royal  12mo.  vol.  of  312  pages,  with  72  illustra- 
tions. Cloth,  $1  75.  {Just  ready.) 
GRIFFITH  (ROBERT  E.)  A  UNIVERSAL  FORMULARY,  CON- 
TAINING THE  METHODS  OF  PREPARING  AND  ADMINISTER- 
ING OFFICINAL  AND  OTHER  xMEDICINES.  Third  and  Enlarged 
Edition.  Edited  by  John  M.  Maisch.  In  one  large  Svo  vol  of  800 
pages,  double  columns.     Cloth,  $4  50  ;  leather,  $5  50. 

QROSS  (SAMUEL  D.)  A  SYSTEM  OF  SURGERY,  PATHOLOGICAL, 
DIAGNOSTIC,  THERAPEUTIC,  AND  OPERATIVE.  Illustrated 
by  1403  engravings.  Fifth  edition,  revised  and  improved.  In  two 
large  imperial  Svo.  vols,  of  over  2200  pages,  strongly  bound  in 
leather,  raised  bands,  $15. 

GROSS  (SAMUEL  D.)  A  PRACTICAL  TREATISE  ON  THE  Dis- 
eases, Injuries,  and  Malformations  of  the  Urinary  Bladder,  the  Pros- 
tate Gland,  and  the  Urethra.  Third  Edition,  thoroughly  Revised 
and  Condensed,  by  Samuel  W.  Gross,  M.D.  In  one  handsome 
octavo  volume,  with  about  200  illus.    Cloth,  $4  50.     {Lately  issjied.) 

A  PRACTICAL  TREATISE  ON  FOREIGN   BODIES  IN   THE 

AIR  PASSAGES.     In  one  Svo.  vol.  of  468  pages.    Cloth,  S2  75. 

QIBSON'S  INSTITUTES  AND  PRACTICE  OF  SURGERY.    In  two  Svo. 
vols,  of  about  1000  pages,  leatner,  $6  50. 
HAMILTON    (ALLAN   McLANE).     NERVOUS   DISEASES,    THEIR 
DESCRIPTION  AND  TREATMENT.     In  one  handsome  Svo  vol. 
of  512  pages,  with  53  illustrations.     Cloth,  $3  50.      {Just  isstied.) 

HEATH  (CHRISTOPHER).  PRACTICAL  ANATOMY  ;  A  MANUAL 
OF  DISSECTIONS.  With  additions,  by  W.  W.  Keen,  M.  D.  In  1 
volume;  with  247  illustrations.     Cloth,  $3  50;  leather,  $4. 

HARTSHORNE  (HENRY).  ESSENTIALS  OF  THE  PRINCIPLES 
AND  PRACTICE  OF  MEDICINE.  Fourth  and  revised  edition. 
Inonel2mo.vol.    Cloth,  S2  63  ;  half  bound,  $2  88.    {Lately  issued.) 

CONSPECTUS  OF  THE  MEDICAL   SCIENCES.      Comprising 

Manuals  of  Anatomy,  Physiology,  Chemistry,  Materia  Medica,  Prac- 
tice of  Medicine,  Surgery,  and  Obstetrics.  Second  Edition.  In  one 
royal  12mo.  volume  of  over  1000  pages,  with  477  illustrations. 
Strongly  bound  in  leather,  $5  00  ;  cloth,  $4  25.     {Lately  issiied.) 

^ A  HANDBOOK  OF  ANATOMY  AND  PHYSIOLOGY.     In  one 

aeat  royal  ]2mo.  volume,  with  many  illustrations.     Cloth.  $1  75. 


HENRY  C.  LEA'S  SON  &  CO.'S  PUBLICATIONS. 


HABERSHON  (S.  0).  ON  THE  DISEASES  OF  THE  ABDOMEN. 
Second  American,  from  the  tliird  English  edition.  In  one  handsome 
8vo.  volume  of  over  500  pages,  with  illustrations.  Cloth,  $3.50. 
{Novj  ready.) 

HOLMES  (TIMOTHY).  SURGERY,  ITS  PRINCIPLES  AND  PRAC- 
TICE. In  one  handsome  Svo.  volume  of  1000  pages,  with  41 1  illus- 
trations. Cloth,  $6;  leather,  with  raised  bands,  $7.  {Lately  issued.) 
HAMILTON  (FRANK  H.)  A  PRACTICAL  TREATISE  ON  FRAC- 
TURES AND  DISLOCATIONS.  Fifth  edition,  carefully  revised. 
In  one  handsome  Svo.  vol.  of  SoO  pages,  with  344  illustrations.  Cloth, 
$5  75  ;   leather,  $6  75. 

HOBLYN  (RICHARD  D.)  A  DICTIONARY  OF  THE  TERMS  USED 
IN  MEDICINE  AND  THE  COLLATERAL  SCIENCES.  In  one 
12mo.  volume,  of  over  500  double-columned  pages.  Cloth,  $160; 
leather,  $2. 

H OLDEN  (LUTHER).  LANDMARKS,  MEDICAL  AND  SURGICAL. 
From  the  Second  English  Edition.  In  one  royal  12mo.  vol.  of  128 
pages.     Cloth,  88  cents.      {Lately  issued.) 

HUDSON  (A.)  LECTURES  ON  THE  STUDY  OF  FEVER.  1  vol. 
Svo. ,  316  pages.  Cloth,  $2  50. 
HODGE  rHUGH  L.)  ON  DISEASES  PECULIAR  TO  WOMEN,  IN- 
CLUDING DISPLACEMENTS  OF  THE  UTERUS.  Second  and 
revised  edition.  In  one  Svo.  volume.  Cloth,  $4  50. 
THE  PRINCIPLES  AND  PRACTICE  OF  OBSTETRICS.  Illus- 
trated with  large  lithographic  plates  containing  159  figures  from 
original  photographs,  and  with  numerous  wood-cuts.  In  one  large 
quarto  vol.  of  550  double-columned  pages.  Strongly  bound  in  cloth, 
$14. 

HOLLAND  (SIR  HENRY).  MEDICAL  NOTES  AND  REFLECTIONS. 
From  the  third  English  edition.  In  one  Svo.  vol.  of  about  500  pages. 
Cloth,  S3  50. 

HUGHES.      SCRIPTURE    GEOGRAPHY  AND   HISTORY,    with    12 
colored  maps.     In  1  vol.  l2tio.     Cloth,  $1. 
HORNER  (WILLIAM  E.)     SPECIAL  ANATOMY  AND  HISTOLOGY. 
Eighth  edition,  revised  and  modified.     In  two  large  Svo.  vols,  of  over 
1000  pages,  containing  300  wood-cuts.     Cloth,  $6. 

HILL  (BERKELEY).     SYPHILIS  AND  LOCAL  CONTAGIOUS  DIS- 
ORDERS.    In  one  Svo.  volume  of  467  pages.     Cloth,  $3  25. 
HILLIER  (THOMAS).     HAND-BOOK  OF  SKIN  DISEASES.     Second 
Edition.     In  one  neat  royal  12mo.  volume  of  about  300  pp.,  with  two 
plates.     Cloth,  $2  25. 

HALL  (MRS.  M.)  LIVES  OF  THE  QUEENS  OF  ENGLAND  BEFORE 
THE  NORMAN  CONQUEST.  In  one  handsome  Svo.  vol.  Cloth, 
$2  25;  crimson  cloth,  $2  50  ;  half  morocco,  83. 

JONES  (C.  HANDFIELD).  CLINICAL  OBSERVATIONS  ON  FUNC- 
TIONAL NERVOUS  DISORDERS.  Second  American  Edition.  In 
one  Svo.  vol.  of  348  pages.     Cloth,  $3  25. 

KNAPP  (F.)  TECHNOLOGY :  OR  CHEMISTRY,  APPLIED  TO  THE 
ARTS  AND  TO  MANUFACTURES,  with  American  additions,  by 
Prof.  "Walter  R.  Johnson.    In  two  Svo.  vols.,  with  500  ill.    Cloth,  $6. 

KENNEDY'S  MEMOIRS  OF  THE  LIFE  OF  WILLIAM  W^IRT.     In 
two  vols.  12mo.     Cloth,  $2. 
LAURENCE  (J.  Z.)   AND   MOON  (ROBERT  C.)     A   HANDY-BOOK 
OF  OPHTHALMIC   SURGERY.     Second  edition,   revised   by  Mr. 
Laurence.     With  numerous  illus.     In  one  Svo.  vol.     Cloth,  $2  75. 


8  HENRY  C.  LEA'S  SON  &  CO.'S  PUBLICATIONS. 

T  EE  (HENRY)  ON  SYPHILIS.     In  one  8vo.  voL     Cloth,  $2  25. 


L 


EA  (HENRY  C.)    SUPERSTITION  AND  FORCE  ;  ESSAYS  ON  THE 
WAGER  OF  LAW,  THE  WAGER  OF  BATTLE,  THE  ORDEAL, 
AND  TORTURE.      Third  edition,  thoroughly  revised  and  enlarged. 
In  one  handsome  royal  l2ino.  vol.     Cloth,  $2  50.      (Just  issued.) 
STUDIES  IN  CHURCH  HISTORY.     The  Rise  of  the  Temporal 


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Power — Benefit  of  Clergy — Excommunication.  In  one  handsome 
12mo.  vol.  of  515  pp.     Cloth,  82  75. 

—  AN  HISTORICAL  SKETCH  OF  SACERDOTAL  CELIBACY 
IN  THE  CHRISTIAN  CHURCH.  In  one  handsome  octavo  volume 
of  602  pages.     Cloth,  $3  75. 

A  ROCHE  (R.)     YELLOW  FEVER.     In  two  Svo.  vols,  of  nearly  1500 
pages.     Cloth,  $7. 

—  PNEUMONIA.    In  one  Svo.  vol.  of  500  pages.     Cloth,  $3. 


LEISHMAN  (WILLIAM).  A  SYSTExM  OF  MIDWIFERY.  Includ- 
ing the  Diseases  of  Pregnancy  and  the  Puerperal  State.  Third 
American,  from  the  Third  English  Edition.  With  additions,  by 
J.  S.  Parry,  M.D.  In  one  very  handsome  Svo.  vol.  of  nearly  SOO 
pages  and  over  200  illustrations.  Cloth,  $4  50;  leather,  $5  50. 
{Just  ready.) 

LEHMANN  (0.  G.)  PHYSIOLOGICAL  CHEMISTRY.  Translated  by 
George  F.  Day,  M.  D.  With  plates,  and  nearly  200  illustrations. 
In  two  large  Svo.  vols.,  containing  1200  pages.     Cloth,  $6. 

A    MANUAL   OF    CHEMICAL    PHYSIOLOGY.     In    one   very 

handsome  Svo.  vol.  of  336  pages.     Cloth,  $2  25. 

LAWSON  (GEORGE).  INJURIES  OF  THE  EYE,  ORBIT,  AND  EYE- 
LIDS,  with  about  100  illustrations.  From  the  last  English  edition. 
In  one  handsome  Svo.  vol.     Cloth,  $3  50. 

LUDLOW  (J.  L.)  A  MANUAL  OF  EXAMINATIONS  UPON  ANA- 
TOMY, PHYSIOLOGY,  SURGERY,  PRACTICE  OF  MEDICINE, 
OBSTETRICS,  MATERIA  xMEDICA,  CHEMISTRY,  PHARxMACY, 
AND  THERAPEUTICS.  To  which  is  added  a  Medical  Formulary. 
Third  edition.  In  one  royal  12mo.  vol.  of  over  800  pages.  Cloth, 
$3  25  ;   leather,  $3  75. 

LYNCH  (W.  F.)     A  NARRATIVE  OF  THE  UNITED  STATES  EX- 
PEDITION TO  THE  DEAD  SEA  AND  RIVER  JORDAN.     In  one 
large  octavo  vol.,  with  2S  beautiful  plates  and  two  maps.    Cloth,  §3. 
. Same  Work,  condensed  edition.    One  vol.  royal  12mo.    Cloth,  $1. 

LYONS  (ROBERT  D.)  A  TREATISE  ON  FEVER.  In  one  neat  Svo. 
vol.  of  362  pages.  Cloth,  $2  25. 
MEIGS  (CHAS.  D.).  ON  THE  NATURE,  SIGNS,  AND  TREATMENT 
OF  CHILDBED  FEVER.  In  one  Svo.  vol.  of  365  pages.  Cloth,  §2. 
MILLER  (JAMES).  PRINCIPLES  OF  SURGERY.  Fourth  American, 
from  the  third  Edinburgh  edition.  In  one  large  Svo.  vol.  of  700 
pages,  with  240  illustrations.     Cloth,  $3  75. 

THE  PRACTICE  OF  SURGERY.     Fourth  American,  from  the 

last  Edinburgh  edition.  In  one  large  Svo.  vol.  of  700  pages,  with 
364  illustrations.     Cloth,  $3  75. 

MONTGOMERY  (W.  F.)  AN  EXPOSITION  OF  THE  SIGNS  AND 
SYMPTOMS  OF  PREGNANCY.  From  the  second  English  edition. 
In  one  handsome  Svo.  vol.  of  nearly  600  pages.     Cloth,  $3  75. 

MORRIS  (iVlALCOLM).  SKIN  DISEASES:  Including  their  Defini- 
tions, Symptoms,  Diagnosis,  Prognosis,  Morbid  Anatomy,  and 
Treatment.  A  Manual  for  Students  and  Practitioners.  In  one 
12mo.  vol.  of  over  300  pages,  with  illustrations.  Cloth,  $1  75. 
{Just  ready.) 


M 


M 


HENRY  C.  LEA'S  SON  &  CO.'S  PUBLICATIONS.  9 

ULLER  (J.)     PRINCIPLES  OF  PHYSICS  AND  METEOROLOGY. 

In  one   Lirge  Svo.  voL  with  550  wood-cuts,  and  two  colored  plates. 
Cloth,  $4  50. 
TUriRABEAU  ;   A  LIFE  HISTORY.     In  one  12mo.  vol.     Cloth,  75  cts. 

MACFARLAND'S  TURKEY  AND  ITS  DESTINY.     In  2  vols,  royal 
12mo.     Cloth,  $2. 
ARSH  (MRS.)     A  HISTORY  OP  THE  PROTESTANT  REFORMA- 
TION IN  FRANCE.     In  2  vols,  royal  12mo.     Cloth,  $2. 

NEILL  (JOHN)  AND  SMITH  (FRANCIS  G.)  COMPENDIUM  OF 
THE  VARIOUS  BRANCHES  OF  MEDICAL  SCIENCE.  In  one 
handsome  12ino.  vol.  of  about  1000  pages,  with  374  wood-cuts. 
Cloth,  $4;  leather,  raised  bands,  84  75. 

NETTLESHIP'S  MANUAL  OF  OPHTHALMIC  MEDICINE.  In 
one  royal  12pjo.  vol.  of  over  350  pp.,  with  89  illustrations.  Cloth, 
$2.      {Just  ready.) 

PLAYFAIR  (W.  S.)     A  TREATISE  ON  THE  SCIENCE  AND  PRAC- 
TICE OF  MIDWIFERY.     Third  Americnn  Edition,  revised  by  the 
author.     Edited,  with    Additioris,   by  R.   P.  Harris,  M.D.     In  one 
handsome  octavo  vol.  of  about  700  pages,  with  nearly  200  illustra- 
tions and  two  plates.     Cloth,  $4;  leather,  $5.      {Just  ready..) 
PAVY  (F.  W.)    A  TREATISE  ON  THE  FUNCTION  OF  DIGESTION, 
ITS  DISORDERS  AND  THEIR  TREATMENT.     From  the  second 
London  ed.     In  one  Svo.  vol.  of  24fi  pp.     Cloth,  $2. 
pARRISH  (EDWARD).     A  TREATISE  ON  PHARMACY.    With  many 
J-      Formulae  and  Prescriptions.  Fourth  edition.  Enlarged  and  thoroughly 
revised  hy  Thomas  S.  Wiegand.     In  one  handsome  Svo.  vol.  of  977 
pages,  with  280  illus.     Cloth,  $5  50  ;  leather,  86  50. 
piRRIE  (WILLIAM)      THE  PRINCIPLES  AND  PRACTICE  OF  SUR- 
J-      GERY.     In  one  handsome  octavo  volume  of  780  pages,  with  316 
illustrations.     Cloth,  $3  75. 

PULSZKY'S  MEMOIRS  OF  AN  HUNGARIAN  LADY.  In  one  neat 
royal  12mo.  vol.     Cloth,  $1. 

PAGET'S  HUNGARY  AND  TRANSYLVANIA.  In  two  royal  12mo. 
vols.     Cloth,  $2. 

TjEYNOLDS  (J.  RUSSELL)      A  SYSTEM  OF  MEDICINE,  with  Notes 

-•■^     and  Additions,  by  Henry  Hartshorne,  M.D.     In  three  large  Svo. 

vols.,  containing  about  3000  closely  printed  double-columned  pages, 

with  many  illustrations.     Sold  only  by  subscription.     Per  vol.,  in 

cloth.  $5;  in  leather,  $6.      {Just  ready.) 

"DEMSEN  (IRA).     THE   PRINCIPLES   OF   CHEMISTRY.      In   one 

•*■"     handsome  12mo.  vol.     Cloth,  81  50.     {Just  issued.) 

ROBERTS  (WILLIAM).  A  PRACTICAL  TREATISE  ON  URINARY 
AND  RENAL  DISEASES.  Third  American,  from  the  third  re- 
vised and  enlarged  London  edition.  With  numerous  illustrations 
and  a  colored  plate.  In  one  very  handsome  Svo.  vol.  of  over  600 
pages.     Cloth,  $4. 

RAMSBOTHAM   (FRA.NCIS   H.)     THE   PRINCIPLES  AND    PRAC- 
TICE OF  OBSTETRIC  MEDICINE  AND  SCRGERY.     In  one  im 
perial  Svo.  vol.  of  650  pages,  with  64  plates,  besides  numerous  wood- 
cuts in  the  text.     Strongly  bound  in  leather,  $7. 

ANKE'S    HISTORY   OF    THE    REFORMATION    IN    GERMANY. 
Parts  I.,  II.,  IIL     In  one  vol.     Cloth,  §1. 


E 


10  HENRY  C.  LEA'S  SON  &  CO.'S  PUBLICATIONS. 

RIGBY  (EDWARD).     A  SYSTEM  OF  MIDWIFERY.     Second  Ameri. 
can  edition.    In  onehandsome  Svo.A'ol.  of  422  pages.     Cloth.  $2  60. 
SEILER  (CARL)      HANDBOOK  OF  DIAGNOSIS  AND  TREATMENT 
OF  DISEASES  OF  THE  THKOAT  AND  NASaL  CAVITIES.     In 
one  small  12mo.  vol.,  with  illustrations.     Cloth,  $1.     {Now  Ready.) 

S CHAFER  (EDWARD  ALBERT).  A  COURSE  OF  PRACTICAL  HIS- 
TOLOGY :  A  Manual  of  the  Microscope  for  Medical  Students.  In 
one  handsome  octavo  vol.  With  many  illust.  Cloth,  $2.    {Just  Issued.) 

SMITH  (HENRY  H.)  AND  HORNER  (WILLIAM  E.)  ANATOMICAL 
ATLAS.  Illustrative  ofthe  structure  of  the  Human  Body.  In  one  large 
imperial  Svo.  vol.,  with  about  650  beautiful  figures.     Cloth,  $4  50. 

STIMSON  (LEWIS  A.)  A  MANUAL  OF  OPERATIVE  SURGERY. 
In  one  very  handsome  royal  ]2mo.  volume  of  488  pages,  with  332 
illustrations.     Cloth,  $2  50.     {Just  issued.) 

S WAYNE  (JOSEPH  GRIFFITHS).  OBSTETRIC  APHORISMS.  A 
new  American,  from  the  fifth  revised  English  edition.  With  addi- 
tions by  E.  R.  Hutchins,  M.  D.  In  one  small  12mo.  vol.  of  177  pp., 
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TANNER  (THOMAS  HAWKES) .  A  MANUAL  OF  CLINICAL  MEDI- 
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ON   THE   SIGNS  AND  DISEASES  OF  PREGNANCY.     From 

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THOMPSON  (SIR  HENRY).  THE  PATHOLOGY  AND  TREATMENT 
OF  STRICTURE  OF  THE  URETHRA  AND  URINARY  FISTULA. 
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THOMPSON  (SIR  HENRY).  CLINICAL  LECTURES  ON  DISEASES 
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ATSON  (THOMAS).  LECTURES  ON  THE  PRINCIPLES  AND 
PRACTICE  OF  PHYSIC.  A  new  American  from  the  fifth  and  en- 
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OHLER'S  OUTLINES  OF  ORGANIC  CHEMISTRY.  Translated 
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ELLS  (J.  SOELBERG).  A  TREATISE  ON  THE  DISEASES  OF 
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with  6  colored  plates  and  many  wood-cuts,  also  selections  from  the 
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EST  (CHARLES).  LECTURES  ON  THE  DISEASES  PECULIAR 
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—  LECTURES  ON  THE  DISEASES  OF  INFANCY  AND  CHILD- 
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—  ON   SOME   DISORDERS    OF    THE    NERVOUS   SYSTEM   IN 


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CHILDHOOD.  From  the  London  Edition.  In  one  small  12mo. 
volume.     Cloth,  $1. 

WILLIAMS  (CHARLES  J.  B.  and  C.  T.)  PULMONARY  CONSUMP- 
TION:  ITS  NATURE,  VARIETIES,  AND  TREATMENT.  In 
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WILSON  (ERASMUS).  A  SYSTEM  OF  HUMAN  ANATOMY.  A 
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THE  STUDENT'S  BOOK  OF  CUTANEOUS   MEDICINE.     In 

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WINCKEL  ON  PATHOLOGY  AND  TREATMENT  OF  CHILDBED. 
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WOODBURY  (FRANK).  A  HANDBOOK  OF  THE  PRINCIPLES 
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